AF 447 Thread No. 11 [Archive] - Page 3

TTex600

27th Oct 2013, 07:28

My neighbor Airbus captain swears their procedure with loss of IAS is max climb power and 5 degrees nose up and laughed because I have 8 jet type ratings and have never been taught that. I said 5 degrees nose up at 35,000 ft means you will eventually stall and go through the altitudes above you belonging to other flights. He says I wouldn't be following the Airbus checklist and laughed some more. With a good altimiter do all Airbus pilots fly like that? We were taught to hold last attitude and power and use the UAS checklist in all 8 jets I was a captain in. With a good altimiter with AP disconnect I wouldn't even call it a big emergency but to fly through unauthorized altitudes would be. This is at least Spirit Airlines procedure.

Your neighbor is either pulling your leg or just plain wrong. I don't know him/her so I'll let you be the judge of that.

The Spirit COM says the same as the Airbus COM.

I'll paraphrase: If safety of flight is affected..... turn off AP/FD/AT, adjust pitch and power as necessary to reach acceleration alt, gear up, flaps leave at existing position, when at safe circuit alt level off and troubleshoot.

Tables are then provided to supply pitch and power settings for various weights/alts/configurations.

Nowhere do I see a combination of "max climb" power and 5deg nose up.

FWIW, the initial settings offered for cruise flight are 3 deg nose up and 80% N1

Note: Spirit (NK) flies A319/320/321. The pitch/power are for 319.

rudderrudderrat

27th Oct 2013, 07:58

Villas,
On the plus side aircraft still auto trims and maintains wings level/bank so it is always stable.
With UAS, the aircraft was in ALT LAW.
Please explain why you think the aircraft was able to maintain wings level/bank.
What is the advantage of auto-trim of the stabiliser during UAS? Surely you would want to maintain the last trimmed AoA before the event?

vilas

27th Oct 2013, 09:44

RRR
In DSC-20-20-20 P 5/8 all it says is
BANK ANGLE PROTECTION
Not provided.
and in PRO-SUP 27-30 P 4/6 it says
Bank stability and protections are no longer active and the flight crew should take care to stay within normal limits.
The protection part is clear but what do you make out of the bank stability? If you bank more than 33 degrees it won't return to 33. But if your bank is within 33 degrees and zero will it hold or not. If not then it is laterally unstable. What's your take?

vilas

27th Oct 2013, 09:53

RRR
Auto trim is not trimming for speed bu the flight path. Provided you hold the correct pitch it will trim that. Isn't that the difference between Alternate and direct law? Makes things easier.

Winnerhofer

27th Oct 2013, 10:27

Airbus is vector-stable.
Boeing is speed-stable.
This is why Boeing AutoTrims for speed and not for pitch.

Related links:

http://www.pprune.org/tech-log/503326-b777-secondary-mode-v-a330-alterante-laws-1-2-a.html

http://www.pprune.org/tech-log/501818-memory-item-uas-a330-flawed.html

http://www.pprune.org/tech-log/503720-b777-procedure-blocked-aoa-probes.html

RetiredF4

27th Oct 2013, 13:46

@vilas,
the mode was Alt2B. In this mode the roll channel is not stabilized like in Normal Law or in Alt1, no bank stability except the natural one is available then.

Therefore the reaction of the aircraft after AP disconnect was:

Final report page 172
2.1.2.3 Control of the flight path
When the autopilot disconnected, the roll angle increased in two seconds from 0 to +8.4 degrees without any inputs on the sidesticks. The PF was immediately absorbed by dealing with roll, whose.........

We have been through this before.

vilas

27th Oct 2013, 14:19

RetiredF4
Thanks. I will look for older posts.

DonH

27th Oct 2013, 16:04

vilas;
Re, "Thanks. I will look for older posts. ",

The following link to a PPRuNe search engine may be of assistance: AF447 Search Index for PPRuNe Forums (http://countjustonce.com/pprune/)

The UAS discussion is interesting.

A change in pitch attitude at cruise altitude destabilizes a stable airplane and so should be a consideration before executing the UAS memorized items which require an initial pitch change where none is required.

Establishing a 5° pitch would mean an increase of about 2.5° to the cruise pitch attitude...not destabilizing right away but would be if held too long.

The remarks in FCTMs, (Flight Crew Training Manual(s)) indicate that:

ADR CHECK PROC / UNRELIABLE SPEED INDICATION QRH PROCEDURE

The flight crew may enter this procedure, either upon ECAM request (ADR DISAGREE or ANTI-ICE PITOT caution), or because he suspects an erroneous indication, without any ECAM warning.

When to Apply this procedure
1, 2, 3, etc;

5. Rely on the stall warning that could be triggered in alternate or direct law. It is not affected by unreliable speeds, because it is based on angle of attack.

6, 7, etc

If the safe conduct of the flight is affected, the flight crew applies the memory items. They allow "safe flight conditions" to be rapidly established in all flight phases (takeoff, climb, cruise) and aircraft configurations (weight and slats/flaps).The memory items apply more particularly when a failure appears just after takeoff. Once the target pitch attitude and thrust values have been stabilized, as soon as above safe altitude, the flight crew will enter the 2nd part of the QRH procedure, to level off the aircraft and perform trouble shooting. This should not be delayed, since using the memory item parameters for a prolonged period may lead to speed limit exceedance.

(Note: SOPs published, early 2007)
The subject is discussed widely on many of the previous 10 threads. Some further discussion is available here, (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-40.html#post6600248) and on this thread, here. (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-22.html#post8108762)

Blind Squirrel

27th Oct 2013, 22:02

Capt Jim Lovell said it was basic flying skills that allowed him and his crew to navigate their way back to Earth after an oxygen tank exploded during their voyage to the moon in 1970.

Recent air disasters such as Air France flight 447, lost over the Atlantic in 2009, and the Asiana Airlines plane which crash landed in San Francisco this summer indicate that pilots have become too reliant on autopilot, he added.

Apollo 13 commander: bring back traditional flying skills - Telegraph (http://www.telegraph.co.uk/science/space/10406584/Apollo-13-commander-bring-back-traditional-flying-skills.html)

ShyTorque

27th Oct 2013, 22:48

He might have been better saying "some airline pilots".

Not all pilots even have an autopilot in the aircraft.

BARKINGMAD

28th Oct 2013, 01:14

The 73NG spends most of the cruise phase with about 3 degrees nose up pitch, nearly 90% N1 on the thrust and stab about 6.0.

All #s easily divisible by 3, a frequent and useful number in aircraft, so if I was ever to end up in AF447s predicament I would set these and keep the blue side up and the brown side down til we fell out of the other side of ITCZ or whatever was giving us grief, then reassemble the flight profile and if appropriate, carry on.

Thanks to this accident & forum for causing me to note these NORMAL settings, so's I have an instantaneous datum to set whilst waiting for my oppo to come back from the bog, when we can then start chasing QRH and DODARing and all the follow-up housekeeping items.

Has anyone else quietly looked at their own 'frames settings since and filed it away for ready reference til there's time to perform the UAS drill?

This is in addition to the normal pitch 'n power settings we hopefully know for other flight phases. :)

bubbers44

28th Oct 2013, 01:36

JS, thanks for the loss of IAS checklist not being applicable in cruise but my Airbus captain neighbor still doesn't believe it so the debate goes on. Actually it is good because when he comes over he drinks all of our alcohol so him calling me stupid and and idiot saves me lots of money because we disagree a lot. He usually stays mad for a month. Thanks.

flarepilot

28th Oct 2013, 04:41

I'd love to meet the pilot who would correct James Lovell. I would think that would be a very small group of pilots...Wilbur, Orville, Charles, Jimmy...not too many others.

bubbers44

28th Oct 2013, 09:56

But I am sure they got lots of correction from all of their wives. They don't need a pilots license to tell their pilot he is AFU.

Chris Scott

28th Oct 2013, 20:00

Quote from Flarepilot:
"I'd love to meet the pilot who would correct James Lovell. I would think that would be a very small group of pilots..."

Jim Lovell is widely revered by pilots, myself included, who were ordinary professional fliers at the time of Apollo 13. His leadership on that trip is considered to be a classic model of CRM before NASA defined the concept. (They say there is nothing new under the sun.) That being the case, it goes without saying that Swigert and Haise would have had no hesitation in challenging any misconception of his that might have compromised the success of the operation.

Quote (http://www.telegraph.co.uk/science/space/10406584/Apollo-13-commander-bring-back-traditional-flying-skills.html) from Jim Lovell, part of an interview reported by the Daily Telegraph (London):
"I think that aviators these days have to go back and do a lot of hand flying really to be the final judge of controlling the aeroplane.
"There was the example of the Air France plane that was lost. They were on autopilot and the autopilot stalled the aeroplane."

Whether or not you understand and agree with the opinion he expresses in the first paragraph I've quoted, his statement in the second paragraph is simply wrong. A pity, because we need respected personalities to raise the profile of current discussions on the pros and cons of automation.

bubbers44

29th Oct 2013, 00:07

All the heros Flare pilot mentioned are dead heros. He wasn't talking about CRM in my opinion. We all believe in CRM. I've in jet cockpits corporate flying taken an airplane away from the captain when talking didn't work. It is your responsibility as FO. If you get fired it wasn't a big loss because your life is not worth a job.

bubbers44

29th Oct 2013, 02:52

AF447 is an example of autopilot dependency and they did not know how to hand fly at altitude. We are headed that direction in the US with the pilot mills. I guess there is no turning back now. I think the simplified Airbus procedures are designed for them. We could use the altimeter in my era to set cruise power and not bust altitudes but guess it is not possible with the new guys. God help us.

bubbers44

29th Oct 2013, 03:39

Spirit needs to change their procedure and maintain altitudes and set cruise power by last pitch and power like Delta and not require pilots to bust altitudes in RSVM airspace. It is quite easy. You just have to know how to handfly in AF447 case. Why climb if the nearest obstacle is 7miles below you.

TTex600

29th Oct 2013, 03:52

Bubbers, being a Spirit Capt I agree with you on needing a change. BUT, Spirit is using Airbus procedures. It is Airbus that needs to change.

Desert185

29th Oct 2013, 04:27

Sorry haven't read the entire thread, but let me ask this. Why not design an aircraft so that the autopilot does not trip off when the pitots ice over? I currently fly a 1969 model designed in 1958 that will not trip the autopilot when the airspeed goes to zero.

If the 'Buses are so sophisticated, why does this happen, particularly when the majority of the crews are so dependent on the automation being reliable?

gums

29th Oct 2013, 15:03

Sorry, but I don't feel the A/P should stay engaged with loss of air data unless it reverts to pure "attitude" hold.

The 'bus and my little jet 40 years ago used, and still uses, the "q" for "gains", which limits the rate of control surface movement accordingly. Doze and A33z can add to this explanaiton and correct me. For example, you wouldn't want the THS to move at the same rates when at 300 knots versus 200 knots. In our little jet, imagine yanking on the sidestick at 400 or 500 knots in "direct" mode such as the 'bus has ( we never had a "direct" mode except in pitch when we were in a deep stall and used a special switch to "rock" the thing outta the stall).

However, body rates are still in play, and they are simple rate sensors that do not need air data. Then there's the attitude reference systems, inertial or basic gyros we have had since the 1930's. So the basic control laws of the 'bus are still inplay, including the AoA inputs, which have a reversion implementation we see in the AF447 once the troop kept pulling with the stall horn blaring.

Next, the basic pitch laws are "gee". Ours did not have the pitch attitude correction due to operational requirements, but BFD. The 'bus system was designed for heavies and their mission/flight profiles. It looks very good to this old FBW pioneer, and my only complaint is the plethora of reversion modes. I would have preferred a single mode between "direct" and "normal" instead of what we see. In other words, no big change at all with loss of air data except you use "standby" gains as we did. Ours used 300 knots gear up and 160 or so with gear down, and we still had body rate inputs to help.

bubbers44

30th Oct 2013, 00:57

Maybe us Boeing pilots should have some kind of warning when an Airbus is approaching us in the clouds at high altitude in RVSM airspace that the Airbus below you if losing IAS will by procedure fly through your altitude because of their procedures.

5 degrees nose up and climb power will definately take your aircraft out if you are not lucky enough to be not in their trajectory. AF 447 went through 3 altitudes to finally stall. Thank God no aircraft were there. AB, join the rest of the universe and in level flight just stay level and do the check list, don't fly through other airliners altitudes because mid air collisions can be dangerous. If your altimiter works use it, don't be stupid because AB said to do it. The procedure at the top of the checklist says to use it if you need to for safety of flight. Level at FL 350 it was not necessary, just set or leave power what it was and maintain attitude 2.5 to 3 degrees nose up and do the UAS checklist. Remember, we are not robots following every procedure because we also are pilot who know how to fly an airplane. Maintain altitude if your altimiter is working and do the simple check list.

vilas

30th Oct 2013, 07:03

bubbers44
You are seeing ghosts of your own imagination. There is simply no such procedure in Airbus aircraft. The procedure of 5 Degrees and Climb power is only applicable if UAS happens during climb above 10000ft. In cruise above 34000ft. the pitch is 3 degrees and 85%N1 for weights between 180T and 220T. About your neighbour captain, don't worry there will be some like him even in Boeing.What does SFO accident prove? Boeing type rating doesn't involve brain transplant.

DonH

30th Oct 2013, 07:23

Sigh...

:ugh:

bubbers44

30th Oct 2013, 08:14

Hopefully you are right. His two buddy pilots both agree with him so hope you are right. I said that would be fine in a climb but not stabilized in level flight but it was 3 against one. Hopefully they fix all the probes.

BOAC

30th Oct 2013, 10:32

Sorry DonH - we'll get that bird shot some time......................:}

In this case bubbers is correct - "Airbus approaching - Airbus approaching" needs to be built into TCAS.

AAIB Bulletin No: 6/2001 Ref: EW/C2000/10/2

Air Accidents Investigation: Download PDF document (http://www.aaib.gov.uk/cms_resources/Airbus%20A330,%20C-GCWD%20Airbus%20A340,%20TC-JDN%2006-2001.pdf)

Capn Bloggs

30th Oct 2013, 10:50

Bl@@dy Hell! Would have made a nice mess over the Atlantic.

I notice no recommendation to stop Airbii unilaterally pulling up when overspeeding...

Turbine D

30th Oct 2013, 13:15

@ vilas:
There is simply no such procedure in Airbus aircraft. The procedure of 5 Degrees and Climb power is only applicable if UAS happens during climb above 10000ft. In cruise above 34000ft. the pitch is 3 degrees and 85%N1 for weights between 180T and 220T.

So what you are saying is there is no memory list item for UAS at high speed high altitude cruise. You gotta get out the charts and tables to find out what to do. I think a lot of pilots would disagree with you. But your point does confirm what some of us have believed for sometime, the standard Airbus UAS memory list is poorly written and needs to be changed.

Lonewolf_50

30th Oct 2013, 13:50

Sorry, but I don't feel the A/P should stay engaged with loss of air data unless it reverts to pure "attitude" hold.
If I may second this notion. :ok:

From the A330/A340 incident ...
The pitchup trend continued for 17 seconds reaching a peak of 15° nose-up shortly before the first nose-down sidestick command was applied.

I don't get why it takes so long to make a pitch correction when such a pitch excursion is made. Can anyone familiar with AB FBW suites in that family of aircraft provide a bit of insight?

vilas

30th Oct 2013, 15:02

TurbineD
Memory items are there for after takeoff and climb phase. However the wording used is "If the safe conduct othe flight is affected".For cruise you are expected to level off and follow the unreliable airspeed procedure for trouble shooting. Boeing is not much different. It mentions crew should be aware of appx.pitch attitude for each maneuvre and then asks you consult the table. The problem is you are dealing with pilots who do not monitor anything,not even speed in visual approach like the experienced pilots of the Asiana accidents. Then what can you expect at night, in turbulence with confusing airspeeds.It appears that these pilots were really not trained or explained the complications of this perticulare problem and they did not remember the memory items correctly. They would not have done anything better even in a Boeing or any aircraft.

flyboyike

30th Oct 2013, 16:15

For crying out loud. Since when has flying an appropriate approximate pitch and power setting required the title 'Memory item'?

Since airlines started hiring people who don't care about flying, who could have just as easily become accountants and just happened to end up in flight school.

DonH

30th Oct 2013, 16:40

BOAC, re, "Airbus coming, Airbus coming", now that has made my day! ;-)

Thanks - I recall the event and had downloaded the AAIB Report of course.

On this particular entry into the conversation, it's not possible nor is it wise to take Bubbers' statements seriously. This is a Tech Forum: - There is much more to the problem, as evidenced in the AAIB Report.

The failure but primarily the humour in such suggestions for TCAS as made by Bubbers is, as the Report determines, the circumstances demand a far broader and perceptive comprehension of the problem at hand.

That we have an ATC system that is placing airplanes in closer proximity to one another purely for economic reasons is a major contributor to the issue. and the report makes observations on mitigating strategies. The critical statement in the Report which may lend the scent of credibility to an otherwise-humourous statement is, "Therefore, the RVSM safety case should not be driven by any assumption that a different crew might have contained the situation by making an earlier nose-down sidestick command than the A340 crew involved in this incident.". As John Smith correctly observes, it is not an Airbus-specific problem and as such requires serious and imaginative solutions to deal with the problems that financial considerations and not safety considerations have created. That is happening, as stated in the Report, though glacially, as these things do.

BOAC

30th Oct 2013, 17:07

DonH - while not wishing to keep on clapping my hands to keep the damn Oozlum bird flying, surely it is equally an 'onus' on any crew, knowing the existing reduced seperation, to add to John S's simple doctrine "I must try not to climb or descend into/through another aircraft's level". Hence the 447 PNF should have been 'screaming' to PF about the excursion in no uncertain terms and taking control if necessary?

chrisN

30th Oct 2013, 17:28

A question from a glider pilot, if you professionals would be kind enough to inform me:

In the A330/A340 incident, there was a sudden increase in what glider pilots call total energy - the sum of kinetic (speed) and potential energy (altitude). Presumably this was caused by windshear, or rising air (wave or whatever) caused by the nearby jetstream or front. In gliding, if the energy increase is not wanted, we counteract the increase by spilling it – with increased drag (e.g. airbrakes) or letting the speed bleed off gradually should circumstances permit.

It sounds as if they had only two quick choices, since power reduction would be slow – climb, or go into overspeed. Is that right? If climb is too dangerous leading to a level bust, can overspeed temporarily be tolerated? Or could drag be increased (airbrakes?)?

A33Zab

30th Oct 2013, 17:37

Bubbers:
Maybe us Boeing pilots should have some kind of warning when an Airbus is approaching us...

Bloggs:
I notice no recommendation to stop Airbii unilaterally pulling up when overspeeding...

BOAC:
In this case bubbers is correct - "Airbus approaching - Airbus approaching" needs to be built into TCAS.

" or a B777/B787. "

http://i474.photobucket.com/albums/rr101/Zab999/787Ospeed_zpsdb5bad00.jpg

BARKINGMAD

30th Oct 2013, 17:58

OH DEAR OH DEAR OH DEAR ! ! ! !

Now Mr Boeing has done down the zoom-climb route to solve a kinetic energy problem.

The inmates really are running the asylum and having the keys to the pharmacy as well they've gone on one helluva trip?!!

Gawd help us airframe drivers and the hapless SLF! :ugh:

HazelNuts39

30th Oct 2013, 18:19

chrisN,

From another glider pilot, also an ex-professional though not as a pilot,

Yes, there was an overspeed condition that caused a warning an disconnection of the A/P. However, that overspeed condition was very brief and not really a problem. Shortly after that the airplane encountered a vertical gust that increased the AoA to alpha-prot and put the FCS in high-AoA protection mode which caused the zoom climb.

chrisN

30th Oct 2013, 19:12

HN39, Thanks.

DonH

30th Oct 2013, 19:30

Turbine D (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-27.html#post8125549) But your point does confirm what some of us have believed for sometime, the standard Airbus UAS memory list is poorly written and needs to be changed. Yes, agree, the Airbus UAS drill, as still published, can be confusing. However, numerous Airbus publications available on the web indicate how the UAS drill and QRH checklist were, and are to be handled and the FCTM notes do reflect this although they could be much clearer still.

Earlier in this thread I pointed out where in the original (now closed) threads that this discussion began taking place. However, if some comments here are an indication of the broader piloting community, then, without blaming anyone as to why this may be so, there remains a great deal of misunderstanding on when and how to apply the memorized drill and when not to and instead proceed directly to the QRH checklist items. In fact, the memorized drill and the checklist are NOT sequential, they are an "if/then" decision point.

First, when loss of airspeed information occurrs, the qualifying condition, "If the safe conduct the flight is affected" is not clearly defined in the drill-checklist, nor is it defined in the Boeing checklist, (there are no memorized items or initial pitch-thrust memorized combinations in the B767/B777 UAS responses). The drill-checklist is not a sequential drill - rather, the "safe conduct of the flight affected" is a primary "if-then" decision point in the UAS response - the safety of the flight IS affected at takeoff, initial climb or descent/approach/landing.

Loss of airspeed information at cruise altitude is not an emergency and because the airplane is, for all intents, stable in pitch and power, then "nothing" needs to be done (except keep the airplane stable), because the safe conduct of the flight is not affected, (in comparison to the takeoff/landing case). The crew, (PF) assumes control of the airplane to maintain aircraft stability by maintaining thrust and pitch at current settings, (Aviate), maintains/alters heading as required, (Navigate) and calls for the ECAM actions, (Communicate), to be done followed by getting out the QRH Checklist to set pitch and power for the remainder of the cruise.

The graphic below illustrates this and I think this is the source of much of the confusion:

http://batcave1.smugmug.com/photos/i-kXr5vDx/0/L/i-kXr5vDx-L.jpg

The "Pitch/Thrust settings for initial level off" are just below this point in the drill. The balance of the QRH provides pitch and thrust settings for varying weights in cruise, descent, approach, landing and go-around. However, in all cases of a UAS event in cruise, airspeed indications returned within about one minute, including AF447's airspeed indications, but the stall had been entered by that time.
vilas (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-27.html#post8125726) However the wording used is "If the safe conduct othe flight is affected".For cruise you are expected to level off and follow the unreliable airspeed procedure for trouble shooting. Boeing is not much different. It mentions crew should be aware of appx.pitch attitude for each maneuvre and then asks you consult the table. Yes. This is the way the drill & checklist were always intended to be done. Airbus stated as much in its December, 2007 "Safety First" magazine (http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCsQFjAA&url=http%3A%2F%2Fwww.ukfsc.co.uk%2Ffiles%2FSafety%2520Briefi ngs%2520_%2520Presentations%2FAirbus%2520Safety%2520First%25 20Mag%2520-%2520Dec%25202007.pdf&ei=DTpxUsCpLaWGyAHuhYGQDQ&usg=AFQjCNFPaXHrzTxWOpzyu8l3X4fWvoYuoQ&sig2=1M4GQtgESiYv5iPo1Sn6Sw&bvm=bv.55617003,d.aWc&cad=rja) (pg 14): in the oft-quoted-in-original-threads Joelle Barthes article entitled, "Unreliable Speed":
1) If the safe conduct of the flight is affected, APPLY THE MEMORY ITEMS, i.e. fly a pitch with TOGA or CLB thrust,
2) If the safe conduct of the flight is not affected, or once the memory items have been applied, LEVEL OFF, if necessary, and start TROUBLESHOOTING,
3) If the affected ADR can be identified, fly with the remaining ADR. 4) If the affected ADR cannot be identified or all airspeed indications remain unreliable, FLY WITH PITCH/THRUST REFERENCES. - Safety First magazine, December, 2007, Joella Barthesfollowed by the a graphic, describing what is intended by the above:

http://batcave1.smugmug.com/photos/i-65CQmXw/0/M/i-65CQmXw-M.jpg
- Safety First magazine, December, 2007, Joella Barthes

In fact, in an Airbus presentation in September 2006 (http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCsQFjAA&url=http%3A%2F%2Fwww.smartcockpit.com%2Fdownload.php%3Fpath% 3Ddocs%2F%26file%3DUnreliable_Speed.pdf&ei=eUpxUu-AGaa0ygGzoYHgBg&usg=AFQjCNHK4lbEt-L0tEywH7DQHQ2LgAGydQ&sig2=OGqw_xPMZoyJ38fY0Vi0Tw&bvm=bv.55617003,d.aWc&cad=rja), it is clearly stated that what constitutes "safe conduct affected" is defined in training:

http://batcave1.smugmug.com/photos/i-xMfgFdR/0/M/i-xMfgFdR-M.jpg
Airbus OLM FBW 2006, (Unreliable Speed) - Toulouse - 23-28 September 2006

In my opinion and from what I have researched for a long time now, the UAS response is NOT a sequential drill-checklist - never was.

What is confusing about this is not entirely nor necessarily the Airbus UAS drill and checklist. The large black dot is a decision-point, not a "start here and follow all items" point. Buy down below, the "Level Off..." action item has the same black dot, making the drill-checklist appear "sequential". It is not.

A large part of the problem is knowing the way checklists are written in terms of these "decision points" and the meaning of correct indentations, (which this drill-checklist appears to not have). The decision point regarding safe-conduct-of-the-flight-affected permits/requires that the crew either execute the memorized items OR, (in cruise for example), they do the QRH checklist after stabilizing the aircraft in level flight.

This has all been reviewed and discussed in the original threads (part of which has been pointed out but, I assume, not viewed or referenced by some in the present thread.

DonH

30th Oct 2013, 19:55

Hi BOAC;
...while not wishing to keep on clapping my hands to keep the damn Oozlum bird flying, surely it is equally an 'onus' on any crew, knowing the existing reduced seperation, to add to John S's simple doctrine... No worries BOAC - I think we're all clapping in unison!

Yes, agree with you entirely - this goes to the "giving in to automation / not understanding one's airplane / maintaining situational awareness" discussion though. Solutions, offered in the AAIB Report, suggest that among a few, offsets may be routinely considered. Here's one reason why - he's 2000ft above. And I've been hit by wake turbulence from a B744 1000ft above, opposite direction as we passed right under him - very sharp, 20deg roll, then nothing.

http://batcave1.smugmug.com/photos/i-fx3zxH4/0/L/i-fx3zxH4-L.jpg

bubbers44

30th Oct 2013, 20:07

Thanks DonH, that was what I trying to tell him but not as clearly as you put it. I'm not going to bring the subject up with him again because I will just be the idiot again.

DonH

30th Oct 2013, 21:14

Hi Bubbers;
...because I will just be the idiot again. , Yes, probably best to let it be. There will always be, 'yeah, but's...'

These are Airbus' own documents, available on the web - I just did a lot of research over time because I remember being confused about the drill myself when doing the initial training from Boeing to Airbus equipment.

And, I like to keep the tech topic on topic!

BOAC

31st Oct 2013, 08:43

DonH - "And, I like to keep the tech topic on topic! " - agreed, but unfortunately 447 opens a large can of worms. Whether the 'automatics' brigade like it or not, some of the programmed features of the AB system contributed to both 447 and the 330/340 events. Note I say 'contributed to' and not 'caused'. Autotrim and the 'software' decision to abandon the stall warning did not help 447 or the 330/340 Shortly after that the airplane encountered a vertical gust that increased the AoA to alpha-prot and put the FCS in high-AoA protection mode which caused the zoom climb. - why? These features are good features and have useful functions in many situations BUT they can cause problems where they should not, and the training is inadequate in 'teaching' crews to defer to the automatics. There were, after all, two hopefully sentient beings in the cockpit who could have decided how to handle an overspeed without having HAL do it for them. Now apparently Boeing are going the same way (with overspeed) - again why?

On the topic of the UAS checklist, we have unfortunately 'lost' the on-going most valuable inputs from PJ2 due to bizarre modding, but it is well worth searching his posts on the topic on the 447 threads. Again, in both 'events', we have crews without the 'big picture' and mesmerised like the proverbial rabbit by the systems.

I have, along with others, for a long time advocated a major change in training for the 'glass/auto' environment. BA recognised it years ago (late 20th century) with their short 'don't get mesmerised' ('EOI') course. The increasing lack of real experience in cockpits plus the over reliance on highly seductive systems is taking us down a clearly defined one-way street. There are some side street exits, but we are running out of them.

vilas

31st Oct 2013, 11:23

DonH
I have the documents you have quoted and I am in agreement. However the real problem was I think UAS was not considered seriously as a possibilty as let's say an engine failure. During type rating it is conducted only as a DEMO in after takeoff scenario. I am not sure if it is ever practiced threafter. It is not in regulatory tick boxes. Recognition of UAS can be quite confusing and if you are confused or ignorant of the procedure then anything can happen. Even 757 has crashed before.

john_tullamarine

31st Oct 2013, 11:58

During type rating it is conducted only as a DEMO in after takeoff scenario

I'm a tad out of touch with the training game these days but some of us used to make it a private requirement using spare time during an endorsement to ensure that pilots could handle several of the unlikely but very high risk scenarios.

For me and several of my colleagues in a previous life that included a total (or as close as we could make it in the particular sim) loss of pressure readouts - low vis takeoff with a single pilot no help recovery via an ILS to minimums.

It goes without saying that included no FMS, FD, etc. Realish sim flying.

Allowed us to sleep well at night.

gums

31st Oct 2013, 14:50

Gotta go with BOAC.

I also wonder how AoA protection laws could have caused a climb as 'nuts suggests.

The various factors resulting in the crash are all worthy of discussion and some "learning", IMHO. CRM, flight control laws, aircraft performance, instrument/sensor failures, basic piloting skills, and the beat goes on.

I can tell you that 34 years ago we all learned a lot that wasn't in the "books" and had not been exposed to us in the sim ( we didn't have a sim for 3 years after becoming operational, heh heh). Our control laws were primitive compared to the 'bus, mainly due to only two autopilot modes that worked with the FLCS. And of course, our operational requirements demanded flying to the limits, personal and aircraft. Nevertheless, we all learned a lot and we passed on lessons to the next generation and the one after that. Now, I am here trying to contribute something for you heavy dudes to think about. And you must realize that CRM is foreign to me. Only crewed jet I flew only had one set of controls and the guy in the back seat was a "systems operator".

Desert185

31st Oct 2013, 15:24

Sorry, but I don't feel the A/P should stay engaged with loss of air data unless it reverts to pure "attitude" hold.

Don't discount the fact that the autopilot is still available with a loss of IAS. There is a selected Pitch Damp mode that the pilot can select to maintain attitude if desired. Options are nice.

I maintain that if AF447 were flying an aircraft with an operable autopilot during a loss of IAS, the airplane would still be flying today and all the folks would be alive. Another nice option.

The question of why such a sophisticated airplane could trip the autopilot with a loss of IAS and abandon the automation dependent crew has yet to be answered.

bubbers44

31st Oct 2013, 16:10

Or from the other side of looking at this how about we make the crews not automation dependent?

rudderrudderrat

31st Oct 2013, 16:13

Hi Gums,
I also wonder how AoA protection laws could have caused a climb as 'nuts suggests
I believe Alpha Floor was triggered (at a certain Alpha threshold). The thrust goes to TOGA power despite the TLs being somewhere else. With no side stick input, the aircraft will then maintain Alpha Prot angle of attack.

All that was required was a side stick input to maintain current FL and disengage Auto Thrust.

To protect against over speed, L1011 - 500 had RSB (recovery speed brake). Full speed brakes were automatically deployed and had to be manually stowed.
PFM.

Chris Scott

31st Oct 2013, 16:44

Quote from HN39:
Yes, there was an overspeed condition that caused a warning an disconnection of the A/P. However, that overspeed condition was very brief and not really a problem. Shortly after that the airplane encountered a vertical gust that increased the AoA to alpha-prot and put the FCS in high-AoA protection mode which caused the zoom climb.

Yes, and I've always been curious about the implementation (in pitch) of AoA Protection Law ("Alpha Prot"), which can only happen if the AP is off (caused here by the windshear-induced overspeed). Clearly it is advantageous to stop the AoA increasing unless the pilot commands such by "pulling" the sidestick (aft of neutral). The bit I don't understand is why the FBW is programmed to maintain Alpha Prot even if normal-G exceeds 1 (I'm referring to the situation at cruise speeds; not low speeds). To put it another way: on the face of it, it seems bizarre for the FBW to "grab" a transient, higher-than-normal AoA even if it results in more than 1G with a neutral sidestick (assuming wings level). No doubt there are good reasons for doing so - perhaps the likes of OwainGlyndwr may explain? ;)

In this case (http://www.aaib.gov.uk/cms_resources/Airbus%20A330,%20C-GCWD%20Airbus%20A340,%20TC-JDN%2006-2001.pdf), the AAIB and AI decided that a "phase advanced" value of AoA - caused by a vertical gust - triggered Alpha Prot Law (mode). "Phase advanced" means that the AoA was rising rapidly, and going into Alpha Prot Law was a pre-emptive move (as-per stall protection systems, including stick-shakers, on old a/c like the BAC 1-11 and VC10). Once the FBW system has engaged in Alpha Prot, the AoA presumably rises further to the stable value of Alpha Prot. If so, that would further exacerbate the situation in this particular scenario. Forward (down) sidestick is ncessary to restore Pitch-Normal Law. (Does anyone know how much?)

There is no message to inform the crew of the change of the Pitch Law (mode). In this case, attempts to re-engage the AP seem to have caused the delay in sidestick intervention by the PF.

BTW, in the AAIB's DFDR trace, the sidestick parameter seems to give negative values for "up" inputs, i.e., stick back.

The common factor this incident had with the much later AF447 accident is that of the unexpected transition from automatics to "manual": specifically from AP to FBW, in a pitch law other than Normal. In this AIRPROX case, the FBW system forced the a/c into an undesired zoom-climb which needed positive crew intervention to counter. In AF447, the FBW made no such input; the PF forcing the a/c into a zoom-climb by inappropriate sidestick inputs.

Chris Scott

31st Oct 2013, 17:14

Desert185,
Don't discount the fact that the autopilot is still available with a loss of IAS. There is a selected Pitch Damp mode that the pilot can select to maintain attitude if desired. Options are nice.

We had APs with pitch wheels a bit like that on the B707 and other types of the 1960s and 70s, used to select pitch in climb and descent, plus a "height" (ALT) lock. Not sure if the ALT lock tripped with loss of IAS - probably not. On Airbus FBW, tripping the AP is normally a non-event, because the FBW effectively holds the current attitude at least as well (initially).

bubbers44,

Are you saying the Tristar airbrakes do not retract themselves automatically after the aoverspeed? And does the lever move to reflect their extension?

DonH

31st Oct 2013, 17:23

BOAC;

Re, "Whether the 'automatics' brigade like it or not, some of the programmed features of the AB system contributed to both 447 and the 330/340 events. Note I say 'contributed to' and not 'caused'. "

In the sense that all complex systems are capable of inciting inappropriate interactions with users, yes, I agree with you BOAC. "What's it doing now?" isn't a state of mind limited to Airbus aircraft. And when one encounters such moments, one quietly and calmly disconnects everything (including thrust levers) and flies the raw airplane - and as has been observed, the Airbus, as does the Boeing, fly beautifully, manually from takeoff to cruise altitudes, descent & landing - one just has to know a bit about high altitude, high Mach number, swept-wing aerodynamics.

But given this, what do we do with the Tripoli A330 (and for that matter, the Gulfair A320) accidents? Both aircraft were perfectly serviceable. What kind of automation would be able to "decide" in time, that the pilot was suffering from somatogravic effects? If the assumption is that automation can be designed/created to serve any ends, then how do such solutions differ from the present "zoom climb" issue, (extremely rare though both "contributions" may make in a fatal accident)?

If I may be permitted to wander slightly, the "possibility-potential", (possibilistic thinking (http://leeclarke.com/docs/clarke%20thinking%20possibilistically%20-%20Significance.pdf), according to Lee Clarke (http://leeclarke.com/)), is what facilitates this thinking. To me anyway, the difficulty for the designers and the engineers becomes making an assessment between two polar opposites - What's probable?, vice What's possible? The question goes beyond "excusing or blaming" - it's just trying to find out what the causal pathway (to which you referred) was; in the case of AF447 I think we have it.

It seems to me as a retired pilot, that in terms of the designer/engineer's work (speaking specifically of Airbus), we can only say that the approach was(is) sufficiently cognizant to consider and expect that an airline pilot would be trained against, and would avoid-like-the-plague, stalling his/her aircraft and would understand those circumstances which would lead to stall entry.

On the question of "NCD" and the cessation of the stall warning, such circumstances may be imagined as "possible", but (at the time) reasonably concluded as "improbable". We now have the one single outlier (in tens of millions of flight hours), that, we might say disproves the thinking, (and inadvertently led to confusion in circumstances so far from normal as to be beyond test-pilot territory), so now, what do do but find a way to keep the stall warning on at all times if the airplane is indeed stalled. I believe (but do not know) that this is more complex and difficult than those who may liken such "obvious" solutions as the C-150 or other mechanical devices, etc) to present day computer/software systems but no doubt it will be done and certified; I believe the B777 system behaves the same way, (not sure about the B787) - perhaps someone here can confirm either way?).

The present call by some for "more automation" is, to me, folly, however the perhaps-two-dozen stall accidents, most fatal, over the past dozen years or so means there is a trend and not just an anomaly.

The discussion of why and in what condition the airplane (B or A) is "handed back" to the crew precisely at the moment when they could use "automation" is a very complex question having to do with "decidability" in computing systems and has, I truly believe, been exhausted in the ten AF447 threads, (for those new to the discussion, you can use the AF447 Search Index tool (http://countjustonce.com/pprune/) and look up "Byzantine fault"!),

When a complex system like a transport aircraft is taken into areas beyond its operational limits, the risk and possibility of confusion, particularly if one does not know one's aircraft well, compounds and heightens, quietly at first, and rapidly if one has been building/maintaining only a "surface" situational awareness.

The other aspect is the continued operation of the THS while the stall warning was active. As we know well,, the THS reached about 12°NU by about FL350 on the way down after almost continuous nose-up stick inputs. (it should be noted that with continued ND stick inputs, the THS would have returned to its normal position of about 2° NU).

What is to be done in terms of "automation" design under such rare and inappropriate circumstances, that won't cause other, unimagined and perhaps more serious circumstances when someone else wanders well off the beaten track? How are such scenarios imagined and "protected" against? As others have observed, if/when changes highlighted by AF447 are installed and certified, the "automatics brigade" and the hand-bombers could still ask your question with equal reasonableness.

So, not disagreeing with you...just pondering where your (and others') comments on the two primary observations on this accident, (stall warning quits; THS continues to trim), do take us in terms of solutions.

BOAC

31st Oct 2013, 19:21

DonH - to try to answer your questions:

The stall warning 'quit' due to airspeed and not AoA reading, I believe? Simple solution - keep it functioning whatever the speed without WoW. Unless the AoA readings are 'borked' due to failure/icing/whatever, at least there will be a 'nudge' to the crew (did they really need it!!??) to see if alpha might be a touch on the silly side.

THS - moons ago on one of the interminable threads, I flippantly suggested a spring loaded boxing glove in the dash, but then offered a more serious proposition that 'we' derive a suitable boundary for 'reasonable' nose up THS (surely not difficult?) and then insist on a physical over-ride to exceed it - such as a 'cancel the limit' button.

Desert185

31st Oct 2013, 19:30

Or from the other side of looking at this how about we make the crews not automation dependent?

A friend who flies a 7X (he calls it a 7 Edsel) hand flies it as much as possible. I do the same raw data, even in the sim. Preventing automation dependency can be a self-regulating endeavor. Obviously, some departures and arrivals require automation, but outside that there are opportunities if one has the stomach and professional integrity for it.

Its a start...

HazelNuts39

31st Oct 2013, 19:44

With no side stick input, the aircraft will then maintain Alpha Prot angle of attack.

All that was required was a side stick input ....That is correct, I'm not so sure about the rest. The report doesn't say that alpha-floor was activated. It should have activated somewhere between alpha-prot and alpha-max, but maybe that threshold wasn't reached?

Chris Scott

31st Oct 2013, 21:06

Quotes from rudderrudderrat:

"I believe Alpha Floor was triggered (at a certain Alpha threshold)."
Yes, the AAIB thinks it probable because the captain saw a PFD message starting with "Alpha...". They also said that Alpha Prot was (briefly?) exceeded, which - as HN39 says - would be necessary for Alpha Floor.

"With no side stick input, the aircraft will then maintain Alpha Prot angle of attack."
Quite. Re my question in a previous post, I've recently "gone to specsavers" and found the criteria for Alpha Prot disengagement on the A340 clearly stated :ouch: in the AAIB Bulletin:
Sidestick forward more than 1 second
OR
Sidestick more than half forward.

Turbine D

31st Oct 2013, 21:45

Hi BOAC,

The stall warning 'quit' due to airspeed and not AoA reading, I believe?
You are correct. Normally the stall warning is tied to AoA, but because the sensed valid airspeed dropped to below 60 knots, the aircraft believed it was no longer flying and the stall warning ceased. At least that is my interpretation of this.

OK465

31st Oct 2013, 22:01

In the 330/340, alpha floor is inhibited above 0.53 IMN, which at 37000 feet is 166 KCAL. Doubt they got that slow.

According to the report, the message was 'alpha lock', which in the 330/340 is slat/flap related.

Desert185,

NG autopilot also disconnects with an ADR module discrepancy(s). And it has no fallback to fixed gains and flight path stability, just piloting.

If you recall the early 727, both the block 50 (and later 150) A/P would not disconnect in a situation where it really would have been desirable for it to do so. With a complete hydraulic failure the A/P remained engaged (electrically) when it in fact could exercise no control over the flight control surfaces.

A little red light with both A & B system bulbs was added right below the 'stab out of trim' amber light to warn that the A/P was engaged and either the selected A, B, or AB function was not available.

You takes your chances.

HazelNuts39

31st Oct 2013, 22:09

Turbine D,

Slightly more accurate would be to say that the ADIRU which processes the data it receives from the AoA sensor (and other air data sensors) considered the AoA value invalid and sent the code NCD to the other airplane systems.

To my knowledge, the ADIRU doesn't know and doesn't care whether the airplane is flying or not.

Turbine D

31st Oct 2013, 22:24

DonH,

Thanks for your reply on the memory list. In the early days of the AF447 Technical threads and the R&N threads, we went through this a few times. Although the information was made available in Airbus presentations several years prior to the AF447 incident, some of us questioned whether or not this was really made available to all airline line pilots through initial training or reoccurring training. If you look at the thirty some incidents of UAS involving Airbus aircraft, responses to UAS at cruise speed and altitude varied considerably, but no end results duplicated AF447, somehow they figured it all out successfully. I think you would agree, far more time in training and subsequent examination has been spent on critical low level UAS memory list possibilities, than on high altitude high speed UAS possibilities. Hopefully that has changed, AF447 being a lesson learned.

bubbers44

31st Oct 2013, 23:14

some of us used to make it a private requirement using spare time during an endorsement to ensure that pilots could handle several of the unlikely but very high risk scenarios

Yes, we could ask to, after check ride was over to do something not required with time left over to see how it worked out in the sim. I was flying into Caribbean islands with a lot of birds in a B727 at the time so asked to have two engines fail at 500 ft at V2+15 and the check airman said it wouldn't fly. I asked to try it anyway so he did and guess what, if flew. We had to descend about 200 ft to get to clean climb speed and climbed on one engine. We are usually over water so ground effect wasn't even needed to not have to ditch.

Using the sim is a great way to try not normally trained methods of surviving.

Machinbird

1st Nov 2013, 01:20

The stall warning 'quit' due to airspeed and not AoA reading, I believe? Simple solution - keep it functioning whatever the speed without WoW. Unless the AoA readings are 'borked' due to failure/icing/whatever, at least there will be a 'nudge' to the crew (did they really need it!!??) to see if alpha might be a touch on the silly side.
Since stall AOA varies with Mach No., and the ADRs requires >60 knots dynamic pressure to have a valid (i.e. 'acceptable' airspeed value), the aircraft had no way to calculate the stall AOA using the available data when the AOA got so high that the pitot tubes could not work. It could calculate the AOA, just not what the stall AOA was and thus, it could not provide a warning.

The programming was inadequate for this condition of being airborne with very high AOA.

There are a number of things that could have been done to determine how much stall AOA correction for Mach was necessary, but since it wasn't written into the code, it didn't happen.

If, for example, the aircraft could compare g to measured AOA, it should then have been possible to estimate IAS with sufficient accuracy to set flight control gains as well as estimating Mach number based on OAT and altitude.

In any case, when NCD was encountered while airborne, the stall warning AOA should have at least been set to the backup value of 8.6 degrees and not just turned off simply because the airspeed didn't make sense. See Hazlenut's post for additional data. http://www.pprune.org/7210355-post943.html

I'll imagine that we will hear from Dozy on this.:}

gums

1st Nov 2013, 01:50

C'mon, 'bird.

As you and I and Retired have said, the AoA vanes/cones should be taken as gospel unless they are all in disagreement or some other criteria is applied, and CAS isn't one of them.

The simple fact is that the 'bus control law reversion logic is complicated and has a plethora of modes and sub-modes and......... Sheesh.

AoA should be the primary "protection" according to the jet's aero capabilities. I have no problem with the 'bus "gee" implementation due to its mission. The fact is that planes fly using lift by wings that can produce whatever at whatever AoA. So the 'bus might use a law resembling ours that limited commanded gee versus AoA. Take our law and divide by 8 gees and you have it.

Make no mistake, I do not like a "direct" control law for the heavies due to many technical and aero reasons. If you have a FBW system, then you use whatever still works to fly the plane as the old ones used to fly. You don't have force feedback, but you can sense rates and gees. The planes since the mid-50's had hydraulics and a few direct mechanical connects to the control surfaces. They have not been like an Aeronica or Chipmunk since then, so enough of this macho direct control stuff. My ilk flew most of the time in pure "manual" with hydraulic valves at the base of the stick. No mechanical connections of any kind to flaps or spoilers or anything. We done just fine. And then came along fly-by-wire, and I was one of the initial cadre.

Glad to have a "final" few posts to get some things off our chests.

Machinbird

1st Nov 2013, 02:23

Hi Gums,
Just 'cause there isn't an AOA gauge for the pilots doesn't mean that the aircraft doesn't know what value it is. All we need to do is instruct the aircraft properly what to do with the AOA data when it's usual stuff like airspeed starts to drop off the line.

The problem seems to be that the engineers have been thinking in terms of airspeed and not in terms of it's alter ego, AOA.

You know how to fly an aircraft using just AOA and so do I, but for some reason they didn't tell F-GZCP how to do it.:{

tdracer

1st Nov 2013, 03:46

Apologies if this has been covered previously - I really have little to add to the discussion that isn't rather biased - but I'm curious.

How does Airbus enunciate stall warning? I'm thinking a 'stick shaker' type alert isn't consistent with the side stick controller, so is some sort of verbal "STALL"? :uhoh:
I know there have been accidents in the past where the flight crew - when confronted with a stick shaker combined with UAS - apparently concluded it was Mach buffet and continued to do the wrong thing. I'm trying to understand how this flight crew could have dismissed a stall warning (even if it subsequently went away). Hence am curious on how that warning gets enunciated.

HazelNuts39

1st Nov 2013, 07:35

tdracer,

the stall warning is a synthetic voice shouting "STALL","STALL","STALL" followed by an irritating "cricket" noise. It 'goes away' whenever the AoA is greater than 42.5 degrees.

IMHO one has to be unrealistically optimistic to believe that this crew would have been able to recover from an AoA greater than 42.5 degrees, even if the controllability of the airplane would theoretically have allowed it.

But then I hasten to add that I'm not a pilot.

bubbers44

1st Nov 2013, 09:49

I guess if you are at 38,000 feet and keep hearing stall, stall, stall and you keep pulling back on the stick on any airplane and fall into the ocean with the controls full back all aircraft will do what AF447 did and all will die.

mm43

1st Nov 2013, 09:52

HazelNuts39,.... one has to be unrealistically optimistic to believe that this crew would have been able to recover from an AoA greater than 42.5 degrees Having diligently piloted the aircraft to this unrealistic attitude, I doubt even that particular crew (if they could) would argue that point.:\;)

Owain Glyndwr

1st Nov 2013, 10:04

@machinbird

The programming was inadequate for this condition of being airborne with very high AOA.Yes that must be true. It is a case where the "requisite imagination" failed to envisage such a case as a necessary condition. But if some engineer had dared to suggest before publication of the AF447 DFDR traces that the aircraft might be driven into a 42 deg plus AoA situation and held there by pilot action they would have been howled down with scornful cries of "You are not a pilot" and "No pilot would do such a thing". I find it difficult to accept that the designers and their test pilot colleagues acting ten years earlier would have any reason to conclude differently.

There are a number of things that could have been done to determine how much stall AOA correction for Mach was necessary, but since it wasn't written into the code, it didn't happen.
As you say, it wasn't written into the code so it didn't happen, but it is not obvious that it needs to happen. If you are at 45 deg AoA or more it hardly matters whether the threshold for warning is 8.6 deg or 17.2 deg. The warning should be sounding.

I think you are missing a point however. If the warning were to be latched until safe conditions were restored (as suggested by BOAC and myself) the airspeed indications would necessarily be restored to normal and the proper stall warning threshold for the Mach number computed before the warning would be cancelled. You will remember that when the AoA was reduced temporarily the airspeed came back on line and the stall warning with it. That is why I think your next suggestion -
If, for example, the aircraft could compare g to measured AOA, it should then have been possible to estimate IAS with sufficient accuracy to set flight control gains as well as estimating Mach number based on OAT and altitude.
is an unnecessary complication.

In any case, when NCD was encountered while airborne, the stall warning AOA should have at least been set to the backup value of 8.6 degrees and not just turned off simply because the airspeed didn't make sense.Yes I agree with you there.

Owain Glyndwr

1st Nov 2013, 10:31

To put it another way: on the face of it, it seems bizarre for the FBW to "grab" a transient, higher-than-normal AoA even if it results in more than 1G with a neutral sidestick (assuming wings level). No doubt there are good reasons for doing so - perhaps the likes of OwainGlyndwr may explain?

Sorry Chris, but the likes of Owain Glyndwr have no explanation other than the obvious; that the logic designed to protect against stall at low Mach numbers had unexpected side effects when applied at high Mach numbers.

The low speed logic is not stupid. If the system has reason to expect that stall AoA might be reached in a short time if current trends continue then it puts the aircraft into a temporary protection mode. If the pilot genuinely wants more AoA then it is available by moving the sidestick back. Otherwise the protection can be removed and the aircraft returned to "normal" behaviour by moving the stick forward. [Looking carefully at a digitised version of the traces it looks as if the "short time" is about 1.5 seconds]

In this particular case the autopilot dropped out because of a strong temperature shear (not the windshear you suggest). I personally suspect that designers do not currently give enough attention to temperature shifts, perhaps because they are not specified in FARs or CS25. On Concorde, which was designed against its own special (and generally more severe) rule book, we had to consider temperature changes of up to 21 deg C in one mile. This A340 incident was only 10 deg C in that distance.

Just after the A/P dropped out the aircraft met some reasonably strong turbulence. Again not extreme; working from the normal acceleration record one might deduce gusts of up to 15 fps (EAS) which is just under half the design gust for those altitudes. However, some of those gusts were sharp edged, so the rate of change of AoA was high. The actual AoA remained well below the deterrent buffet stall level - round about 2 deg below the Vs1g level, but the predicted AoA for 1.5 secs later went over the stall limit and triggered the alphaprotect mode.

Accepting that the subsequent motion was unexpected, it was not IMHO intrinsically unsafe. This was not an embryo AF447. The EFCS was, after all, acting to prevent a stall. There were no injuries and no aircraft damage. Dare I say that were it not for the proximity of the A330 and consequent possibility of a midair collision this incident would not have received the attention it has had. That seems to me an ATC problem and I note that the AIB made two ATC recommendations but nothing on the airplane.

Owain Glyndwr

1st Nov 2013, 10:47

DonH

If I may be permitted to wander slightly, the "possibility-potential", (possibilistic thinking (http://leeclarke.com/docs/clarke%20thinking%20possibilistically%20-%20Significance.pdf), according to Lee Clarke (http://leeclarke.com/)), is what facilitates this thinking. To me anyway, the difficulty for the designers and the engineers becomes making an assessment between two polar opposites - What's probable?, vice What's possible? The question goes beyond "excusing or blaming" - it's just trying to find out what the causal pathway (to which you referred) was; in the case of AF447 I think we have it.

It seems to me as a retired pilot, that in terms of the designer/engineer's work (speaking specifically of Airbus), we can only say that the approach was(is) sufficiently cognizant to consider and expect that an airline pilot would be trained against, and would avoid-like-the-plague, stalling his/her aircraft and would understand those circumstances which would lead to stall entry.

As a retired designer, I have to agree with your assessment here. In order to design an aircraft one has to make certain assumptions. One of those is that the pilots will fly like - errr well like pilots actually ;)

One assumes that flying to respect the techniques and limits prescribed for the airplane will be the norm, but one must also recognise that techniques will not be followed exactly and limits not strictly respected. The problem is to know, or guess, the magnitude of these deviations that must be safely available.

Would you, for example, have predicted the AF447 actions? Or would you have imagined, when designing the autobrake logic that an aircraft might be landed on a flooded runway, with worn tyres, 29 kts above Vref in a 15 kt tailwind and put down with a long flare?

It is always easier to make these flights of imagination with hindsight :ouch:

Chris Scott

1st Nov 2013, 12:57

Quote from Owen Glyndwr (my underscoring):
In this particular case the autopilot dropped out because of a strong temperature shear (not the windshear you suggest).

Whoops! :{ Thanks for the reminder that the sudden increase in Mach to beyond Mmo was due to the sudden fall in temperature, not a headwind shear.

Quote:
...the logic designed to protect against stall at low Mach numbers had unexpected side effects when applied at high Mach numbers.

It's the logic at low Mach numbers that I'm questioning. As I wrote:
on the face of it, it seems bizarre for the FBW to "grab" a transient, higher-than-normal AoA even if it results in more than 1G with a neutral sidestick (assuming wings level).

Here's the best scenario I can think of at the moment. I'm hand-flying at low altitude in the holding stack and there's a severe, momentary up-gust, causing a momentary (rapid) rise in AoA towards alpha-prot.

Phase-advanced alpha-protection puts the FBW into AoA Protection Law. Meanwhile, the AoA has returned (fallen) to what it was before the gust. However, FBW uses up-elevator to increase the AoA to alpha-prot. The a/c climbs suddenly until I push the stick forward more than half-travel, OR use less-than-half forward stick for more than a second.

Although I'm unlikely to allow the a/c to climb much (unless I'm having a bad day at the office, or get distracted), maintaining AoA Law seems an unnecessary presumption by the FBW.

So my question remains: why does it not revert to Normal Law once the AoA falls to a safe value?

Owain Glyndwr

1st Nov 2013, 14:39

Here's the best scenario I can think of at the moment. I'm hand-flying at low altitude in the holding stack and there's a severe, momentary up-gust, causing a momentary (rapid) rise in AoA towards alpha-prot.

Phase-advanced alpha-protection puts the FBW into AoA Protection Law. Meanwhile, the AoA has returned (fallen) to what it was before the gust. However, FBW uses up-elevator to increase the AoA to alpha-prot. The a/c climbs suddenly until I push the stick forward more than half-travel, OR use less-than-half forward stick for more than a second.

Although I'm unlikely to allow the a/c to climb much (unless I'm having a bad day at the office, or get distracted), maintaining AoA Law seems an unnecessary presumption by the FBW.

So my question remains: why does it not revert to Normal Law once the AoA falls to a safe value?

Hang on a minute! Suppose it is an A320 at say 60 tonnes - holding at 200 kts?
That will be about 5.5 deg AoA with stall at 12 deg. The alphaprotect logic is a combination of alpha and rate of change of alpha, but take just alpha for the moment. You are going to need a gust of 38 fps to get to the stall and from published A320 flight statistics you will need to fly half a million flight hours at 200 kts before you hit that sort of gust. OK one needs to back off a bit to account for the phase advance contribution, but it will still be a helluva lot of hours :=

So in theory you may be right about the possibility but it would be an extremely rare case I think.

As for why it doesn't revert to normal law, surely it cannot, because once alphaprotect has taken charge the AOA is held at the alphaprotect value?

OK465

1st Nov 2013, 14:49

Another question for OG,

I'm still struggling with the contents of the AAIB bulletin concerning the 330 & 340 near miss....

....specifically the 340 Captain's statement that he observed an 'alpha lock' message and then the board's conclusion that it was probably an 'alpha floor' annunciation when under the circumstances, the lowest IAS & IMN stated as 205 & 0.67, it seems highly likely that neither of these messages would or even could be displayed.

Why would the board glom onto 'alpha floor' as a probable when it's inhibited above 0.53 IMN?

What am I missing here? Has someone else covered this earlier?

Owain Glyndwr

1st Nov 2013, 15:12

@OK465
Why would the board glom onto 'alpha floor' as a probable when it's inhibited above 0.53 IMN?

What am I missing here? Has someone else covered this earlier? The straight answer is that I don't know :O Partly because I'm not sure what "alpha lock" entails and partly because the recorded behaviour of the engines is consistent with an 'alphafloor' occurrence regardless of what the book says said about its 0.53M threshold.
The AIB report text is:
Alpha floor is an autothrottle function which applies full thrust, irrespective of the position of the thrust levers, if the airspeed is likely to reduce to a value approaching alpha maxIts all a bit confusing, as the thrust increase came at about the same time, or even a little after, the A/T was disconnected, but the report makes no mention of any throttle increase by the PF, only the thrust reduction. Also the phraseology "if airspeed is likely to reduce to a value approaching alpha max" leaves one wondering! It does imply though that alpha floor switching is also a function of rate of change (of speed?)

Ducking the issue somewhat, I imagine that the AIB will have taken advice from Airbus on what might have been and I would think (well hope anyway) that AI would understand their own system :ok:

Edit: OK I now understand what alpha lock is, (prohibiting slat retraction in certain circumstances) but so far as I can see it would in no way be relevant to the cruise condition where this incident occurred.

OK465

1st Nov 2013, 15:58

Thanks OG,

Just an observation....

....if done as a demo or ops check in a level D FFS, using idle thrust just to expedite a level entry from say a weight dependent ~200 KCAS at FL350 into AOA protection, hands-off it will drift on down at alpha prot no thrust increase, if the SS is cycled full aft aggressively to achieve a short term transient alpha max there is still no thrust increase....

Like clockwork at around Fl280 (0.53 IMN) thrust comes up and alpha floor is then annunciated.

But it is only a sim, and real air can do some strange things. :)

I agree it is unlikely it was an SFCC alpha lock indication, I believe that is annunciated by the slat/flap indicator display anyway (don't recall for sure).

It's just the word probably that is intriguing and the fact that the Captain would have had to take positive action to exit alpha floor and one would think observe the alpha floor annunciation extinguish. Of course he was 60 years old and I noticed myself that at that point my powers of observation were waning somewhat also. :}

Chris Scott

1st Nov 2013, 16:06

Quotes from Owain Glyndwr:

"Hang on a minute! Suppose it is an A320 at say 60 tonnes - holding at 200 kts? That will be about 5.5 deg AoA with stall at 12 deg."

Yes, Owain, that's very much the speed I would expect for holding an A320 (clean) at 60T - "Green Dot" speed would be 205, which is well above VLS, and the FMGC sometimes suggests a slightly lower figure than Green Dot for holding. A level-flight pitch of about +5 or so is typical, suggesting an AoA of that value. You quote an AoA of "stall at 12 deg". Bearing in mind that AoA Protection Law is based on alpha-prot, is that figure alpha-prot, or alpha-max? (I presume the former.)

"The alphaprotect logic is a combination of alpha and rate of change of alpha, but take just alpha for the moment. You are going to need a gust of 38 fps to get to the stall..."

Agree that a sudden up-gust of 38 fps (2280 fpm) must be extremely rare, but you admit that 38 fps doesn't take phase-advance into account.

"As for why it doesn't revert to normal law, surely it cannot, because once alphaprotect has taken charge the AOA is held at the alphaprotect value?"

...Precisely the logic I'm calling into question! :ok:

Owain Glyndwr

1st Nov 2013, 16:50

Bearing in mind that AoA Protection Law is based on alpha-prot, is that figure alpha-prot, or alpha-max? (I presume the former.)

No, that is stall for a completely clean airframe (slats and flaps retracted) at low Mach No.

HazelNuts39

1st Nov 2013, 17:20

So my question remains: why does it not revert to Normal Law once the AoA falls to a safe value?That is a very intriguing question. I would love to know the answer to that.

A33Zab

1st Nov 2013, 17:48

So my question remains: why does it not revert to Normal Law once the AoA
falls to a safe value?

Probably to prevent osicillations between NORMAL and AoA Law, so it needs a positive ND SS input to revert to NORMAL Law.

Owain Glyndwr

1st Nov 2013, 18:08

A33Zab
Probably to prevent osicillations between NORMAL and AoA Law, so it needs a positive ND SS input to revert to NORMAL Law.

Now that sounds a very sensible answer :ok:

DozyWannabe

1st Nov 2013, 18:39

And lest we forget, when talking about the airprox incident (as opposed to AF447) - I think it would be wise to remember - before getting tied up in suggesting problems with the systems - that all the crew had to do, both to arrest the climb and exit the AoA/Alpha Prot mode, was to *push forward on the stick*. Hardly rocket science and, by my estimation, fairly intuitive piloting** - no?

Of course, the same held true in many ways for AF447. I continue to believe that the Stall Warning issue is to some extent a red herring in the grand scheme of things, because the thing was working fine for more than enough time to have been picked up by the crew before the aircraft and its sensors went too far into the unknown.

Also, I'm still seeing references to "automation-dependent crew", which as I said before doesn't square with the sailplane qualifications of the AF447 PF - there is no automation (or for that matter TOGA power) on a glider!

** - In the sense that whether you're flying anything from a Cessna to Concorde, if the aircraft isn't pointing where you want it to go - point it where you want it to go!

Owain Glyndwr

1st Nov 2013, 18:49

@Dozy
that all the crew had to do, both to arrest the climb and exit the AoA/Alpha Prot mode, was to *push forward on the stick*. Hardly rocket science and, by my estimation, fairly intuitive piloting - no? Which is what they did of course!

@Chris Scott
BTW, in the AAIB's DFDR trace, the sidestick parameter seems to give negative values for "up" inputs, i.e., stick back.

Reason for that is that with the pretty well universal right handed system of axes used to describe airplane motions a clockwise (nose up, tail down) rotation is positive. That means that 'down' elevator is positive. Although the RHS axes don't have to be applied inside the aircraft it makes sense to have a positive (forward) movement of the stick correspond to a positive (downwards) elevator movement.

DozyWannabe

1st Nov 2013, 18:51

Which is what they did of course!

Agreed, although it is definitely concerning that it didn't occur to them until they'd already busted their flight level.

Chris Scott

1st Nov 2013, 19:10

Quote from Owain Glyndwr:
"...the recorded behaviour of the engines is consistent with an 'alphafloor' occurrence regardless of what the book says said about its 0.53M threshold... ...the thrust increase came at about the same time, or even a little after, the A/T was disconnected, but the report makes no mention of any throttle increase by the PF..."

I can't shed any light on the alleged (by OK465) maximum of M0.53 for Alpha-Floor initiation. Just in case there's any misunderstanding, however, my recollection is that Alpha-Floor itself engages A/THR if the latter is currently OFF, regardless of thrust-lever position.

DozyWannabe

1st Nov 2013, 19:22

@Chris Scott:

If I recall correctly the Alpha Floor functions with A/THR OFF, but it will not function if A/THR is *disabled*, if not in Normal Law, or below 100ft RA. I'm not sure about the Mach limit** - OK465, would you have a reference handy?

One thing that struck me when I read the airprox report was that the A340 Captain said he noted "ALPHA LOCK" on his PFD, which the AAIB took as a misreading of "A. FLOOR". The thought occurred to me that it might possibly have been a misread of ALPHA PROT (from the transient AoA anomaly) and THR. LOCK (from the AP disconnect). Just a thought...

** - I should note however, that in my experience OK465 is usually correct! :ok:

Owain Glyndwr

1st Nov 2013, 19:25

Well that would clear up one mystery!

gums

2nd Nov 2013, 01:07

Salute!

Fer chrissakes, we are back to the basic design and such of the magenta line jets and the associated autopilot modes and their connection with the FBW systems or even the old systems.

I simply cannot understand the rationale of all the sub-modes of the FLCS ( flight control system) and the autopilot (AP) connections and on and on. Good grief!!!

I do understand that the heavies appreciate some of the AP modes and such to reduce workload and so forth. Funny for me, as I was the only guy in the jet and didn't have a PNF or anyone but Otto to help.

I must insist upon iterating my view of the Viper's FBW contol laws and some of the logic behind the design. This is compared to the 'bus design and more importantly, the implementation. I feel that most of the old school farts here would have liked what I flew with 35 yerars ago.

I cannot understand an implementation that switches modes and laws and such based upon "noise level" variations in temperature or mach changes or whatever. This is especially true for the heavies, that have basic inertial flight paths like most objects zooming thru the air, and lots more inertia than I ever had. And then there's the connect with nav systems and AP functions and on and on and on.

It all came down to AoA for we Viper pilots. Our FLCS trusted the AoA vanes all the way unless deemed FUBAR for a few seconds. I once went vertical and was looking over my shoulder when the "slow speed horn" sounded. "Gums, you are below 120 knots and gear is up!" OK, let go of the sidestick and let HAL do what it can do. So came back down in a tailslide and all the FLCS warning lights came on, Master Caution light came on, and so forth. Jet pitched down and I didn't touch a thing and forced myself not to pull back or forward. A few seconds later I was flying again and reset all the stuff and the fight was still on.

I realize that the heavy pilots here don't have those situations, but they sure as hell have some situations that require basic airmanship and a complete understanding of all the capabilities of their plane and maybe even all the modes and sub-modes of all the the FLCS and the AP modes and so forth. I empathize with them.

'nuf philosophy from this old FBW pioneer.

DozyWannabe

2nd Nov 2013, 02:26

@gums:

You must know by now that I have the deepest respect for you. That said, you're not really saying anything you haven't said before. We covered the rationale behind the law changes repeatedly long ago - if you don't like it, that's all good, but it doesn't make the implementation bad.

Our FLCS trusted the AoA vanes all the way unless deemed FUBAR for a few seconds.

Well yes, because it was a fighter and the expected operating parameter ranges of those AoA vanes was significantly different. The current flight control law has absolutely no effect on the validity of data from the AoA vanes on the A330, so I'm at somewhat of a loss to understand the point you're making.

Machinbird

2nd Nov 2013, 02:44

I think you are missing a point however. If the warning were to be latched until safe conditions were restored (as suggested by BOAC and myself) the airspeed indications would necessarily be restored to normal and the proper stall warning threshold for the Mach number computed before the warning would be cancelled. You will remember that when the AoA was reduced temporarily the airspeed came back on line and the stall warning with it. That is why I think your next suggestion -

Quote: Machinbird
If, for example, the aircraft could compare g to measured AOA, it should then have been possible to estimate IAS with sufficient accuracy to set flight control gains as well as estimating Mach number based on OAT and altitude.

Is an unnecessary complication
But OWAIN, if you can still set the gains for the flight control system, do you need to drop out of Normal Law in the first place?
I don't believe that the accuracy would be sufficient to manage an auto throttle system, but it should be possible to calculate gain settings that would permit Normal Law or perhaps a variant of Alternate 1 Law. Any improvement in stall warning calculation is just icing on the cake.

bubbers44

2nd Nov 2013, 03:26

For us non Airbus pilots that don't really care if the autopilot or autothrottle even works because we don't rely on them at all why is automation so important to Airbus pilots and how can it be blamed for any crash? We like to let it relieve our work load but if it quits we just hand fly. If the IAS goes away on all three air speed indicators we fly attitude and power using a QRH. We don't have to know any laws. We are either in automatic or manual. One is a little more work but no big deal. I don't get it.

vilas

2nd Nov 2013, 04:32

bubbers44
That is the advantage of flying archaic aircraft. its like somebody staying in remote regions of the world saying why do you need internate we don't have it and we don'tcare. Why do you need calculators mug up multiplication tables. You will care about automation if you were flying long range if you were in RVSM. If there was any virtue in 737 design Boeing wouldn't have changed to fly by wire.

bubbers44

2nd Nov 2013, 04:53

I guess us flying these Boeings around the sky knowing we don't need the automation isn't important to you but it is to us. We don't go into a full stall at FL350 like two Airbus pilots did out of RIO on AF447 just because the pitot tubes froze over but you are right we don't rely on automation much and you do.

Good luck with your automatic airplanes. Hope automation doesn't fail like AF447. It could get nasty.

vilas

2nd Nov 2013, 06:45

BUBBERES44
There are pilots, pilots and pilots. In a 737 pilot came high and fast in VMC with speed brakes did a 360 stalled and killed everyone. In A320 with Alpha floor TOGA is set and speed brakes go in. That is protection. What's your problem? Air India express crash new 737-800 ATC cleared descent late due approach radar NA. 7000 ft vertical offset.. Expat Pilot didn't do anything to descent faster. Almost same offset through the approach, at 1DME dived 4000ft/mt.despite the pleas of the FO to go round, touchdown deep, reversed and went round sorry went down the hill 150 dead. What automation got to do with this? So stop your cry in wilderness the aviation has changed Boeing included. 737s will take their place in history along with Tigermoth, DC3,707 and 747 classic ( I was a captain on).

Owain Glyndwr

2nd Nov 2013, 07:18

Machinbird

But OWAIN, if you can still set the gains for the flight control system, do you need to drop out of Normal Law in the first place?
I don't believe that the accuracy would be sufficient to manage an auto throttle system, but it should be possible to calculate gain settings that would permit Normal Law or perhaps a variant of Alternate 1 Law. Any improvement in stall warning calculation is just icing on the cake.

We seem to have been slightly at cross purposes. My remarks were aimed specifically at the minimal changes necessary to fix the stall warning anomaly whereas I now recognise that you had a more general application in mind.

For sure if you have no IAS information you cannot work an autothrottle system, but I don't think the problem is one of setting gains for the flight control system. The current system reverts to a constant gain setting I believe, which is perfectly adequate to fly the aircraft. The only change (in pitch at least) is that the response time may vary with altitude as it does on conventional aircraft rather than being constant in all flight phases. The problem, as I understand it, would be to find a way to maintain the envelope protection functions. Dozy has made the point several times, and I can but reinforce his comments that one really should differentiate between the "handling laws" and envelope protection functions. Lumping them together under the general label of "laws" tends to obscure important features

A33Zab

2nd Nov 2013, 10:17

Alpha floor protection:

This function enhances windshear survivability.

Alpha floor detection is available from lift off to a 100ft RA in approach.

When the alpha floor condition is activated, the FCPCs send a signal to the
FMGECs(Autothrust Function)which controls the TO/GA engine thrust, whatever the throttle control lever position.

The activation conditions are:

Alpha filtered (3s) greater than a threshold depending on aircraft configuration, the GS variation and the difference between GS and airspeed.
or

SS NU demand <-14° and theta >25°
or

SS NU demand <-14°and alpha protection.
Alpha floor is inhibited when Mach is above 0.53

The Alpha floor can also be inhibited by the FMGEC under certain engine failure conditions with flaps extended.

(When a TLA is below 5° the system may consider the engine failed and therefore alpha floor may be inhibited)

Alpha Floor is displayed A.FLOOR on the FMA (in green and amber boxed) and at LH upper area of EWD.

Alpha lock function:

If alpha exceeds 8.5° or the speed goes below 148 kt, the slat retraction from position 1 to 0 is inhibited.

This inhibition is removed whenalpha goes below 8.2° and when the speed exceeds154 kt, in this case the slats automatically retract to 0.

Alpha lock activation isdisplayed as pulsing A LOCK instead of the regular S indication of the S/F positionindicator on the EWD.

Thealpha lock function is not active after the S/F lever has been set to 0.

roulishollandais

2nd Nov 2013, 12:32

Thank you A33Zab for these two clear mementos.

Why is the final design of Airbus and Dreamliner full of failures, weakenesses and non-K.I.S.S. conception when not Babel's Tower chating in the manuals and enquiries? Engineers, please, do less, fire the bad built brains. Pilots have not hours and months to take decisions and chose or know about all these laws born in competition of office without taking the risk.

Passengers paying their ticket and sitting in the Cabin with smiling steward(esse)s are hostage of the Menkind's curiosity trusting in goodfaith from engineers and are allowed to think that presence of pilots in the cockpit are warantees for their own lifes. That is the first difference between fighters and airliners.

Gums, yes, said it already -as everything in our hamsterwheel- but really he is emphasizing the fact that they are too many and unknown - included in the official report - different flight laws and conditions to go from one to another and how. And, in that, fighters are not different from airliners. All the pilots, military and cvilian, are in their right to request the engineers do their best to keep them alive, included if it means pilots chose to reject the last wonderinvention. That has a name : Freedom.

DozyWannabe

2nd Nov 2013, 19:03

Why is the final design of Airbus and Dreamliner full of failures, weakenesses and non-K.I.S.S. conception

In systems design terms, the Airbus design is very much built on the KISS principle, it's just that airliners are by their very nature complex devices and thus even a simplified interface will appear complex.

Pilots have not hours and months to take decisions and chose or know about all these laws

While I think it's imperative that a pilot should be as knowledgeable about their aircraft as practical, there is no need to fathom the minutae of the flight control/handling "Laws" in order to fly the aircraft, even in a degraded state. Putting the envelope protections to one side, it may be helpful to think of those systems as performing the function of a flight engineer - and in a crisis situation all you need to remember is that all of the laws are designed to provide an aircraft which handles as close as possible to the way it would if everything was working correctly. As long as the aircraft is handled gingerly and with care, there should be very little standing in the way of her bringing you and your passengers to the ground safely.

EDIT: Additionally, I couldn't help but notice something recently. When an A320 scraped a wingtip on landing, the discussion from some parties was all about how interconnected yokes would have solved the problem, and yet when a similar incident happened on that SWA 737 (which has interconnected yokes) recently a lot of the same posters acted as judge, jury and executioner to the Captain. Double standards much?

exeng

2nd Nov 2013, 23:28

Do you remember Aeroperu 603 and Birgenair 301? Both B.757's with blocked pitots which both ended in tragedy in 1996. Both accidents were it seems due to the two aces up front not recognising the unusual pitch attitude and allowing the aircraft to stall.

So not so different to the AF Airbus situation on the face of it.

I've flown numerous Boeing types in all seats plus the A320. To be honest I happen to prefer the Boeing philosophy, and for me the 777 FBW was in some ways better than the Airbus FBW - although both have their advantages and disadvantages.

With all aircraft types knowing the appropriate pitch attitude and power setting for a given configuration is always important.

We all use automation for obvious reasons. But average to good pilots, whether Airbus or Boeing will be able to fly the aeroplane when the sh*t hit the fan.

Thing is Bubbers these days we do all need automation because I fail to see how well any of us would fare flying an 8 to 16 hour sector in RVSM (which would not be allowed anyway), or a multi sector day (in RVSM). I flew six sectors today in a little 737 and was very grateful for the A/P. I flew 2 sectors the other day with both A/P's inop (Stab trim unit) and it was quite hard work, particularly given the weather here in West Africa - the F/O and I never exceeded a 30 ft deviation but the normal task allocation and work sharing went to hell in a handcart. Give me an A/P any day on any aircraft.

I suspect there have many incidents similar to AF 447 that have occurred on both Airbus and Boeing where there was a happy outcome - thing is those incidents don't tend to hit the headlines.

roulishollandais

2nd Nov 2013, 23:54

@DozyWannabe
Perhaps Airbus tries to use K.I.S.S. principles, but the result is all but "simple". Since four years posters are unable to get a complete list of the flight laws, that list seems long like a day without bread, they are thousand (perhaps a little less I agree) exceptions, inhibitions, considerations, litterary-philosophical descriptions instead of equations. No reason to think that in a normal flight things are simpler they are only hidden until they pop-up when the captain takes his rest crossing Inter Topical Front and then all these hidden things, appear with an orchester of warnings and alarms, THS does is dance alone, zoom climbs appear, Wonderful! Everything but simple in the final "design" . Something works not as wanted!

Boeing is not better with his dreamliner. The idea to use these Li-Ion batteries seemed to be K.I.S.S. Now we see them reparing the burned fuselage in Heathrow...(not in! out! winter coming, inventing how to repare carbon fiber and inject resine, and losing much money, but at the end it will be said Crew are expensive and dangerous... etc. etc.

Today nor Airbus nor Boeing keep it simple in facts and result. It is theory, dream and narcicism.

And airlines don't do better : I cannot trust it , I read that more than 500 Air France people are supervising so said "human factors", how is that possible? Asiana tried an ultimate simplification : no more show outside at landing and don't push throttles.

You are right if you say it is sarcastic, but isn't it time to wake up and see that reality is diverging from the wants and wills?

Still an exemple : despite A33Zab does the best he can to do the things simpler, clearer, he had to write that sentence : "The Alpha floor can also be inhibited by the FMGEC under certain engine failure conditions with flaps extended". Why all these secrecy theater? I suppose these "certain conditions" are no so simple.

Double standard? At theater every actor plays a role.

tdracer

3rd Nov 2013, 01:00

Do you remember Aeroperu 603 and Birgenair 301? Both B.757's with blocked pitots which both ended in tragedy in 1996. Both accidents were it seems due to the two aces up front not recognising the unusual pitch attitude and allowing the aircraft to stall.

exeng

Perhaps nit-picking, but Aeroperu was not due to blocked pitots, it was due to blocked statics (due to maintenance failing to remove protective tape after washing the airplane). Lost of static pressure is far worse since it effectively wipes out airspeed and altitude. I felt sorry for Aeroperu flight crew since there would be no flight deck indication of a problem until after takeoff - unlike Birgenair where they continued with takeoff knowing full well there was a major problem with airspeed.

Also, if I recall correctly, Aeroperu did not stall, it hit the water in controlled flight because air traffic (not realizing the transponder was corrupted by the same static pressure problem as the flight deck instruments) told them they were flying much higher than they were.

However Birgenair was a prime example of the pilot flying totally ignoring what the other pilots in the flight deck were trying to tell him...:mad:

DozyWannabe

3rd Nov 2013, 01:24

Since four years posters are unable to get a complete list of the flight laws

The list has appeared several times over the course of these threads, try the search function.

that list seems long like a day without bread, they are thousand (perhaps a little less I agree) exceptions, inhibitions, considerations, litterary-philosophical descriptions instead of equations.

Oh, believe me there are equations - I've seen a lot of them! But they wouldn't make sense to anyone without a background in software engineering, just as most pilots without an engineering or mathematical background would not fully understand all the physics equations in HTBJ without Dai Davies' prose explaining it to them.

No reason to think that in a normal flight things are simpler they are only hidden until they pop-up when the captain takes his rest crossing Inter Topical Front and then all these hidden things, appear with an orchester of warnings and alarms, THS does is dance alone, zoom climbs appear, Wonderful! Everything but simple in the final "design" . Something works not as wanted!

Nothing's hidden. Throughout the sequence the aircraft did it's level best to tell the crew what was happening - from the initial "ADR DISAGREE" on the ECAM, through the Stall Warning sounding for over a minute - finally to the rapidly unwinding altimeter and everything inbetween. The zoom climb did not just "appear" - it was explicitly ordered through the PF's flight control commands, as was the THS. The THS didn't really become an issue until well into the stall regime, which - and let's not mince words here - it should be reasonable to expect that with the warnings they had that a crew should have been able to diagnose and either avoid or recover from. All they had to do was push forward on that stick.

Today nor Airbus nor Boeing keep it simple in facts and result. It is theory, dream and narcicism.

Depends on your definition of "simple", really.

Put it this way - throughout the history of civil aviation and its technical advances, pilots have not needed to understand the principles of things like cams, tensile strength of metals, hydraulic flow management and the like to fly the aircraft of those eras - because all of those technologies required specialist knowledge to some extent, and as such were not actually that simple. Some pilots did go the extra mile in understanding, some continue to do so and some in this era have extended that understanding to the modern electronics and computer technology behind their aircraft.

The point I'm trying to make is that it's no different. Whether we're talking about tensile load on a cable, hydraulic fluid flow to actuators or electronic signals it's all the same thing.

Did you see the part of my post where I likened modern aircraft management systems to an electronic flight engineer? I think it's a useful concept to understand. I'm sure some will argue that it would be better to just bring back the flight engineer, to which I'll say this; I had the pleasure of visiting the Hiller Aviation Museum in California a little while ago, and had a walk around their exhibit of a B747-100 flight deck. Now for its time, the B747 was a technically advanced aircraft - though by the standards of today the systems were relatively basic in themselves. I stuck my head into the flight deck and what jumped out at me was the sheer number of dials, switches, controls etc. at the FE station - to say nothing of the humungous bank of CBs overhead. I have to admit that to the layman's eye, the amount of things that needed monitoring, checking, activating and deactivating looked to be pretty close to the limit of what one human being could be reasonably expected to manage. This is absolutely no slight on FEs - if anything, seeing that in front of me elevated my level of respect even further - it just looked incredibly daunting, and far from "simple". Now bear in mind that "under the hood", the systems on more modern aircraft - not just Brand A, but even the venerable B757 and 767, are massively more technically involved in many ways (not because of the technology as such, but purely because of the greater number of parameters involved), and you can see why managing those systems with computers had to happen.

"The Alpha floor can also be inhibited by the FMGEC under certain engine failure conditions with flaps extended". Why all these secrecy theater? I suppose these "certain conditions" are no so simple.

Think about it for a second - why would you not want full thrust commanded with flaps extended and an engine out? Sudden asymmetric thrust during take off/climb-out or final approach/landing could really ruin your day!

@tdracer - Correct. Though I'd be inclined to be a bit less harsh on the Birgenair crew - the LHS ASI did "come alive" during the takeoff roll, and in that circumstance there was very little time to cross-check. By the book it was a major error, but nevertheless understandable. What was common to both, if I recall correctly, was that at various points both the overspeed warning and stall warning (stick-shaker) were active. Additionally, and I've said this in the past, the Birgenair Captain was an ex-Air Force pilot - no "child of the magenta" - and even he was flummoxed by the information he was being given.

bubbers44

3rd Nov 2013, 01:39

We all know some pilots need automation and others can fly attitude and power using QRH. If the altimiter works, use it, if the attitude indicator works, use it, if automation works use it. Use what ever still works and any competent pilot will make it work. I wouldn't want to be on an aircraft with a pilot that had to have automation to fly his airplane.

Many here disagree with that but I have considered loss of all power in my B757 including battery power and with no eletrical power know I could navigate and land safely if I had visual reference to a horizon. Whiskey compass and clock with standby altimiter would navigate and standby airspeed and alternate gear and flaps would handle landing.

I even played around with the whiskey compass in the 757 heading southbound over Cuba just using the compass to keep wings level for fun and it works just like a J3 cub. With the lead error you will not bank if you hold a south heading. You don't even need an attitude indicator in the clouds with all dead electronics. I learned that as a student pilot in an Aeronca Champ with 3 hrs. Those aircraft had no battery so no automation and it worked just fine. Funny how some newer pilots depend on it but we never had it and didn't need it.

DozyWannabe

3rd Nov 2013, 01:49

Bubs - with all due respect, and as vilas has said - what does automation have to do with what's being discussed at this point?

Airbus aircraft have not had a greater or more complex level of automation than their Boeing or MD counterparts for more than 30 years (almost 40 in fact). Airbus never pushed automation harder than any of their competitors either. The trajectory indicator line on the NAV display isn't even magenta on an Airbus!

Your 757 would still require some power supplied by the RAT to land as you describe, and RATs are fitted across the Airbus range too.

bubbers44

3rd Nov 2013, 02:47

The 757 didn't have a RAT, the 767 did. The 757 could be flown just fine with no electrical power including battery. If my 757 had a RAT I am sure somebody would have told me.

DozyWannabe

3rd Nov 2013, 03:03

Err... Looks like it has one to me...

File:757 ram air turbine.jpg - Wikimedia Commons (http://commons.wikimedia.org/wiki/File:757_ram_air_turbine.jpg)

It'd be lunacy not to have one on an all-hydraulic (i.e no manual reversion) design like the 757.

bubbers44

3rd Nov 2013, 03:17

My airline career started in 1979. We rarely used the autopilot for approaches, just for the boring enroute portion. Automation was optional. A major airline bought us and guess what, nothing changed, automation was optional except for certain category approaches. Now airlines are hiring pilots from pilot mills that can barely fly and teach them how to push the right buttons.

I know this is going to irritate a lot of people here but I wouldn't want to have this kid as my copilot before I retired. I want a solid qualified seasoned FO that knows how to fly. As a brand new 737 captain I got this kid that couldn't copy a clearance, couldn't fly, didn't know 24,000 ft meant FL 240 and our autopilot was broke. It was a charter to Minneapolis from LAS and I was single pilot both ways. A check Airman got him in as a favor to his neighbor and gave him all his training and check out.

Everybody else knew how to handfly and copy a clearance but he didn't. I don't have a lot of patience for pilots who don't bother to learn how to hand fly.

bubbers44

3rd Nov 2013, 03:46

Kind of strange we had no procedure to use it and it was on our airplane without our knowledge. Maybe it is an option Airlines can buy. Thousands of hours on a 757 and nobody told me? Maybe it is an option our airline didn't buy. The 767 had it.

Wally Mk2

3rd Nov 2013, 05:26

'bubbers' you mentioned in one of yr posts that if all 3 A/S's indicators go away in yr Boeing you use Att & Pwr from the QRH, well that's the same for a 'Bus' in fact any A/C, very basic airman-ship stuff there. This is the basic crux of why AF447 ultimately crashed.
I believe the real reason why these guys let a fully serviceable machine (other than the probes) take the lives of many was that they simply didn't believe what they were seeing in front of them & therefore any corrective decisions are ultimately overridden, their brains remember cannot act unless it's getting info either from stored memory (IE Knowledge/experience) or 'believable' info thru the eyes (the most powerful sense we have), the latter actually fooled them into believing the A/C could climb aggressively at that weight & at that Alt due a perceived over-speed initially hence the full back stick for the majority of the event.
They crashed simply 'cause they had no idea what to do, confusion reigned Capt included 'till too late.
Also 'bubbers' I gather that there is no external evidence of a RAT on the 757 like there is on an A320 for Eg as these closed doors form part of a pre-flight inspection.

vilas

3rd Nov 2013, 06:13

bubbers44
Thousands of hours on a 757 and nobody told me?
No offence meant but if that is the case on aircraft you flew even if your airline didn't opt for it what chance is there that you would know or care to know anything about the Airbus. You don't fly Airbus, you don't know anything about Airbus, you don't care to know about Airbus but you want to comment about Airbus incidents. How correct is that?

DozyWannabe

3rd Nov 2013, 17:32

...even if your airline didn't opt for it...

I very much doubt the RAT would have been an optional fit on the B757. As I said before, as an all-hydraulic design with no mechanical reversion the RAT would have been required to keep the hydraulics functioning in the case of dual engine and APU failure (e.g. fuel starvation). Even if bubs was able to navigate minus batteries with his whisky compass and outside horizon reference, it wouldn't do him any good if the flight surfaces stopped working (which without the RAT supplying hydraulic power, is exactly what would happen)!

...you don't care to know about Airbus but you want to comment about Airbus incidents. How correct is that?

There's an old saying that I adhere to along the lines of "I may disagree with what you are saying, but I'll vigorously defend your right to say it". I don't think any of us have the right to suggest members shouldn't contribute, even if we feel they're misinformed or misguided.

tdracer

3rd Nov 2013, 20:16

I don't recall off hand if the 757 has a RAT or not. But the fact that it's a all-hydraulic airplane doesn't mean a RAT is necessary. The 747 is all hydraulic, and prior to the -8 it never had a RAT - it wasn't needed. In the case of an all engine out event (and there have been a handful of 747 all-engine out events) there is sufficient hydraulic pressure provided by the windmilling engines to provide control of the aircraft.
Since the 747 all engine out events that I can recall had happy endings (volcanic ash encounters) the Boeing engineers apparently got it right. :ok:
The 747-8/8F did get a RAT - the combination of greater hydraulic requirements (due to the new wing) and engines that windmilled slower (big fan/small core) meant a RAT was needed.

DonH

3rd Nov 2013, 20:20

For Bubbers' information, there are AD (http://www.faa.gov/regulations_policies/airworthiness_directives/search/?q=Boeing+757&makeModel=&type=Current&sort=effectiveDate&direction=desc&filter=Ram+Air+Turbine)'s referencing the B757-200 RAT from early 1988. Even as the original type certificate was issued in 1982, the B757 appears to have always had a RAT. The site for FAA TCDS (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/MainFrame?OpenFrameSet)'s are available but do not prescribe system specifics.

[Federal Register Volume 60, Number 83 (Monday, May 1, 1995)] [Proposed Rules] [Pages 21054-21056]
From the Federal Register Online via the Government Printing Office [www.gpo.gov (http://www.gpo.gov)] [FR Doc No: 95-10585]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION 14 CFR Part 39 [Docket No. 95-NM-26-AD (http://www.gpo.gov/fdsys/pkg/FR-1995-05-01/html/95-10585.htm)] Airworthiness Directives; Boeing Model 757 and 767 Series Airplanes Equipped With Sundstrand Ram Air Turbine (RAT)/Hydraulic Pumps
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 757 and 767 series airplanes. This proposal would require replacement of the hydraulic pressure transfer tube of the ram air turbine (RAT) system with a new hose assembly. This proposal is prompted by reports that, during flight tests, the hydraulic pressure transfer tube of the RAT cracked when the RAT was extended on a Model 767 series airplane. The actions specified by the proposed AD are intended to prevent such cracking, which could result in the loss of hydraulic fluid of the center system and the inability of the RAT to pressurize the center system; this situation could lead to loss of all hydraulic system power in the event that power is lost in both engines.

Cont'd . . .
DonH

flyboyike

3rd Nov 2013, 21:00

For Bubbers' information, there are AD's referencing the B757-200 RAT from early 1988. Even as the original type certificate was issued in 1982, the B757 appears to have always had a RAT.

I'm afraid not, Don, and that AD certainly doesn't prove it. At best, it proves RAT was available. The electrical chapter of the systems manual (look it up on smartcockpit) makes not a peep about a RAT. The only thing mentioned is a hydraulic-driven generator for PW-powered birds. The chapter on RR-powered ones doesn't even reference that. Perhaps there was an STC of some kind, but if the manual is to be trusted, it wasn't standard equipment.

In fact, it appears it was optional on the 767 as well.

Turbine D

3rd Nov 2013, 21:17

Boeing 757 RAT

I think some B-757s indeed had a RAT If you look at this FedEx B-757 landing after an aborted landing and go around, you will see the RAT deployed. Look carefully after the landing and the thrust reversers are activated and you will see the RAT. Going to full screen helps… I believe a division of Hamilton Standard manufactured the RAT.

Aborted Landing - FedEX Boeing 757 Go-Around London Luton Airport - 757 Awesome Power - YouTube

TD

Winnerhofer

3rd Nov 2013, 21:27

Myths and Training | Flight Safety Foundation (http://flightsafety.org/aerosafety-world-magazine/july-august-2011/myths-and-training)

tdracer

3rd Nov 2013, 21:31

For what it's worth, I checked 'generic' 757 AFMs for both PW2000 and RB211-535 and they both make mention of a RAT that will automatically deploy if both engines drop below 50% N2/N3 in flight or via a manual guarded flight deck switch.

BTW, I've never heard of Boeing certifying a RAT as "optional".

Tim

flyboyike

3rd Nov 2013, 21:34

That's odd. The same generic manual I checked mentions only an hydraulic-driven generator.

tdracer

3rd Nov 2013, 21:39

Flyboy, check Non-Normal procedures under Hydraulic Systems. It has a dedicated RAM AIR TURBINE (RAT) heading.

DozyWannabe

3rd Nov 2013, 21:42

Makes sense - it would be a hydraulic RAT only, as electrical power would be supplied by the aforementioned batteries.

bubbers44

3rd Nov 2013, 21:46

Thanks flyboyike, for a few posts it made me wonder if my memory was fading away. Our 767 had RAT but 757 didn't. Windmilling engine hydraulic pressure would get you down with total engine and electrical failure.

I made my example just a total electrical failure and was my plan if it ever happened. I usually was outside the 30 minute battery life of an airport over water so considered turning off the battery and navigating until approaching suitable airport and turning it back on to make the approach.

DozyWannabe

3rd Nov 2013, 21:57

@bubs - check tdracer's posts at #628 and #630 - the Mighty 757 does indeed use a RAT for emergency hydraulics. Now - where were we regarding AF447? ;)

B757 Hydraulics (http://www.smartcockpit.com/aircraft-ressources/B757-Hydraulics.html)

(see pages 5 and 6)

Wally Mk2

3rd Nov 2013, 22:18

This thread is becoming somewhat concerning. Does the B757 have a RAT or not? Checking quite a few sources via Google (smart cockpit for one) shows a RAT in the hyd system every time.
I'll ask again ( to anyone out there whom is B757 rated) upon an external insp of the A/C is there any evidence of a RAT? You know closed doors under the belly etc?

Wmk2

exeng

3rd Nov 2013, 22:29

Talk about thread drift.

Mods where are you?

Regards
Exeng

DozyWannabe

3rd Nov 2013, 22:32

Talk about thread drift.

Mods where are you?

Agreed, though I reckon the 757 RAT question and topic is worth hiving off into a separate Tech Log thread rather than simply deleting the posts, as there seems to be a considerable amount of confusion on the point.

In other words, it seems worth discussing, but not in a thread about AF447!

bubbers44

3rd Nov 2013, 22:40

I was concerned with electrical not hydraulic systems. It is automatic for hydraulics so no training is required. That is why it was never taught except maybe in initial ground school once. It does not affect the electrical system.

From my memory over 10 years ago the 767 had a hydraulic driven generator that would be driven by the Hyd system. All my manuals drowned in Hurricane Wilma in 2005 so have no references to go to, only memory. If RAT would have taken care of total electrical failure I wouldn't have put my 'battery saving plan in my last resort checklist when I was current.

bubbers44

3rd Nov 2013, 22:43

I agree, let's get back on topic. I am done. Hooray

john_tullamarine

3rd Nov 2013, 22:46

Talk about thread drift. Mods where are you?

Watching on with interest, good sir.

Suggest we can tolerate a small digression on RATs for a few posts in however many thousands of posts we are up to in this sequence of threads.

If it persists, I'll hive the relevant posts off into a separate thread.

Not all will agree with me but, personally, I find the smaller digressions we see in threads part of the rich PPRuNe tapestry.

Wally Mk2

3rd Nov 2013, 23:07

ok answer me this you thread drift haters what possible HARM can it do?
Is there a law we are breaking here? So what if a thread drifts off it happens all over PPrune everyday it can hardly hurt a soul. Most subjects drift off, ALL conversations go off on a tangent at some point or another but generally drift back. If anyone finds it offensive then simply don't read it or reply. This particular thread drift seems (well to me anyway) somewhat important & if it makes some out there whom fly these Boeings increase their knowledge base then good & well NO HARM done.....sheez I know the Mods love to dictate but boy it must be a personal agenda they have!!

Wmk2

DozyWannabe

3rd Nov 2013, 23:31

I find the smaller digressions we see in threads part of the rich PPRuNe tapestry.

Likewise - I certainly learned something today. In fact I think I'm right in saying that despite being of dubious relevance to the thread subject, we're looking at the first honest-to-goodness new information to be discussed since several threads ago - shame it's tangential!

So, returning - albeit with a somewhat heavy heart - to the subject:

@bubs - I know you were referring, at least in part, to electrical power in your post #614. The tangent occurred because you said in your next post there was no RAT, period, on the 757, which I thought was iffy.

Getting back to that first post, and acknowledging that you seem to have performed some very useful preparation and experimentation for total electrical failure, I ask again - as did vilas and a couple of others - why all this talk of automation, and what relevance does that post of yours have to the subject?

Airbus aircraft have not had a greater or more complex level of automation than their Boeing or MD counterparts for more than 30 years (almost 40 in fact). Airbus never pushed automation harder than any of their competitors either. The trajectory indicator line on the NAV display isn't even magenta on an Airbus!

Also, given that the AF447 PF was a sailplane pilot, and that there are to the best of my knowledge no, or at least very few, automated sailplanes - it's a bit of a stretch to assume he was across-the-board dependent on automation, do you not agree? Not to mention that to fly sailplanes one has to be able to manage the flightpath by handflying and managing pitch, roll and energy - understanding stall - and particularly how to recover from it - is a prerequisite because gliders don't have TOGA power.

What we don't know is how recently he'd been practicing those skills, but it's fair to assume that he was proficient in them at some point, and remained proficient for some period of time. The recurrent training and practice both the F/Os lacked was of *high-altitude* manual handling only.

The airline industry previously made a dubious move to focus on stall *avoidance* in recurrent training and stopped practicing recovery which, to say the least, didn't help - but the continuing bafflement remains as to how they got themselves into that position in the first place!

I know there's an issue with automation dependence in the industry, and I don't think that anyone posting on this thread seriously supports the notion that increased use of automation is a good idea. What I was trying to understand from you is - why the continued assertions that the F/Os didn't know how to handfly at all and were automation-dependent, when the evidence suggests otherwise, and why you insist that Airbus was the prime mover behind increased use of automation, when the evidence is clear that it wasn't?

mm43

3rd Nov 2013, 23:54

DW,

You'd have to accept that their automation dependance was to a degree revealed when following the initial "we've lost the speeds" that the PF didn't call for the FDs to switched off, and their no apparent attempt to follow SOPs or to call for the QRH guidance.

Put it down to a one-off CRM problem, but there may have been some other Human factors involved here, which may surface with the passage of time.

DozyWannabe

4th Nov 2013, 00:07

@mm43 - That's one interpretation. Another is that he was so startled that he lost focus from the start of the sequence and never recovered. There was no call to turn off FDs, but there was no call to initiate UAS procedure either.

I've said it before, even if you're among the best pilots in the world, a mistake - even a small one - which causes you to lose SA, can kill you with frightening ease.

vilas

4th Nov 2013, 02:45

mm43&Dozy
Our underlying likes, dislikes, attitudes and suspicions about automation go to form our opinions. We may be entitled to them but for the truth to emerge if we keep ithem aside what we see? Lets take a case where a pilot has regularly hand flown normal approaches and is profficient in it. But he was never explained the principle of the UAS procedure nor was he current or profficient in it. Another pilot who practices minimum handflying but is knowledgeable and had recently practiced UAS at high altitude. Who do you think would have managed the situation better? The human factor here is lack of proper knowledge or misunderstanding of UAS and stall recovery procedure. This particular abnormality is not straight forward and calls for investigation first, memory items and then paper procedure. If 447 pilot knew the procedure but was not very profficient in it might have saved the situation, may be he would have stalled 3 times on the way down but the flight would not have ended in 3 mts.

RetiredF4

4th Nov 2013, 06:41

Not to mention that to fly sailplanes one has to be able to manage the flightpath by handflying and managing pitch, roll and energy - understanding stall - and particularly how to recover from it - is a prerequisite because gliders don't have TOGA power.

A short comment from someone, who has done handflying for the most time in his flying life albeit a suitable autopilot was not available.

To compare handflying a glider in the heart of its envelope with handflying an airliner at the top of its flight regime as being similar or equal is far fetched. Aditionally the mental picture needed for flying a heavy against flying a glider is completely different as well. Therefore being able to handfly a glider does not qualify at all for flying an heavy airliner.
What does qualify is training with the specific aircraft in the required environment.

At the end of my military turn i started flying a PA28 prop, and nearly nothing of my previous flying hours helped me in doing so. By the way, my instructor had the same impression.

Wally Mk2

4th Nov 2013, 08:00

'RF4' whilst I can see yr beliefs as being true to some degree I cant subscribe totally to it all. As I am sure you know the basics of flight are no diff from an A380 to a model plane just the handling of that energy which is wildly different as well as the vast implications of Re (Reynolds No's).
Most likely the author of that statement 'same as flying a glider' or words to that effect had good intentions but it was probably not a good comparison in this case.

RetiredF4

4th Nov 2013, 10:14

As I am sure you know the basics of flight are no diff from an A380 to a model plane just the handling of that energy which is wildly different as well as the vast implications of Re (Reynolds No's).

The basics of flight knowledge can be obtained by different sources and using different devices, you named one yourself like flying a model plane. Does flying a model plane qualify to fly a glider, or a SE or Twin Prop, or a jet or a transport?
You agree that it does not? Therefore the fact, that one FO was a qualified glider pilot has nothing to do at all with the AF 447 desaster. Because the basics of flying you are talking about should be a knowledge base any pilot from model pilot to transport pilot should have, and that's the point i totally agree with you.

DozyWannabe

4th Nov 2013, 10:27

Because the basics of flying you are talking about should be a knowledge base any pilot from model pilot to transport pilot should have, and that's the point i totally agree with you.

That's essentially what I'm saying too - however I do think that his sailplane qualifications and experience have some bearing on the *reporting* and *discussion* of AF447. You've got several posters waving around accusations of total automation dependency - saying the crew were incompetent and unable to handfly in any way, when that was clearly not the case.

I'm not, and never was arguing that flying a glider does or should "qualify" one to handle an airliner, I was simply saying that the PF could handfly to a reasonable level - certainly proficient enough to know that you neither maintain a straight and level flightpath nor escape a stall by consistently pulling up.

RetiredF4

4th Nov 2013, 11:55

You've got several posters waving around accusations of total automation dependency - saying the crew were incompetent and unable to handfly in any way, when that was clearly not the case.

They clearly demonstrated, that they were not able to handfly this aircraft in this particular situation. And they clearly demonstrated, that they could not cope with the loss of some part of automation.

If we look at other happenings in this new world of commercial airplane flying and in the way automation flying is trained and stressed, and in part manual flying is even most times prohibited by the respective training departments of some airlines (and not few of them as the saying is here), how can one not see a lack in handling skills caused by too much automation dependency?

Yes, this crew might have been able to handfly once and the FO might have been an excellent glider pilot (which nobody knows so far), but at that special moment in that aircraft and at that flightlevel with the loss of valid airspeeds they only proved the following:

After loss of Airpeed indication, which caused the loss of automation devices like Autopilot, autothrust and degraded the flight envelope protection they crashed an airwothy airliner within a few minutes due to their inability to fly this aircraft straight and level by their own hands.

Whatever you like to call that, it never should have happened and it never should happen again. I go with those, who call that incompetent and unable to handfly, period.

Our concern should be, who is to be made responsible for this kind of incompetence and for this kind of automation dependency and how can we promote further training to stop the degradation of those required skills. More glider flying is not on my list though.

Lonewolf_50

4th Nov 2013, 12:59

They clearly demonstrated, that they were not able to handfly this aircraft in this particular situation. And they clearly demonstrated, that they could not cope with the loss of some part of automation.
The rest of your post is well put. I'd like to add a slightly different emphasis to your clear identification of some root causes:
in a class of aircraft and on a mission where crew coordination and CRM are required fundamentals, a profound lack of same was in evidence from early in the event on this flight deck. Beyond hand flying difficulties, it seems from the evidence available that possession and use of an instrument scan (another fundamental requirement of flying in that class of aircraft on that mission) was beyond at least one of the pilots on the flight deck.

Scan problems and poor hand flying are related to one another. The concern this accident raises in my mind is linked to the standing complaint about "Children of the Magenta line:" how pervasive is the skill limitation exposed by this particular crew?

Not common, or very common?

I don't know if that is an answerable question given the size of the industry and how practices may vary from carrier to carrier. It's an answer worth pursuing, IMO.

DozyWannabe

4th Nov 2013, 13:10

Scan problems and poor hand flying are related to one another. The concern this accident raises in my mind is linked to the standing complaint about "Children of the Magenta line:" how pervasive is the skill limitation exposed by this particular crew?

That's just it though - I think that a lot of posters here are putting too much into this "Children Of The Magenta" scenario, which is not necessarily the case. After all, the ex-Air Force Captain of the Birgenair B757 did exactly the same thing as the AF447 crew, and he was a veteran.

And let's not forget, there are far fewer smoking holes with automation at this kind of level than there were when handflying was more prevalent in the early part of the jet age.

Frankly a lot of this "much better in my day" routine (the "magenta" talk often overlaps with disparaging remarks on new 200hr cadets) smacks to me of people who miss their youth, then see the ongoing changes in their industry - and it makes them feel old. No-one enjoys that feeling - but I swear there's a lot more to this case and others that have been conveniently swept into the "Magenta" pile without sufficiently examining the evidence at hand. Dismissing pilots and crews as generally 'incompetent' is a little dangerous, as it can lead to complacency - "After all", thinks Captain Hypothetical, "I'm not incompetent, so it could never happen to me!".

Ian W

4th Nov 2013, 13:41

That's just it though - I think that a lot of posters here are putting too much into this "Children Of The Magenta" scenario, which is not necessarily the case. After all, the ex-Air Force Captain of the Birgenair B757 did exactly the same thing as the AF447 crew, and he was a veteran.

And let's not forget, there are far fewer smoking holes with automation at this kind of level than there were when handflying was more prevalent in the early part of the jet age.

Frankly a lot of this "much better in my day" routine smacks to me of people who miss their youth, then see the ongoing changes in their industry - and it makes them feel old. No-one enjoys that feeling - but I swear there's a lot more to this case and others that have been conveniently swept into the "Magenta" pile without sufficiently examining the evidence at hand.

These aspects can all link together,

In one life in the nice shiny transport you follow the magenta line and if you are lucky and it is your 'turn' you may get to hold the controls for a few minutes in an 8 hour flight but only with full system support.

In another life you fly a sailplane that is responsive to the controls even if you have to use full deflection at times, stalls are big nose drops that cannot be overcome by even full back stick. And you get that wind noise that gives you the impression of speed....

Then one dark and stormy night the nice shiny transport decides to have a problem - and you are in a sub-state of Alternate law which you have NEVER flown and you are at close to the ceiling of the aircraft. You have to fly manually - and you revert to flying manually the way that you do in sailplanes and perceive the performance as you do in sailplanes - it can't have stalled - the nose is still above the horizon and that noise means we are going fast....

If there is no sufficient training then people will revert back to what they knew from previous experience - it is all they can do. If your previous experience was sufficient that's fine. But it would appear that modern 'streamlined' training and limited experience is starting to show signs of insufficiency.

Lonewolf_50

4th Nov 2013, 14:05

Dozy, the problem of overdependence on automation is not a chimera. Ran into it two decades ago in the fleet. Here is another example:

On a CAVU to the moon day, at SFO a Boeing 777 crashed, thank God more didn't die.
Hand flying, not done.
Scan, broken.
CRM: out to lunch.

Core competency issues.

DozyWannabe

4th Nov 2013, 14:14

@LW_50:

I know there's an issue with automation dependence in the industry...

See above - I'm not saying the problem doesn't exist, I'm saying we should be careful not to prematurely shove all mishandling/loss of control incidents and accidents into the "COTM" bucket.

Lonewolf_50

4th Nov 2013, 14:42

I asked a few pages ago, and got no answ (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-27.html#post8125606)er.

Can you, Dozy, or anyone, explain to me why it takes 17 seconds for the pilot to make a control input during the A330/A340 altitude excursion that is of such interest in discussing the various features of the A330 flight control system?

From the A330/A340 incident ...
The pitchup trend continued for 17 seconds reaching a peak of 15° nose-up shortly before the first nose-down sidestick command was applied.

I asked for anyone who flies that family of aircraft, as the flight control systems seem to be similar enough.

My impression from that statement was that no corrective stick command was made. If I misunderstand what that tells us, that would be nice to know.

DozyWannabe

4th Nov 2013, 14:53

My impression from that statement was that no corrective stick command was made.

That would be my reading too. As to your question, the obvious answer would be that for at least some of those 17 seconds, neither of the flight crew were paying attention to their attitude - but as to why that might have been, we can only speculate.

RetiredF4

4th Nov 2013, 17:03

That would be my reading too. As to your question, the obvious answer would be that for at least some of those 17 seconds, neither of the flight crew were paying attention to their attitude - but as to why that might have been, we can only speculate.

Wouldn't be another possibility that they froze in a "what's it doing now" mode or / and were trying to resolve the problem by pushing buttons instead of using the obvious, the SS?

DozyWannabe

4th Nov 2013, 17:14

It'd be possible, certainly - however the possibility would rely on the idea that neither of them recognised that the AP had disconnected. As I said above - the "why" is something on which we can only speculate.

OK465

4th Nov 2013, 17:49

Can you, Dozy, or anyone, explain to me why it takes 17 seconds for the pilot to make a control input during the A330/A340 altitude excursion that is of such interest in discussing the various features of the A330 flight control system?

You could ask this guy:

On the 26th of December 2012, Norwegian Air Shuttle with flight number NAX5630 serviced a regular passenger flight from Helsinki airport Vantaa (EFHK) to Kittilä airport (EFKT) in Finland. The aircraft in use was a Boeing 737-800 delivered new to Norwegian Air Shuttle in 2011.

Enroute the flight was uneventful and the aircraft was established on the approach to runway 34. When the aircraft passed approximately 3,250 ft on the instrument approach (ILS) with flaps 5 and autopilot engaged, the aircraft started an unintentional steep climb with full engine power. The aircraft climbed approximately 1,500 ft and the airspeed dropped so that the aircraft came close to a stall. However the pilots managed to regain control of the aircraft. Some later a new approach was executed and an uneventful landing was made in Kittilä. After the incident, the aircraft has been flown on a test without any remarks.

The Accident Investigation Board Norway has access to the aircraft digital flight data recorder and some aircraft components. In corporation with the US National Transportation Safety Board (NTSB), Boeing and the airline, it is initiated an ongoing investigation as a result of the incident.

DonH

4th Nov 2013, 17:59

Retired...re, "Wouldn't be another possibility that they froze in a "what's it doing now" mode or / and were trying to resolve the problem by pushing buttons instead of using the obvious, the SS? "

Yes, that is absolutely a possibility.

Here on the forum, we can quite reasonably assess "17 seconds" with no SS input as a very long time to respond but in such an environment the moment is fleeting indeed. Such turbulence also makes it nearly impossible to a) physically read the instruments and the various warnings, timed as they are, and b) to mentally "re-cognize" what's actually occurring, primarily with the pitch, vertical speed and altitude - the same phenomenon which would challenge the A330 crew to respond to the CLIMB-CLIMB TCAS RA in a timely way.

BTW, none of this applied/applies to AF447. The failure was benign - lots of messages and aural cautions/warnings but other than the potential distractions from momentary ECAM re-prioritizing the system failures as they occurred and the dozen or so single-chimes associated, the airplane itself was stable, and fine.

OK465, indeed, we could probably ask a few crews about this same phenomenon!...

Lonewolf_50

4th Nov 2013, 20:39

You could ask this guy:
no, I can't, as I don't think he flies the family of aircraft I am curious about.

I'd like to ask him about his own excellent adventure, but I doubt I'll get an answer. Did the AAIB come up with a final report on that flight?

EDIT:
DonH, thank you.

OK465

4th Nov 2013, 22:05

LW50 original question:

I don't get why it takes so long to make a pitch correction when such a pitch excursion is made. Can anyone familiar with AB FBW suites in that family of aircraft provide a bit of insight?

bit of insight:

60 year old 340 Captain with 15131 hours, 5175 on type, who told the board he remembered seeing something he wouldn't have seen and.....

.....a board that said he probably saw something he couldn't have seen.

no, I can't, as I don't think he flies the family of aircraft I am curious about.

It appears not to matter that much. :)

Wally Mk2

4th Nov 2013, 22:45

In the a330/340 pitch up event the initial biggest non reaction here was purely due to the 'startle effect'. Remember in the Crz we would be at a low eb or state of mind especially after hrs of continuously the same noise levels & body movements. This is why people fall asleep at the wheel of a car & crash. These factors coupled with something that we are rarely exposed to (sudden pitch up)accounted for those 17 secs.

As I mentioned in an earlier post re the AF447 there's no way an Airliner operating close to it's highest performance Alt limit could suddenly have the ability to aggressively Clb & sustain it (other than using the energy avail initially ) due an over-speed in Lvl flight. To have the pilot/s react with full back stick to compensate (a natural reaction when first confronted with this rather odd & totally unexpected indication) is almost plausible when you think about it.
As we all know a blocked Pitot system effects just one primary system, Airspeed/Mach & it's associated connected elements (A/P FD etc) so any rapid increase in indicated AS/Mach isn't something that naturally occurs in Lvl flight to any major degree with thrust set.
It all boils back to basic airmanship....PITCH (or Att)/POWER & with 2day's extensive auto flight systems doing ALL the work for us our brains are becoming slowly de-tunned & desensitized to erroneous indications such as in this event.

Man will continue to fly perfectly serviceable flying machines into the side of a hill, such is the tenuous joining of man & machine despite all the technology.
It won't be long now when all the drivers in a typical Airliner will only ever have had exposure to highly sophisticated automation at transport level & raw flying skills will have been pretty much bred out as they are essentially no longer needed.

Chris Scott

4th Nov 2013, 23:13

Lonewolf_50 and respondents,

You discuss a period of 17 seconds before the first sidestick intervention. Re the AAIB Bulletin into this incident, I still find the description on Page 11 ("A340 Data") confusing, and the time scale on its DFDR trace virtually unreadable on the version I have. However, it states clearly enough (my underscoring):
"The first recorded sidestick input was made at 14:22:08 which was some 28 seconds after the commencement of the Master Warning."

The Master Warning and CRC (continuous repetitive chime) coincided with the AP disengagement (due to MMO exceedance, mainly caused by a sudden fall in temperature), but the aural warning (cavalry charge) was delayed because the CRC and a TCAS warning took priority. 10 seconds after the Master Warning, an up-gust briefly increased the AoA towards alpha-prot. That resulted in a phase-advanced engagement of AoA (protection) Law, after which the EFCS was tasked to reach and maintain alpha-prot, a much higher AoA than desired. That started the pitch-up, and after (roughly) a further 8 seconds the aircraft started climbing in earnest. After that, it was about 10 seconds until the first sidestick input.

So I presume your 17 seconds is the crucial period between engagement of AoA Law (+ Pitch-up) and the first (rather tentative) sidestick movement? This was less than half down, and it is unclear if it was sustained for the period of more than one second that was required to disengage AoA Law. The first application of more than half down-stick (which would disengage AoA Law instantly) started about 5 seconds later. It is only then that the a/c starts to pitch down rapidly, i.e., 22 seconds after the engagement of AoA Law.

RetiredF4 and DonH have identified the likely reason for the lack of sidestick action by either pilot. To be a bit more more specific, one or both pilots were probably trying to re-engage one of the two APs, possibly trying them both alternately. Many of us have seen this kind of behaviour: priority given to re-engaging the automatics, rather than flying the aeroplane.

This zoom climb involved an error of omission by the PF; AF447's an error of commission.

As I wrote a few days ago:
"The common factor this incident had with the much later AF447 accident is that of the unexpected transition from automatics to "manual": specifically from AP to FBW, in a pitch law other than Normal. In this AIRPROX case, the FBW system forced the a/c into an undesired zoom-climb which needed positive crew intervention to counter. In AF447, the FBW made no such input; the PF forcing the a/c into a zoom-climb by inappropriate sidestick inputs."

In both cases, there were extenuating circumstances - if only minor ones.

Most of us are in agreement that, had the AF447 PF sat on his hands for a while, the A330 would have maintained a good pitch attitude at least. In the A340 AIRPROX case, however, we are all (myself included) chiding him/her for failing to prevent the EFCS (FBW) from pitching the aircraft into a zoom-climb which - in the absence of any collision - would have become an embarrassing phugoid. So although the initial parts of the "zoom climbs" are rather similar, their causes are very different.

In this case, at least two unusual met phenomena and the logic of the EFCS conspired in such a way that PF inactivity was not an option - if flight separation was to be assured. The AAIB avoids censorship, as follows:
"Such was the vigour of the A340’s climb in AoA law, the aircraft could well have climbed through FL 363 (thus provoking a TCAS RA with revised software version 7.0) in a very short time, even if the crew had applied nose-down sidestick as soon as they heard the (delayed) autopilot disconnect warning."

Lonewolf_50

5th Nov 2013, 14:49

Thank you Chris.

OK:
60 year old 340 Captain with 15131 hours, 5175 on type, who told the board he remembered seeing something he wouldn't have seen and ... a board that said he probably saw something he couldn't have seen.

That leaves me more confused than before. :(

I appreciate the mind set of "let's not be hasty."

flyboyike

5th Nov 2013, 15:03

'RF4' whilst I can see yr beliefs as being true to some degree I cant subscribe totally to it all.

It's hard to argue with a word like "whilst". If somebody says "while", it's no big deal, but once they throw "whilst" into the discussion, the opponents pretty well clam up. Another such word is "fraught". If somebody says something is dangerous, it's not that big a deal, but once it's "fraught with danger", the party is over.

Kudos to Wally for excellent rhetoric skills.

Chris Scott

5th Nov 2013, 15:17

Quote from Lonewolf_50:
That leaves me more confused than before.

Thanks? Not sure if you were referring to the piece from OK465, or mine! :uhoh:

Coincidentally, I was just labouring heavily to improve (edit) my post while you and flybyike were posting yours. So let me know what you think - if you've the stamina to re-read it...

OK465

5th Nov 2013, 16:25

That leaves me more confused than before.

You're not the Lone Ranger, Lone Wolf. That AAIB narrative has a number of confusing statements and has me scratching my head.

Here's the first two:

The commander could not remember the sequence of warnings but he did recall being unable to reengage either autopilot which prompted him to make manual control inputs. He also remembered seeing an ‘Alpha Lock’ warning displayed on his Primary Flying Display..

The indicated airspeed dropped below VLS (the lowest selectable) as the aircraft climbed and the commander took manual control of the aircraft because neither autopilot would engage..

Confusing to me because I would think a 5000+ hour on type Captain ought to know that 'alpha lock' is not displayed on the PFD and is slat/flap related.

And a 5000+ hour on type Captain ought to know the autopilot cannot be re-engaged below VLS.

Next taken together confusing statements 3, 4 & 5:

For 18 seconds after the autopilot disengaged the aircraft remained within 200 feet altitude of FL 360 but once AoA law was invoked at 14:21:50 hrs, the aircraft’s attitude began to pitch nose-up..

and automatically disengaged the autopilot. One second later
the TCAS issued an RA with a “DESCEND, DESCEND, DESCEND”audio warning..

Such was the vigour of the A340’s climb in AoA law, the aircraft could well have climbed through FL 363 (thus provoking a TCAS RA with revised software version 7.0) in a very short time,

A TCAS DESCEND RA evidently WAS indeed provoked within 1 second of A/P disengagement, but for 18 seconds the 340 remained within 200 feet of FL360 (the 330 encountered a 200 foot altimeter drop), so what's the point to be made with the 'climb vigour' and 'could well have climbed thru FL363' statement. RA occurred without either of these. Time to do some pilot stuff with the SS.

And here's the kicker (board statement):

The commander’s reported sighting of an ‘Alpha Lock’ message was probably an alpha floor warning on the flight mode annunciator portion of the PFDs.

Read A33Zab's previous post on these functionalities (alpha lock 'pulses' bright/dim on the EWD slat/flap display, alpha floor is a PFD FMA steady indication) and you can see why I'm confused. Of course I don't have 5000+ hours on type. :}

And as Chris Scott alludes to, the DFDR traces are almost worthless....it would be interesting to see a TLA trace, 'cause the whole thing is screwy IMO.

DozyWannabe

5th Nov 2013, 18:37

RetiredF4 and DonH have identified the likely reason for the lack of sidestick action by either pilot. To be a bit more more specific, one or both pilots were probably trying to re-engage one of the two APs, possibly trying them both alternately. Many of us have seen this kind of behaviour: priority given to re-engaging the automatics, rather than flying the aeroplane.

I'd say they identified a *possible* reason, and acknowledged this at the time. To say it's a "likely" reason is objectively inaccurate - as we have no corroborating evidence to support the assertion, and subjectively unfair - as it assumes a degree of automation dependency on the part of the crew on the basis of anecdotal reporting (i.e. "Many of us have seen this kind of behaviour").

I'm sure the anecdotal reporting is correct, but at the same time I think it's wrong-headed to try and squeeze this particular incident into a "...Magenta"-shaped mould without any real evidence to back it up. Finding repeatable patterns in a series of mishaps can be something of a double-edged sword, because while spotting and working to eliminate that behaviour will help, it won't help in the case of those incidents where, while outwardly similar in nature, that pattern wasn't involved - and can mask other problems that can be equally as dangerous.

tdracer

5th Nov 2013, 20:03

FAA unveils pilot training to avoid stalling airliners

FAA unveils pilot training to avoid stalling airliners (http://www.usatoday.com/story/travel/flights/2013/11/05/faa-pilot-training-colgan-fatal-crash-huerta/3305509/)

Weener cited four fatal crashes in the last two decades where pilots continued to pull up on their controls too much until the aircraft crashed, rather than leveling off to regain power and speed. Those crashes were Colgan, Air France 447 in June 2009, Pinnacle Airlines 3701 in October 2004 and USAir 427 in September 1994. In the Air France and Pinnacle crashes, the planes plummeted several minutes from tens of thousands of feet in the middle of flights, rather than near the landing.

I would have added the Birgenair 757 to that list....

Chris Scott

5th Nov 2013, 20:15

Quote from me:
"RetiredF4 and DonH have identified the likely reason for the lack of sidestick action by either pilot. To be a bit more more specific, one or both pilots were probably trying to re-engage one of the two APs, possibly trying them both alternately. Many of us have seen this kind of behaviour: priority given to re-engaging the automatics, rather than flying the aeroplane."

Quote from DozyWannabe:
"I'd say they identified a *possible* reason, and acknowledged this at the time. To say it's a "likely" reason is objectively inaccurate - as we have no corroborating evidence to support the assertion, and subjectively unfair - as it assumes a degree of automation dependency on the part of the crew on the basis of anecdotal reporting (i.e. "Many of us have seen this kind of behaviour")."

From the AAIB Bulletin:
"The A340 commander's report
"...Shortly before the AIRPROX event he experienced moderate turbulence and noticed outside air temperature changes. Suddenly the aircraft began to climb, the Master warning soundedand the autopilot self-disengaged as the aircraft exceeded the speed limit of 0.86 Mach. The indicated airspeed dropped below VLS (the lowest selectable) as the aircraft climbed and the commander took manual control of the aircraft because neither autopilot would engage. The crew subsequently reported the incident to Shanwick on HF radio and, using their TCAS, they descended back to FL 360 in a safe area...
"The commander could not remember the sequence of warnings but he did recall being unable to re-engage either autopilot which prompted him to make manual inputs. He also remembered seeing an 'Alpha Lock' warning displayed on his Primary Flying Display."

My use of the word "likely", rather than "possible", was to specify my opinion. I cannot think of any other legitimate activity to explain the delay that we are discussing. It was not necessarily to imply what Dozy describes as "dependency"; rather that the crew prioritised re-engaging the AP during a period of time when the pitch attitude and flight profile were becoming abnormal, and clearly compromising the safety of the flight.

Clandestino

5th Nov 2013, 21:33

I would have added the Birgenair 757 to that list....I would have definitively removed USAir 427 from the list - putting it up there with Colgan, Pinnacle and AF447 is so terribly wrong. Given dr. Wiener's track record, this just has to be something misheard.

Lonewolf_50

5th Nov 2013, 21:47

Chris, I put two replies into one post.

My thanks to you was for you clearing a bit of the fog out of the air.

My response to OK465, which I simply addressed to OK, was to show that even with a bit clearer air, my brain is still fogged with not getting it. His further explanation makes me feel a bit better about my own lack of seeing how it went down, given the testimony of one of the crew. Glad it all worked out, all said and done.

Sorry if I added to confusion by using OK, which may have come across as other than a reference to his PPRuNe nomme de post.

tdracer

5th Nov 2013, 22:51

I would have definitively removed USAir 427 from the list - putting it up there with Colgan, Pinnacle and AF447 is so terribly wrong. Given dr. Wiener's track record, this just has to be something misheard.

Agreed - although it's the second recent press release on the subject that referenced the USAir 427. After the first I actually Googled it to make sure it was the same crash that I was thinking about.

DonH

5th Nov 2013, 23:07

Hi Dozy, Re, "I'm sure the anecdotal reporting is correct, but at the same time I think it's wrong-headed to try and squeeze this particular incident into a "...Magenta"-shaped mould without any real evidence to back it up. Finding repeatable patterns in a series of mishaps can be something of a double-edged sword, because while spotting and working to eliminate that behaviour will help, it won't help in the case of those incidents where, while outwardly similar in nature, that pattern wasn't involved - and can mask other problems that can be equally as dangerous. "

I too, would use Chris Scott's term, "likely" to describe what happened. This isn't jamming behaviour into the magenta-mold, it is recognizing factors that I, and probably Chris, (don't want to speak for you!), really do know about from having done too many simulator sessions! ;-) where that very phenomenon occurs.

Each sim session's script usually has a few very busy moments where "all hell is breaking loose" with a serious system failure, sometimes combined with a go-around from a low-vis approach.

The single chime and Master Caution are going off constantly, (and one is constantly resetting it), as the ECAM catches up with the FWC messages being displayed and re-prioritized, there may be warnings that the autoflight system has disconnected, perhaps voice-audio warnings, (such as the TCAS warnings) are occurring depending upon the scripted failure(s) - lots of times this usually occurs at/just-after takeoff or, far busier, the go-around, when one is making sure the gear is up, (if no one calls "positive rate", almost invariable the gear is left down while concentrating on other things!), the climb-thrust is set and so on.

The procedures are set out and well-trained as you will know from reading previous threads, but one is working hard, maintaining concentration, anticipating the next step while remembering/executing the drills in sequence. It is a very, very busy airplane when something major goes wrong or one is in cruise and all of a sudden the cautions and warnings come.

As I've mentioned previously, there are perhaps two, possibly three times when decisive, timely actions are required of the pilot-flying or the captain; they are the rejected takeoff, (captain only - and I do know this is controversial in some circles), stall, TCAS, EGPWS warnings and the go-around. All the other times, including engine failure-fire-damage one can & must take one's time, and by that, (it's been mentioned before), I mean 4, 5 or more seconds, to do nothing but collect one's thoughts and communicate with the PNF calling the failure and calling for the ECAM actions, etc. while taking the radios.

To your point, I would be quite certain that the A330/A340 event wasn't a "magenta-line" matter, nor is it startle; I would characterize it as re-grouping & otherwise marshaling one's resources which heretofore had been "at rest" so to speak, and while only partly due to the maintenance of cockpit discipline before launching, is an adjustment of focus while dealing with the inevitable surprise, (none of which is startle - startle is the result of a "comfortable unexpectedness" and perhaps a knowledge-complacency where "relaxed-but-ready" is that which is borne of thorough training, an abiding passion for the books and discussions and a desire to "read" in one's chosen profession which means reading accident reports, studies on current topics as well as staying in the books and knowing one's airplane....going beyond the minimum required to build depth and resourcefullness which can be called upon even once or perhaps twice in one's career and not waiting for, or complaining that one's airline isn't teaching one!

Automation is fabulous and I loved it but if that's all that one knows, one is at risk of being quickly overwhelmed, (startled) by the airplane.

gums

5th Nov 2013, 23:40

I like this newbie "Don". Good thots.

@ Doze

Put it this way - throughout the history of civil aviation and its technical advances, pilots have not needed to understand the principles of things like cams, tensile strength of metals, hydraulic flow management and the like to fly the aircraft of those eras - because all of those technologies required specialist knowledge to some extent, and as such were not actually that simple. Some pilots did go the extra mile in understanding, some continue to do so and some in this era have extended that understanding to the modern electronics and computer technology behind their aircraft.

Well, as most here know, I am in the latter grope of pilots. Got my engineering stuff from USAFA and was always a curious type. I even looked into the code for the A-7D computers and then the Viper's. Got the charts and block diagrams for the Viper FLCS and had to instruct the first few folks back in 1979 and 1980. Ya gotta know your plane, and it's a poor craftsman that blames his tools for a botched approach or incident.

I was and still am a proponent of using Otto to reduce workload and to provide some time to hit the head or eat a sandwich or... Otoo also helps after a missed approach and divert to a new field, especially when in a single seater and no "PNF".

But what bugs me is the seeming over dependence upon Otto for things that the pilot in command should be on top of. I think Asiana. I think of my buddy in the Cali crash. And I think of at least one Viper pilot friend that died because the altitude hold function had a lower AoA protection than the "normal" law. But he wasn't a child of the magenta line, he was trying to get his act together after aborting a low level route.

I am confused about the alpha protect laws and implementation. My documents show that the jet won't let you go above a certain AoA except in sub-law 2 (b) iii part three ( sarc off). So the zoom climb in the other 'bus plane is confusing if the pilot(s) did not command a climb.

Gretchenfrage

6th Nov 2013, 01:50

DonH throws in some good thought. I'd still like to contest some.

The procedures are set out and well-trained

Well, procedures might be set out, but they do not cover every situation. Therefore to put it right at the beginning of an argument seems to imply this. We need to be careful and vigilant that the same over reliance to automation is not aped with procedures. We definitely need procedures, but as with automation and sops, if there starts to be a religious thirst for all these things to replace basic skills and common sense, then we end up full backstick at FL350.

To pretend that procedures are well trained is somewhat preposterous. We all know how the bean counters cut back on anything they can in training, we all know how the operations bosses limit anything outside hand-cuffing sops, to invalidate such arguments. By simply reading the training syllabus of most airlines, you will discover that it rarely goes one little step beyond the bare minimum set up by regulators under pressure from the managers lobby.

As I've mentioned previously, there are perhaps two, possibly three times when decisive, timely actions are required of the pilot-flying or the captain; they are the rejected takeoff, (captain only - and I do know this is controversial in some circles), stall, TCAS, EGPWS warnings and the go-around. All the other times, including engine failure-fire-damage one can & must take one's time, and by that, (it's been mentioned before), I mean 4, 5 or more seconds, to do nothing but collect one's thoughts and communicate with the PNF calling the failure and calling for the ECAM actions, etc. while taking the radios.

Well put. However todays sops from industry and airlines and especially todays freshmen TRI/Es go the other way. The pandemic of "memory items" and additional "procedures" is creeping up even more after every incident. Just look at some airlines who want UAS to be a memory item, a procedure (see above) that should be well trained (see above) and readily dispatchable by a brain under sudden fire. In sim sessions i regularly, and by that i mean regularly, see UAS, rapid descents and severe damage assessments and memory items badly screwed up. Why? Because there is way too much emphasis on memory items and wording. When a brain is utterly stressed, it does not perform well. To put it under even more stress with the above is purely and simply counterproductive. I have seen newbees completely blocked because they could not recall the correct name for a checklist or stuttered for seconds to produce the correct pronunciation or term for an item. The TREs were taking notes like wild and elaborated for hours in the debrief of how important it was to know that kind of stuff. Maybe the poor AF-FO was torturing his mind to find the right wording, memory item or "absolutely correct procedure" and by doing that he was blocked-cramped pulling.
Checklist have been introduced to counter such phenomenons and to counter blockage, to give a straw to cling to. I once reverted to the checklist for a emergency descent, becasue i was really surprised in that sim session, just to be marked down for that.

On the other hand there are times where the only thing that is left is your rear side. For a few seconds, after that you have to go back to the marvels of modern aviation, because your bird has become mainly digital.

I contest the statement that todays pilots are still able to do that.
They are NOT well trained enough and NOT free enough from the limiting constraints of over reliance on automation, procedures and sops.

The moment we admit to that we can start working with these wonderful birds A and AB give us.

HazelNuts39

6th Nov 2013, 11:44

A similar incident: Air France A340-313, over the North-Atlantic on 22 july 2011 (http://www.bea.aero/docspa/2011/f-zu110722.en/pdf/f-zu110722.en.pdf)

Chris Scott

6th Nov 2013, 12:11

Thanks for that link to the BEA Report into this "Serious Incident", HN39.

Judging from the Synopsis, this incident had elements in common with both AF447 and the A340 AIRPROX. It promises to make for shocking reading.

Better to take the dogs out first, methinks...

BOAC

6th Nov 2013, 14:30

Don't let the dogs see it, Chris....................

A quick scan through that report leaves me very puzzled as to who was PF and who was PNF and exactly what were they playing at?

Sadly again absolutely no credit to AF, selection, training and abilities in that incident. I cannot relate to the timeline portrayed in this report.

3 minutes from 'Overspeed' before ANY action is taken - then by PNF?
After 4 minutes the 'Overspeed' ceased and they were practically back at cruise Mach BUT at 6 minutes 'someone' decides to select a slower speed? AND
at 7 minutes extend the speedbrakes when almost at cruise Mach?
At 8 minutes after the 'event' they are still almost 'level' (+200')

Speedbrakes come in after 13 minutes, so I guess they had power against speedbrake for 6 minutes?

Either the world has gone mad or the report has been corrupted in translation. Look what they 'missed':mad:

Nose-up attitude, which had reached 12° pitch up,
ˆ High vertical speed, which had reached 5,700 ft/min,
ˆˆThe flashing frame around the altitude display on the PFD when the altitude
passed 35,200 ft,
ˆˆThe position of the FD cross bars,
ˆˆAltitude until it reached more than 38,000 ft,
ˆˆThe “AP1” display which had disappeared from the FMA strip,
ˆˆThe amber ECAM “AP OFF” message which remained displayed for 9 seconds after the AP disengagement.

The report also says 'Because of the absence of CVR recording, it was not possible to evaluate CRM in order to explain the lack of monitoring of the basic parameters and the flight path.' - Do we really need that?:ugh:

All this AFTER 447.

rudderrudderrat

6th Nov 2013, 15:49

Hi BOAC,
At 8 minutes after the 'event' they are still almost 'level' (+200') I think you are misreading minutes instead of seconds.

"At 1 h 00 min 27 (point n°2), ......., the PNF manually disengaged the AP by pressing the
takeover pushbutton on the side-stick. A pitch-up input on the PNF’s side-stick going as far as ¾ to stop was recorded for 6 seconds.

At 1 h 02 min 06 (point n°9),...... the aeroplane descended past 36,520 ft. The PF then became aware of the disengagement of the AP and made a pitch-down input on his sidestick."

The total amount of time between AP disconnect and PF (Captain) actually taking control was "only" 1 min 39 secs.

Is it the ergonomic design of the Airbus flight deck or AF crews?

On previous AC types, we had large red letters on the PFD telling whether the AP was engaged "CMD" or only the Flight Directors "FD" in addition to all the other alarms, bells and whistles.
Airbus simply removes "AP(1)(2)" from the top right hand corner of the PFD - it is easier to miss.

Chris Scott

6th Nov 2013, 15:55

Hello BOAC,

Re. the BEA Report on the AF A340 Serious Incident of 2011, should your time values be in seconds, rather than minutes?

Aso, you write:
Either the world has gone mad or the report has been corrupted in translation. Look what they 'missed'http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/censored.gif

You then go on to quote what the BEA has written on Page 14. Are you merely remarking that the crew may have gone mad, or perhaps you can explain what has been "corrupted in the translation"? At a superficial glance, their script seems to be in line with the DFDR traces in the Appendix.

Re PF vs PNF, I am inferring that the PF is the pilot (in this case, the captain) who was nominated as such at the beginning of the flight. it's always been a potential source of confusion (particularly in an airline like BEA/BA, which switches PFs for the "monitored approach"). Airbus itself used to add the terms CM1 and CM2 to avoid the ambiguity. In this case, the copilot seems to have remained the PNF (i.e., as far as we know there was no formal handover of control), but made sidestick inputs - whether intentionally or not.

BOAC

6th Nov 2013, 16:29

Ok - I did say "A quick scan through that report" and I can see it is me that has gone mad:rolleyes:. It certainly did not make sense as minutes. Still an unholy mess, even in seconds.

CS - there are two sentences in the para you quote - the 'missed' is a separate sentence - there is a full stop there.

The query on PF/PNF was that PNF appears to have been operating the sidestick?? Not my understanding of the operation. Certainly disconnecting the A/P should have been PF - unless incapacitated.

OK465

6th Nov 2013, 17:07

Just a quick sidebar,

From the F-GLZU report:

....and displays the amber "AP OFF" message for 9 seconds on the ECAM

Pedantic point concerning reports and accuracy....in the A346 & A332, the "AP OFF" ECAM message is red not amber when the A/P is disengaged with the takeover button. The red ones usually tend to get my attention.

Is it, or was it at one time, amber in the A343?....or is this a translation problem?....a tech writer problem?....or a report quality control problem?

(Some of these reports make a substantial amount of the info on PPRuNe look surprisingly studied. :})

Chris Scott

6th Nov 2013, 17:20

The new (to this thread) BEA Report on the AF A340 Serious Incident of 2011 describes the conditions that allow AoA Law to disengage back into Normal Law (which it refers to correctly - in the context of high altitude - as "load-factor control"). The OR-gate conditions that it lists include a third condition that we seem to have been unaware of so far in our discussion of the A340 AIRPROX event of October 2000.

I raised some controversy recently when I questioned the disengagement logic of AoA Law, having been led to believe that, in the A340 AIRPROX case, once AoA Law was triggered by a short-term, phase-advanced (gust-induced) identification of alpha-prot, it remained engaged until the PF finally made a substantial push on the sidestick. This seemed to be despite the fact that - after the trigger-gust subsided - the AoA and phase-advanced AoA appear to have been below the trigger threshold for a couple of seconds until the EFCS (FBW) in AoA Law selected up-elevator to increase the AoA to alpha-prot.

Accordingly, I wrote:
"...Phase-advanced alpha-protection puts the FBW into AoA Protection Law. Meanwhile, the AoA has returned (fallen) to what it was before the gust. However, FBW uses up-elevator to increase the AoA to alpha-prot. The a/c climbs suddenly until I push the stick forward more than half-travel, OR use less-than-half forward stick for more than a second."

Well, in this new report into the 2011 incident, the BEA lists the disengagement conditions as follows (newbees, note that a sidestick is spring-loaded to neutral):

sidestick forward more than half-travel;
OR
sidestick forward less than half-travel for 1 s while AoA < Alpha MAX;
OR
sidestick neutral or forward for 0.5 s while AoA < Alpha Prot.

It seems now that, either my understanding of the disengagement conditions for the A340 in 2000 was wrong, or they were subsequently modified?

PS by EDIT

Re the report appendix, am looking forward to interpretation by those who are more experienced and better than I am in interpreting FDR traces. (Mentioning no names!) In the interim, I notice that AoA Law disengages (to Normal Law) and re-engages on 5 occasions prior to its final disengagement. So there are 6 periods of AoA Law.

The first period ended in disengagement after only 8 seconds, apparently because the sidestick was released to neutral and an up-gust ceased (or a down-gust was encountered), reducing the AoA below Alpha-Prot (see the third condition listed above) for > 0.5 s. Although this restoration of Normal Law lasted less than 3 seconds, the report suggests it would have been maintained, but for the turbulence and speedbrakes, with the sidestick neutral. During this short period of Normal Law, the pitch increased rapidly from about +5 to about +8.5. The increase in pitch rate and AoA rate was so great that, when AoA Law re-engaged, it was unable to stop the AoA briefly exceeding Alpha-MAX.

Notwithstanding my doubts, expressed a few days ago, about the logic of engagement/disengagement of AoA Law (see above), the DFDR traces in this BEA Report seem to show that the periods of its disengagement may have resulted in greater divergences from normal flight parameters than when it was engaged.

One assumes that, if AoA Law was maintained, the flight profile would approximate a phugoid? That view may be supported by the last (and longest) period of AoA-Law engagement, which started just after the FL382 apogee. During the descent, the VS increases gradually to about 4000 ft/min; then decreases gradually to zero (at FL365). It is at that point that the PF applies just under half forward-stick for more than a second, disengaging AoA law.

Chris Scott

6th Nov 2013, 17:46

BOAC,

I thought that was what you meant - just checking!

As I said earlier, the "PNF" made (substantial and inappropriate) sidestick inputs, but IMO the BEA is right to continue to refer to him as PNF. We don't even know if his inputs were intentional.

Quote from OK465:
"....in the A346 & A332, the "AP OFF" ECAM message is red not amber when the A/P is disengaged with the takeover button. The red ones usually tend to get my attention.
Is it, or was it at one time, amber in the A343?....or is this a translation problem?....a tech writer problem?....or a report quality control problem?"

Must admit that red is my recollection from the A320, too, but any error is not in the translation.

Here's the French original (my emphasis):
"L’équipage n’a pas vu les différents changements d’affichage (message « AP OFF » ambre de l’ECAM, disparition de l’indication « AP1 » du bandeau FMA)."

Lonewolf_50

6th Nov 2013, 19:31

In this case, the copilot seems to have remained the PNF (i.e., as far as we know there was no formal handover of control), but made sidestick inputs - whether intentionally or not.
A pity the CVR isn't available, there may have been a brief verbal exchange which would explain that. Seems out of place.

Chris, your estimation of the "chasing" of air data sensors by the A/P in such entries into turbulent air is confusing to me.

I learned a long time ago that if you were entering turbulent air that has a lot of vertical component, that you need to work on holding pitch and power for the proper "turbulent air penetration" airspeed. You could expect both A/S and altitude to vary a bit as the air mass bounces you about.
"Don't chase it!" was some of the teaching then.

Is that still current teaching?

DonH

6th Nov 2013, 19:41

Hello, Chris Scott, OK465, BOAC;

Since AP1 was engaged at the time of the event, and re-engaged subsequent to the recovery I think the PF was the captain. While not strictly SOP, normally a left seat PF engages AP1 and a right seat PF engages AP2.

However, the captain was eating dinner, with the retractable tray out and it is common for the PNF to temporarily take over PF duties as well as communications while the other crew member is having a meal. The AP is left in AP1, again informally.

Where something like this 'interruption in smooth flight' occurs, the "PNF" would continue the PF's duties and mind the store until the PF can put the meal and tray away and resume PF duties to deal with the event.

The Report mentions and describes the incorrect priorities and evident loss of CRM and the "command-control" process as both crew members were fussing with getting the dinner tray onto the observer's seat and getting out the PA handset for an announcement. Even as we don't have the CVR, this is clearly another breakdown in cockpit discipline, placing "Communicate" ahead of "Aviate, & Navigate". Without the CVR we dont' know if control was actually, verbally handed back to the PF, ("You have control....I have control", etc).

Further, it was the PNF's SS instinctive-disconnect button that was pressed and disconnected the AP but he clicked twice on the button which cancels the aural and ECAM warnings. From long observation, pressing the instinctive button to cancel the AP warning is not atypical behaviour; - this would have been out of habit, but here the cancellation robbed the PF of information that the AP had been disconnected and the altitude alert was also missed. The BEA Report states that such cancellation of the warning was an amber AP OFF, (OK465 you know, I do recall an amber "AP OFF" ECAM message somewhere in the dim past (perhaps on the A320?), but I can't find reference to it in either older A340 or recent A330 FCOMs. I can only find "red warnings" reference, (see below). Certainly, under the circumstances of this intentional, by the instinctive button disconnect, the warning was/is always red and the AP cavalry charge continues until the button is pressed again so the BEA Report is incorrect in its reference to the "amber AP OFF" ECAM message.

The PF who was distracted getting his meal put away, was unaware that the AP was disconnected and the airplane was under manual control. The PF remained unaware until he realized that the airplane had climbed well above its cleared altitude and when he went to set the AP to descend to their cleared altitude, did not see "AP" annunciated on the FMA, (p.5 of the Report).

The Report explains the fact that it was the "PNF" who disconnected the AP, but leaves us there as to who was flying once the PNF made the HF call to advise New York Aeradio of the level bust, while the airplane was essentially still out-of-control), nor does the Report explain why the "PNF" chose to disconnect the AP and then do what he did, which was to pitch the airplane up.

The use of airborne radar has been a topic of considerable interest since June 1, 2009 particularly. I have noticed that air carriers began publishing in their FCOMs supplementary notes on the use of current radars including various techniques of using antenna tilt and gain. It's about time.

Given history and the formally recognized need to address certain cultural issues within the carrier*, I would hope that this got a thorough internal review (I wonder if their flight data program picked this up?), because, "If the AP had not been manually disengaged, it would have remained engaged; there would not have been a significant trajectory deviation, with a gain in altitude of about 200 ft.

Note: Without the high angle of attack protection, the aeroplane would have kept its ascending trajectory until the triggering of the stall warning. p.9"

*Operational Safety Review, Dec, 2009 (http://corporate.airfrance.com/en/the-company/flight-safety/independent-safety-review/) - the contents of, and I believe, links to this review have been previously reported on PPRuNe.

HazelNuts39

6th Nov 2013, 20:23

Chris,

It seems now that, either my understanding of the disengagement conditions for the A340 in 2000 was wrong, or they were subsequently modified?Both incidents have been discussed on PPRuNe when the respective reports were published. I do remember that the disengagement conditions were modified after the AIRPROX incident, but I don't remember the details.

Chris Scott

6th Nov 2013, 20:38

Hi DonH,

Think the report says the copilot only pressed the AP instinctive-disconnect PB on his sidestick once (top of Page 13)?

Am in full accord with your analysis of CRM aspects. Quite shocking mis-prioritisation of actions from start to finish of the incident. Hard to know where to start...

Yes, it also reflects my experience of the common underuse of wx radar, and misunderstanding of how to use it effectively to avoid flying into or over the upper parts of Cbs.

'Evening HN39,
Quote:
I do remember that the disengagement conditions were modified after the AIRPROX incident, but I don't remember the details.

Thanks, but it was news to me. The only recommendations in the AAIB Bulletin relate to RVSM procedures.

Chris Scott

6th Nov 2013, 21:23

Quote from Lonewolf_50:
"I learned a long time ago that if you were entering turbulent air that has a lot of vertical component, that you need to work on holding pitch and power for the proper "turbulent air penetration" airspeed. You could expect both A/S and altitude to vary a bit as the air mass bounces you about.
'Don't chase it!' was some of the teaching then. Is that still current teaching?"

Afraid I'm the wrong person to ask about current teaching! But you raise a very valid point - in line with my own experience.

However, I think the only "chasing" by the EFCS/FBW visible in the DFDR traces is of the AoA when it is in AoA Law? I can only suggest that perhaps that is inevitable, bearing in mind the (presumably) narrow margin between Alpha-Prot and Alpha-MAX at cruise Mach - not to mention the stall. (That is: I'm out of my depth here, call an aerodynamicist!)

I doubt that, at normal cruise speeds and AoAs, Normal Law would be "chasing" the AoA, or even the Nz that it has been commanded to achieve by the sidestick position.

aircrashesandmiracle

7th Nov 2013, 16:17

Although the post to which you were replying incorrectly stated that the Aeroperu 603 crash was caused by the aircraft stalling on account of the wrong PITCH was incorrect, the aircraft did finally stall.

As pointed out in my book Air Crashes and Miracle Landings--60 Narratives (http://chrisbart.com) the Aeroperu pilots flew out over the sea for safety (and presumably because there would be no mountains there did not use their radio altimeter). Not realizing that the altitude of 9,700 ft confirmed by ATC was merely that given out by their transponder in turn dependent on the barometric altimeter (not working properly due to the blocked static ports) flew into the sea.

The aircraft bounced and rose 200 ft before STALLING, inverting and falling back into the sea. Although one of engines had ingested some water on initial impact with the sea and was impaired, it might have been have been a different story had the engines not already been throttled back due to a spurious overspeed warning and had no time to spool up.

As you rightly said, blockage of the static ports is even more serious than blockage of the pitots. The AF447 pilots could see that after a considerable climb (causing the a/c to stall) they were falling downwards which is more than the Aeroperu pilots could. In the circumstances they (Aeroperu pilots) did well.

vilas

7th Nov 2013, 16:20

ChrisScott
In posts abot A340 incidents I want to clarify some misunderstanding about FBW control laws.
Alpha Lock function cannot be triggerred in clean configuration. If anything it was alpha floor protection and experienced pilot should be able to recall if it was engaged because he would have manually disconnected it.
In normal law from Valpha prot to alpha Max side stick commands alpha directly which is desirable because it gives the pilot direct control over AOA for recovery.
Alpha prot is not same value when below Vls and when at cruise speeds. In cruise it is about 5 degrees.
Once in alpha prot with stick neutral AOA does not increase but is decreased to Valpha prot. In this case phase advanced means it triggered before 5 degrees may be 2or 3 degrees. So FBW will try to maintain that and not increase as you suggest.
Manual flying skill is not a panacea for automated aircraft problems. Manually flying Airbus is very easy but it is more important to understand automation thoroughly. in this case the experienced pilot had he understood the auotmation he would not have wasted precious time trying to engage autopilot which does not engage when the protection is active.
It is necessary to study each line and between the lines of Autoflight system and Flight control system. Merely Flying 4 sectors manually everyday does not necessarily make you a better Airbus pilot. When the speed is below V alpha prot you should know that side stick is commanding alpha there is no need for any further display.

Lonewolf_50

7th Nov 2013, 16:44

Thanks to Chris, Don, and vilas. Makes a bit more sense now, with all of that presented. :ok:

OK465

7th Nov 2013, 17:15

I'm having flashbacks to the line in "A Few Good Men" when Tom Cruise is asked, "Is that clear?"

And he says, "Crystal".

Well I'll tell ya folks, even if you pitch up from 35000 feet and 265 KCAS to 20 degrees nose high with idle thrust, the lowest Mach you will see before 'prot' finally gets the nose down is about 0.58....no alpha floor.

And 0.67 was the lowest Mach recorded in the near miss.

Someone please 'splain' to me how it's possible to get alpha floor activated above 0.53. :)

Chris Scott

7th Nov 2013, 17:26

Hello vilas,

Thanks for listing many of the areas we have been discussing in relation to the A340 AIRPROX and (since yesterday) the AF A340 Incident, and summarising your understanding of them.

I particularly welcome your explanation of the Alpha Lock and Alpha Floor functions in relation to the captain's statement to the UK AAIB after the A340 AIRPROX incident. Some of us are still trying to confirm that Alpha Floor could be engaged at a speed greater than M0.53. Do you have any information?

Some of your points, however, contain significant differences from my understanding. I shall now quote them in the order of your post, and respond.

"In normal law from Valpha prot to alpha Max side stick commands alpha directly..."
I think you are referring to AoA (Protection) Law, not Normal Law? ***

"Once in alpha prot with stick neutral AOA does not increase but is decreased to Valpha prot."
I think that would be true if AoA (Protection) Law was triggered as the AoA was increasing through Alpha-Prot, but not necessarily true if the trigger criterion was phase-advanced Alpha-Prot, i.e., below Alpha-Prot.

"...phase advanced means it [is] triggered before 5 degrees may be 2or 3 degrees. So FBW will try to maintain that and not increase as you suggest."
How could it do that? I think you may be misunderstanding the principle of phase-advanced Alpha-Prot. Even if you do understand it, I think it may be helpful at this point to share my own (tentative) understanding in case it helps some of our readers. No doubt better brains than mine will correct me if necessary.
"Phase-advanced" stall-protection existed, to my knowledge, nearly 50 years ago on the VC10 and BAC 1-11. On Airbus FBW, when the AoA is increasing rapidly in Normal Law, the EFCS/FBW needs to anticipate the exceedance of Alpha-Prot and trigger/engage AoA (Protection) Law in "advance". So it is constantly extrapolating what the AoA may be a short time after the present. We do not know the precise figure of that time-period, but it is probably between 1 and 2 seconds. That means that the precise AoA at the moment of engagement is a function of the rate-of-change of AoA (i.e., delta-alpha), as well as the current value of Alpha-Prot. Delta-alpha obviously depends on a number of variables, including recent/current pilot inputs and gusts. Therefore, for the EFCS to use the engagement AoA as the target for the duration of the period of AoA Law would seem unlikely and inappropriate.
I stand to be corrected, but my money is on the EFCS targeting current Alpha-Prot - which is variable for the reasons you have implied.

"When the speed is below V alpha prot you should know that side stick is commanding alpha there is no need for any further display."
True but - sitting comfortably here on terra-firma - I would simply remind you that the speed indications on the PFD, excellent as they are, may be quite difficult to interpret when you and they are jumping up and down in severe turbulence?

*** (added by edit)
Apologies, vilas! I now see from DonH's post (below) that you are right. Although the AAIB Bulletin into the A340 AIRPROX incident of 2001 refers to it as "AoA (Protection) Law", the FCOM extracts from both 2001 and 2010 that DonH displays clearly refer to it as the "High Angle of Attack Protection" mode of Normal Law.

DonH

7th Nov 2013, 17:40

Chris Scott, Re, "Think the report says the copilot only pressed the AP instinctive-disconnect PB on his sidestick once (top of Page 13)?"

Yes, agree thanks - I had misread the para. on P13, believing that the button had been pressed a second time.

To clarify for OK465 regarding the "AP OFF" ECAM message, some collective in-depth research through historical FCOMs has revealed nothing in the way of an amber ECAM message - the "AP OFF" ECAM message is red, no matter what conditions, (instinctive disconnect on the SS, pushing the AP1/2 button, moving the SS when AP engaged, aircraft self-disconnect) the AP was disconnected under.

- edited to add: OK465, Re, "Someone please 'splain' to me how it's possible to get alpha floor activated above 0.53. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif"

Alpha-floor is an A/THR mode - (in that the A/THR is provided with AoA information and invokes Alpha-floor when other conditions are satisfied). Alpha floor is inhibited above M0.53 because, (I'm guessing here!) there probably isn't sufficient thrust to respond alone to an alpha-prot event, (meaning, the pitch must also be reduced to unload the wing/reduce AoA).

Alpha-prot on the other hand is a pitch flight-law reversion from Nz (load factor) to AoA and is not inhibited at any time, (but, logically, isn't available outside of Normal Law). This may explain why the recent "A340-2011" event moved into, and out of "Alpha-prot" several times.
-end edit

HN39, Re, "I do remember that the disengagement conditions were modified after the AIRPROX incident, but I don't remember the details. "

It appears as though the disengagement conditions were changed some time after June 01 2001 and prior to July 01 2010:

http://batcave1.smugmug.com/photos/i-RB8j9ft/0/XL/i-RB8j9ft-XL.jpg

Chris Scott

7th Nov 2013, 20:00

'Evening DonH,

See you've finally confirmed by the 2010 FCOM the third condition that was in the BEA Report of 2011 into the AF A340 Incident - but absent from the AAIB Bulletin about the A340 AIRPROX.

Thanks for posting the relevant extracts of a 2010 FCOM and a 2001 FCOM. We can infer that the 3rd condition/criterion may have been added as a result of the A340 AIRPROX event, although the AAIB's recommendations did not include it.

As one who has recently been arguing for easier disengagement conditions than those that seem to have applied at the time of the A340 AIRPROX, I must reiterate that the AF A340 Incident of 2011 does little to support that contention, as I admitted yesterday (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-35.html#post8138531).

Re. Alpha Floor inhibition
Do you have access to FCOM 2.22.30? Does it mention an inhibition at speed > M0.53?

DonH

7th Nov 2013, 22:34

Hello Chris Scott, Re, "Re. Alpha Floor inhibition
Do you have access to FCOM 2.22.30? Does it mention an inhibition at speed > M0.53? "

Yes, M0.53 is mentioned in relation to an A/THR Reversion Mode, (but not a change from Nz to AoA law - that is a different matter, I think): - from 2.22.30 in an FCOM:

A/THR MODE REVERSION
For detail refer to “Speed mode protection”.

Alpha floor
The ALPHA FLOOR protection is triggered when the FMGCs receive a signal elaborated by the PRIMs. This signal is sent when the aircraft angle of attack is above a predetermined threshold function of the aircraft configuration. The A/THR is automatically activated and commands TOGA thrust regardless of thrust lever positions. This protection is available from lift off to 100 feet RA in approach.

Following indications are then provided :
– A-FLOOR on the FMA and on the EWD as long as α floor conditions are met;
– TOGA LK on the FMA when the aircraft leaves the α floor conditions.

TOGA thrust is then frozen.

A FLOOR and TOGA LK are displayed in green and surrounded by an amber flashing box.

In order to cancel the ALPHA FLOOR or TOGA LK thrust, disconnect the A/THR.

Note: Alpha Floor is inhibited :
– in case of engine failure with flaps extended
– in case of engine failure with derated TO selected
– below 100 feet at landing
– above M.53

Alpha Floor protection is lost in case of A/THR failure.I have to say that the differences between "Alpha-prot" and "Alpha-floor" have eluded me all these years, perhaps even still !

In addition to the FCOM descriptions of both, I think there is some imprecise use of terms in the FCOM, specifically the word, "protection". The word is used in both contexts to describe "prot" and "floor" and so is informal, whereas the terms alpha-prot, (or "α prot") and alpha-floor are formal terms.

I think the words, "prot" and "floor" are being understood as inter-changeable but am thinking that they are not. I think it is significant that "alpha-floor" is discussed only in ATA22 (Autoflight) but "alpha-prot" is not. Alpha-prot is only discussed in ATA27 (Flight Controls), with "alpha-floor" only being used in the context of, and with reference to, "alpha-prot".

Put differently, I think one can be in "alpha-prot", (a pitch-law mode) without being in alpha-floor, (an A/THR mode), but one cannot be in alpha-floor without first having "gone through" alpha-prot. The schematic in the graphic above even shows this.

So you can be in "alpha-prot" at any Mach number, but alpha-floor mode is restricted as described in the para. from the FCOM.

The important key to understanding this and using all this information from a pilot's pov is to remember what Chris Scott has outlined in the discussion on "disengagement of the AoA law". Both the AirProx and the A340 2011 Events were controllable either by leaving the stick alone, (but that leaves the airplane to "select" Max AoA in a phase-advanced scenario and is therefore not a good option), or to take control to gently push the stick forward to take the airplane back to Nz law (because, as has been observed previously, one is 'unloading the wing', so to speak) and deal with the airprox on the one hand, and sort out the mess the crew of the A340 - 2011 made for themselves on the other.

Chris Scott

7th Nov 2013, 23:23

Thanks Don,

That nails it in line with what OK465 has been telling us all along?

My (perhaps simplistic) understanding has always been that Alpha-Prot and Alpha-MAX relate to the flight control laws, whereas Alpha-Floor is purely an A/THR mode, albeit an extremely powerful one at low altitudes.***

AFAIK, Alpha-Floor is always higher than Alpha-Prot. As you know, it has always been necesssary to inhibit Alpha-Floor below a certain height on landing (IIRC, 50R on the A320, but I see 100R on the big 'buses), although it was widely thought that one fellow captain did not take that into account during his cavalier fly-by at Habsheim...

Quote from OK465:
Well I'll tell ya folks, even if you pitch up from 35000 feet and 265 KCAS to 20 degrees nose high with idle thrust, the lowest Mach you will see before 'prot' finally gets the nose down is about 0.58....no alpha floor.

YES...! :ok:

***(by edit)
You may not be aware that AI originally introduced Alpha-Floor on the A310 in 1983. The A310 has conventional flying controls (except for the roll-spoilers, which are FBW). So, on the A310 and A300-600, you have to push very hard if Alpha-Floor engages...

DonH

7th Nov 2013, 23:34

Hello Chris;

Re, "That nails it in line with what OK465 has been telling us all along?"

Yes, I think so! So I probably mis-read his comment about 'splainin' how alpha-floor can occur below M0.53! - it was a statement, not a question! Ahh, me.

CONF iture

8th Nov 2013, 00:00

As you know, it has always been necesssary to inhibit Alpha-Floor below a certain height on landing (IIRC, 50R on the A320, but I see 100R on the big 'buses), although one fellow captain did not take that into account during his cavalier fly-by at Habsheim...
Please do not spread disinformation, that captain was definitely not relying on A-FLOOR to get the thrust on.

CONF iture

8th Nov 2013, 00:22

Both incidents have been discussed on PPRuNe when the respective reports were published. I do remember that the disengagement conditions were modified after the AIRPROX incident, but I don't remember the details.
DonH has now confirmed that earlier comment (http://www.pprune.org/6435681-post874.html)

Winnerhofer

8th Nov 2013, 07:41

@ DonH
AlphaFoor is strictly A/THR and only triggers within certain parameters.
It also triggers based on a set of variables not just indicated airspeed.
No relation to AlphaProts in flight controls other than Normal Law must be active.

vilas

8th Nov 2013, 12:02

Valpha prot is the AOA threshold from where the side stick will command AOA directly instead of load factor demand. Valpha max is the maximum AOA that flight control computers will let the side stick achieve and/or hold. With AP is off and side stick neutral if the aircraft is pitched up beyond Valpha prot due to disturbance it will try to pitch down to Valpha prot and not pitch up to alpha Max. If the pitch up is rapid then Phase advance will bring this threshold to a lesser value. The effect of activation of this protection mode is that trim freezes at entree point and the aircraft will stabilize at that AOA when stick free, But Pilot's action in A340 case would be same push forward to stop climb and that would bring flight controls out of protection mode to load factor demand which was not done and instead attempt was made to engage AP which does not engage when in protection. So this incident is not attributable to FBW characteristic.

Chris Scott

8th Nov 2013, 13:34

Quote from vilas (my underscoring emphasis):
"With AP is off and side stick neutral if the aircraft is pitched up beyond Valpha prot due to disturbance it will try to pitch down to Valpha prot and not pitch up to alpha Max. If the pitch up is rapid then Phase advance will bring this threshold to a lesser value."

In an otherwise accurate and succinct analysis, I think you may still be confusing the phase-advanced threshold of an AoA-mode engagement with the target AoA once AoA mode is engaged. For the reasons I stated in my earlier reply to you, with neutral sidestick that target can only be Alpha-Prot itself; not the AoA value at its phase-advanced engagement, which has no further relevance.

vilas

8th Nov 2013, 14:32

Chris
I am in agreement with you that after initial lowering of threshold subsequently it will stabilize at actual V alpha prot because the purpose of phase advance is to preempt the change over point. I was explaining the normal change over at Valpha prot.

vilas

8th Nov 2013, 16:25

Chris
Somewhere you have said "So my question remains: why does it not revert to Normal Law once the AoA falls to a safe value?" I take it you mean normal AOA (Vls)
Let me attempt to answer that. Basically the high angle of attack protection is provided to prevent stall while dealing with wind shear or terrain issues where you are likely to deliberatally invoke the protection. When the angle of attack has fallen to a safe value (I presume it as less than alpha Max) any attempt to increase speed beyond Valpha prot by lowering the pitch is left to the pilot as conscious decision. If it was automatically done without assessing the situation it would have been unsafe.
You will remember that when you change from NAV to HDG, CLB changes OPCLB but in descent it does not change to OPDES but to present VS. The reason is same. In CLB or OPCLB the thrust is in THR CLB but in DES it need not be in thrust idle and in such a case change to THR IDL as it would in OPDES will pitch the aircraft down increasing ROD. So this is left to the pilot as a conscious decision.

DozyWannabe

8th Nov 2013, 18:18

Please do not spread disinformation, that captain was definitely not relying on A-FLOOR to get the thrust on.

I don't think Chris was intentionally misinforming - let's face it, the story has been misremembered and re-told in slightly different ways so many times over the years - especially in the media - that deviations like that are pretty much the norm. It's pretty much only pedants like me and you who are militant about getting it right! :8

DonH has now confirmed that earlier comment (http://www.pprune.org/6435681-post874.html)

Indeed - however your comment here:

Nothing is that simple with the airbus, a very complex machine indeed.

seems at odds with what was actually changed. It used to be that to cancel AoA protection - in which the nose comes up - one had to push the nose back down, which seems reasonably intuitive to me. The change meant that leaving the stick in neutral for a certain period of time would also return you to Normal Law - again, not exactly rocket science.

HazelNuts39

8th Nov 2013, 19:03

The change meant that leaving the stick in neutral for a certain period of time would also return you to Normal Law - again, not exactly rocket science.It may just need a little help from atmospheric disturbances. Without those, it would just maintain alpha-prot in a phugoid motion which may be damped.

P.S. I think you mean Nz-law. The 'normal' protections are included in Normal Law, and may not exist in Alternate Law.

DozyWannabe

8th Nov 2013, 21:32

Agreed. Picky, picky, picky... ;)

Chris Scott

9th Nov 2013, 00:01

Quote from Dozy Wannabe:
"I don't think Chris was intentionally misinforming - "

I don't think anyone will ever know for sure, so - more out of respect for Conf_iture than the gentleman concerned - I amended my post this morning to reflect fact, rather than supposition.

Hi vilas,

I like your explanation of why AoA mode used to remain engaged until a sidestick was displaced forward (as in the first two disengagement conditions listed in the FCOMs posted by DonH). The interesting development is that, sometime after the A340 AIRPROX incident of 2001, the introduction of the third disengagement condition seems to have been completed across the fleet.

The third disengagement condition is not unlike what I was proposing a few days ago in reaction to the A340 AIRPROX. (That was prior to HN39 drawing our attention to the BEA Report into the AF A340 Serious Incident of 2011.) I was concerned that a short-term up-gust had triggered AoA mode by phase-advance, and AoA mode had initiated the undesired climb with neutral sidestick which the crew were (admittedly) slow to correct.

Having studied the traces provided by the BEA of the AF A340 incident, where the third disengagement condition operated five times, I am reviewing my opinion. The first disengagement into normal (Nz) mode was, as you know, shortly followed by a significant exceedance of Alpha-MAX. It seems probable that the wing effectively stalled at that point, which probably would not have happened but for the temporary disengagement of AoA mode.

DozyWannabe

9th Nov 2013, 00:52

Having studied the traces provided by the BEA of the AF A340 incident, where the third disengagement condition operated five times, I am reviewing my opinion.

Chris - the ultimate question at the end of the day is "how much hand-holding is a good idea to provide?". It's reasonable to assume that Alpha Prot and Alpha Floor as designed were in the main intended to assist a pilot who is already commanding nose-up with the stick, such that the pilot's command is followed to the best of the aircraft's ability while the aircraft remains flying. In this airprox incident we have a situation where one or both of the alpha protection modes were triggered by transient weather conditions, which were outside of the original spec.

Contrary to legend, the protections were designed to assist a pilot who, for whatever reason, has been forced to take the aircraft to the edge of the safe operating envelope - counteracting handling mistakes is and always was a secondary design consideration.

In this case we have an incident during which - for whatever reason - a protection mode has actually had a negative impact on the safety of the flight, hence the change in logic.

vilas

9th Nov 2013, 08:33

Chris &Dozy
Some more thoughts on the A340 incident:

The report states “ The over speed warning(“OVERSPEED”) was triggered(3) andthe “Master Warning” warning light came on. The crew stated that they were very surprised by this warning. Mach reached 0.87.” The warning is set to trigger at MMO+.006 i.e.M.866 and it triggered correctly why was the crew surprised? The report says “during the event the high speed protection was not activated”. This is surprising as it should have activated and according to A340 FCOM “The autopilot disconnects when high speed protection goes active”.

The report says” F-GLZU recorded data showed that the AP would have remained connected if it had not been manually disengaged”.I don’t see any guarantee of this as high speed protection should have activated or was about to activate and that would have disconnected the AP.

Then the PF disconnected the AP and applied ¾ back stick which put the aircraft in high AOA protection.

“From the start of thepitch-up input until point n°9, the high angle of attack protection was activated several times”. This statement has been misunderstood by some bloggers as automation causing unnecessary pitch up to Valpha MAX. This is not what happens in AOA protection rather it only can cause pitch down to Valpha prot with stick neutral. However if AOA is left at Valpha prot then the mode of pitch control may keep changing from load factor to AOA mode as the AOA changes due to disturbances. That is not same as pitching up and down. The only thing is if left alone, in AOA mode it will stabilize at alpha prot speed. In any case Pilot’s action should have been to push the nose down and recover the speed. So automation has not played any adverse role in this.

CONF iture

9th Nov 2013, 10:08

The change meant that leaving the stick in neutral for a certain period of time would also return you to Normal Law - again, not exactly rocket science.
This has nothing to do with 'returning to Normal Law'.
Your approximations generate confusion on a complex System that on top of it keeps changing with time.
As 'it is not exactly rocket science' why do you get it wrong then ... ?

CONF iture

9th Nov 2013, 10:13

AFAIK, Alpha-Floor is always higher than Alpha-Prot. As you know, it has always been necesssary to inhibit Alpha-Floor below a certain height on landing (IIRC, 50R on the A320, but I see 100R on the big 'buses), although it was widely thought that one fellow captain did not take that into account during his cavalier fly-by at Habsheim...
Sorry Chris but I just can't understand your thinking here as part of the procedure to present the Airbus at high AoA is specifically to inhibit A/THR to prevent Alpha Floor to spoil the demonstration.
How can you suggest the guy was waiting for Alpha-Floor to kick in when his initial intention was to prevent it to interfere in the first place ?

vilas

9th Nov 2013, 14:13

DozyWannabe

"It used to be that to cancelAoA protection - in which the nose comes up - one had to push the nose backdown, which seems reasonably intuitive to me. The change meant that leaving thestick in neutral for a certain period of time would also return you to NormalLaw - again, not exactly rocket science".
I am sorry but it appears that you have completely misunderstood normal law and protections. Normal side stick fore and aft movement is a load factor demand and computers position elevator and stab to give you that. Pitch control through load factor demand has an advantage in that aircraft response remains same at all speeds. High angle of attack protection which begins at Valpha prot the pitch control is changed to directly achieve through AOA change and not through load factor demand. Valpha Max is maximum AOA aircraft can be pitched upto. When the angle of attack increases deliberately as in case of wind shear and GPWS issues or through atmospheric disturbance the pitch control is changed to AOA mode since that is more appropriate for the situation, this does not mean aircraft pitches to alpha max, rather it tries to pitch down to alpha prot which is the first low speed threshold and pilot has to overcome it by backward pressure if he wants more pitch up.. If you release the stick aircraft will pitch down and maintain that AOA (Valpha prot). If the contingecy is over and you want return to normal speed you push the stick forward as you would do in any aircraft and the pitch control changes back to load factor demand. You have to remember that only method of pitch control is changed aircraft doesn't pitch up on its own. During all this aircraft remains in normal law. In the incident we are discssing the protection mode had no negative impact whatsoever. It is definitely not rocket science but you have not understood it at all.

HazelNuts39

9th Nov 2013, 14:51

You have to remember that only method of pitch control is changed aircraft doesn't pitch up on its own. During all this aircraft remains in normal law.With the sidestick left in neutral the airplane will pitch up on its own -

-- in AoA law at alpha=alpha-prot if the speed is greater than Valpha-prot
-- in Nz law when the pitch attitude is greater than the pitch which will maintain constant airspeed - AoA increases to maintain Nz=1 when airspeed reduces.

vilas

9th Nov 2013, 15:53

HN39
With the sidestick left in neutral the airplane will pitch up on its own -

-- in AoA law at alpha=alpha-prot if the speed is greater than Valpha-prot
-- in Nz law when the pitch attitude is greater than the pitch which will maintain constant airspeed - AoA increases to maintain Nz=1 when airspeed reduces.
No way. I think you should read flight controls chapter. It is high angle of attack protection. It begins at alpha prot. A protection can only be called protection when it prevents the pilot from doing it. In high speed protection if it pitches down it is not a protection it is destruction. Similarly in high AOA protection if AOA increases what kind of protection is that? Your first case, the speed is greater than Valpha prot you are not at all in any protection zone and side stick commands load factor so why would it go to alpha prot? If you intentionally keep pitching up it pitches up to alpha max and no more. if you release the SS it will not maintain alpha max but pitch down to alpha prot.

Chris Scott

9th Nov 2013, 16:17

vilas,

I agree with nearly all of your latest thoughts (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-36.html#post8142870) about the AF A340 Incident. You make some valid points, including the apparent discrepancy in relation to the overspeed protection. The latter had disengaged the AP in the A340 AIRPROX of 2001, but seemed already overdue to do so on the AF A340 when the backward movement of the F/O's sidestick manually disengaged it. Like you, I find the BEA statement that you quote to be confusing.

Where our respective understandings do still differ, however, is in what may happen after AoA-mode engages by phase-advance resulting from a brief up-gust.

It's worth noting here that the extra (3rd) disengagement condition available on the a/c in the AF A340 incident of 2011 caused the first 5 of the 6 reversions to Nz mode, for which the sidestick remained neutral. In the case of the A340 AIRPROX incident, where the 3rd condition had not been incorporated, AoA mode consequently persisted throughout the main event - even after a small push-forward on the sidestick for less than a second - until instantly disengaged by a selection of more than half-forward sidestick.

Quote (my emphasis):
"This is not what happens in AOA protection rather it only can cause pitch down to Valpha prot with stick neutral."

I disagree here, as I tried to explain in my last reply to you. A brief up-gust can cause the phase-advanced value of AoA to exceed alpha-prot briefly. Actual AoA can remain below alpha-prot, and when the up-gust ceases the phase-advanced value will return to the real AoA. Meanwhile, however, AoA mode has engaged. Under the present-day three-condition disengagement logic, AoA mode would disengage after 0.5 sec if both sidesticks were neutral. Under the two-condition disengagement logic in the A340 AIRPROX of 2001, it would remain engaged with neutral sidesticks. So in the latter case the EFCS will have to increase the AoA to Alpha-Prot, which will probably involve a pitch-up. This is what I think happened in the AIRPROX case, and why I questioned the disengagement criteria.

One of the vulnerabilities of my argument in the A340 AIRPROX case is that, AFAIK, we don't have any estimates for what would have happened to the pitch (and, therefore, the flightpath) if the AoA mode had reverted to Nz, delivering 1.0 G for the long period that the sidesticks remained neutral.

Quote:
"In any case Pilot’s action should have been to push the nose down and recover the speed. So automation has not played any adverse role in this."

Your first sentence is correct for both events. Your second sentence is arguable in the A340 AIRPROX case, as I've explained above. In the AF A340 case, however, the F/O's early action (pulling the stick) was - like AF447 - what started the zoom-climb. Once he had released the stick, the AoA mode was free to disengage each time the AoA happened to fall below Alpha-Prot for half a second. Each time, Normal mode targeted 1.0G, which on 5 occasions led to re-engagement of AoA mode. As previously noted, the first re-engagement was too late to prevent an exceedance of Alpha-MAX (perhaps in a gust).

These two events may present conflicting arguments for and against the third disengagement condition. I suspect that AI engineers may have been revisiting AoA-mode engagement and disengagement criteria since 2011.

Owain Glyndwr

9th Nov 2013, 16:40

No way. I think you should read flight controls chapter. .Vilas,

I think you will find that HN39 understands flight mechanics as well as any writing in these pages.
Although I agree with much of what you write, I think you nevertheless have some things wrong:

Alphaprot is NOT the same as normal law, so when you wrote:

You have to remember that only method of pitch control is changed aircraft doesn't pitch up on its own. During all this aircraft remains in normal lawthis was not correct.

I think you are failing to distinguish between angle of attack and pitch. When HN39 writes
With the sidestick left in neutral the airplane will pitch up on its own -

-- in AoA law at alpha=alpha-prot if the speed is greater than Valpha-prothe is properly relating the flight dynamics. With stick neutral, alphaprot will control the aircraft to a constant AoA, to whit the alphaprot for the applicable Mach Number. It controls AoA; it does NOT control pitch. If the airspeed at this time is greater than that appropriate to 1g at alphaprot then the aircraft will develop a normal acceleration and start to change its flight path. Unless corrected by a change in pitch this will result in a change in AoA. But the system is trying to control to a constant AoA so it must apply a pitch up to compensate. This, I think, is what HN39 is alluding to.

Chris Scott

9th Nov 2013, 16:51

Quote from Dozy Wannabe (my insertions in square brackets):
"In this [A340 AIRPROX] case we have [had] an incident during which - for whatever reason - a protection mode has actually had a negative impact on the safety of the flight, hence the change in logic."

Hi Dozy,

Prior to our attention being drawn to the AF A340 case, I caused some controversy here by opining that the disengagement criteria for what we are now calling the AoA mode (of Normal Law) should be relaxed. I'm now having second thoughts, because the new (third) criterion MAY have allowed the AF A340 to stall during the second engagement of AoA mode. This followed a brief (3-second) resumption of Nz mode, during which the a/c pitched up by about 4 degrees.

vilas

9th Nov 2013, 17:46

Owain Glyndwr
My comments are strictly based on Airbus documents and I don't lay any claims to greatness. I am aware that some of the people who comment here have better qualifications than i have.
The way FCOM describes this chapter is responsible for some confusion. First these are protections and they are available only in normal law. What is described as load factor law or AOA law are in facts modes of normal law Valpha prot is the defining boundary. FCOM is quoted below
HIGH ANGLE OF ATTACK PROTECTION
Innormal law, when the angle-of-attack becomes greater than α PROT, the systemswitches the elevator control from normal mode to a protection mode, in which the angle-of-attack is proportional to sidestick deflection. That is, in the α PROT range, from α PROT to α MAX, the sidestick commands α directly. However the angle-of-attack will not exceed αMAX, even if the pilot gently pulls the sidestick all the way back. If the pilot releases the sidestick, the
angle-of-attack returns to α PROT and stays there.

I don't see where is the problem?

gums

9th Nov 2013, 17:50

OG has the best description of the "laws" I have seen in many moons.

The discussion here amongst the heavy pilots emphasizes a point I have made ( fire a way Doze) , and several others, that you must have a simple degredation sequence when so many aspects of flying the jet are not pure hydraulics with minimal inputs like dampers and such.

I would think that the primary "law" would be related to AoA. You know, the basic parameter that keeps us using all those lifties. Overspeed comments here puzzle me, as most bent wing jets airfoils can safely get to higher mach than is normal for cruise. Even near "critical mach", there should be some aero feedback to the pilot that controls are reversing, an unusual buffet, and so forth. I only flew one jet that had a nasty tendency if close to the critical mach, and the sucker would "tuck" and unless you could pull back power and extend speed brakes then you were toast. It was a straight wing attack jet. 20 or 30 knots below the bad zone you would start having aileron problems, so I never flew the thing that fast again on bombing runs.

My main point is that the 'bus has so many "protections" and so many conditions when one "protection" is active and another is not. Sheesh.

IMHO, pilots need to have control logic that they can hang their hat on. I don't think I could pass a test on all the reversion modes of the 'bus and the sub-modes. Of course, none of this applies to those jets that are not fully FBW and have a plethora of Otto inputs to the same.

Owain Glyndwr

9th Nov 2013, 17:55

I don't see where is the problem?The problem is, or was, that you are, or were, claiming that HN39 was wrong to suggest that the aircraft would pitch up with neutral sidestick in certain circumstances.

If you want to say that it is merely a 'mode' of the normal law then fine, do so. But for me it would be truer to say that it is another control law which can only be accessed from normal law. In practice there is no similarity between the two things. In normal law stick movement commands 'g' in alphaprotect it commands AoA; in normal law there is a C* feedback, in alphaprotect there is no such thing.

vilas

9th Nov 2013, 18:13

Chris
I think your assumption of post phase advance needs to be modified. Let's say Valpha prot is 5 degrees (in cruise) and rapid increase in angle of attack causes protection mode to engage at 3 degrees but the rapid pitch up will take it past 5 degrees and when the gust has passed it will pitch down to 5 degrees. Where is the problem? If pitch up was gradual there won't be any phase advance and it would have engaged at 5 degrees and it will resist any more pitch up if possible or will come down to alpha prot when possible. Valpha Max gets adjusted and it is successfull maintained even in windshear. You cannot compare 447 because it was in alternate2. There is another likely misunderstanding about change in AOA mode to Load factor mode. From FCOM below
Thesystem will regain the normal load factor law if the stick is pushed forward ofneutral, but it will re-enter alpha protection if the stick is released with the angle of attack still greater than the value set for alpha protection. Thus to exit alpha protection properly, the pilot should reduce angle attack to a value less than the value set for alpha protection.

These are only mode changes and not pitch ups.

Chris Scott

9th Nov 2013, 18:15

Quote from Conf_iture, re the A320 Habsheim accident of 1988:
"Sorry Chris but I just can't understand your thinking here as part of the procedure to present the Airbus at high AoA is specifically to inhibit A/THR to prevent Alpha Floor to spoil the demonstration.
How can you suggest the guy was waiting for Alpha-Floor to kick in when his initial intention was to prevent it to interfere in the first place ?"

Salut Confit,

My off-topic reference to Habsheim was merely to illustrate that speed greater than M0.53 is not the only inhibition criterion for Alpha-Floor.
What you say suggests the game plan was even more cavalier than I remembered, and my memory of the tortuous, much-criticised investigation has faded.

That accident was 25 years ago, in our first summer of A320 ops. We fellow A320 pilots were naturally riveted by the excellent camcorder footage of the a/c descending gently into the treetops as the engines spooled up. Much speculation followed, but it was clear to us that the a/c had stabilised safely at Alpha-MAX, but lacked enough thrust to maintain its height.

I assumed the plan had been to stabilize at about Alpha-Prot, maintain height at that speed by increase of manual thrust while passing in front of the crowd, and then go-around. It never occurred to me at the time that the crew would have been reckless enough to attempt to stabilise at Alpha-MAX, as you seem to believe, disabling Alpha-Floor to enable that. I presumed that Alpha-Floor was being retained as a back-up, but that its inhibition below a certain height had been overlooked.

Chris Scott

9th Nov 2013, 19:15

Quote from vilas:
Let's say Valpha prot is 5 degrees (in cruise) and rapid increase in angle of attack causes protection mode to engage at 3 degrees but the rapid pitch up will take it past 5 degrees and when the gust has passed it will pitch down to 5 degrees. Where is the problem? If pitch up was gradual there won't be any phase advance and it would have engaged at 5 degrees and it will resist any more pitch up if possible or will come down to alpha prot when possible.

Forgive me, but I'm finding it difficult to be sure which of your figures are AoA, and which are Pitch. My original concern about AoA-mode was that, if engaged by a brief up-gust, it may initiate the entry to a zoom climb with zero stick. This may have happened in the A340 AIRPROX incident, although the overspeed was also a factor in the pitch-up.

We seem to be repeating ourselves?

HazelNuts39

9th Nov 2013, 20:46

... although the overspeed was also a factor in the pitch-up.
Was it ? ....

A33Zab

10th Nov 2013, 00:55

If you want to say that it is merely a 'mode' of the normal law then fine, do so.
But for me it would be truer to say that it is another control law which can only be accessed from normal law

AoA law (ALPHA 1 law) is a 'NORMAL' law.
In 'ALTERNATE 1' ALPHA 1 law is replaced by ALPHA 2 law.

Let us see what airbus has to say:

Control laws referred to as 'NORMAL'

- Roll and Yaw

in flight

Lateral normal law
on ground

Lateral ground law
- Pitch

in flight

Nz law
High angle-of-attack protection (ALPHA 1 law) [replaces Nz law]
High speed protection (VMO 1 law) [modified Nz law)
Pitch attitude protection [modified Nz law]
at flare

Flare law
on ground

Pitch direct law on ground

text between brackets is mine.

aterpster

10th Nov 2013, 01:07

Help me AB guys.

Had the pitot heaters not been frozen over the AB laws would not have allowed the AF crew to crash into the ocean. Do I have that correct?

CONF iture

10th Nov 2013, 02:52

Chris, more than anything, why Habsheim has not a thread on its own ...?

I assumed the plan had been to stabilize at about Alpha-Prot, maintain height at that speed by increase of manual thrust while passing in front of the crowd, and then go-around. It never occurred to me at the time that the crew would have been reckless enough to attempt to stabilise at Alpha-MAX, as you seem to believe, disabling Alpha-Floor to enable that.
Taking advantage of the electronics it is much easier to stabilize at Alpha-Max, A/THR system being disconnected for the remainder of the flight, than trying to find Alpha-Prot without triggering Alpha-Floor.

vilas

10th Nov 2013, 04:24

Chris
It is not that I am averse to consider your view but in absence of any specific document or evidence I am unable to understand it. I am always looking for more information. I found something that may interest you. The change to AOA protection mode disengagement was done through MOI in 2005. With this software change AOA protection is no longer active when alpha is less than alpha prot and side stick has not been deflected since the last autopilot disconnection.

HazelNuts39

10th Nov 2013, 08:19

No way. I think you should read flight controls chapter.I think a quick look at the annex of the BEA report proves my point.
The sidestick was neutral between 01:00:33 and 01:02:06. During this time the pitch attitude increased "on its own" from 4 to 12 degrees, reduced to zero and increased again to 6 degrees.

Chris Scott

10th Nov 2013, 11:20

vilas,
Thanks for the following information (my emphasis):
"The change to AOA protection mode disengagement was done through MOI in 2005. With this software change AOA protection is no longer active when alpha is less than alpha prot and side stick has not been deflected since the last autopilot disconnection."

Must say that the part that I've underlined is news, and doesn't concur with the 2011 FCOM extract posted here by DonH, or the BEA Report into the AF A340 Incident of 2011.

Have you quoted the MOI in 2005 verbatim? If so, in an identical repeat of the A340 AIRPROX of 2001, it would have prevented the engagement of AoA mode (referred to by the AAIB as AoA protection Law). Taken literally, that would represent a radical inhibition of engagement, not an additional means of disengagement.

If, on the other hand, "is no longer active" actually means "will disengage", it would be an additional means (condition, or criterion) for disengagement. But it would not apply if either sidestick had been moved during a period of hand flying. That would seem odd, but perhaps I'm overlooking something.

Chris Scott

10th Nov 2013, 14:38

Quote from me, commenting on A340 AIRPROX of 2001:
"... although the overspeed was also a factor in the pitch-up."

Reply from HN39:
"Was it ? ...."

I'm rather hoping you can answer that, HN39. After the overspeed of Mach triggered the disengagement of the AP, was the peak Mach of M0.882 corrected by EFCS overspeed protection, involving a pitch-up with neutral sidesticks?

There are obstacles facing many of us when reading the AAIB Bulletin.
(1) After AP disengagement, the precise timings of the increase in speed from M0.855 to M0.882, and the rate of speed decay thereafter, are not included in the narrative.
(2) The absence of a trace of the Mach parameter in their DFDR presentation. Many of us are unable to apply the necessary parameters of SAT and FL to calculate Mach from the CAS trace. So we cannot observe the changes of Pitch alongside Mach. An associated, perhaps minor, difficulty is the unclear annotations on their time scale.
(3) We do not have the overspeed-protection criteria pertaining to the a/c at that time. Was an overspeed of about M0.02 sufficient to trigger it?

On the other hand, did the rise of CAS in itself cause or contribute aerodynamically to the pitch-up? And what effect would such a rise of pitch have on the AoA, and its rate-of-change?

DozyWannabe

10th Nov 2013, 14:55

I am sorry but it appears that you have completely misunderstood normal law and protections.

As it happens I'm pretty au fait with it. I did however phrase it somewhat badly - probably my fault for posting under the influence. I wasn't saying that protection *causes* the nose to come up, I was saying that when the protections are active, the pitch angle will invariably be nose-high, therefore putting the nose down to reduce the AoA - and disengage the protection - should be a fairly intuitive action for a pilot.

@CONF - I've invited you on several occasions to start your own Habsheim thread in AH&N (the logical place to have it, as the incident is over two decades old) - but you have not as yet done so.

@Chris - I think we do know that Alpha Floor was not a consideration for the pilot of AF296, as he *disabled* A/THR (and thus A. Floor) by holding down the disconnect switches to perform the flypast.

OK465

10th Nov 2013, 14:55

That is interesting HN39, but is it FCS elevator related?

Is the pitch variation because of the frozen trim in 'prot' and a potential for a speed change due to say pilot commanded thrust variation (basic speed stability)....with varying degrees of FCS 'AND' elevator command at times to hold alpha prot during the flight path changes either direction? I'll have to go back and find those traces for N1 and elevator and trim.

Hands off SS, I'm not sure that the FCS will ever command ANU elevator in a 'prot' situation. But I could be wrong. Range and direction of possible neutral SS FCS elevator commands in 'prot' seems to me to be the real question.

From a flight path stable entry to alpha prot with constant thrust, the elevator only goes 'AND' or neutral. Maybe the pitch/FPA variation has more to do with the trim effect during the FPA stable periods 'prot' was exited. But I may be missing something here as to the strange air mass effects.

(edit: I see Chris Scott is asking some of the same type questions.)

DozyWannabe

10th Nov 2013, 15:11

I thought the Airprox theory was along the lines of:

Gust triggered overspeed warning, probably engaging high-speed protection
High speed protection raised the nose - possibly only a degree or so
Second turbulent gust erroneously triggered either alpha protection or alpha floor
If it was alpha prot, then the existing thrust settings were sufficient to cause the aircraft to climb as a result of the false overspeed protection
Or if it was alpha floor, the increase in thrust caused the aircraft to climb in the same manner

We know from AF447 that at cruise level, there was enough kinetic energy at cruise thrust settings to allow the aircraft to climb when the PF pitched the nose up. So in the case of the airprox, an increase in thrust caused by A. Floor would not be necessary to make that aircraft climb.

"What's it doing now"? Simple - it's nose-high and climbing. Best get the nose down and back to our cleared FL, then. No need to worry about laws, modes, or pushing buttons - just do the intuitive thing and the aircraft's systems will comply in a fairly transparent manner.

Chris Scott

10th Nov 2013, 17:49

Quote:
"Help me AB guys.
Had the pitot heaters not been frozen over the AB laws would not have allowed the AF crew to crash into the ocean. Do I have that correct?"

Hi aterpster,

Yes, we've rather shifted off topic... Probably in our efforts to increase our understanding of Airbus FBW, and its evolution, and thereby the mechanisms of FBW and CRM that were involved in AF447. Sometimes the shortest questions are the toughest to provide a short and straight answer! As none of the experts has picked up your question, I'll give it a go.

In your middle sentence, if we replace the clause "...would not have allowed the AF crew to crash into the ocean" with "...would not have allowed the a/c to enter and maintain a stall, even with the sidesticks fully back", the sentence would be correct. As it is, it's plainly wrong.

HazelNuts39

10th Nov 2013, 18:17

Chris Scott

Reply from HN39:
"Was it ? ...."

I'm rather hoping you can answer that, HN39. After the overspeed of Mach triggered the disengagement of the AP, was the peak Mach of M0.882 corrected by EFCS overspeed protection, involving a pitch-up with neutral sidesticks?Why me? I probably know much less of the airplane than you do. My understanding is that activation/deactivation of any protection is recorded by the DFDR by a dedicated discrete parameter changing from OFF to ON, from ZERO to ONE, or whatever, and vice versa. (*) I think it would have been a very strange omission if overspeed protection had been activated and caused the pitch-up and the AAIB report had made no mention of that fact. It says instead: "For 18 seconds after the autopilot disengaged the aircraft remained within 200 feet altitude of FL 360 but once AoA law was invoked at 14:21:50 hrs, the aircraft’s attitude began to pitch nose-up."

On the other hand, did the rise of CAS in itself cause or contribute aerodynamically to the pitch-up? And what effect would such a rise of pitch have on the AoA, and its rate-of-change? Perhaps Owain G is better placed to answer that question. I think that an increase of CAS does not cause a pitch-up. It causes an increase of lift, and hence loadfactor ('gee'), and an AND response of the FCS in Nz law.

(*) A single byte in the data frame can contain up to eight 'discretes', each bit indicating the on/off status of a particular system function.

P.S.
I found a rather interesting description of the phase-advance logic for the A320 in this accident report:
"http://www.rvs.uni-bielefeld.de/publications/compendium/incidents_and_accidents/EC-HKJ.pdf"
The url failed for me, you have to go to PBL's site "rvs.uni-bielefeld.de" and follow the crumb-trail to the report.

Please note that this describes the A320 system and not the A330/340.

DozyWannabe

10th Nov 2013, 18:18

@aterpster - Chris Scott is correct. I see a little mixing of terminology creeping into the discussion though, so I'm hoping that this crosspost from another thread may help. It is a very simplified description, but I think it's valid:

FBW is simply a concept whereby the link between the flight controls and flight surfaces is electronic as opposed to mechanical or pure hydraulic
"Protections" in a FBW system are comparatively basic systems which will in most circumstances keep an aircraft that is already flying within a safe operating envelope
FCS "laws" are simply a shorthand for system configurations that keep the aircraft handling as close to normally as possible in the event of systems failures
FBW systems are *not* automation in the usual sense - they will not fly the aircraft for you, and they certainly won't prevent you from messing up an approach and landing!

It is the *protections* that, as Chris says, "...would not have allowed the a/c to enter and maintain a stall, even with the sidesticks fully back". Where flight control laws come into it is that the hard alpha protections only function when the systems are in Normal Law.

The existence of those protections was never intended to allow the industry to cut back on training in manual handling and stall recovery.

gums

10th Nov 2013, 19:06

Doze has iterated the basic concept of FBW.

Where application/implementation problems come into play is how much "protection" is included in the software or hard-wired analog systems we had in the early years.

- GAINS: When we had mechanical connections like push rods or cables, you could actually feel the aero pressure on the control surfaces. Then we went to "augmented" systems with hydraulics. And then we went to pure hydraulics in just about all military fighters, but not the heavies. There were still mechanical connections for another 30 years for a few control surfaces.

To keep the plane from exceeding aero/gee limits, we had "gains". The pure hydraulic systems that I flew had springs and pneumatic bellows and bob weights and such. You could "feel" what the jet was doing and adapt. One jet that I flew had "protections" - the VooDoo. AoA and gee were monitored, and unless in a pure reversion mode we had AoA "protection" to keep from the dreaded "pitch up", so I was familiar with such when checking out in the Viper 13 years later.

FBW offered the opportunity to increase the "feel", but basically it simply limited the control surface movement and rates to make the jet "feel" like the old days. Ours was a force/pressure system, but the 'bus and Boeing systems have "movement" of the stick/yoke. Big deal. Most of my ilk never yanked the stick about but used small movements or simple pressure ( the hydraulic valves got lots better, and the A-7 had some electronics that used stick pressure to "augment" actual hydraulic valve commands). So checking out in the Viper was a breeze.

- PROTECTIONS: The Viper had real "protections" for both gee and AoA. We had no "direct control laws" unless the jet went out of control and AoA was above 30 degrees. Even then, we could only control the elevator ( stabilators) directly, and rudder/aileron surfaces remained under control of the computers.

Forget the gee protection. The big one was AoA protection, hence my interest in this discussion of the 'bus 340 uncommanded climb.

We did not have a mach protection for obvious reasons, but we did lose one fellow that tried to see how fast he could go. The motor fried, not the airframe.

- AUTOPILOT/NAV connections: This disturbs me more than the modes/laws of the 'bus and the Boeings.

We did not realize that our autopilot could not command above "x" AoA for a year or more. The GD flight control folks were scared about connections with their super FBW implementaion. So we had very limited otto inputs - heading select and altitude hold. That was all. So no flight management system connects or such.

Later jets had an auto throttle system ( Hornet), and I am not sure of the implementation. Most Nasal radiators and some of us in the SLUF and Viper flew AoA on approach and cross checked the speed to make sure we had the correct configuration.

So I get very concerned when I read about all the "protection" modes and the combinations of the nav system and otto and the FBW computers.

As a full-time SLF dude nowadays, I sometimes wish I could ride the jump seat to see how good the pilots are when Hal or Otto go FUBAR.

Sorry so long a post, but had to get this off my mind.

OK465

10th Nov 2013, 20:12

FWIW, the way I read the traces shows....

Except for the initial pilot commanded pitch up (FO SS ANU -11) in the first period of alpha prot activation (and maybe the reason for it?), every subsequent entry into alpha prot shows an initial pitch attitude decrease as Mach decays, particularly pronounced at the lowest Mach numbers which is what I would expect.

True, there are minor <1 or so degree pitch variations after those initial pitch downs that I would think could be attributable to 'rough air' and FCS lag. Pitch trend is down or stable.

There are 3 or 4 very minor pitch oscillations (time scale proportioned) in that final long period of apha prot, but in general, with the trim frozen ('prot' occurred at around minimum Mach) in alpha prot, pitch does not trend an increase until calculated Mach number tends to increase continuously from a low of around 0.68 and I would assume there would be a noticeable CAS increase and associated frozen trim pitch up effect to maintain trim speed with this, especially since altitude is still generally decreasing further increasing CAS for the Mach. Possibly even FCS 'AND' elevator commands during this pitch increase. Elevator trace would be nice.

However with the apparent errors (pedantic or not) in the 2 AAIBs, i.e. 'probably alpha floor' with the minimum Mach of 0.67 in the Airprox event and the reference to an 'amber AP OFF' message in this event, I'm beginning to lose my warm fuzzy about the learning value of some of these reports.