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Asiana flight crash at San Francisco

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Asiana flight crash at San Francisco

Old 12th Jul 2013, 06:38
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Knot Apilot wrote:

Also I imagine they would be designed to not wake-up because you do want the A/Ts to spool up uncommanded after you've made a successful touch down on the runway!
Well… We’re talking about A/T in Flight Level Change (FLCH), right? I imagine an approach and landing is not a flight level change (although technically it is; a flight level change to runway altitude).

Assuming FLCH is not a common/normal mode during approach and landing, I repeat: Why would anyone want A/T HOLD when throttle leavers reaches idle in FLCH mode? This is obviously an intended design.
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Old 12th Jul 2013, 06:44
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Originally Posted by Indarra
Note that in her press conference on 11 July Deborah Hersman appeared to state that all of the passenger seating structures remained in the aircraft. This suggests that the two pax were ejected because they were not properly seated for the final phase of landing with belts tight across hips. If so, sounds like a CC responsibility, not fulfilled.
Indarra, with respect that's a very premature call. Given the impact, the forces, and nature of the injuries reported, they could easily have just broken their belts.
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Old 12th Jul 2013, 07:12
  #1823 (permalink)  
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Originally Posted by Knot APilot
Also I imagine they would be designed to not wake-up because you do want the A/Ts to spool up uncommanded when you're about to make a successful touch down on the runway!
- this would be avoided by the inhibition below 100'RA and one would hope a crew would be 'on speed' at 100' anyway, and if not, then 'spool up' would probably be desirable..

I too have commented on the lack of reversion in FLCH and would like to hear why it is part of the programme.

I hope the quote by Lorimer from Deborah was inaccurate - "This was a visual approach which is a completely normal approach flown on a nice day with 10 mile visibility." - I would not classify a 'request' for 3-400 ft high and several kts fast at 5 miles to be 'a completely normal approach' and I hope the NTSB comment on this SFO procedure. I await the transcript/video of the conference. It is certainly another of those 'holes in the cheese'.
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Old 12th Jul 2013, 07:14
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Ranger 1

Thanks your comment, maybe so. But I kind of think that two Chinese teenagers (aged 14 and 15, I recall) are unlikely to be of a body mass that would cause failure of seatbelts and their fixtures. Such safety equipment is crash tested to restrain people much bigger than these two girls, by substantial margins. I have seen reporting that they survived for a period outside the aircraft, being missed by triage teams, and one showing signs of being run over by a vehicle. We're not talking about the overwhelming trauma one would see when breaking a seat belt. A Chinese school group, maybe first or second flight ever for these kids. The two girls were best friends, I understand. Perhaps they might have been in the WC.
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Old 12th Jul 2013, 07:16
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Cavok69

7-4-1. VISUAL APPROACH

A visual approach is an ATC authorization for an aircraft on an IFR flight plan to proceed visually to the airport of intended landing; it is not an instrument approach procedure. Also, there is no missed approach segment. An aircraft unable to complete a visual approach must be handled as any go-around and appropriate separation must be provided.

7-4-4. APPROACHES TO MULTIPLE RUNWAYS

a. All aircraft must be informed that approaches are being conducted to parallel, intersecting, or converging runways. This may be accomplished through use of the ATIS.

b. When conducting visual approaches to multiple runways ensure the following:

1. Do not permit the respective aircrafts' primary radar targets to touch unless visual separation is being applied.

2. When the aircraft flight paths intersect, ensure standard separation is maintained until visual separation is provided.

c. In addition to the requirements in para 7-2-1, Visual Separation, para 7-4-1, Visual Approach, para 7-4-2, Vectors for Visual Approach, and para 7-4-3, Clearance for Visual Approach, the following conditions apply to visual approaches being conducted simultaneously to parallel, intersecting, and converging runways, as appropriate:

1. Parallel runways separated by less than 2,500 feet. Unless standard separation is provided by ATC, an aircraft must report sighting a preceding aircraft making an approach (instrument or visual) to the adjacent parallel runway. When an aircraft reports another aircraft in sight on the adjacent final approach course and visual separation is applied, controllers must advise the succeeding aircraft to maintain visual separation. However, do not permit a heavy/B757 aircraft to overtake another aircraft. Do not permit a large aircraft to overtake a small aircraft.

http://www.faa.gov/air_traffic/publi...C/atc0704.html

Last edited by nigegilb; 12th Jul 2013 at 07:17.
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Old 12th Jul 2013, 07:19
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Not being a jet pilot I'm curious why there isn't an audio warning if you get a bit slow on approach? Triggered say 10kts below Vref and slowing?
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Old 12th Jul 2013, 07:26
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Regarding the delay in starting the evac I can understand the delay. In the sim you don't practice evacs from a position of just having crashed the aircraft, it usually the result of some sort of non-normal possibly a gear collapse but often some sort of uncontained fire. As has been posted previously these guys do things strictly according to their training so doing an evac without going through any checklists is not within their thinking.

With the engines having been ripped off and the avionics possibly u/s I doubt that they had any fire warnings in the cockpit. They were trying to work out what happened given that they thought they were conducting a go-around.


From what has been released by the NTSB,(not a big fan of the drip feeding of the investigation day by day BTW, why not wait until the 30 days for the prelim as required by ICAO? Just sayin'). As soon as the pilots were made aware of the fire they ordered an evac.
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Old 12th Jul 2013, 07:26
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Originally Posted by cwatters
Not being a jet pilot I'm curious why there isn't an audio warning if you get a bit slow on approach? Triggered say 10kts below Vref and slowing?
Another poster addressed this issue a few posts back and referenced the following article:

Source:

"Boeing could still end up being on the hook for never having installed an aural warning system of low airspeed on the 777, a system which the NTSB had recommended the FAA look into requiring 10 years ago"
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Old 12th Jul 2013, 07:29
  #1829 (permalink)  
 
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Not being a jet pilot I'm curious why there isn't an audio warning if you get a bit slow on approach? Triggered say 10kts below Vref and slowing?
There is its called the stick shaker. It is an aural and tactile warning that bad things are about to happen. On an Airbus there is also something called Alpha Floor which in this instance might have been useful and was possibly what the trainee was relying on given his previous experience on A320.
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Old 12th Jul 2013, 07:38
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Originally Posted by bobcat4
Well… We’re talking about A/T in Flight Level Change (FLCH), right? I imagine an approach and landing is not a flight level change (although technically it is; a flight level change to runway altitude).

Assuming FLCH is not a common/normal mode during approach and landing, I repeat: Why would anyone want A/T HOLD when throttle leavers reaches idle in FLCH mode? This is obviously an intended design.
Hmm, yes I think I see what you mean. Why does the FLCH let the airplane stall or get close to stall even at altitude. In other words, what are the protections, if any, vs. A/T off?

Several posters a few posts back explained the FLCH mode in more detail.

I did some digging(aka google) and I found these explanations on another forum. They are quite interesting!

Source:

From the 777 FCOM, in the flight controls section (Pitch Envelope Protection & Stall Protection):

"The autothrottle can support stall protection if armed and not activated. If speed decreases to near stick shaker activation, the autothrottle automatically activates in the appropriate mode (SPD or THR REF) and advances thrust to maintain minimum maneuvering speed"

I spoke to a friend of mine who flies the 300 variant, and he told me something I also validated in the FCOM: the EEC enters an "approach idle" mode when certain criteria is met... one of these being using flaps 25 or 30 (which was the case). This prevents "under spooling" the engines in case of a GA or if an engine goes out.
Just for the sake of completeness: the 777 FLCH trap is described as follows.

When flying with both A/P and A/T engaged, and the AFDS working in a speed-on-elevator mode such as FLCH, for a descent the A/T will sit at idle and then HOLD as you expect. If you then disengage the A/P but leave the A/T engaged, the AFDS will keep the A/T in the speed-on-elevator mode -- i.e., it does not activate the throttle servo if your speed drops under the target MCP speed. It simply expects its other half (the now disengaged A/P or the real pilot) to fix the speed by pitch.

It is quite possible there is another protection far lower down the speed tape, just above stall speed, but either that didn't work or it wasn't in time. I can imagine that if you pull up hard enough to get the PAPIs back to two red, two white, you bleed off speed so rapidly that by the time the A/T comes back up, you face spool-up times longer than time to impact.
Also remember that although Asiana 214 got pretty close to stall (103kts!) it never did actually stall. I believe speed at time of impact was 122kts as engines were starting to kick in.

Last edited by Knot Apilot; 12th Jul 2013 at 08:45.
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Old 12th Jul 2013, 07:45
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Former pilot?s animation re-creates Saturday?s SFO crash | SFGate Blog | an SFGate.com blog

Simple animation of what it should've been like.
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Old 12th Jul 2013, 08:03
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ghw78,

thanks for the information on Vref. In the final seconds the airplane was more than 30 kts below the intended speed of 137 kts. That is equivalent to more than 300 ft of height. At the intended speed a slight pull-up would have easily recovered the glideslope, the engines would have been at a higher trust and would have spooled up more rapidly. If the airplane was not already stalled at 105 kts (I think it was) then the pitch-up would have caused it to stall.
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Old 12th Jul 2013, 08:21
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Originally Posted by armchairpilot94116
That's fantastic!

Also, he says this:

“this was a very unique crash that will be influential in evaluating pilot training and qualifications.”
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Old 12th Jul 2013, 08:27
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Sadly it's not all that unique and I fear we'll be seeing more of it.
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Old 12th Jul 2013, 08:35
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So at the end of a long night, the Airbus-experienced OZ 214 pilot may have mistakenly thought he had alpha floor protection on a B777? Perhaps this shouldn't surprise us - after all, the pilots of AF 447 seem to have thought they had alpha floor protection on their A330 too, even while their aircraft was operating outside Normal Law and they were in a deep stall...
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Old 12th Jul 2013, 08:37
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Why wait for the Alfa floor? Add thrust sooner....
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Old 12th Jul 2013, 08:41
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All about FLCH mode and Auto-Throttles...

Here's a tremendous post on the aerowinx.com forums that bears posting here.

A nice gentleman has indexed all the best posts here on PPRuNe regarding the the 777 A/Ts and FLCH issues. Great job!

Most definitely I'm not a pro (I sometimes wonder even about "amateur"), but FWIW: after ploughing through 1360+ posts (the dole lets you do that...) in the "Asiana Crash" thread of PPRuNe, the following consensus regarding the "FLCH trap" seems to emerge:

¤ The "trap" notwithstanding, FLCH is still useful (and popular),
¤ because it provides the fastest way to lose altitude
¤ while still offering automatic overspeed protection.
(V/S, by contrast, may require too much "fiddling" (quote) with setting the rate and/or deploying speedbrakes, in order to keep the speed in check.)

But to avoid the "trap", FLCH is a no-no (per personal rule or company policy) for any or all of the following:
¤ on approach
¤ below 3000 ft
¤ with the MCP altitude set to 0000 (or runway altitude)

If anyone wishes to dig deeper: To spare you the ploughing, here is a list of links to posts from the PPRuNe thread which I found helpful for understanding the issue:
(Disclaimer: subjective selection, FWIW and YMMV apply; in chronological order; no guarantee of completeness or correctness; posts ploughed through up to #1372, 10th Jul 2013, 06:44 GMT)
* asterisks denote posts I personally (!) found especially illuminating

¤ Link01
¤ Link02
¤ Link03
¤ Link04
¤ Link05*
¤ Link06
¤ Link07*
¤ Link08
¤ Link09
¤ Link10*
_ but see also Link11 and Link12
¤ Link13 (picture!)

The FLCH 'trap' is just speculation of one the possibilities that led to underspeed.

We don't know what mode the A/Ts were in prior to crash yet .

For all we know, the Asiana crew were well aware of this 'trap'.

All we know about Asiana 214 is that the Auto-Throttles were in fact in the 'armed ' position

It does appears the crew erroneously believed the A/T setting they had selected would automatically control their descent rate.

Last edited by Knot Apilot; 12th Jul 2013 at 10:02.
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Old 12th Jul 2013, 08:43
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Looking at the released FDR readings for the last part of the flight, it's appears that a crash was probably inevitable a significant distance/height from the runway, whatever the crew actions after that point.

When a jet aircraft is undershooting just above the stall not far from the surface, with gear and full flap deployed plus a significant rate of descent and engines at idle, the recovery options are severely limited, if present at all.

Increasing the pitch would reduce lift and bring it down faster. Reducing pitch would have the same effect. The engines would need five seconds or more to produce significant thrust and then would be working against an airframe in a very high drag configuration to reduce the rate of descent. It's like "coffin corner" only at the other end of the flight envelope. In days of old it would have been noted as: "running out of height, speed and ideas"...
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Old 12th Jul 2013, 08:54
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So at the end of a long night, the Airbus-experienced OZ 214 pilot may have mistakenly thought he had alpha floor protection on a B777? Perhaps this shouldn't surprise us - after all, the pilots of AF 447 seem to have thought they had alpha floor protection on their A330 too, even while their aircraft was operating outside Normal Law and they were in a deep stall...
I disagree in principle.

I've flown A340, B757/767 and now A320 series in commercial aviation. We spend some training time on seeing / practicing the protections. However the only occasions I can think we actively rely on them are:
  1. (E)GPWS Pull Up
  2. Windshear Pull Up
when in the Airbus types we use Full Back stick relying on AoA protection. Even in these cases we do not rely on Alpha Floor but manually select TOGA.

In my operator, and I would guess most, if you trigger any "Protection" (Alpha Floor, Alpha Prot, Pitch, AoB) you are going to trigger all sorts of "events" on the Flight Monitoring kit, and potentially ATC as well. You will both professionally and practically do all you can to avoid this, and the resulting enquiries / investigations...

It is also fine to say pilots must monitor speed, and use Thrust Levers to correct as required. Trouble is, if you have never flown Manual Thrust on your type, have always had your ATHR system work perfectly, then on the day your workload goes up, you are tired, you are getting "mode confusion" (be under no illusion, we all get confused by the modern levels of technology), then the risk goes up that someone will get it VERY wrong. Maybe here, certainly THY @ AMS and others...
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Old 12th Jul 2013, 08:59
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In days of old it would have been noted as: "running out of height, speed and ideas"..
That's a bit like another saying:
" Speed, Height, and Skill......you always need two of them"
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