How safe is (airbus) fly by wire? Airbus A330/340 and A320 family emergency AD

[737Jock]

EASA Airworthiness Directives Publishing Tool (http://ad.easa.europa.eu/ad/2012-0264-E)

An A330 aeroplane, equipped with Angle of Attack (AoA) sensors with conic plates installed, recently experienced blockage of all sensors during climb, leading to autopilot disconnection and activation of the alpha protection (Alpha Prot) when Mach number was increased.
Based on the results of the subsequent analysis, it is suspected that these conic plates may have contributed to the event. Investigations are on-going to determine what caused the blockage of these AoA sensors.
Blockage of two or three AoA sensors at the same angle may cause the Alpha Prot of the normal law to activate. Under normal flight conditions (in normal law), if the Alpha Prot activates and Mach number increases, the flight control laws order a pitch down of the aeroplane that the flight crew may not be able to counteract with a side stick deflection, even in the full backward position.
This condition, if not corrected, could result in reduced control of the aeroplane.
condition on Airbus A330 and A340 aeroplanes.
AoA conic plates of similar design are also installed on A320 family aeroplanes, and installation of these AoA sensor conic plates was required by EASA AD 2012-0236, making reference to Airbus SB A320-34-1521 for in-service modification. This requirement has now been removed with revision 1 of that AD.
To address this condition on A320 family aeroplanes, Airbus developed an “AOA Blocked” emergency procedure, published as a temporary revision (TR) of the Airplane Flight Manual (AFM), to ensure that flight crews, in case of AoA sensors blockage, apply the applicable emergency procedure.
For the reasons described above, this Emergency AD requires insertion into the AFM of the Airbus TR.
This AD is considered to be an interim measure and further AD action may follow.


With multiple frozen/blocked AOA probes and an increasing mach no, the flyby wire system might trigger alphaprot mode. As the system thinks the aircraft is stalling the flybywire system induces a constant nose-down input to the aircraft.
The speed indication however will be normal as the pitot-probes are functioning normal.
The nose-down input is not fedback via the sidestick, nor on the screen. And pilot full nose-up input might not be able to counter the nose-down input of the alpha-prot system.

So the brilliance of engineering instructs us in a procedure to turn off 2 ADR's in order to revert the aircraft to Alternate law, in which no alpha prot exist. Off course first you have to realise what is going on, which could be difficult as there is no feedback from the system to the pilot.

But yes you read it correctly, the system is able to completely override pilot input despite being completely wrong. And the only way to recover from uncontrolable situation is to switch of ADR's.

The procedure:
At any time, if the aircraft goes to an unmanageable pitch down attitude despite continuous deflection of the sidestick in the full backward position (in case the flight crew missed the below symptoms or delayed the application of one of the below procedures):
Keep one ADR ON. Turn OFF two ADRs.

And before anyone asks, yes I fly Airbus A320 family. (not 737 as my name might suggest)

[PENKO]

I asked a sim instructor this very same question: what if the aircraft thinks it is in a stall whilst it is clearly not. How do I safely deactivate normal law.

I only got an answer after a lot of huffing and puffing, whilst I think this should have been standard knowledge to all pilots.


Fine. My biggest worry: what if this happens shortly after lift off in IMC? Is there enough time to realize what is wrong and press the appropriate switches?

[rudderrudderrat]

Hi Penko,

My biggest worry: what if this happens shortly after lift off in IMC? Is there enough time to realize what is wrong and press the appropriate switches?

I agree. Why did Airbus never fit a simple "big red switch" like B777 etc.

[David Horn]

It's interesting that Airbus advice is to turn off two ADRs, which immediately adds to confusion in the flight deck with only one air data reference available.

Is there any reason why the FACs couldn't be switched off instead to drop the aircraft into alternate law?

Edit: Presumably this only applies to aircraft fitted with a specific type of AoA vane, as we've heard nothing about this for our Airbus fleet.

[John Farley]

737Jock

Big topic which I do not wish to trivialise in the least.

However there are two things involved here the first being the question

How safe is (airbus) fly by wire?

and the second the event and all the technicalities that gave rise to the question.

I only feel competent to comment on the question and my response is 'safe enough'. That word 'enough' results from the simple fact of the number of people killed in Airbus accidents compared with those killed in other makes in current use. When I started in the industry wings fell of Electras and fuselages split on Comets in the cruise and that was clearly not safe enough. Today so many people fly so cheaply (and safely) all over the world that their seat on an airliner is just another commodity ruled by market forces. This means (whether we like it or not) that the large amounts of money needed to sgnificantly improve the current safety level cannot be justified commercially and so will not be found. You or I might well be prepared to pay double or treble for a safer seat but you or I are not the market.

[CONF iture]

A thread on the subject is here also :
http://www.pprune.org/rumours-news/502079-a330-a340-ead-aoa-probes.html

[Lyman]

Yes, safety is a commodity. That means it is negotiable.

The fog enters when the consumer makes a choice. As a commodity, should the consumer be apprised of his/her choices? Chances?

I think after all the recent kerfuffel, that Airbus is mostly guessing at what constitutes a hard floor for safe flight.

Again, pilots of type cannot agree on what is safe re handling the airbus.

Not comforting.

[BOAC]

Correct me if I am wrong, but it drops into Alt2? Wasn't that the mode that killed AF447?

[Lyman]

ALT II (b) killed 447.

[The African Dude]

It is highly debatable that ALT II (b) actually killed 447. Some could argue that misidentification of a stall situation is the result of many different inputs and if the aircraft control law was at fault then Air France wouldn't have got so upset when the safety recommendations were published.

The very nature of our operation in aviation is such that an almost unlimited combination of failures and events can occur, with the likely, unlikely and even remotely conceivable designed for and considered by Airbus.

This AoA vane has been shown not to work after operational experience; the problem has been identified quickly, OEBs have been issued and (as uncomfortable as it is to think our aircraft can behave in erratic ways) the truth is that we as pilots make many more mistakes. How about the incident involving mis-selection of the rudder trim switch instead of the cockpit door lock? What happened after that?

As an A320 pilot, I did not feel comfortable reading the new OEB and background information. However, we can only follow the advice given, and for the rest rely on our training and experience, as we do in any other situation. Our job has inherent risks which we manage. Better we know about it now.

[Lyman]

Not single handedly. Call it a group effort.

[CONF iture]

Correct me if I am wrong, but it drops into Alt2? Wasn't that the mode that killed AF447?
But which option is preferable ?

The computer takes over following erroneous data
The pilot has still the option to discard that computer

[Lyman]

It strikes me as extremely counterintuitive to disable a protection?

Especially if one must change the Law to get there?

[BOAC]

But which option is preferable ?

The computer takes over following erroneous data
The pilot has still the option to discard that computer

- 2. You may recall I have long argued for pilots who can fly and a big red button that makes AB into an 'aeroplane'.

[CONF iture]

Your view is mine too BOAC.
I'd like to see those who think differently how they feel as pax or pilot when their Airbus is going in the mad mode ... I have not seen them commenting yet btw.

[tuskegee airman]

B737JOCK
"Off course first you have to realise what is going on, which could be difficult as there is no feedback from the system to the pilot."

The OEB does identify the warning signs to look for PRIOR to activation of the ALPHA PROT. So we should realise "what is going on". Admittedly, switching off ADRs is not very comforting.

[TyroPicard]

David Horn...
It's interesting that Airbus advice is to turn off two ADRs, which immediately adds to confusion in the flight deck with only one air data reference available. But that is preferable to seeing increasing nose-down pitch which you cannot correct in Normal Law...

Is there any reason why the FACs couldn't be switched off instead to drop the aircraft into alternate law?Short answer: A330/340 do not have FACs.

Thinking of the A320....?
1. The ADR pb's are located together on the overhead panel, directly above the captain's head, whereas the FAC pb's are one either side of the same panel. Much easier and quicker to use the ADR pb's.

2. Switching off both FACs has more effect on the rudder - it leads to Mechanical Yaw instead of ALT.

[roulishollandais]

@Conf_iture #12

2! Agreed with BOAC and you!

Waiting that moment i continue to fly my bicycle!

Honest people cannot operate flying machines with random SOPs and call them SOPs and CRM. Automation designers have 100% responsibility, not 99.999...

[4Greens]

Agree BOAC. Red switch off to turn the computer driven object back into an aeroplane.

Second, perhaps more important, return to control columns so that either pilot can see what the other pilot is doing.

[Jonty]

Emergency electrical config, gear down. Last section of the smoke and fumes drill in the QRH.

Direct law is your friend.

[DozyWannabe]

Even with the "button" activated, the T7 remains computer- (or at least electronically-) controlled. The only difference is that the protections are disabled and some of the functions are bypassed. Airbus's temporary solution of switching off ADRs will essentially give you the same result.

It's not an ideal situation, certainly - but at least the problem has been diagnosed and a fix is forthcoming. I think this only affects a relatively small number of the current fleet.

Additionally, those calling for a manual switch to Direct Law demonstrate either a lack of understanding of, or in some cases wilful disregard for, the way the system was designed (by a team that included pilots) to operate. Hard protections of the kind identified as an issue in this case are disabled in any law outside of Normal and the aircraft will follow any command given by the pilot in this circumstance. Alternate Law is far closer in response terms to the handling characteristics Airbus FBW pilots encounter on a daily basis and as such makes far more sense than Direct in terms of keeping aircraft behaviour as consistent as possible in an abnormal situation.

It's also worth pointing out that in the situation described in the EAD and OP, Alpha Prot will not suddenly order a fistful of control input.

[Bpalmer]

The stall angle of attack does not start to increase with Mach until above about .3M, which in the "shortly after takeoff" range is about 200 knots. Obviously, the indicated equivalent to that goes down with altitude.


So, you have to be maneuvering with a high enough g load to have a fairly high angle of attack, then be in the right kind of icing conditions for the vanes to freeze in position, then increase your Mach.


If crews are made aware of it (and they certainly should be made aware), and they see the warning signs (alpha prot on airspeed indicator in an unusually high place), then they can take preventive measures : Don't go any faster, and turn off two ADRs to disable the alpha protect.

AF447: >>ALT II (b) killed 447.<<
ALT 2 b, didn't kill them. They killed themselves. More specifically, the PF in the right seat killed them all by not being able to fly straight and level without the flight director.

[737Jock]

The OEB does identify the warning signs to look for PRIOR to activation of the ALPHA PROT. So we should realise "what is going on". Admittedly, switching off ADRs is not very comforting.

I was Saying that the system is giving no feedback on what it is doing. In other words there is no feedback given that alpha prot is active. No Ecam, no message on PFD, no feedback through sidestick. If the system would drive the sidestick to the FWD stop and you can't pull hard enough to make the nose come up you know what is going on.

The OEB's identifies warning signs after an A330 nearly fell from the sky... So I conclude that it is NOT that easy to realise what is going on. And even the original solution of turning all ADR's off was based on a wrong diagnosis, although it fixed the problem by returning control to the pilots.

But why does airbus design a protection that cannot be overrided by the pilots through simple sidestick input/ possibly holding the AP disconnect button to get full control and deactivate the protection.

It's also worth pointing out that in the situation described in the EAD and OP, Alpha Prot will not suddenly order a fistful of control input.

How would you call a gradual and continouos nose-down input that cannot be overrided by the sidestick? Half a fist full?

It's clear that you have zero understanding of what is going on. A pilot is trained to intervene through control-inputs, initial pilot training is the basis for this.
The airbus system, thinks it is superior and does not allow the pilot to override protections that are not always correct.
In short the system is designed to create a struggle for control between pilot and FBW system, that can only be resolved by turning off ADR's.

[roulishollandais]

After 10 -15 and more threads about "what killed AF447" nobody cood explain in detail the laws, the stability, the systems of that damned flying computer. The best of us trie during three years and a half. How may it be sure pilots would succed??

But it has been made sure that INDEPENDANT AoA sensors could help.
And now they continue with embeded AoA!!
It is CRIMINAL.
rh

[rudderrudderrat]

Hi 737Jock,
A pilot is trained to intervene through control-inputs, initial pilot training is the basis for this.
I agree.
It is interesting to note that Airbus went in the direction of the computer has control; Boeing designed the 777 so the pilot has ultimate control.
See para 11.3 of B777TheAvionicsHandbook (http://www.blackholes.org.uk/PP/B777TheAvionicsHandbook_Cap_11.pdf)

"What should be noted, however, is that none of these features limit the action of the pilot. The 777 design utilizes envelope protection in all of its functionality rather than envelope limiting . Envelope protection deters pilot inputs from exceeding certain predefined limits but does not prohibit it. Envelope limiting prevents the pilot from commanding the airplane beyond set limits. For example, the 777 bank angle protection feature will significantly increase the wheel force a pilot encounters when attempting to roll the airplane past a predefined bank angle. This acts as a prompt to the pilot that the airplane is approaching the bank angle limit. However, if deemed necessary, the pilot may override this protection by exerting a greater force on the wheel than is being exerted by the backdrive actuator."

[DozyWannabe]

Truth be told, both approaches are designed around the pilot - the only difference is the philosophy behind the implementation. With respect, I'm not really inclined to open that can of worms again for now... :oh:

[Young Paul]

With regard to the OP - how safe is (airbus) fly by wire? The answer is - statistically, very safe. What is the hull-loss rate for airbus FBW aircraft, and how does this compare with (say) Boeing non-FBW aircraft? And how many of those hull losses can be classified as a failure either of FBW or of SOP associated with the FBW system?

Now let's imagine we put in a big red button that switches off the FCCs and returns the aeroplane to direct law (say). Please can someone do a risk analysis which compares the current setup with the benefits of switching off all these protection systems and replacing them with a pilot seeking to interpret raw data at short notice in extreme circumstances. And then add to that the risks of people overriding safety systems at times when it's not appropriate, or because they want to get a bit more out of the aeroplane - perhaps like switching off the alpha floor system so that they can do a demonstration high angle of attack flyby at 100 feet ....

[FANS]

moving side sticks and moving throttles - can't understand why they don't (but then I'm not French)

[A and C]

The Airbus is very safe !

Is the A320 as safe as the Boeing 737NG, as an aircraft the Boeing is probably marginally more safe as if all the electrics & hydrulics fail the flight controls have manual reversion. Having said that I can't think of an incident were an airbus has lost enough systems to force the crew to fly it on the rudder & stab trim.

Rather than a debate about the merits of the aircraft I think an examination of why the crew from a major airline could not set a safe pitch & power combination when the airspeed system was malfunctioning or why three pilots let the Autothrottle come back to flight idle and the airspeed drop to the point were the aircraft stalled into the ground when simply pushing the throttles forward would have resolved the situation.

I would suggest that the de-skiling of pilots who are being forced by the SOP's in some companies to be over reliant on the automatic systems is far more of a threat to flight safety than the mechanical reliability of the aircraft be it Boeing or Airbus.

[DozyWannabe]

moving side sticks and moving throttles - can't understand why they don't (but then I'm not French)

That approach has its own problems, mainly in increased complexity (i.e. more things to go wrong) and limited benefits, once the design is understood as a whole. The T7 feedback relies on the same kind of sensors that are causing a problem here. Thus far there has not been a well-known incident where bad data caused problems for the feedback, but that doesn't mean it won't happen.

For the record, the Airbus FBW design team was multi-national, not just French.

[FANS]

That approach has its own problems, mainly in increased complexity (i.e. more things to go wrong

The complexity & reliability of having two side sticks moving in tandem isn't a valid argument; yes there's more to go wrong but you'd hope that risk associated to this would be miniscule.

limited benefits, once the design is understood as a whole

From a training perspective, I'd say say there are huge benefits to having them both move, as cadets rarely understand the "design as a whole" from the outset!

It's still a very safe aircraft!

[DozyWannabe]

There are benefits and drawbacks to both connected/force-feedback and independent implementations which I've detailed in depth before. I don't think either approach is inherently better than the other in an objective sense - some may feel differently, and that's fine! :)

[IcePack]

Sometimes if an aircraft starts "gyrating about" pulling G's etc it can be nigh impossible to get your hands on any switch/knob to turn it off. Those that think differently have not been in the rough stuff. So trying to turn 2 ADR's off or get into emg elec config may not be that easy.

[CONF iture]

Now let's imagine we put in a big red button that switches off the FCCs and returns the aeroplane to direct law (say). Please can someone do a risk analysis which compares the current setup with the benefits of switching off all these protection systems and replacing them with a pilot seeking to interpret raw data at short notice in extreme circumstances.
But the aim to switch 2 ADRs OFF is just exactly what is requested from a crew to deactivate a mad protection, with the associated risk to turn off 2 IRs instead ... Not easy to locate the proper switches on the overhead panel in the middle of such critical situation.
What about a single red guarded switch in the middle of the dash to give back control to the crew ... ?

[Kimon]

Yes, the A400M has a red panic button to go into Direct Law.

[BOAC]

replacing them with a pilot seeking to interpret raw data at short notice - I suppose it depends whether an AB pilot can do that? You may well have a point there.:ugh:

Well done A400M. Why, I ask? Is it because it will be flown by pilots?

[A4]

Not easy to locate the proper switches on the overhead panel in the middle of such critical situation.

ADR is simple push button, IR is a rotary knob which has also to pulled before being turned so you'd have to be pretty hamfisted to get the wrong one.

They're just above the Captains head so it's a bit of a stretch for the FO. Who's going to be PF in the reversion from uncommanded Alpha Floor to ALTN Law..... CM1 I would imagine so not an ideal set up for carrying out the switching - but if you're wise to it and practice reaching across before hand it may relieve a bit of the drama.

A4

[CONF iture]

ADR is simple push button, IR is a rotary knob which has also to pulled before being turned so you'd have to be pretty hamfisted to get the wrong one.
An IR pb is very similar to an ADR pb.
An IR rotary knob is something else.
At least that's the setup for a 330 ...


Yes, the A400M has a red panic button to go into Direct Law.
That's very interesting ... would you have more info ?

[Kimon]

The A400M was engineered ground-up with the French Air Force's savoir-faire.
When you are transporting hundreds of dedicated military personnel who've cost the taxpayer many trillions, you don't have time to start fiddling with PRIMs, SECs, ADRs, IRs AFM, FCTM and FCOM.
As soon as I got the exact details, I shall gladly share them.
Now, hazarding a guess, I'd bet the A330 MRTT has the same setup but I can't confirm it but I'll find out.
The A350 will surely have the panic mode.

[DozyWannabe]

Sometimes if an aircraft starts "gyrating about" pulling G's etc it can be nigh impossible to get your hands on any switch/knob to turn it off.

The Alpha Prot response is not going to cause significant gyrations - it's a gradual thing - unlike the A300 protections it will not command significantly opposite pilot input because it is designed to hold a steady flightpath while giving as much authority to the pilots commands as it can within the flight envelope.

Personally I think this talk of panic switches is premature, but whatever floats your boat, I guess...

[BOAC]

Can the F/O action this selection strapped in?

[CONF iture]

How very tall is he ... ?

[Bpalmer]

How would you call a gradual and continouos nose-down input that cannot be overrided by the sidestick? Half a fist full?

When above the AOA at which alpha Prot activates, the sidestick becomes an angle-of-attack demand input. Thus, at neutral the sidestick commands the AOA equal to the onset of alpha prot. At full back, it commands alpha max (just shy of stall AOA).

The scenario at hand has the AOA vanes freezing in a fixed position and the Mach number increasing such that that AOA now moves within the alpha prot range with the increase in Mach number . (recall that the stall angle of attack decreases with Mach numbers > 0.3).

So, as the Mach number is increased to the initial alpha Prot value there is no change, except the stripped alpha prot band is now visible on the airspeed scale - where you would not normally expect to see it.
As the Mach number increases, the fixed AOA is now closer to the critical AOA, and the sidestick must be pulled slightly farther back to maintain this same AOA which is now farther within the AOA range. (So, yes, perhaps "half a fist full")
If the airplane continues to accelerate, the problem continues until such point that the frozen AOA equals Alpha max at the higher Mach no. and now despite full back stick input the airplane attempts to reduce the AOA by pitch down. (which will of course, increase the speed /Mach and make speed/Mach reduction - even with idle power - shall we say "difficult."

Thus, the solution is to not accelerate (increase Mach) when this happens (or to decrease Mach to below 0.3), which in and of itself, would probably be enough. Of course to take the AOA out of the control picture is a more complete immediate solution, and one that would be required once you got to the point of having full back sidestick. Switching off two ADRs, leaves the computers with one source of AOA data (not enough to rely on) thus removing them from the flight control protection picture, and solving the erroneous AOA protection problem.

[BOAC]

Since both SS are relatively useless at this point and the TL's don't move anyway, - and in some airlines, both pilots are 'relatively useless' too.

[DozyWannabe]

- and in some airlines, both pilots are 'relatively useless' too.

With all due respect, it appears that the crew in this incident were perfectly able to handle the problem and recover the aircraft with no forewarning of the failure mode. Given that, is it fair to say that we should hold off on getting on our hobby horses about automation, pilot skills etc. before we have more facts to hand?

[roulishollandais]

:uhoh:There is something wrong in the absence of feeling restitution by the feedback of some FBW flight laws. It was already stigmatized by gums' experience in flight.

In the direct loop you have the human feeling/sensors. From the feedback you get no feeling coming to the comparator.

In automation/system design it means there is a faulty transmission of information, with a resulting faulty OBSERVABILITY / CONTROLLABILITY of your closed loop system.:uhoh:

We know that OBSER ABILITY / CONTROLLABILITY are the minimum design qualities for a dynamic system to work.
RH

[DozyWannabe]

:uhoh:There is something wrong in the absence of feeling restitution by the feedback of some FBW flight laws. It was already stigmatized by gums' experience in flight.

That's a matter of conjecture and debate.

Those who favour the "traditionalist" line that all aircraft should be flown in the manner of a Cessna will probably agree, but others - of which there are a growing number - do not.

The former group are undoubtedly more vocal, but scratching the surface among many of them reveals a tangle of political motivations and technical misunderstandings that in truth serve only to cloud the real issues and hinder discussion.

The fact that in the years since their introduction, FBW Airbus models have maintained a safety record that equals or betters types with the traditional layout, and we have examples of safe returns after engine failures, successful deadstick landings (one of which was on water) and runway overruns in which every person on board survived. At the very least, the safety records of those types imply that the worst fears of the sceptics were somewhat overstated and never realised.

[roulishollandais]

Dozy
Analyzing which information comes to the comparator of closed loop system is not "traditionalist", or cessna " ,or "political", or "ground scratching", etc!
Your imagination has no limit ,nobody is attacking you, hiden behind equations :=:8

[DozyWannabe]

As someone who speaks practically no French, I can't fault you for trying to express yourself in a language that is not your own, but I must admit I'm having real trouble understanding you - my apologies.

All I can say is that I read the article you pointed me at regarding "observability", and if I recall correctly I do not think it means what you think it means. It seems to me that you're making an argument for variable tactile feedback as a necessity (which is an assertion not supported by evidence as there has not been a crash caused by the lack of it in 24 years). Furthermore if that is what you're trying to say, I can't see the relevance to the subject under discussion. Forgive me if I'm reading you wrong.

[roulishollandais]

Shortened, "observability" ("observabilite " in french system theory language) means that you have enough SENSORS. "Controllability" ("gouvernabilite" in french system theory language) means you have enough and coherent ACTUATORS. Put that in a closed loop with a feedback coming to the comparateur, and "pilot " the multivariable difference (we say "piloter l 'erreur " in french)).
It is the center of automation, regulation, robotik, system theory,call it as you want.
RH :)

[CONF iture]

As the Mach number increases, the fixed AOA is now closer to the critical AOA, and the sidestick must be pulled slightly farther back to maintain this same AOA which is now farther within the AOA range.
If engaged, that's also the time for the AP to disconnect.
Now, depending on the angle at which the AoA probes froze, there is even a possibility for the A/THR to trigger TOGA With no way around to cancel it except than reaching those 2 ADR switches ... What a potential MESS !

[DozyWannabe]

Chances of that are pretty remote though, and even in the worst case scenario you'd have a lot of time to sort things out before that happened.

Remember this is just a temporary workaround that applies to only a tiny fraction of the fleet, no need to go clutching at our pearls just yet...

[CONF iture]

Chances of that are pretty remote though, and even in the worst case scenario you'd have a lot of time to sort things out before that happened.
Only a guy with absolutely no Experience being in the air in the front seat would dare making such comment ...

[DozyWannabe]

OK, so why is there no mention of Alpha Floor engaging in the incident concerned? Theoretically speaking it will eventually engage, certainly - but only if the Mach number increases sufficiently for it to do so, or if an attempt is made to pull up that is sufficient to trigger it.

[rudderrudderrat]

Hi DozyWannabe,
or if an attempt is made to pull up that is sufficient to trigger it.If the AOAs are frozen in their present position, then pulling up won't have any effect on the AOAs.

I still don't understand why a simple "big red button" was never designed to turn HAL off and restore control to the pilots. Turning off 2 ADRs, with the subsequent loss of one PFD's Altimeter and airspeed information, does not seem to be an ideal way to accomplish that simple effect.

[DozyWannabe]

I still don't understand why a simple "big red button" was never designed to turn HAL off and restore control to the pilots. Turning off 2 ADRs, with the subsequent loss of one PFD's Altimeter and airspeed information, does not seem to be an ideal way to accomplish that simple effect.

Because dropping to Direct Law means that pilots who aren't used to manually trimming the thing outside of a simulator will have to very quickly get used to doing so in what is likely to already be a high-pressure situation.

Agreed that the workaround procedure is not ideal, but as I said before, and as the EAD clearly states, this workaround is temporary and only applies to a relatively small number of airframes.

[rudderrudderrat]

Hi DozyWannabe,

The same pilot will have to complete the approach and landing in Direct Law anyway once the Landing Gear is lowered.
If you are so concerned about a pilot's ability to fly this aircraft in Direct Law, then don't you think that perhaps it should have been designed so that the average pilot could do so easily?

this workaround is temporary and only applies to a relatively small number of airframes.
I am told there are 690 aircraft affected.

[CONF iture]

Because dropping to Direct Law means that pilots who aren't used to manually trimming the thing outside of a simulator will have to very quickly get used to doing so in what is likely to already be a high-pressure situation.
Big deal !
If manually trimming became one of those scary things ... (?), maintain the auto-trim but keep the bloody protections away on a single switch activation.

Manual trim or mad protection ? ... Maybe your choice is difficult, but it is not to anyone flying those things.

[Stuck_in_an_ATR]

I've read the EAD/OEB and the following passage puzzled me:

"In stabilized flight path (out of maneuvers involving an increase in load factor such as turns or
pitch variations), the Alpha Max strip (red) on the speed scale of the PFD can hide completely
the Alpha Prot strip (black and amber)"

Are Valphaprot and Valpha calculated from different parameters? The passage suggests that Valphamax is AoA and Mach dependant, while Valphaprot isn't (otherwise it would move up too?). Correct?

Then, this passage:
"With the AutoPilot (AP) engaged, and with the speed brakes in the retracted position, during
maneuvers involving an increase in load factor such as turns or pitch variations, the Alpha Prot
strip (black and amber) can move rapidly by more than 30 kt"

Why would that happen? does it mean jamming and then sudden movement of AoA vanes? If the AoA vane remained fixed during a maneouver, why would Alpha Prot move up?:confused:

[CONF iture]

Alpha Max and Alpha Prot are dependent of the weight, config and Mach.
I would think the quoted extract : In stabilized flight path (out of maneuvers involving an increase in load factor such as turns or pitch variations), the Alpha Max strip (red) on the speed scale of the PFD can hide completely the Alpha Prot strip (black and amber) is related to the flight at higher altitude where Alpha Max is so close to Alpha Prot that the only visible strip on the PFD is the red one.

Regarding the second extract : With the AutoPilot (AP) engaged, and with the speed brakes in the retracted position, during maneuvers involving an increase in load factor such as turns or pitch variations, the Alpha Prot strip (black and amber) can move rapidly by more than 30 kt, it just make sense that V Alpha Prot increases under load factor, just as V Alpha Stall does. The question, as you put it yourself earlier, could be, why V Alpha Max does not at the same rate ?

For the 330/340, IIRC alpha floor won't activate above 0.53 mach. This would be a Question for HazelNuts39, at which angle the AoA probes should freeze for Alpha Floor to activate before M.53 is reached ?

[Kimon]

Le SPECIAL COMETEC N°5 est disponible pour tous les pilotes | Syndicat National des Pilotes de Ligne (SNPL) (http://www.snpl.com/technique_reglementaire/actualites_cometec/lire/2459/)

French pilots union demand that Airbus change the following:
* Get rid of ALT 2.
* Get rid of AutoTrim in all modes bar Normal.
* For UAS, jump to Direct.
* AutoTrim when values are extreme, aural warning à la MD-11 "Stabiliser Motion".
* Rethink A/THR and non-moving levers.
* Link SSs.
* Replace Vector Stability with Speed Stability.
* Abnormal Attitude needs to be re-tested as it didn't function properly in Perpignan.

[BOAC]

Hoorah!! Apart from number 7 which I do not comprehend (and NB do not need to!!!), commonsense at last. What took so long? Was it the horrendous loss of life that triggered this?

[A33Zab]

with such demands....
they better taxi (ground mode = direct) to destination.:hmm:

[Gretchenfrage]

French pilots union demand that Airbus change the following:
* Get rid of ALT 2.
* Get rid of AutoTrim in all modes bar Normal.
* For UAS, jump to Direct.
* AutoTrim when values are extreme, aural warning à la MD-11 "Stabiliser Motion".
* Rethink A/THR and non-moving levers.
* Link SSs.
* Replace Vector Stability with Speed Stability.
* Abnormal Attitude needs to be re-tested as it didn't function properly in Perpignan.

As a former Airbus pilot, I intended and managed to leave this technology, being convinced that it is not safe enough.
I had always asked for some of the above, plus the "instant direct law button", enabling to get away from wrong protection.
I am happy and comforted today, after being constantly belittled by the AB-lobby, that an union of pilots that fly such aircraft finally ask for some common sense.
We should have done that long ago, unite and ask for implementation of an apparent safer solution.

It did certainly not need the cynical QED written with blood. All the responsible that withheld improvement of the system, and still refuse to see its flaws, should go to look at themselves in the mirror and try to convince what they face, that such a union of professionals must be wrong.

Thanks dear colleagues, it's in Airbus' and the regulators hands now.

[Smilin_Ed]

Well, it seems that maybe, just maybe, reason has prevailed with at least one group of pilots. It's about time.

[BOAC]

I have always read Dozy's posts on Airbus and found his views interesting and informative. He has always, when the topic of 'pilot involvement' was raised, maintained that 'pilots' WERE involved in the development of the AB FBW/systems. Now it appears that perhaps some 'pilots'/users have other views on it. I wonder what Dozy will make of that?

[Lyman]

BOAC

I never bought Dozy's knee jerk defense of AB. The pilots to whom he referred were company pilots, paid by the airframer, and owned, proprietarily by the airframer.

Much admiration and great respect to the pilots of AirFrance, they forced the line to replace the pitot tubes immediately, and now have forced the hand of the manufacturer to correct glaring and dangerous shortcomings in the controls systems.

bonne chance mesdames et messieurs........

[FANS]

What is the opinion of the rest of the world's pilots' unions on this list, or is that not something of interest any more?

[Kimon]

Had AF447 dropped directly into Direct, would it have made a difference?
I think on B777s if one of Pitots go loopy, it goes into direct as per the 2005 incident.
Regarding Unions, AF so far are the most vociferous than the rest - ipso facto - because AF is appears to be in a forced marriage with Airbus and that their relationship between flag carrier and home-turf framer got off in such an inauspicious manner that they both still live under Habsheim's shadow.
The relationship between Airbus and AF is like no other.
The endless blame game will never end so the solution is simple:let the Unions decide if they want to be all-Boeing or all-Airbus.

[jcjeant]

Hi,

Airbus, un avion fou ?
PNC Contact, hôtesse de l'air et steward, formation et information. – Airbus, un avion fou ? (http://www.pnc-contact.com/2012/12/17/airbus-un-avion-fou-11541)
Airbus, a crazy plane ?
Google Traduction (http://translate.google.be/translate?sl=fr&tl=en&js=n&prev=_t&hl=fr&ie=UTF-8&eotf=1&u=http%3A%2F%2Fwww.pnc-contact.com%2F2012%2F12%2F17%2Fairbus-un-avion-fou-11541&act=url)

[BOAC]

jc - Airbus could not regain control of their aircraft when they reproduced stall Rio . - do we have any information on this 'test'? Have I missed it on the forum?
BOAC
I never bought Dozy's knee jerk defense of AB. The pilots to whom he referred were company pilots, paid by the airframer, and owned, proprietarily by the airframer. - I did not intend this to be a discussion on how we individually view Dozy's inputs but to see what they are. If you don't like them ignore them. Dozy has long argued that because certain 'pilots' were involved in the whole concept it was 'ok'. Now we have other 'pilots' involved.

[HazelNuts39]

This would be a Question for HazelNuts39, at which angle the AoA probes should freeze for Alpha Floor to activate before M.53 is reachedSorry, I don't know the values of alpha-prot and alpha-floor.

[cattletruck]

Whether we like it or not automation is here to stay, as it's essentially a profit driven concern.

Most complex automation systems only work well within a narrow set of parameters. Inside this known zone of expectation the operator (pilot) and the computer can produce efficiency gains that are substantial. When the system falls outside it's comfort zone, which is possible due to many reasons like an input not catered for, or a malfunction, or an operator encountering an unfamiliar situation, the role of the operator, although unchanged in goal (fly the plane), changes in implementation (from being 30 seconds ahead of the plane to asking "what's it doing now") - the operator is reduced to fighting a complex computer in a complex battle to perform the simplest of tasks with the likely consequence of producing another unexpected outcome that makes the situation worse than before.

The solution is to have a voting button (please don't call it a panic button) that demotes the computer to observer status. But this still doesn't get the operator into the clear as the information presented by the computer may not be correct. However the operator, if experienced enough, is free to make a sound judgement on the quality of the data presented and discount it as he/she see's fit, unlike the computer. And there is the rub.

[CONF iture]

Sorry, I don't know the values of alpha-prot and alpha-floor.
I would think the values of alpha-prot and alpha-max are a percentage of alpha-stall. I have seen some figures already but cannot remember where exactly at the present time ... Don't think it was official documentation either.
I believe the value for alpha-floor can be variable somewhere between alpha-prot and alpha-max.
I'll try to remember where I have seen those data ... ?

[A33Zab]

Alpha floor is activated:

if filtered AoA(3s) > threshold; which depends on CONFIG, GS variation and difference between GS and Vc.
or
SS NU >14° and theta > 25°
or
SS NU >14° and AoAprot.

Alpha floor is inhibited > M 0.53 or by FMGEC @ certain engine failures.
---

but that's what the book says, in your opinion it could be anywhere...

[DozyWannabe]

Some members of the SNPL* have been involved in a long-standing political dispute with Airbus which is obviously going to have an effect on those demands. I personally (for all that may be worth) think it's wrong-headed, and it's certainly not based on a thorough understanding of the systems design. Others will feel differently, and that's their prerogative.

I doubt much will come of it because the existing system is demonstrably as safe as any of the alternatives on offer - the narrative history of the types and the stats bear this out.

Airbus hired engineering pilots like the late Capt. Corps and others of his calibre because they *wanted* that kind of input on the design - you don't hire a former ARB chief test pilot simply to make him toe the company line. It's almost slanderous to imply that may have been the case, or that his focus was on anything other than professionalism and safety above all else. Remember that he died in the Himalayas - he didn't need to be there but nevertheless he personally demanded to head up the technical investigation team on that accident. Understand that he not only dedicated his life to making your lives up front - as well as ours in the back - as safe as possible, he ended up *giving* his life in pursuit of that cause.

You can deride my input as "knee-jerk" (it isn't), you can throw as much mud at me as you please and I won't give a flying glob of monkey-spunk - but to refer to a pilot of Corps' character by putting his life's calling in sarcastic quotation marks, or to claim that he and his team would ultimately be little more than rubber-stamps for company policy is, in my opinion, utterly beyond the pale. Shame on you.

* - Aided and abetted by fringe agitators like Henri Marnet-Cornus and Norbert Jacquet...

[Lyman]

I have no idea who Monsieur Corps is. Other than having an unfortunate surname, I understand he worked for Airbus in the development of the Ziegler system. I found this from one of your posts on another thread, in reference to this unfortunately now deceased pilot.

"but also because he had a knack of explaining and proving the systems in public in a way that pilots could get behind (and as DP Davies' successor at the ARB before he joined Airbus, Corps had the "old-school" clout to make people listen)."

Sorry, that makes the gentleman a salesman. That he believed in it is not the question. He was paid.

The standard in business is to avoid "the appearance of impropriety". Objectivity is hampered by money. Assumptions mean nothing.

On the list the Pilots are demanding are certainly items that were approved by your paragon. Being fallible is human, and no reason for lack of respect. However, there is no shame in calling to question said fallibility.

Shame on me? You sure you're not a Lawyer?

[DozyWannabe]

You're a piece of work, Lyman. Aside from a heartfelt suggestion to do your homework - and you can start here:

Gordon Corps - overview (http://tinyurl.com/bnzyozz)

Guardian article reporting his passing, with mini-bio (quoted in an email from my late professor) (http://www.kls2.com/cgi-bin/arcfetch?db=sci.aeronautics.airliners&id=%[email protected]%3E)

Old Flight article on the A320 and Captain Corps' involvement (http://www.flightglobal.com/pdfarchive/view/1986/1986%20-%202148.html)

Another old Flight article (http://www.flightglobal.com/pdfarchive/view/1987/1987%20-%200873.html)

...a refutation - specifically that there is not and never was any such thing as "the Ziegler system" (he was effectively merely a figurehead on the A320 project) and the explanation that "Corps" is a noun that refers to a group of people, usually military in nature - at this point I have nothing more to say to you. So many posts of yours seem to be deliberately phrased to elicit an extreme response and ignore information that I know you've been privy to in the past that I can no longer trust anything you say.

To the rest of you - I sincerely request you reflect a little harder and longer before repeating things that are demonstrably untrue about the Airbus system - no matter what you personally may think of it - if only out of respect for one of your own, who has tragically been largely forgotten in the maelstrom of bitterness and politics regarding Airbus, and did the best job he could with the tools and team he had to make our lives as trouble-free and safe as possible.

[EDIT : Note also that the SNPL "Special COMETEC" dates from September and as yet we have heard no further word on the matter.]

[Chris Scott]

BOAC,

Dozy Wanabee has a tendency to regard Airbus FBW through rose-tinted spectacles, but he provides a comparatively mild, rational counterbalance to the ill-informed bigotry of many armchair critics who, like himself, have little or no flight time on them. Seems a pity that, despite all the time you have devoted to the AF447 threads and others on the subject, your own knowledge of the Airbus cockpit remains unashamedly negligible.

As for the SNPL, their opinion has to be seen in the light of their consistent opposition to Airbus technology since the introduction of the first two-pilot glass cockpit on the A310 in 1983, and the Habsheim affair in 1988. As usual, some of their demands are rhetorical; others may be arguable.

In case anyone infers otherwise, I've argued in principle against non-driven throttle levers and non-interconnected sidesticks since 1986, despite flying them full-time from 1988 - 2001. I doubt that even the highly-respected Gordon Corps (Lyman, please note) could have overruled Mr. Ziegler on those fundamental engineering issues. But the overall package is a good one. The fact that airlines discouraged, or even banned their pilots from timely removal of certain automatics (such as A/THR, AP and FD) is ultimately their fault, and contributed to AF447.

[DozyWannabe]

@Chris Scott - in general, thanks for the support, but I want to be clear here - no offence:

Dozy Wanabee has a tendency to regard Airbus FBW through rose-tinted spectacles

I most certainly do not. I am as well aware of its potential drawbacks as I am of its positive aspects and I completely understand why a departure from the de facto control setup that had been engineered to resemble the post-war state-of-the-art would cause consternation, particularly among the piloting community. Despite being a software man, my late Prof. was actually a dyed-in-the-wool sceptic and he taught us all to always question, test and evaluate in the way that all engineers should.

As an engineer, it is central to my credo that there is no such thing as a perfect system. The Airbus FBW control setup is an imperfect evolution of an imperfect system - that is not in question. The debate is therefore a subjective assessment of whether the benefits of the newer system outweigh the drawbacks, as opposed to the very real benefits and drawbacks inherent in the old system and as such it is not going to be resolved any time soon, if ever.

I doubt that even the highly-respected Gordon Corps (Lyman, please note) could have overruled Mr. Ziegler on those fundamental engineering issues.

Capt. Ziegler, despite having a degree in engineering, never really exercised that qualification. He may have been the project lead and arbitrator, but he had absolutely no authority to overrule Capt. Corps and his team on engineering matters. In fact all the teams had ultimate power of veto - if any aspect of the design could not be accepted by all, they all went back to the drawing board and started again.

That aside, I acknowledge and respect your opinion on interconnected PFCs and moving throttles. However I hope you will agree that the much-feared negative impact on safety held over these factors in the late '80s has not been borne out by the record of the Airbus FBW types. In fact we've had plenty of accidents in the interim where these elements were present and yet made no material difference to the outcome. Loath as I am to give much weight to anecdotal evidence, it does at least raise the question of how necessary such things are, does it not?

[Gretchenfrage]

As for the SNPL, their opinion has to be seen in the light of their consistent opposition to Airbus technology since the introduction of the first two-pilot glass cockpit on the A310 in 1983, and the Habsheim affair in 1988. As usual, some of their demands are rhetorical; others may be arguable.


Chris Scott, what authority are you claiming to be as to usurp the right to pretend this? Do you want to join the dw-camp that admittedly have vaste knowledge of Airbus systems, but feel entitled to be in a rightful position to belittle pilots who disagree and criticise this system.
The opinion of a professional pilots union, even french, are to be taken extemely seriously in terms of safety, any other approach is biased and puts the author into a somewhat shaded light.

It is time to accept that too many parties ask for a closer look into the Airbus design. The bipartisan comitee from the 90's (i can't remember the title), an article of your homonym the much regarded Robert Scott, a comparative article in the Swiss aviation publication Cockpit and even Sullys contribution, that's too many professionals who ask for the very same corrections, notwithstanding the many contributors on pprune.
I am tired of all the smokes amd mirrors that are set up to take the attention away from these critics. I am just as tired of being cried down by people who have not operated the system themselves, or those who have operated only this very system. Some of us have been priviledged to fly the other major competitors as well and no longer silently accept to be disregarded.
Where there's smoke, there's a fire and in aviation we tend to take fire seriously, even if it's only a warning, don't we? I hope we at least agree on that.

[DozyWannabe]

I love the smell of false equivalency in the morning...

Do you want to join the dw-camp that admittedly have vaste knowledge of Airbus systems, but feel entitled to be in a rightful position to belittle pilots who disagree and criticise this system.

Says who? There's no belittling going on here, simply a reasonable request that the vocal minority acknowledge that they are just that - unless they can prove otherwise - and that they answer questions put to them honestly.

The opinion of a professional pilots union, even french, are to be taken extemely seriously in terms of safety, any other approach is biased and puts the author into a somewhat shaded light.

Given that this particular union's motives are reasonably considered somewhat suspect in terms of objectivity, Chris's scepticism is not only reasonable, but also logical. Given the 29 years (5 of which pre-date the introduction of Airbus FBW) of opposition from factions within this union, it's a little rich to accuse others of bias in this matter.

It is time to accept that too many parties ask for a closer look into the Airbus design. The bipartisan comitee from the 90's (i can't remember the title), an article of your homonym the much regarded Robert Scott, a comparative article in the Swiss aviation publication Cockpit and even Sullys contribution, that's too many professionals who ask for the very same corrections

This is a thoroughly false assertion. The naysayers are, and always have been, a minority - no matter how vocal they have been. If the "bipartisan committee" you refer to is the IFALPA ADO group, then the non-binding resolution dates from the '80s - not the '90s - and is due for a re-appraisal soon (according to current member Capt. Terry Lutz). Capt. Sullenberger's view on the matter amounted to little more than a commentary - he certainly did not call for a change in the systems design.

notwithstanding the many contributors on pprune.

There are at most maybe 10 contributors on PPRuNe who hold a view on the matter comparable to yours (and who make it their business to zero in on every Airbus thread to make their viewpoint known). They may be consistently vocal, but that does not indicate a consensus on the matter - not even slightly.


I am tired of all the smokes amd mirrors that are set up to take the attention away from these critics.

What smoke and mirrors? The "Airbus-sceptic" position has been repeatedly challenged with cogent arguments from parties that include as many pilots as non-pilots. Some parties among the sceptics have repeatedly promised new evidence and yet failed to deliver. Neither you nor anyone else among the sceptics has been able to prove your position is held by a majority of pilots, let alone whether that position is objectively correct.

I am just as tired of being cried down by people who have not operated the system themselves, or those who have operated only this very system. Some of us have been priviledged to fly the other major competitors as well and no longer silently accept to be disregarded.

And yet I can recall clearly posts by pilots on here who have openly admitted to missing the relative simplicity and reliability of the Airbus system, having transferred to other types. I repeat - no-one, least of all myself, is trying to disrespect you for the position you hold. On the other hand, if you try to portray your position as reflective of a majority of pilots without supporting evidence, then don't be surprised if you and your fellow sceptics are challenged on that point.

Where there's smoke, there's a fire and in aviation we tend to take fire seriously, even if it's only a warning, don't we? I hope we at least agree on that.

Thus far there is no smoke (in the form of objective data) suggesting Airbus FBW is any less safe than the alternatives available. None. Neither you nor anyone else is capable of wishing such data into being, no matter how much you may want it to be so.

[737Jock]

Thus far there is no smoke (in the form of objective data) suggesting Airbus FBW is any less safe than the alternatives available. None. Neither you nor anyone else is capable of wishing such data into being, no matter how much you may want it to be so.

Would be interesting to see how many FBW related incidents (involving protections) are recorded for airbus vs 777 (the first Boeing FBW with protections).

For airbus there are at least 4 where it is questionable if the protections did not make matters worse.

As for your heroic statement that the EVA pilots correctly switched off ADR's... Since AF447 every airbus pilot will know how to get the aircraft in direct law!

[Gretchenfrage]

There's no belittling going on here, simply a reasonable request that the vocal minority acknowledge that they are just that.
The naysayers are, and always have been, a minority - no matter how vocal they have been.


And what other than belitteling is just that? How educated is it to call a minority to acknowledge what they are and by this implying that their opinion is worth less than the majority’s? Isn’t it the very right, legitimate and civilised weapon for a minority to speak up?
Are we back to those kind of times??


If the "bipartisan committeee" you refer to is the IFALPA ADO group, then the non-binding resolution dates from the '80s - not the '90s - and is due for a re-appraisal soon (according to current member Capt. Terry Lutz)

Maybe, but ….. is only criticism of the Airbus system due for a re-appraisal? You do imply by this that the system would be immune to a re-appraisal itself, don’t you?
Such self imposed “immunity” is revealing and exactly what many criticise.

Thus far there is no smoke (in the form of objective data) suggesting Airbus FBW is any less safe than the alternatives available. None. Neither you nor anyone else is capable of wishing such data into being, no matter how much you may want it to be so.

The smoke is admittedly not in form of objective data, but that is the very nature of “smoke” used as a metaphor in this case by the way. It is the many threads on forums, in the press and the many publications about the matter that form the smoke. There is not a tiny fraction of the same for the competing system, which tells a story!
Additionally there are the beloved statistics (hull losses and fatalities) that point clearly to one side. You can always debate about the higher number of airframes of one, but you cannot dismiss that one system has had NO fatalities so far and the other one has. That in itself should raise big flags if your concern is safety at all!

I stand by my argument, even if I am a despised minority:
The Airbus system needs modification.

Happy new year, I'm leaving for the party now.

[DozyWannabe]

Would be interesting to see how many FBW related incidents are recorded for airbus vs 777 (the first Boeing FBW with protections).

Difficult to do quantatively as there are fewer T7s in service than there are A330s and A340s combined, let alone the narrowbodies of the A320 series. The truth is that in terms of hull losses in normal operations the numbers are too small to make a statistically valid comparison, which - lets face it - is a good thing for all types.

There are no accidents or incidents for any of the above types that can be attributed to the FBW systems, at least in isolation. Automation is a different matter, but automation and FBW are two very distinct aspects of airliner operation. For example, there are plenty of automation-related hull losses for the B757 and B767, neither of which are FBW. The Turkish 737 that pancaked short of Schiphol can also be considered an automation-related accident but - as you know - the 738 is certainly not an FBW design. In that case, moving thrust levers signalled a reduction in thrust way beyond what the crew were expecting, but they never picked up on it. The same goes for the Birgenair B757 crash where despite having the yoke in front of him, the F/O neither stopped the Captain from pulling into a stall nor corrected him after he had done so.

The truth is that while it may be comforting to believe that a more traditional setup will make fault diagnosis easier for pilots, the evidence does not support that supposition. The PF of AF447 may have pulled into a stall, but so did the Captain of Birgenair 301 and ColganAir - neither of which had spent any time on a FBW Airbus.

Similarly while I do not doubt the existence of design problems in the Airbus systems, I am equally convinced that some remain in the B737s that you fly among others.

...and by this implying that their opinion is worth less than the majority’s?

No-one's implying that - you added that assertion yourself.

Maybe, but ….. is only criticism of the Airbus system due for a re-appraisal? You do imply by this that the system would be immune to a re-appraisal itself, don’t you?

Not at all - the system as a whole will be re-evaluated on the basis of the data acquired since the original statement was released.

The smoke is admittedly not in form of objective data, but that is the very nature of “smoke” used as a metaphor in this case by the way. It is the many threads on forums, in the press and the many publications about the matter that form the smoke. There is not a tiny fraction of the same for the competing system, which tells a story!

If the threads on forums are shown to be based on inaccurate information and argued by the same posters over and over again (as many are in this case), then it's only natural that the veracity of the information be questioned. Likewise, given that the press are routinely mocked when reporting incidents on this forum, why should it be any different when they try and stir up scandals where none exist?


Additionally there are the beloved statistics (hull losses and fatalities) that point clearly to one side. You can always debate about the higher number of airframes of one, but you cannot dismiss that one system has had NO fatalities so far and the other one has. That in itself should raise big flags if your concern is safety at all!

As I said on the AF447 thread, if we were to apply that same analysis technique in 1980 to the three US-built widebody types introduced in the '70s then we would be forced to conclude that the 747 was the most dangerous design of the three and should be withdrawn forthwith. With benefit of hindsight we know that's rubbish, not just because of the 747's exemplary record since then but because, as with the T7-A33/40 comparison, the numbers are too small to be statistically significant.

I stand by my argument, even if I am a despised minority

You're not despised, you're simply being asked to show the work from which your conclusions are drawn.

[BOAC]

your own knowledge of the Airbus cockpit remains unashamedly negligible. - correct, and never claimed otherwise so you are more than welcome to claim that medal if you feel the need to.

Having 'grown up' in aviation as a real pilot (unlike many on here) well before the magenta line days I merely try to look at it from a real pilot's pov (unlike many on here) and comment on what I would wish to see/have (and find myself amazed at some of what I do see).

By the way, if you care to look at a dictionary, you will see that 'bigotry' can be a subjective word.

[Cool Guys]

The AB FBW controls with all their complex protections and laws obviously work OK in normal situations and statisically there seems to be no fundamental issues with the system however there seems to be some agreement from those who fly the plane that there are some refinements that could be made. No device made from a complex system of interacting mechanical and electrical components is perfect. There is always room for improvements. With any breakdown, failure or crash there is an opportunity for improvement and refinement. The requests from the AF pilots union seem like a good list of sensible refinements. The AB engineers may have all ready been looking into these points. At the end of the day we must learn and improve the product so there is less opportunity for further accidents. I hope AB don’t try to save face and insist their existing system is perfect. I hope they can be professional, look at it objectively and refine their product to make a better,safer plane.

[737Jock]

Well that's a load of BS Dozy... Nobody was talking hull losses.

But while we are at it only one 777 has been a hull loss and FBW could not have saved that nor did it play a role.

Airbus however has had many unfortunate incidents, due either the system not being understood or simply the FBW fighting with the pilots for control. Some crashed!

[HazelNuts39]

Question for HazelNuts39, at which angle the AoA probes should freeze for Alpha Floor to activate before M.53 is reached ?
I believe the value for alpha-floor can be variable somewhere between alpha-prot and alpha-max.Agreed. But even without knowing the threshold value, it is unlikely that alpha-floor would be activated due to freezing of the alpha sensors below M.53 in a typical climb speed schedule. The green line in the following graph shows the AoA at significant points of the climb speed schedule for an A330 at 229 tons / 29% cg. That supports the remark in the PNC CONTACT article that blockage of the alpha sensors occurred fairly early in the climb, in the graph before the acceleration to 300 kt at FL100.

http://i.imgur.com/H8MfX.gif?1

[BOAC]

I'll ask again, jcjeant: - Quote:
Originally Posted by the Google translation
Airbus could not regain control of their aircraft when they reproduced stall Rio .

- do we have any information on this 'test'? Have I missed it on the forum?

[DozyWannabe]

Airbus however has had many unfortunate incidents, due either the system not being understood or simply the FBW fighting with the pilots for control. Some crashed!

Actually there are zero FBW-related crashes for either type. I don't think there are any serious FBW-related incidents either. Some argue that the scraped wingtip in Hamburg counts, but in that case the crew were trying to land in excess of minimums and the Captain violated control handover protocol.

Don't get automation confused with FBW - two very different things. In fact the automation on the A320 is no more complex than that on your 737NG, which is why automation-related crashes and incidents are comparable in number across all types and manufacturers.

@Cool Guys - read Chris Scott's post. The SNPL press release is a political statement, and their "requested changes" are not common-sense. They constitute a fundamental misunderstanding of the design and if implemented would not only have very little - at best - in the way of safety benefit, but would also effectively undermine the commercial edge Airbus have, which is arguably the SNPL's goal.

[Chris Scott]

Some of these exchanges are reminiscent of a Rumour & News thread. Perhaps we might all calm down a bit?

I'll start by admitting that my knowledge of Boeing-style FBW is negligible, and flight experience nil; rather like BOAC's in relation to Airbus FBW. ** That's why I never presume to comment favourably or otherwise on a Boeing FBW package that seems to have many merits - as does the Airbus one. As I said, it's a pity that BOAC's condemnations are based - as in the case of Lyman/Bearfoil - mainly on intuition and hearsay.

Lyman,
Further to your comments on Gordon Corps, have you not heard of the US Army Corps? The American pronunciation may be different from ours, where the p and s are normally silent. However, when my airline took delivery of the A310 in 1984, and Airbus pilots were training us, there was one West African service crewed by Captains Dave Deadman and Gordon Corps.

DozyWannabe
(sorry for the spelling error in my previous),
Thought you'd appreciate "rose-tinted spectacles" in relation to a product of "la Ville Rose"? ;)

You talk of Airbus's departure from existing flight-control-system design causing "consternation... particularly in the piloting community" I think the arguments that we in the technical study groups of BALPA and IFALPA raised in the mid-1980s in opposing the non-driven throttle levers and non-interconnected sidesticks, were correct, but their ergonomic deficiencies have caused fewer problems than we predicted. (Of course the other big concern was the general reliability of computer systems, including Airbus's decision to use modest, tried-and-tested, commercial microchips - rather than purpose-built, mathematically-correct ones - and their decision to avoid triplex architecture. It was also widely predicted that system anomalies would be untraceable by accident investigators. Nevertheless, we didn't black-ball the inevitable.)

The day after tomorrow (January 1st) will be the 25th anniversary of the start at Blagnac of the first BCAL/BA A320 pilot-conversion course (AF's first course had started a few days earlier). Except for two of us line pilots, plus a CAA inspector, the captains were BCAL management, including the A320 project manager. We had come from a variety of aircraft types: the B747-200, DC10-30, and BAC 1-11. Two of us had earlier flown the A310: from 1984-6. Once on the simulator, we quickly adapted to the sidestick, and soon learned to live with the non-driven throttle levers (which, however, provide the sweetest manual-thrust control of any aeroplane I've flown). We had to wait for the completion of mods to the electrical system, and the type to be certificated, before we could fly an aeroplane.

Gretchenfrage,
Although I see you predate me on PPRuNe, I don't recall your User Name from the many Airbus FBW discussions I've contributed to - forgive me. Judging from your post, you are in a similar position. I have no intention to belittle anyone; only to express my opinion, and challenge weak or false arguments (usually politely) when I recognise them. It's apparent on this thread that the flak is coming, as usual, almost entirely from those who are anti-Airbus (and usually praising Boeing); very little is going in the opposite direction. That's fine when the author is someone who has considerable Airbus flight experience, like Conf_iture.

The ideal, however, would be to hear from pilots who are literate, dispassionate and technically perceptive, who have at least several years' flying experience of both FBW philosophies. You seem a little reticent to reveal your own, but do you perhaps fit those criteria?

It may be that some A320 pilots posting here have found themselves on type against their inclination, as a stepping stone to something else - perhaps a bigger Boeing. The A320 has been so successful that it has become the ubiquitous, boring, short-haul workhorse - like the B737 was in the 1980s and '90s. It's no longer the cutting-edge, exciting challenge that I relished 25 years ago. The A330 has been eclipsed for size and range by the B777, so is somewhat lacking in charisma. The A340 got a suitable engine too late in its development because, in the 1980s, Rolls Royce abandoned plans to supply a more powerful engine than the CFM-56. A380 jobs are still at a premium. Are their criticisms influenced in any way by disenchantment, I wonder?

I regard myself as a Francophile, so it gives me no pleasure to point out that my former opposite numbers in SNPL bring a lot of baggage to any discussion on Airbus FBW. By the 1980s, BALPA had a more pragmatic approach to new technology. For instance, we did not demand a third crew member in the A310 cockpit. My copilot on the A320 course was the chairman of the BALPA new-aircraft study group, of which I was a member (as mentioned above). The fact that we were so critical of some of the concepts was extra motivation for doing the conversion; to see for ourselves. Our attitude was sceptical, but positive. If we had discovered anything dangerously unacceptable, we would have been reporting it to the aviation world. We found no such thing, although my friend did manage to persuade Bernard Ziegler to modify the speed index on the ASI during an Airbus/IFALPA meeting the following year. Two fatal accidents later brought AFS ergonomic weaknesses to light. Admittedly, although we were aware of the features concerned, we had failed to predict that they might contribute to an accident, and I don't think SNPL did.

I was an A320 skipper at the time of the Habsheim accident that first summer, the captain of which had overlapped us in Airbus Flight Training. Having looked at the video, formed an understanding of the cause, and listened to the hysteria from the media (and even doom merchants in our own airline), we just had to keep on flying passengers as normal - no thanks to SNPL. When I say that some of SNPL's demands are rhetorical, I mean that we lost the battle for those in the 1980s. I say again, the overall package is good; warts notwithstanding.

737Jock,
There's no doubt that the B777 is an excellent airplane. But, until a few months ago, it was the only Boeing in service with FBW. Also, it is a long-haul type, each A/C performing far fewer flight cycles per year than an A320.

　

** The last Boeing I flew was the 707. Its only powered flight control was the single rudder, protected by a crude Q-feel unit, and incorporating - on later models - the luxury of a series yaw damper. The ubiquitous FD108 flight director was excellent for its 1970s era. There was a single AP, with a height (altitude) lock. On one occasion, after it failed at top-of-climb out of Caracas, the captain and I took 20-minute turns to hand-fly the big beast home to Gatwick, finishing the cruise at FL410.

[mm43]

Originally Posted by the Google translation
Airbus could not regain control of their aircraft when they reproduced stall Rio ...
@BOAC;

May I suggest the above translation is from an agenda driven article.

Furthermore, while there are many references within all the AF447 threads in this forum to the inability of current level 3 SIMs to replicate accurately events outside the designed for flight envelope, Airbus may well have incorporated extended data obtained from this fateful flight into a test SIM, and neglected to tell us.:{

While having a look around, I came across this interesting little report by the NASA Safety Center entitled "What's Happening?" - NASA (http://nsc.nasa.gov/SFCS/SystemFailureCaseStudyFile/Download/276/)

[Lyman]

Hi Chris...

In re Corps...

I was trying, badly, it turns out, for some political satire. My President, Obama, presenting an award to a Marine, announced his rank as:

"Corpseman..." no kidding. I forgot DW was UKish, so would not have known.

My bad....

[BOAC]

Thanks mm - that makes sense..unless......

I'm not sure the NASA paper adds much, but I think the last two ??NASA?? findings are important

•Extensive reliance on automation for normal operations can undermine a time-critical, successful operator recovery from an off-nominal event.If there is a manual mode, operators must become and remain proficient in its use.

•There is no single right answer to the issue of human control versus machine control in human-machine interfaces. But as the need for human intervention follows the value of the system, the need for high-fidelity experience in compound failure scenarios, not just a single component or feature, becomes essential to timely action..

[mm43]

Reminds me of NASA's attitude toward the "shuttle". They reserved the right to take control remotely, but it wasn't until after the Challenger accident that it was pointed out to them that they had forgotten to make provision for remotely lowering the LG!

Something learned, and the necessary mods were made.:ok:

[DozyWannabe]

Thought you'd appreciate "rose-tinted spectacles" in relation to a product of "la Ville Rose"? ;)

I didn't make that connection admittedly, but I was pretty certain you didn't mean any harm. The only reason I wanted to clearly refute the notion is because I am well aware of the system's limitations. That I don't consider it worse than anything else around at the moment is based on a lot of reading and a series of very heavy-duty modules around software engineering and reliability that made up part of my degree. :)

You talk of Airbus's departure from existing flight-control-system design causing "consternation... particularly in the piloting community" I think the arguments that we in the technical study groups of BALPA and IFALPA raised in the mid-1980s in opposing the non-driven throttle levers and non-interconnected sidesticks, were correct, but their ergonomic deficiencies have caused fewer problems than we predicted.

I'd slice things a little more finely than that. As an engineer I know that I'd want concerns laid out as soon as possible in order to make sure that they are dealt with. One thing that was made crystal-clear during the courses I mentioned above was that this was one of the most - if not *the* most - difficult and serious undertakings in aviation engineering of that era. The software angle alone involved heaven knows how many man-hours of testing, re-testing, hardcore statistical maths that would take me years to understand - the tools we take for granted in software metrics and design today didn't exist, so they had to be invented and built with the same level of rigour as the final product.

I'd hope that if you and your colleagues in the technology group had been privy to just how much work went into it at the time, it may have at least eased your worries slightly. The reason the flight controls and thrust levers were designed the way they were had nothing to do with an intent to take anything away from the flight crew, it was simply reasoned that the technology had become reliable enough to make that evolutionary step safe, and provide the feedback in other ways.

I take a little issue with still referring to these factors as "deficiencies" - at this stage, given that their reliability and suitability for the task has been proven I think it can be reduced to "differences".

(Of course the other big concern was the general reliability of computer systems, including Airbus's decision to use modest, tried-and-tested, commercial microchips - rather than purpose-built, mathematically-correct ones - and their decision to avoid triplex architecture. It was also widely predicted that system anomalies would be untraceable by accident investigators. Nevertheless, we didn't black-ball the inevitable.)

The Apollo programme and Concorde were of the era of purpose-built computers and logic - I suspect Airbus took their cue from the introduction of general-purpose microprocessors with the Space Shuttle, and surmised (correctly) that was the way the industry was headed.

Truth be told, with proper application of redundancy, defence-in-depth and tried-and-tested hardware - I suspect that the commercially-available equipment would provide equal or better reliability than a bespoke unit at a fraction of the cost. Of course, only time would bear that assertion out.

Two fatal accidents later brought AFS ergonomic weaknesses to light.

Which are you referring to here?

As an aside, my first ever flight was on a BCAL 1-11. I don't remember much of it however, being only three years old at the time. :)

[Kimon]

Has any noticed that the S/Ss on the A400M have two red buttons each rather than one?
Any idea to its purpose?

[Clandestino]

Which are you referring to here?

I'd guess Bangalore and Strasbourg. Selecting altitude below runway elevation and then trying to open descent to it in first case and selecting 3300fpm descent instead of 3.3 degree flightpath in second, without performing basic instruments scan and crosschecking what was the effect of FCU selection. Besides, had Air Inter crew managed to actually get to ANDLO before commencing descent therefore performing the approach along the designated track (see appendices 11 and 12), they might have missed the mountain but whether they would realize something was terribly wrong at 2000 ft cloudbase or just continue descent into fields southwest of Strasbourg is anyone's guess.

Autopilot is pilot's helper, it is mindless entity that absolutely can not perform pilot's job! OTOH, if this basic fact was understood around PPRuNe, we'd be poorer for many an excellent (if somewhat unintentional) piece of absurdist humour.

[737Jock]

Don't get automation confused with FBW - two very different things. In fact the automation on the A320 is no more complex than that on your 737NG, which is why automation-related crashes and incidents are comparable in number across all types and manufacturers.

That is where you are mistaken Dozywannabe! I have more hours on A320 then on 737, although the 737 is the aircraft I was flying when I created my username. I haven't flown it in years.

I'm not confusing anything here! So unlike you think I know what I'm talking about! Airbus FBW has some serious issues!

SNPL is completely correct, and I'm not french, don't work for AF or am related to boeing or airbus in any other way then a typerating on my licence.

And yes there are incidents accountable to airbus FBW, SNPL mentioned 4 where it played a factor!

But lets trust in an engineer who never flew any of the aircraft or held command on it.

[DozyWannabe]

And yes there are incidents accountable to airbus FBW, SNPL mentioned 4 where it played a factor!

Which four? Apologies, I cannot read French.

[jcjeant]

Hi,

FBW is no more dangerous than another mode .. it's FBC (Fly By Computers) that can be dangerous
Side note .. I wonder why FBW for those latest generation aircraft
A Tiger Moth is a real FBW aircraft :) .. the latest generation aircraft are FBEW (Fly By Electrical Wires)

[Bengerman]

Main problem with Airbus is that they tell you it is straightforward, they tell you that the aircraft will look after you, they tell you all about the protections and how they work, they tell you about what happens when the protections are degraded.

What they don't tell you is that because of all these design "improvements" you, the pilot, have to watch it far more closely than a "conventional" aircraft.

Typical case in point is if you are flying an approach with the autopilot disconnected (standard Cat 1) and you have reason to Go Around. A conventional aircraft will pitch up for you as the power comes up, an Airbus will simply fly you into the ground at a higher speed, unless you do some thing about it!

[Chris Scott]

Quote from Bengerman:
"...if you are flying an approach with the autopilot disconnected (standard Cat 1) and you have reason to Go Around. A conventional aircraft will pitch up for you as the power comes up, an Airbus will simply fly you into the ground at a higher speed, unless you do some thing about it!"

That's a very sweeping statement.
First: if you're talking about jets, you are assuming engines mounted under the wings.
Second: in that case, you are right to say that the conventional aeroplane will lift its nose beautifully. From then on, particularly during flap retraction, you or the APauto-trim will be working furiously to stop the beast sitting on its tail. Have you ever done it?

[BOAC]

an Airbus will simply fly you into the ground at a higher speed, unless you do some thing about it - was this not one of the 'surmises' on the Tripoli AB crash?

[DozyWannabe]

Useful discussion of A320 Go-Around mode, SRS and MAN TOGA here:

http://www.pprune.org/tech-log/371448-a320-toga-selection-go-around-mode.html

Rule Number 1 : Read the flippin' FCOM. :ok:

[Lyman]

Bengerman refers to a manual handling issue, not a managed GA.

Read the flippin' thread?

:ok:

[DozyWannabe]

That may or may not be so - Bangerman's post is not clear as to whether he's referring to the TOGA buttons fitted to some types (which do use their own automation system) or the aerodynamic tendency of podded-engine designs as Chris Scott describes. Until we get clarification either way, I'm just trying to provide some useful background info.

[Lyman]

From Bengerman, I get an auto OFF surmise, and it is clear at least to me he does not refer to underslung thrust, but Airbus g command Pitch, which moots the effect, in any case.

Follow?

[DozyWannabe]

Yes I follow - but I'm not going to presume until the intent is confirmed one way or the other. "Stable flightpath" pitch command or no, if you have positive pitch and select TOGA then the aircraft will climb.

Also, I'd appreciate it if you didn't try to pick holes in what I'm saying to elicit a response. I don't want to get into a slanging match with you - frankly, your dismissiveness of any line of inquiry that doesn't fit your preconceived notions has run its course with my patience - and I'd rather keep schtum and see what others have to say. Hope you're OK with that.

[Lyman]

Perhaps I am misreading your purpose, and you are merely trying to supply background. Because if one looks closely it could appear that your purpose is to smear scent on the trail that is not the animal we track....

:ok:

[Bengerman]

OK.

B737-400 auto throttle in, auto pilot out, CAT 1 approach G/A from, say, 200'. In the time it takes to say "Go Around, Flap X" apply nose down trim to counter over-rotation from pitch couple in a light aircraft....If you do not then you have to push quite hard! All B737 pilots know this!!

Airbus in same config has no pitch couple so after power shoved into TOGA aircraft will simply accelerate UNLESS pitch up is manually applied...result one smoking hole!

The title of the thread is "How safe is (airbus) fbw?

[DozyWannabe]

The title of the thread is "How safe is (airbus) fbw?

As far as I'm concerned the answer is and has always been "not perfect, but nevertheless as safe as anything else out there".

Thanks for the clarification - as I read you the procedure would naturally be different in a FBW Airbus than it would in a 734, but a difference in procedure between types is not a safety hazard as long as the correct procedure for that type is followed. I suspect you'd find similar behavioural differences and quirks between Boeing and MD/Lockheed types if you'd flown in that era (which you may have done) - the late 411A made a pastime of enumerating the benefits (as he saw them) of the L-1011's characteristics versus Boeing types.

My non-ATPL status aside, can it also not be said that the Airbus system actually provides for a simpler procedure? Because trim is automatic one does not have to worry about it - simply point the nose where you want it to go with the sidestick, select TOGA and everything else is handled by the system.

"Conventional" is not a synonym for "what Boeing do", and neither Boeing, Airbus nor any other manufacturer can successfully lay claim to having engineered the safest flight control system (although, salesmanship being what it is, they all try to make that claim).

[Chris Scott]

Bengerman,
I carefully addressed your manual go-around scenario, but you missed my points completely. (Are you a B737 pilot?) I'll start again.

In Direct Law, the Airbus would experience a marked pitch up, because of its under-slung engines, like a B737. A Fokker 100 or B717 would not, because of their engine configurations.

In Normal Law, the A320 pilot simply eases the stick back to achieve the desired pitch change. That is, he/she initiates and controls the pitch attitude, which is intuitive. Later, as the pilot lowers the pitch and the flaps are progressively retracted, the autotrim will respond to keep the elevator close to neutral, and stick movements will be minimal.

You accept that the B737 usually needs to be trimmed forward during the go-around, to stop over-rotation. Hardly intuitive, is it? You presumably also know that it's going to need a great deal more down-trimming during flap retraction. Pilots do what they have to do.

Perhaps I should add that, having flown the VC10 and BAC 1-11, which fall into the B717 category; the B707, A310 and DC10, which fall into the B737 category; and the A320, I've done manual go-arounds in all of them.

Chris

[Chris Scott]

Dozy,
Clandestino is spot-on: Strasbourg and Bangalore. (Right now, I can't remember which came first).

Strasbourg
resulted in a mod to the FCU, and the later addition of the selected rate to the relevant FMA on the PFD (VS or FPA). Because of limitations of space, the relevant FCU selector knob and associated selected-rate window are dual-function: VS or FPA. Changing from VS (actually HDG/VS) mode to FPA (actually TRK/FPA) mode is achieved by a push-button, confirmed by an adjacent indicator. Originally, IIRC, a selected VS of 3300ft/min DOWN would be displayed in the selected-rate window as -33. A selected FPA of 3.3 deg DOWN would be displayed as -3.3, IIRC. The similarity of the two readings is thought to have misled the crew but, as Clandestino also points out, that assumes the crew also failed to ensure that the relevant FMA was indicating FPA (if the theory is correct, it would have been indicating VS). The FCU modification changed the selected VS displayed from hundreds of feet/min to ft/min, giving -3300 in the above case. Once the FMA addition was incorporated, we encouraged crews to use that as the primary read-out, once you had found the knob and started turning it. That way, you observe the changing rate on the PFD, and minimise interruption of your flight-instrument scan.

The following is off-topic, and will be old-hat to pilots of aircraft with full EFIS, but may be valuable news to others:Operating Airbuses (and other modern types) demands the constant use and monitoring of the FMAs (flight-mode annunciators). Incorporated into the PFD, they enable you to confirm you have the desired autoflight mode, while minimising the time your scan is removed from the PFD. (The same applies to the indices of selected speed, selected HDG/TRK, and selected altitude.)

Some FMA changes are worthy of mandatory callouts, but these are all worthless unless made by the pilot NOT operating the FCU. (When the AP is engaged, FCU selections are normally made by the PF.) Unfortunately, no two fleets agree which calls should be made (calling them all would be bedlam). Where available, FMAs are the primary indicators of autoflight configuration, with or without the AP.

Moving on to Bangalore, the same applies. For the descent, the practice of dialling zero feet into the altitude selector and selecting OP DES ("open descent") with A/THR was always a hostage to fortune, but where it became insidiously dangerous was when the PF elected to break off instruments, and fly a visual approach without turning off both flight directors (FD1 and FD2). The reason is that OP DES forces the A/THR into idle mode, which is clearly indicated as IDLE on the thrust FMA. The FD gives pitch-attitude commands to maintain the speed selected by the crew (and displayed on the ASI). If and when the PF ceases to follow those commands, the speed will rise or fall, the thrust staying at idle (unless manual thrust is used). We quickly learned to turn off both FDs, and monitor the thrust FMA change to SPD (speed mode), in which the autothrust controls the speed. Sadly, that lesson had apparently not been learned by the crew at Bangalore. (Note my paragraph above.) After the accident, Airbus introduced an automatic mode change of the A/THR from IDLE mode to SPD mode in the event that the current speed falls below (IIRC) VLS.

[DozyWannabe]

Thanks for the clarification Chris, so if I've understood you correctly the ergonomics problems were primarily autoflight- rather than FBW-related.

[Kimon]

Following the IT148 crash, the display windows were widened to include extra digits IIRC.
This is where Boeing has an edge as all relevant display windows are totally physically separate.

[Kimon]

There are a total of 17 different flying modes on the A320 with all the possible combinations of A/P on/off, A/THR on/off, OP/DES, OP, CL, OP/CL and what have you...from an article entitled "Modal Confusion".

[DozyWannabe]

Following the IT148 crash, the display windows were widened to include extra digits IIRC.

Almost - the relevant display was given different multi-segment components to display a small "00" when in V/S mode.

This is where Boeing has an edge as all relevant display windows are totally physically separate.

Boeing and Airbus bought the autoflight interface components from the same supplier - Honeywell. The change (or similar changes in multi-function windows) was applied across all affected types, including some from both manufacturers - e.g. the 757 and 767 had a shared annunciator window for V/S and FPA mode.

Regarding flight laws (which are a distinct concept from AP/FD/ATHR), they are grouped into three - Normal, Alternate and Direct. Alternate has distinct sub-categories depending on the failure that caused it to activate - but in real terms all the pilot has to keep in mind above Direct is that only Normal Law has hard protections and autotrim is active in Alternate.

Turning the autoflight off renders the alphabet soup you refer to moot (just as it does in all modern airliners).

[CONF iture]

Agreed. But even without knowing the threshold value, it is unlikely that alpha-floor would be activated due to freezing of the alpha sensors below M.53 in a typical climb speed schedulerly in the climb, in the graph before the acceleration to 300 kt at FL100.
Thank you, in the meantime, apparently according to your graph, for Mach 0.5 alpha-max is around 9 deg and alpha-stall warning around 8. therefore it is not entirely far fetched to think that a light 330 with AoA probes blocking around 10 deg early after takeoff would encounter the favorable conditions for alpha-floor activation before reaching the Mach number of .53 ...

Note : Is it possible the dashed blue line should be above the solid blue one ... ?

[CONF iture]

Autopilot is pilot's helper
... as should be a protection !

If Airbus could once for all acknowledge this, they would nicely integrate somewhere in the instruments panel that single guarded switch the pilot could sensibly push to allow him to regain control in the shortest time when protections go wild.

[RetiredF4]

DW
Yes I follow - but I'm not going to presume until the intent is confirmed one way or the other. "Stable flightpath" pitch command or no, if you have positive pitch and select TOGA then the aircraft will climb.

Was 't that what the AF447 crew did, and it didn't work?

[TheRobe]

Mark my words, it will come out that you can't ground an Airbus enough to with stand a direct 100,000 volt lighting strike and not fry something.

Air France went down because those guys lost situational awareness at night in the soup. They didn't know if up was up, down was down, if the plane had air going over the wings or not because the screen weren't given them the information. The CVR conversation confirms this. Three guys looking at the panels and none of them knew what to make of it.

Carry on.

[bubbers44]

No it didn't work and never will. Toga is for go around. Everybody knows that. If you can not hand fly because the autopilot clicks off and you are at night in a bit of turbulence maybe you should try another profession.

[Lyman]

If you have positive Pitch and leave the throttles alone, you may climb. If you leave thrust alone and increase Pitch you will Stall. Increasing Pitch and Throttle sounds like a plan. At least until you Stall. Thirty seconds to sort a touchy roll, fifteen seconds left to live...

[bubbers44]

I don't think either of these guys had a clue what they were doing. Sad that airliners hire people with so low qualifications that they can not hand fly. It didn't happen when I was flying.

[Lyman]

bubbers44

I have always respected your feeling about the 447. So what can we take away from the UAS/UAoA related to safety?

Let's ask the pilots who fly them... In fact, let us read what a complete legacy group have to say, and Demand.

From UAS, NO HAL 'LITE' not even HAL 'MINUS', straight to DIRECT.

They don't get alot of time in ALT 2 (b). SO this group says change the cockpit, make it safer.

AOA INDICATION in the Cockpit, safer, important information, SAFER...

CONNECT the SIDESTICKS... Especially in an emergency, it would be nice to know what is commanded....ya think? Make it safer.

With corrupt AOA, Eliminate the need to trash the airspeed system to gain control, make DIRECT plentiful, and easy.

AIRBUS is not going to start building Boeings,bubbers, but some body in Toulouse needs to get their spanners and voltmeters together and get busy.

[HazelNuts39]

@CONF iture:

In clean configuration VLS = 1.23 Vs1g, AoA approx. 8.5 degrees.
So yes, when taking off on a cold day it is possible to hit alpha-floor at M<0.53.

Alpha_SW > alpha_max? No.

P.S.
On further thought, the AoA sensors could be frozen in any position when taking off at sub-zero temperatures.

[Lyman]

Alpha_SW > alpha_max? No.

What happens with ADR's in the inop box? Doesn't SW bug take a hike?

[Kimon]

http://norbert-jacquet.jacno.com/airbus-af447-rio-paris-et-incidentaccident-eva-air/

[Bengerman]

Chris,

In Normal Law, the A320 pilot simply eases the stick back to achieve the desired pitch change. That is, he/she initiates and controls the pitch attitude, which is intuitive. Later, as the pilot lowers the pitch and the flaps are progressively retracted, the autotrim will respond to keep the elevator close to neutral, and stick movements will be minimal.


First, the question was "How safe is (airbus) fbw?" so we are talking about the aircraft, not the procedures that bolt on to it, just the aircraft.

I am talking about a fully servicable aircraft, I agree with your summary above of a quietly executed manual G/A, I am, for the purposes of this argument, not interested in Direct Law.

My central point is that a conventional aircraft (ie. not fbw, could be an Airbus 300!) with underwing engines will pitch up when TOGA is applied. Since we are going around this is what we want the aircraft to do! So if the pilot does nothing more than push the thrust levers to TOGA the aircraft will go up!

If the pilot of an airbus FBW does nothing more than push the thrust levers to TOGA then the aircraft will accelerate into the ground. Please DO NOT say that this cannot happen, I am relatively inexperienced at this game, still learning after 36 years at it, and I KNOW that if it can be done then it probably will/has been done!

I have time on 737, 744 and Airbus FBW along with others and have no particular axe to grind in favour of any manufacturer, there are simply certain aspects of Airbus design that I feel are fundamentally flawed, the above example being just one of them.

[DozyWannabe]

Was 't that what the AF447 crew did, and it didn't work?

The subject we were discussing at the time was not AF447, it was how the aircraft behaves on approach when there is a need to go around.

[rudderrudderrat]

Bengerman,
If the pilot of an airbus FBW does nothing more than push the thrust levers to TOGA then the aircraft will accelerate into the ground.
If the pilot of a 737 does exactly the same, then he may stall due to the pitch power couple.
http://www.aaib.gov.uk/cms_resources.cfm?file=/Summary%20-%20AAR%203-2009%20Boeing%20737-3Q8,%20G-THOF%2006-09.pdf

"The Boeing 737-300 was on approach to Bournemouth Airport following a routine passenger flight from Faro, Portugal. Early in the ILS approach the auto-throttle disengaged with the thrust levers in the idle thrust position. The disengagement was neither commanded nor recognised by the crew and the thrust levers remained at idle throughout the approach. Because the aircraft was fully configured for landing, the air speed decayed rapidly to a value below that appropriate for the approach. The commander took control and initiated a go-around. During the go-around the aircraft pitched up excessively; flight crew attempts to reduce the aircraft’s pitch were largely ineffective. The aircraft reached a maximum pitch of 44º nose-up and the indicated airspeed reduced to 82 kt. The flight crew, however, were able to recover control of the aircraft and complete a subsequent approach and landing at Bournemouth without further incident."

Would you agree that both crews need to control the pitch attitude?

[BOAC]

Question for the AB experts. If you are on approach and decide to whack on TOGA, while continuing the approach with no demanded change in pitch (yes, I know....), can the elevator/auto-trim cope to prevent a pitch up?

[rudderrudderrat]

Hi BOAC,

Affirm.
It's one of LPC/OPC test items during LVOs with dual AP failure below 200 radio.

[Lyman]

If no one is noticing, we are firmly mired in the salient issues re: AF447.

That is a good thing...imo

BOAC, why would one select TOGA and try to maintain an approach?

Yet that is what AB does, failing input of NU?

The Boeing responds consistent with an intuitive design. Thrust=Altitude.

AB is counterintuitive? Neither Intuitive OR Counterintuitive? AB being AB?

If AB was human, "What a 'character' "

[RetiredF4]

DozyWannabe

The subject we were discussing at the time was not AF447, it was how the aircraft behaves on approach when there is a need to go around.

i´m well aware of that

DozyWannabe "Stable flightpath" pitch command or no, if you have positive pitch and select TOGA then the aircraft will climb.


The need to go around might as well be a situation, were airspeed and / or AOA is critical, stall is imminent or already present, were protections are not available for some reason. And then it might not work that way if not in normal law.

And to be even more nitpicking, if a go around at slow speed is performed a initial pitch of 1 degree, which per definition is a positive pitch, will not lead to a climb in an FBW airbus in normal Law. You have to have at least a pitch, which assures a positive climb rate. I think it is important, because your answer in response to the question Bengerman is therefore quite unprecise and misleading. The connection to AF447 is, because they have been mislead by a similar wrong assumption.

[TyroPicard]

Good heavens, what a fruitless discussion.

If you perform a manual G/A you have a target thrust and a target pitch attitude to achieve, and a target speed to maintain. TOGA achieves the first, PF achieves the second by manipulating the flying controls. In some a/c you have to trim out a considerable push force, in some you pull the sidestick back and then let go,..... what about the VFW- Fokker 614? TOGA thrust presumably produces a nose-DOWN couple... and a DC-10 with one engine out will require slightly different technique to one with all engines operating.

The secret is training..... training .. practice .. and disciplined mental preparation before every approach.

[737Jock]

Interesting is a go-around in direct law, which will require pushing the stick when going toga. In direct law the AB is speedstable and manually trimmed.
Two different movements with the sidestick for the same maneuver.

[jcjeant]

Good heavens, what a fruitless discussion.Certainly not
This discussion has taught me that Airbus had never considered (or tested) that AOA probes (a very important item for collecting data to be used by the flight computers) can be blocked and therefore could not know the impact on automatic flight and thus had never issued a procedure for this kind of incident
This kind of accident was however easy to predict (even if he never occurred before) when you know in what environment these aircraft are operated
EVA Air pilots thus (against their will) made this test and found a procedure
This discovery is worth its weight in gold .. isn't it ?

[DozyWannabe]

This discussion has taught me that Airbus had never considered (or tested) that AOA probes (a very important item for collecting data to be used by the flight computers) can be blocked and therefore could not know the impact on automatic flight

Really? I don't see anyone saying that - I think you just made it up.

Absence of evidence != Evidence of absence.

[jcjeant]

Absence of evidence != Evidence of absence.
Absence of procedure = ?

[Kimon]

These guys are unsung heroes!
They had seconds to find a solution which they did.
They knew A333-343 inside-out beyond any AFM, FCOM, and FTCM.
They had amazing reflexes.
They displayed airmanship of another dimension.

[Chris Scott]

Quotes from Bengerman:

"If the pilot of an airbus FBW does nothing more than push the thrust levers to TOGA then the aircraft will accelerate into the ground."

Yes, but that's a bit like saying that if the pilot of any aircraft fails to level off at the bottom of a normal descent to 2000ft (say) the aircraft will soon crash into the ground. (Thank you for omitting your previous reference to smoking holes this time: uncharacteristically alarmist if you are an airline pilot.)

"Please DO NOT say that this cannot happen..."

I did not, but see above.

"I am relatively inexperienced at this game, still learning after 36 years at it, and I KNOW that if it can be done then it probably will/has been done!"

In which case you must be aware of least one fatal accident following a go-around, in which the pilots and/or autopilot failed to overcome the strong pitch-up tendency caused by under-slung engines at go-around thrust, resulting in a stall.

"I have time on 737, 744 and Airbus FBW along with others and have no particular axe to grind in favour of any manufacturer, there are simply certain aspects of Airbus design that I feel are fundamentally flawed, the above example being just one of them."

You do not mention any jets with tail-mounted engines. I have carefully reminded you that airliners such as the Caravelle, VC10, BAC 1-11, B727, DC9/MD80/B717, F28/F100, etcetera (not to mention numerous business-jets), have little or no thrust-related pitch-up tendency in a normal go-around. If you have never flown one of these aircraft, let me assure you that it is not a problem. Read what TyroPicard says.

You say that this issue is just one of the aspects of Airbus design that are "fundamentally flawed", so I suggest you pursue the others.

[Bengerman]

Chris, thanks for your thoughts, I will bow out now because, like many threads here, we go around in circles with people shooting off all over the place and not actually addressing the original issue.

FYI I only have rear engined time on DC-10 and B727 from some years ago, they were not fbw and both would pitch up with application of TOGA.

Others here have chuntered on about training, procedures blah blah....yes, they are vital but it has to start with the actual piece of kit in the first place! To my mind poor design is that which exists when training has to be given to negate safety issues caused through that poor design.

You say:

You say that this issue is just one of the aspects of Airbus design that are "fundamentally flawed", so I suggest you pursue the others.
1st Jan 2013 23:25


I will not waste my time doing this because of the parochial and, almost, xenophobic nature of some of the posters here, but I will say that thrust levers that do not move is a negative step and non interconnected sidesticks with no feel are also negative steps. Both remove part of the feedback process and reduce the tools available to the pilot.

I bid you farewell.

[BOAC]

Want some real fun, boys and girls? I spent a little while in the 80's carefully teaching someone how to g/a in one of these......................

http://www.abpic.co.uk/images/images/1364545M.jpg

Guess how this handled?

[Cough]

BOAC - my guess - beautifully! - I'm presuming a baulked landing at slow speed off a practice PFL in a wacky field somewhere presented little issue!

:uhoh:

[Cough]

Oh and...

If the pilot of an airbus FBW does nothing more than push the thrust levers to TOGA then the aircraft will accelerate into the ground

Technically, the speed will get to Vfe (flap 3/full) and then the aircraft will pitch up...

However, what bengerman says about the benefits of a conventional set up I can't disagree with!

[Jonty]

One for all those FBW doom merchants.

What do you think would happen on a B757 if you went around from an approach, selected TOGA and then pulled back on the yolk?

I can tell you. In about 30 seconds you and 200+ other people would be dead.

So bear in mind what the FBW is trying to do. A mishandled event in any aircraft, FBW or not, has the potential to kill you.

To my mind the FBW is fine, its the training that has to change. We have to get away from the "it will look after you" type of training, and treat it with the respect it deserves.

[BOAC]

I'm presuming a baulked landing at slow speed off a practice PFL in a wacky field somewhere presented little issue! - nice if the field is actually flooded.................:p

[Cough]

I'll get my seaplane rating out... :}

[Chris Scott]

BOAC,
Have a feeling I may come unstuck on this one! On the face of it, reminiscent of TyroPicard's VFW 614 jet, but with the prop's slipstream improving elevator authority. Unlike the prop-driven types most of us wrinklies started our careers on, this pusher-prop will have negligible effect on wing lift, so back to the VFW 614 situation again. Is that why the thrust line looks to have an up-vector? Bottom-line is: I reckon you'd have to pull fairly hard initially. (You have control!)

Bengerman,
Sorry you feel like that, but I'm not expecting to devote much more of my retirement to this contentious argument, either. (And I much admire others who have to compose their thoughts in a foreign tongue.) Why does it have to be so polarised? Re non-driven thrust levers and non-interconnected sidesticks, if you have seen my posts on this (http://www.pprune.org/tech-log/503248-how-safe-airbus-fly-wire-airbus-a330-340-a320-family-emergency-ad-5.html#post7601883) and other threads, you will see that I have opposed them in principle since the 1980s.

I haven't flown the B727, but your comment surprises me. The DC10s I flew only had a third of their thrust mounted on the tail: the rest was under-slung. I seem to recall that, due to its high thrust-line (unlike the L-1011), a single-engine G/A using that centre engine was quite interesting.

Jonty,
Thanks for endorsing my point. The G/A accident I had in mind was either an A300-600 or an A310 in the Far East: conventional controls and (as some readers may not know) very similar configuration to the B757/767. I remember go-arounds in the A310 only too well.

[BOAC]

Yes, angled thrust-line to 'help' with normal cruise type stuff. The g/a was a 'pull' manouevre but with significantly improved elevator/tailplane response as you say. Overall, as with all a/c, you got used to it.:)

To digress even further from thread:p, I was really proud of my 'student' who subsequently had an engine failure with Mrs Stude aboard heading westwards off Islay, dumped it in the ogg and paddled safely ashore with the onboard oar.:ok:

[TyroPicard]

Chris Scott
Out of interest are you anti side-stick or just anti-the lack of interconnection? I have been thinking about the difficulties and implications of connecting them and have concluded that if you choose side-sticks for their amazing precision you can't connect them.
I never found non-moving T/L a problem - did wonders for my N1 scan!
TP

[SLFinAZ]

Very interesting reading for an SLF, especially the continuing A vs B debate. Personally I do not fly "A" ever as a matter of choice. I firmly believe that the overall level of pilot skill is significantly different.

I recognize that this is not an entirely objective view point...however I do believe that the very name Airbus is telling....the end goal was to create a flying bus service....and the end result has been a drive to the lowest common denominator of pilot "skill" possible.

AF447 epitomizes the inherent issues. The current automation levels created a "qualified" flight crew entirely incapable of dealing with what should have been a relatively minor issue (which had happened dozens of times). From my perspective the entire A culture encourages an almost total dependence on automation for cadet pilots (not sure if that's the correct term).

So when you have a "pilot" who's grown up in a dedicated Airbus culture moving directly into an SO/FO role after 250 hours(?) then flown 800-1000 hours...how much actual hand flying has he done?

While I recognize that current generation planes from both A & B are safer then ever and statistically equivalent I think that those safety improvements now bring pilot skill to the forefront.

Personally the only buses I ride in don't have wings:)

[Lyman]

Chris Scott and SLF

The legacy of rancor is not substantiated by a polar view, from either camp.

Airbus sought to revolutionize the Command and Control of commercial airliners.

They succeeded, and failed. The burden of change is on the novelty, not the status quo. Aviation has historically been conservative in outlook for both good and bad.

Any counterintuitive alteration will get close scrutiny. "Fair" is for the ignorant. Any bold step will attract hostile attention. The knee jerk occurs when the discussion decides on its own to retreat into bunkers, and mortar fire.

The burden of popular acceptance is on the creator.

1. What advantage is there in unconnected control stations? The list of disadvantages is long from the detractors, and the default on the defense is "it is just training"

2. What is the advantage in partially defaulting to a melange of "novel controls" mid-emergency? Intermediate and partial reversion? Again, just "training"?

3. What was the logic and the advantage of leaving AoA display out of the cockpit? Ahh...."training"?

3. The platform is different, by design. With failure comes the responsibility to re-prove the design. This need is natural, and not led by the "enemy".

4. Why remove all sense of "input/response" from the controller? Rely instead wholly on "instruments" to meter the result? Again, with subtraction comes the duty to prove.

Claiming that there exists merely a dearth of "training" is not sufficient to defend the failures. Reality makes that a Lie...The recent loss of AoA vanes without a "trained" procedure makes the builder look sloppy, irresponsible.....

"The other platform is no safer" That is discouraging, because after all the "changes" we see no improvement?

That makes the conclusion for some of us.... "Change for Change' Sake"

If all the goal was to be "notorious" the venture was successful.



That is not enough.

[Chris Scott]

Quote from TyroPicard:
"Out of interest are you anti side-stick or just anti-the lack of interconnection? I have been thinking about the difficulties and implications of connecting them and have concluded that if you choose side-sticks for their amazing precision you can't connect them."

Very tricky question, and perceptive follow-up. You may remember I've stuck my neck out on PPRuNe before on the characteristics of sidesticks, and how some pilots abuse them (physically, not verbally). ;)

Re the first part, I liked the sidestick from the first simulator session at Blagnac. However, certain combinations of roll and pitch commands can become less coordinated than one would like, even in Normal Law. The interface between sidestick and FBW in Roll Normal complicates the handling of the wing-down technique (after de-crab) in crosswind landings, but "bumping" the stick seems to work well. The (AF447) combination of Pitch Alternate with Roll Direct, however, would not be a comfortable one.

Re the second, the lack of interconnection makes it impossible for the PNF to monitor the stick handling of the PF in flight, doesn't it? Can be a real problem, particularly when you are "giving away" a landing in a gusty crosswind. But even in smooth weather I've watched guys from my frequent perch on the P3 seat (line checking), and over-use of the sidestick is all too common. It seems to be a form of occupational therapy for some when the adrenalin is going. Sometimes this leads to PIO, sometimes not. We know that Bernard Ziegler ruled out interconnection at a very early stage in the design process, presumably for weight and reliability, although the latter has been perfected in all other dual-control aircraft.

But now you raise the other problem with interconnection. Due to its size, relatively-small, quick, brief movements are the norm (two exceptions being rotation on take-off, and a roll from full bank one way to full bank the other). I'm no engineer, but if these movements had also to power the complimentary movement of a system of cable and pulleys (or anything else mechanical), the hand force required would be great (and the best way to use the sidestick is with finger-tips and thumb). Is that your point?

Any interconnection, therefore, might have to be via electronics: presumably using servos. The throttle levers work brilliantly in manual thrust, but the command from the transducer is one-dimensional and the signal time to the FADEC may be less critical. Could a sidestick system work in both directions, and would it be accurate enough and quick enough? Could the sticks be allowed to be in different positions, as at present, and would the algebraic sum still apply? How would the PNF assert control as PF?

That brings us to your final point:
"I never found non-moving [non-driven] T/L a problem - did wonders for my N1 scan!"

We know the throttle levers have transducers, but no servos, so could they have both? The reluctance of some fleets and individual pilots to using manual thrust is partly because of the awkwardness of the transition from auto to manual (not to be done at 100ft on the approach, as I’ve seen so often). Also, in my opinion, the pilot desire for extra thrust on the (rare) occasion that the A/THR is too slow to react to a tailwind shear is not adequately catered for by the (retrofitted) feature whereby the pilot briefly advances the levers from the CLB detent. This crude expedient could get you into a lot of trouble on the approach to a short runway like Jersey. That’s why nearly all my “manual” approaches were in manual thrust.

[Chris Scott]

SLFinAZ,
I sympathise with large parts of your post, and am impressed by your grasp of many of the issues. (Sure you haven‘t missed your vocation?)

By the early 1990s, our A320 fleet was taking cadets (yes) straight out of flying school. Even on FBW, it was clear that some had better basic handling skills and hand/eye coordination than others... When they later converted to B747 (to go long-haul, as the airline didn‘t have A330/A340) or the B757/767 (sometimes for commands!) they really had their work cut out. Trimming? What’s that? But, in most cases, they seemed to cope better than we expected.

Where I can’t agree with you is your reluctance to fly in Airbuses. Airbus pilots fly Airbuses as well and as safely as Boeing pilots fly Boeings, IMO; not that I pretend to be an expert on the current skills of either.

Lyman,
I understand your argument (I think!). But you paint a very jaundiced view of what is now a very well-proven system. I’ll leave others to provide the statistics, but the Boeing FBW fleet is still miniscule in comparison with Airbus’s, and it’s all long-haul.

[DozyWannabe]

however I do believe that the very name Airbus is telling....the end goal was to create a flying bus service....and the end result has been a drive to the lowest common denominator of pilot "skill" possible.

Interesting theory, unfortunately the truth is somewhat more prosaic. The term was first used for a BEA (as in British European Airways) specification in the mid-60s that was designed to augment or replace the HS.121 Trident. HS's next design (from DH's old Hatfield office) was the HS.134 - unfortunately it never made it past the drawing board, but here it is (Note the "AIRBUS" spec in the bottom-right corner) :

http://i9.photobucket.com/albums/a94/WtMiller/scan0001-2.jpg

Also note how similar it is to what eventually became the B757 - despite being a 1967 design! The full story can be found here:

British Airliners 'Nearly Get It Right' Shock! (http://www.ww2aircraft.net/forum/post-war/british-airliners-nearly-get-right-shock-17298.html)

Anyway - come the '70s it was clear that the separate European manufacturers could not individually compete with the economies of scale that the big US manufacturers could call upon, and so the UK (who later withdrew), Germany, France and Spain decided to collaborate on a project that would be capable of competing. The consortium decided to use the name "Airbus" - in all likelihood because as it happens, the word "bus" is pronounced the same and means the same thing in all the languages used by those European countries (from "Omnibus" - derived from the Latin "for all").

@Chris Scott - BZ would not have been responsible for implementation details such as whether to interconnect controls or not - that would have fallen to the aeronautical and pilot engineering teams to hash out.

[Cool Guys]

Bengerman and C Scott.

The 1 or 2 people polarising this debate are non pilots who do have parochial views and I think most people would prefer if they were given minimal time and the professional pilots here continue with their interesting and informative discussions.

[Chris Scott]

Dozy,
You say that, contrary to my post, "BZ would not have been responsible for implementation details such as whether to interconnect controls or not - that would have fallen to the aeronautical and pilot engineering teams to hash out."

To indulge in thread drift: whom do you have in mind?
Around 1986, when we were discussing the feature in study groups, we were told informally that it had been insisted on by BZ. After all, he was the senior vice-president for engineering around that time, and we understood he was in charge of the FBW project. He was himself an experienced test pilot, and former chief test pilot of Airbus.
Gordon Corps joined AI in 1982 as an engineering test pilot, with special responsibility for flying qualities. No doubt he would have expressed an opinion on all these matters, but presumably his remit would have extended only as far as advising the handling properties, and the requirements for type certification. Subject to that, major decisions on systems design would rest with the engineers, IMHO.

[Gretchenfrage]

from TP:
Out of interest are you anti side-stick or just anti-the lack of interconnection?

For my part definitely anti-lack of connection. A sidestick is the modern way of guiding an airliner, permitting a table! But it needs to have a backdrive.

from CS:
Could a sidestick system work in both directions, and would it be accurate enough and quick enough?

Is a visual “on instrument” procurement of your fellow’s input, as propagated and necessary on the Bus, accurate and quick enough?? This extensively used argument is futile, don’t you see? I have always said that I don’t ask for a precisely duplicated input, I simply need the tactile presence and direction. Any rumble-stick of the next door game shop does the job, and with almost no weight and cost penalty.


but the Boeing FBW fleet is still miniscule in comparison with Airbus’s

So you call 1000 T7s a minuscule fleet, statistically not worthy of standing up to the Bus FBW fleet? Who has a jaundiced view of how statistics work?


from CG:
The 1 or 2 people polarising this debate are non pilots who do have parochial views and I think most people would prefer if they were given minimal time and the professional pilots here continue with their interesting and informative discussions.

Would be great, wouldn’t it? :}

[A33Zab]

1000 T7s is not a minuscule fleet but only 12,6% of total boeing FWB and airbii FBW combined.


Any rumble-stick of the next door game shop does the job


A350 will have a 'rumble-stick' in case of dual input.

[Gretchenfrage]

1000 T7s is not a minuscule fleet but only 12,6% of total boeing FWB and airbii FBW combined.
Agreed, but in what group would you rather be: in the 12% with no casualties or in the rest with more than 200 perished?
When it concerns losing life, the percentages no longer matter, at least to me. Such numbers are certainly NOT minuscule in terms of casualties.

Concerning the rumble stick, it's not exactly what i'd like, but i have to admit it's a start! But only a very, very small step. It needs more.

[DozyWannabe]

A350 will have a 'rumble-stick' in case of dual input.

Bet it cost more to implement and certify for civil aviation use than a trip to the Toulouse branch of "Game" though! ;)

GF - you seem puzzled as to why they're not doing everything you ask. Last I heard you didn't work for Airbus engineering, so I'm at a loss as to understanding why. Interconnection is not objectively better no matter how much you and others claim it to be so.

Statistical comparisons of the sort you're making are fairly meaningless - the only way to make it so would be to build exactly the same number of T7s as A330s, have them flown by the same airlines on the same routes, with the same pilots trained to the same standards and have the flying conditions be exactly the same for each of the flights. If you wanted to be really accurate you'd also need a control group of the same number of, say, 767s and A300s (non-FBW types) flown in the same manner. Real-world conditions however would make such experiments practically impossible.

[A33Zab]

Agreed, but in what group would you rather be: in the 12% with no casualties or in the rest with more than 200 perished?


It does not matter to me, the 12% can be overconfident in their equipment while the other learned a hard lesson.

[Lyman]

From a previous post, and relative to "statistics".

There are conditions in any complex system that may possess glaringly deficient process, or architecture.

Someone told me once to never believe an engineer who works on his own.

Reason? They work from spec. The format is narrow, and any peripheral vision is considered heresy.

I do not necessarily like working in groups, but I will defer in this thread to the pilot group.

ciao

[DozyWannabe]

What of the pilot engineering group? Also note that there is a distinct difference of opinion within the piloting group itself.

EDIT : And there was never a case in the A320 project, or the experiments that preceded it of an engineer working on his or her own - the teams were large, specialised and picked from the best the European aviation industry had to offer. The information I have suggests that BZ's engineering title was more of an honorific, in the same manner as Bill Gates' was after he stepped down as Microsoft CEO.

[Lyman]

I think isolating sidesticks from view and from feedback, PLUS NO Connectivity, is a terrible idea.

Proposal: Captain, in left seat, operates his SS with right hand. F/O operates his SS with his left hand. The sticks are located on the console, the throttles on the fuselage wall, where the sticks are now.

No connectivity, no Feedback, improved "cooperative visuals" only.

No conclusions. Not yet.

Discuss?

"Climb, then!" ..... "(:ugh:), But I have hald aft stick for some time now!"

Woops.......

[Gretchenfrage]

GF - you seem puzzled as to why they're not doing everything you ask.

Not at all, I repeatedly said why I never expected that. This however did not stop me to ask for the safer solution.

Last I heard you didn't work for Airbus engineering, so I'm at a loss as to understanding why.

So one has to work for Airbus to be allowed to question its design?
By the same reasoning I could say one has to be qualified to operate both systems before being allowed to participate in this discussion, what I never did.


Interconnection is not objectively better no matter how much you and others claim it to be so.

.... and by the same argument not objectively inferior, so it all runs down to personal experience. I presume you will at least have to accept that, in absecnce of your own.

Statistical comparisons of the sort you're making are fairly meaningless.

... and you are just the expert entitled to say so and validate others. Preposterous! At this very moment, the statistics speak a clear language: system 1 - no victims, system 2 more than 200. Twist it as much as you want, decry the one as much as you can, a zero is a zero.

Some professionals pretend its coincidence, others say its due to better design.
It all runs down to that. Most intelligent professionals do not very much accept coicidence as explanation when it runs down to safety.
Thats more like NG sensational air disaster journalism.

[DozyWannabe]

@Lyman - To what benefit? In airliner operation the PNF/PM is supposed to be monitoring the aircraft, not the other pilot.

I want to know why you think such a proposal would be an improvement and to understand your reasoning - a reasonable request, no?

... and you are just the expert entitled to say so and validate others.

Says who? Certainly not me.

Preposterous! At this very moment, the statistics speak a clear language: system 1 - no victims, system 2 more than 200. Twist it as much as you want, decry the one as much as you can, a zero is a zero.

Using the same flawed method to derive conclusions from statistics, one could have argued that the B747 was less safe than the L-1011 and DC-10 by the end of the '70s, yet nobody argued that. Why the rush to do so here?

[Lyman]

Discussion, first, benefit later? You decline?

Hypersensitivity to "heresy"?

[Lyman]

No worse ignorance exists, than rejection prior to investigation...

Perhaps acceptance without question?

Example. A friend was signing off a tail wheel endorsement for her student. She sat in back of the Citabria, the student in front. Citabria has foot operated brakes in front only. Instructor has none. They landed, and the student applied brakes, instructor said "get off the brakes, get off". She had to endure the aircraft rolling over on to its top because she could not prevent her student from screwing things up.....

Bonin was pulling the whole time, even when Robert says: "you climb, GO DOWN"..... Captain DuBois says: "Eh,CLIMB!!". Bonin says... "I have been..."


Well then. We evolve... Sometimes being stubborn can kill, or trash a Citabria.

[DozyWannabe]

I'm not rejecting anything, I just want to know why you think such a setup would be better. If you're going to do nothing but put words in my mouth then I have nothing more to say on the matter.

[Lyman]

No, Dozy, i sincerely want to hear you discuss.....

By rejection, I mean without comment. You refuse to entertain the discussion?

I understand.

[DozyWannabe]

None of what we're discussing here is going to change anything in terms of how any manufacturer implements their PFCs - but that aside what we're talking about is the relative usefulness of being able to feel precisely what one's opposite number is doing.

In modern airliner operations where there is no direct connection between PFC and flight surface and with technology that is reliable enough to make this possible, and given that only one person is ever supposed to be PF at any given time - what is the benefit?

A "rumble" tactile feedback system to warn of dual input seems a fair compromise to me.

"Climb, then!" ..... "(:ugh:), But I have hald aft stick for some time now!"

There was plenty of indication of what the PF was up to on the ADI early in the sequence (and plenty of evidence on the CVR to suggest that the PNF wasn't happy about it) - why the PNF hesitated in taking control is a matter for the HF experts.

[BOAC]

Why not, as an interim measure, enable the stick position display in flight (I understand it displays only on the ground)? I wonder if an obvious nose up demand from PF would then have been visible to the Captain when he re-entered the cockpit?

[DozyWannabe]

Again - to what benefit? Adding more data to the visual perception channel risks overloading it. Why the need to know precisely and at all times what your opposite number is doing with the PFC when only one pilot is supposed to be PF?

I swear I'm not being facetious - I really want to know why it's such a big deal for some.

[BOAC]

Is it just possible, Dozy, that it could have be 'big deal' for 200+folk? I repeat

"I wonder if an obvious nose up demand from PF would then have been visible to the Captain when he re-entered the cockpit?"

[RunSick]

DW

Well, I guess to know the answer to that you would have to be a pilot a be seated next to someone you might not know controlling an aircraft in a way that you are "less able" to monitor. I´m sure you are intelligent enough to imagine it, but then again, I guess you would have to really be there to really know.

(BTW, I fly the Airbus and like it a lot, but IT DOES have some shortcomings, no design is perfect from the start. In the meantime people have to learn to live with it. Users doing that are not the mark of a perfect design, only of human brains working to adapt and do the best with what they have.)

Get a rating, sit in the seat and you will see for yourself I´m sure.

[DozyWannabe]

@BOAC - A "Dual Input" rumbler would have worked just as well in that situation - equally, as I said, the CVR suggests that the PNF was aware of what the PF was doing, but felt unable to take control, instead electing to wait for the Captain to return - by which time the situation was arguably irrecoverable.

And this is but a single incident - one in which the PF acted contrary to procedure and basic airmanship and the level of CRM on the flight deck was insufficient to catch it - an anomaly as opposed to a pattern.

@RunSick - I understand where you're coming from, but on the other hand you're supposed to trust your colleague, no? The instruments are in front of a monitoring pilot telling him or her exactly what the aircraft is doing. Is "Following through" with PFC inputs not something that only really belongs in training?

[Chris Scott]

Quotes from DozyWannabe, in answer to BOAC's suggestion that the PF's sidestick position might be displayed on the PFD in flight, not just on the ground:

(1) "Again - to what benefit? Adding more data to the visual perception channel risks overloading it."

Yes, it couldn't be on the PFD, IMHO. But there might be an argument for a separate, small display. But this would be of little help to the PNF when the aircraft is near the ground, and the PF is struggling. In the latter case, tactile is the only way.

(2) "Why the need to know precisely and at all times what your opposite number is doing with the PFC when only one pilot is supposed to be PF?"

Only someone with command experience in a two-pilot cockpit can really appreciate the desirability of this traditional feature. (See my previous post of Jan 02 @1959Z.) It's particularly so when a trainee, or inexperienced copilot, is the PF.

[DozyWannabe]

Only someone with command experience in a two-pilot cockpit can really appreciate the desirability of this traditional feature. (See my previous post of Jan 02 @1959Z.) It's particularly so when a trainee, or inexperienced copilot, is the PF.

Understood, but please humour me and try to explain. I'm not debating the desirability in this instance, I'm just not convinced - and it seems neither were the pilot engineering team at Airbus - that it's a necessity. I'm fairly well-versed in the Airbus perspective, all I'm asking is help in understanding the other side.

[Lyman]

ASKED (I assume in genuine sincerity)....by Dozy

"I swear I'm not being facetious - I really want to know why it's such a big deal for some."


ANSWERED (By a Captain, in type, with extensive experience, and great respect locally.)

Only someone with command experience in a two-pilot cockpit can really appreciate the desirability of this traditional feature. (See my previous post of Jan 02 @1959Z.) It's particularly so when a trainee, or inexperienced copilot, is the PF.

I have tried, and couldn't possibly put it better.....Especially so since Dozy and yours truly should really defer...

[jcjeant]

The information I have suggests that BZ's engineering title was more of an honorific?
Bernard Ziegler (born March 12, 1933) is the former Airbus senior vice president for engineering. He is well known for his evangelical zeal for the application of the fly-by-wire system in the Airbuses. He is the son of the former Airbus CEO, Henri Ziegler.
Bernard Ziegler was born in Boulogne sur Seine, France. He was educated in the École Polytechnique (1954), as an engineer and École de l'Air (1955), for his pilot training and military commission.
In 1961, he continued his studies and joined the National School of Aeronautics and Space (SUPAERO) and then at the School aircrew testing and reception (EPNER) - School of test pilots. He then entered the flight test center in 1968 and became chief test pilot of the Dassault Mirage G1.
Mr. Ziegler began his career as a fighter pilot in the French air force. He saw action in the Algerian War and was decorated twice. Principal medals and decorations received include the Officier de l’Ordre National du Mérite, Médaille de l'Aéronautique, Croix de la Valeur Militaire and Officier de la Légion d'honneur.It's seems to me that BZ have more than a "honorific tittle" of engineer ...
Honorific are his list of medals ... engineer tittle .. certainly not.
He was certainly not considered in the Airbus project as a "honorific guest engineer" ...

[DozyWannabe]

[Ziegler] was educated in the École Polytechnique (1954), as an engineer

That was his education, but his profession was as a pilot - he was not an engineering pilot from what I've been told. While still at the ARB, Gordon Corps had been working with the technology from the original Concorde "minimanche" experiments in the late '70s where the aspects of the design were refined - that was why Airbus hired him. This all happened before the A320 project was formally begun, and before BZ ever entered the picture.

[jcjeant]

That was his education, but his profession was as a pilot - he was not an engineering pilot from what I've been told. While still at the ARB, Gordon Corps had been working with the technology from the original Concorde "minimanche" experiments in the late '70s where the aspects of the design were refined - that was why Airbus hired him. This all happened before the A320 project was formally begun, and before BZ ever entered the picture. I wonder why many people want to minimize the role of BZ in the genesis of the Airbus project ?
Maybe because his proselytizing without limitation about this project which has proven to be in a certain way damaging for the "Airbus image" ? (my concierge can fly it :) )

[jcjeant]

Lyman
"Climb, then!" ..... "(), But I have hald aft stick for some time now!"
DW
@Lyman - To what benefit? In airliner operation the PNF/PM is supposed to be monitoring the aircraft, not the other pilot.
:confused:

[DozyWannabe]

jcj - It's not about minimising, it's about an honest appraisal of what went on. BZ's role was that of a product evangelist and publicist and for better or worse, his approach rubbed many people up the wrong way.

He did not have the relevant contemporary qualifications or practical experience to make decisions on implementation detail. He did, however, have confidence in the teams under him - but the way he went about expressing it was arguably counter-productive for some.

As an aside, the Space Shuttle programme was pitched to NASA as a "space truck", but at no point did the veteran astronaut crews take umbrage at the term, nor did they consider it demeaning to their role and skillset.

[RetiredF4]

All bolding by me

DozyWannabe
@BOAC - A "Dual Input" rumbler would have worked just as well in that situation - equally, as I said, the CVR suggests that the PNF was aware of what the PF was doing, but felt unable to take control, instead electing to wait for the Captain to return - by which time the situation was arguably irrecoverable.


It is helpful, to reread the report. Your above assumption is just that, an unfounded assumption.

Four seconds after the autopilot disconnection, the rapid increase in nose-up attitude resulted in the triggering of the STALL 1 warning. This warning only appeared to provoke a small aeroplane handling reaction from the PF. The PNF asked “What is that?” which may refer to the stall warning. It is possible that the PNF, faced with a short, truncated warning, did not identify it. However, rather than indicating his failure to recognise the warning, this question seems to mean that the PNF did not consider the warning to be relevant in the context of the fact that he was not necessarily aware of:

ˆˆ- The PF’s significant nose-up inputs that generated an increased angle of attack;
-ˆˆThe relative proximity of a flight envelope limit;
-ˆˆThe reconfiguration to alternate law (which he only called out later): if he thought they were still in normal law, the warning could have seemed to be irrelevant.

It would also seem unlikely that the PNF could have determined the PF’s flight path stabilisation targets. It is worth noting that the inputs applied to a sidestick by one pilot cannot be observed easily by the other one.....



later on...
The PNF had noticed the need to stabilise the flight path, and the need for moderate aeroplane handling inputs. He probably considered that the reduction in pitch and the vertical acceleration sensed was a sufficient sign that the PF would correct the flight path to allow him to devote himself once again to identifying the failure.


he had to consider, but could not confirm what his partner was doing at all.


the following speaks for itself, still no awareness...
The crew never referred either to the stall warning or the buffet that they had likely felt. This prompts the question of whether the two co-pilots were aware that the aeroplane was in a stall situation.


And finally...
When STALL 2 warning triggered and buffet appeared, the PNF was faced with an increasing incomprehension of the situation.
The PNF’s strategy was then above all to call the Captain, which occupied a large part of his resources. Since he was anxiously waiting for him to return, it is possible that the phenomenon of attention selectivity reduced his ability to perceive the STALL warning.

And to top it...
At about 2 h 11 min 38, after the PF said “I don’t have control of the plane at all“, the PNF called out “controls to the left“, took priority and made two lateral left inputs to the stop. The aeroplane was then rolling to the left.

Still no correction of the pitch!

Hell Dozy, from where does your above statement come from?


Chris ScottOnly
someone with command experience in a two-pilot cockpit can really appreciate the desirability of this traditional feature. (See my previous post of Jan 02 @1959Z.) It's particularly so when a trainee, or inexperienced copilot, is the PF.

DozyWannabe
Understood, but please humour me and try to explain. I'm not debating the desirability in this instance, I'm just not convinced

You need a mathematical formula to believe it?

[jcjeant]

jcj - It's not about minimisingWhen you write that a man who have the title of engineer is a "honorific engineer" you relegate the title .. you make it void .. so you minimize any engineering decisions of this man

[RetiredF4]

DozyWannabe
jcj - It's not about minimising, it's about an honest appraisal of what went on. BZ's role was that of a product evangelist and publicist and for better or worse, his approach rubbed many people up the wrong way.

He did not have the relevant contemporary qualifications or practical experience to make decisions on implementation detail. He did, however, have confidence in the teams under him - but the way he went about expressing it was arguably counter-productive for some.

Should be possible for you to produce a reference for that? Or is that your personal oppinion?

[DozyWannabe]

Should be possible for you to produce a reference for that? Or is that your personal oppinion?

I told you - I cannot talk about the info I have, or it's source, without permission from the person who told me. As I do not have that, my hands are tied and I'm sorry.

I'm not asking for a mathematical formula, just a reasoned explanation to aid my understanding.

@jcj - I used an analogy to explain the situation. Bill Gates' title at Microsoft is "Chief Software Architect", but that does not mean he is present at all of the meetings and doing the work of implementing and defining software architecture because he's been out of "the trenches" too long. He understands high-level concepts and acts as arbitrator where necessary - from what I was told BZ's role on the A320 project was similar.

[RetiredF4]

DozyWannabe
I told you - I cannot talk about the info I have, or it's source, without permission from the person who told me. As I do not have that, my hands are tied and I'm sorry.

That´s worthless. I know a lot of people who know something which was told by somebody who doesn´t want to be connect to his saying.....


DozyWannabe
I'm not asking for a mathematical formula, just a reasoned explanation to aid my understanding.


The problem is not, that nobody i trying to explain reasonably, but .........

[jcjeant]

Hi,

DW
I told you - I cannot talk about the info I have, or it's source, without permission from the person who told me. As I do not have that, my hands are tied and I'm sorry.So .. it's seems that for you BZ was just spokesman for Airbus
But ...
Bernard Ziegler was the most influential figure in developing the cockpit design and fly-by-wire control system for the Airbus airliners. He proposed that numerous technological innovations be applied to Airbus aircraft; for example, using composites, twin-engine configuration for the A300, fly-by-wire and many others. He was the guiding force in the creation of the flight envelope protection, incorporated in the Airbus flight-control software. This innovation allows the pilot to apply the maximum control forces considered necessary, while preventing inadvertent inputs that could place the aircraft outside the safety margin. This feature is considered by many to be highly beneficial in avoiding unusual attitudes in flight and in safely maximizing the effectiveness of evasive maneuvers in response to GPWS warnings.
For his efforts in advancing the fly-by-wire cause, he was honoured by the Flight Safety Foundation in 1998. He retired from Airbus after 25 years of service in 1997.It is a wonder why Airbus (and many stakeholders in the world of civil aviation) has always put forward (publicly) the role of BZ and not that of the famous test pilot and technical advisor
It is even BZ who receives the honors ...
Airbus was lucky (and BZ too) that his brilliant career was not stopped by this sad event
In August 1961 the Vallee Blanche Aerial Tramway (http://en.wikipedia.org/wiki/Vallee_Blanche_Aerial_Tramway) was badly damaged when an aeroplane of the French Air Force piloted by Bernard Ziegler tore its hauling cable. Three cars crashed and six people were killed.[1] (http://en.wikipedia.org/wiki/Bernard_Ziegler#cite_note-1)

[RetiredF4]

July 2012: Bernard Ziegler receives the Flightglobal Lifetime Achievement Award.
From Airbus page Press center (http://www.airbus.com/presscentre/pressreleases/press-release-detail/detail/bernard-ziegler-receives-the-flightglobal-lifetime-achievement-award/)

[DozyWannabe]

@jcj - Precisely. High level concepts, not implementation detail.

It is a wonder why Airbus (and many stakeholders in the world of civil aviation) has always put forward (publicly) the role of BZ and not that of the famous test pilot and technical advisor

There's an annual lecture in the latter's name at the Toulouse Branch of the RAES. From what I'm told he wasn't much for self-aggrandisement - the same cannot be said of BZ.

Toulouse Branch Gordon Corps lecture | Branches | The Royal Aeronautical Society (http://media.aerosociety.com/news/2012/01/30/toulouse-branch-gordon-corps-lecture/4211/)

[hoggsnortrupert]

I have never flown anything as complex as a fly by wire system, but!

I do wonder! Can someone give me the answer to this question:

Does Air Bus acknowledge that its machinery is flown by PILOTS, or are they SYSTEM MONITORS:

Authorities and some Air Lines have now recognized the very real threat that their PILOTS have lost their basic airman-ship flying skills, which is what alot of people in the industry, along with myself, have seen happening for the last twenty years:

I have reed the report on AF 447: (Talk about a shinning example of CRM, & Leadership):{

In my opinion the system can have all the bells and whistles, and colored lights, nice female voices, & coffee on tap! but give the PILOTS, the means to IMMEDIATELY BE ABLE TO PUSH A BIG RED BUTTON::mad:

But if it goes pear shaped at 500 ft on take off in hard IMC, and you have to analyze, recognize, then shut down the ADR's, is in my opinion a big ask, of any crew:

In my opinion A/B is ignorant of HUMAN FACTORS::sad:

Now I will twaddle off into my Twin Otter office with 8 sectors, and all my manual flying:

Chr's
H/Snort:(:(:(

PS: exercise for you all, trawl through all this guff from the first posting, and read and sit back and think about what you are discussing! it is quite disturbing:

Let the clubbing and beatings commence::p

[A33Zab]

Why not, as an interim measure, enable the stick position display in flight (I understand it displays only on the ground)? I wonder if an obvious nose up demand from PF would then have been visible to the Captain when he re-entered the cockpit?

:ok:
X-channel on monitoring pilots display only, red/amber on both displays when dual input. shouldn't be to difficult to adopt for current fleet.

But it is up to Airbus pilots to demand for such a system.

Other solutions Interlinking/tactile FB/ Decoupling/ Summation/Disabling adds complexity and far more failure possibilities.

[Chris Scott]

Quote from DozyWanabee:
"Understood, but please humour me and try to explain. I'm not debating the desirability in this instance, I'm just not convinced - and it seems neither were the pilot engineering team at Airbus - that it's a necessity. I'm fairly well-versed in the Airbus perspective, all I'm asking is help in understanding the other side."

Fair enough, and I'll do my best! But please also read my post of January 02 @ 1959Z.

There are, I guess, two advantages to the traditional interconnection.

1) Tactile feedback to the PNF for monitoring, but that only applies if he/she is touching the stick. That needs to be done very gently and carefully, as it can make hard work for the PF. In practice, therefore, we tend not to do it unless we are contemplating a sudden takeover of control. (However, I do remember once or twice, as a PNF trainee, being invited to “follow through” the training captain as he demonstrated the PF job.) This care would be particularly necessary with the sidestick, which the PF best handles with fingers and thumb: NOT the gripped hand. The advantage of the conventional yoke (and this also applies to old-fashioned joysticks in tandem cockpits), is that (peripheral) vision of its movements gives the PNF some idea of what’s going on.

2) The ability of the PNF to takeover control without pushing a button. Pilots are very reluctant to do that, because it would be a clear expression of no-confidence in the PF‘s handling. However, without pushing the button of your Airbus sidestick, you cannot counter a full-deflection on the other stick; only neutralise it. And that would be a recipe for loss-of-control.

Must finish by pointing out that these tricky situations are rare on a well-trained pilot fleet, but not unknown. The reluctance of the PNF to interfere applies on traditional types also (see above). The frailty of the human condition is not unique to Airbus cockpits! But momentary intervention (like correcting an undesired wing-drop on a gusty, crosswind landing) is easier on traditional types. Having said that, the Airbus in Normal Law is, IMHO, a more forgiving aircraft to fly “manually” than most of those. Can’t (and won’t) second-guess the Boeing version.

That's my take on it. Can current pilots comment?

In 14 years of line flying the A320, starting from type-certification, I never found myself in other than Normal Law.

[RetiredF4]

Flying the A320, Flight International 6. July 1985 (http://www.flightglobal.com/pdfarchive/view/1985/1985%20-%202199.html)

In training, the "follow me through on the controls" instruction will no longer be possible. There may also be some room for doubt when a captain, dissatisfied with a copilot's rate of flare, edges in a bit more "wrist back," just as the copilot also makes a correction. A lit caption to warn of simultaneous input has been considered. Airbus has argued that the captain can assess the progress of the flare visually, but not all pilots are convinced that this is the complete answer.

[Lonewolf_50]

@Lyman - To what benefit? In airliner operation the PNF/PM is supposed to be monitoring the aircraft, not the other pilot.
Dozy:

Sorry, old chum. You are wrong about that.

In a crew of two, you do indeed have to keep aware of what the other pilot is doing, particularly when he/she is flying and you are not. A great way to save your own life, his/hers, complete your mission, and retain the confidence of anyone in the back.

Standard CRM.

[DozyWannabe]

Fair enough, and I'll do my best! But please also read my post of January 02 @ 1959Z.

I did then, and I've just re-skimmed it now to remind myself. Thank you very much for taking the time to inform me. Please understand that any of my responses are intended to be in the spirit of discussion only and are not intended to disrespect your view.


1) Tactile feedback to the PNF for monitoring, but that only applies if he/she is touching the stick.
...
The advantage of the conventional yoke (and this also applies to old-fashioned joysticks in tandem cockpits), is that (peripheral) vision of its movements gives the PNF some idea of what’s going on.

Granted - this is a real benefit, but this kind of monitoring in the sense of correcting a less-experienced pilot tends to happen less than it used to. When cadets were being trained by doing go-arounds and circuits in Tridents and the like - essentially doing it for real - this was arguably necessary. But in this modern era, when simulation has progressed to the point that such is the fidelity of the experience in terms of response and handling that the only major difference from the real thing is the psychological knowledge that it is indeed a simulation, could it not be argued that this becomes less of a necessity?

Additionally, the way the A320 should be handled according to Airbus procedure (small input-observe-correct if necessary) is slightly different than for more conventional types to counter any risk of over-controlling, as well as the minima and numbers being determined in a much more scientific and strict fashion than had been done before, with a significant margin of error embedded within the system. I suspect the intent of this was to provide an extra margin of safety compared to the methodologies employed before.

2) The ability of the PNF to takeover control without pushing a button. Pilots are very reluctant to do that, because it would be a clear expression of no-confidence in the PF‘s handling.

Is it really any more of a clear expression than the "I have control" (or "My aircraft" in the US) call-out? Begging your pardon, but to me it simply seems like a technical codification of that procedure, which has been around for as long as aircraft have had dual controls.


The reluctance of the PNF to interfere applies on traditional types also (see above).

Believe me this is something of which I'm well aware, but I'm hoping that coming from you it will have more clout than it seems to coming from me!

The frailty of the human condition is not unique to Airbus cockpits! But momentary intervention (like correcting an undesired wing-drop on a gusty, crosswind landing) is easier on traditional types.

Agreed, however - as with your first point - the procedures for flying the A320 are slightly different from those in conventional types in order to balance that out. The gusts were bordering on minima in the Hamburg incident and the Captain should not have permitted the F/O to continue the approach if he was not confident in her ability to handle it.

Having said that, the Airbus in Normal Law is, IMHO, a more forgiving aircraft to fly “manually” than most of those. Can’t (and won’t) second-guess the Boeing version.

From my understanding it's not a great deal different from the 767. What I have been told is that the software system providing the servo feedback alone is more complex than the A320's flight logic in its entirety. This is why I get a little chagrined when I read posts that berate the Airbus FBW system for being too complex and insist that the T7's system is superior in the same breath.

In 14 years of line flying the A320, starting from type-certification, I never found myself in other than Normal Law.

Quite - while she may not have been an easy bird to love at first, it seems that a growing number of pilots have found that she's not as bad as they feared - and in fact she's a tough, reliable and friendly companion.

@LW_50 - Please permit me to re-phrase. Would qualifying the statement with "the *primary* job of the PM is to monitor the aircraft, not the other pilot", be more acceptable? Otherwise every ride is, in effect, a check ride.

EDIT : This article:

Old Facts, New Insights – Lessons from A-320 » Aviation Medicine :: Aerospace Medicine | Aviation Medicine :: Aerospace Medicine (http://www.avmed.in/2012/10/old-facts-new-insights-lessons-from-a-320/)

posted by jcjeant back in the AF447 thread some time ago contains some interesting information and is worth a read, but it was pointed out to me that on this page:

Old Facts, New Insights (http://www.avmed.in/2012/10/old-facts-new-insights-lessons-from-a-320-part-2/)

of a survey of 167 pilots in a US airline that had adopted the A320 (and I think I'm right in saying US pilots tend to be more conservative than most), after some time with the aircraft only ten of them still had misgivings about the lack of interconnection. That's only 6%!

[Clandestino]

How safe is (Airbus) fly by wire?

Fly-by-wire is just generic technical term like "aileron", "flange", "wheel" , "empennage" or "cable". It is flight control systems, it has nothing to do with automatic flight systems. In real world (the stuff outside internet) any aviation system has to be deemed airworthy. There are entities given the task of airworthiness certification and their approval must be confirmed by the events occurring in everyday use or it gets revoked. That's the way things work in the real life.

Airbus fly-by wire is safe enough that:

1. No civil aviation authority has put its airworthiness as a system into question.

2. No statistics, (and this is statistics as a branch of mathematics, not some numerology liberally applied around PPRuNe posing as statistics) or accident/incident report prove that Airbus FBW is inherently unsafe.

3. Folks trying to sell their gut-feeling that FBW is unsafe as a fact have to use huge amounts of distortion and aeronautical ignorance to have their theories sound plausible. Whether their theories are ignored by aeronautical-powers-that-be because of severe lack of resemblance to anything meaningful and true or due to worldwide conspiracy of Illuminati taking over the all CAAs , well anyone can make his own decision. More or less paranoid.

Anyway, just when I hoped that threads with abundance of nonsense about Airbus here on PPRuNe somehow went the way of the dinosaurs, someone triggered new outburst of same old, hundred times refuted Airbus fairytales.

If you are really interested in AB airworthiness following the EVA incident and not in another A vs B idiocylimpics, investigation is underway. AD is issued as a completely justified overkill measure that should help all the crews cope if that one-in-a-couple-of-million-hours-event reoccurs before we exactly know what happened. It might turn out to be another case of "Perpignan pressure washing". It might be that new probes are worse by design. It might turn out they are not but they were both from defective batch. It might turn out to be freak icing. Or any of other couple of thousand possibilities. Wait and see.

Good heavens, what a fruitless discussion.I beg to differ. Testimonials along the lines"I have flown such-and-such aeroplane for so-and-so hours" followed by hilarious display of ignorance of basic aeronautical facts are some kind of fruit. Not particularly palatable if one is more interested in meaningful aeronautical discussion than Beckettian satire, yet fruit anyway.
The similarity of the two readings is thought to have misled the crew but, as Clandestino also points out, that assumes the crew also failed to ensure that the relevant FMA was indicating FPA (if the theory is correct, it would have been indicating VS). Yes, but it was not just the unread FMA that doomed the flight. David Learmount has nicely summed it up:
As if failure to spot unwanted 3200 fpm descent is somehow on the par with the getting the sum wrong in the first grade arithmetics.So, yes, FCU selector had the design flaw but its redesign was just one small contribution towards prevention of future CFITs. Major points of Strasbourg investigation are: know where you are, know where you need to go and don't trust the autopilot blindly or basically: Flight order says you are a pilot, so act like one for :mad:'s sake!

Some FMA changes are worthy of mandatory calloutsLufthansa and Air Berlin have the right idea; not many of them are. It is important to know what autopilot is doing but it is more important to know what the aeroplane is doing, and despite the doomsayers spilling the bile over alleged lack, there are abundant clues in Airbi to tell the pilot what is going on.

the practice of dialling zero feet into the altitude selector and selecting OP DES ("open descent") with A/THR was always a hostage to fortuneErr.... perhaps that's the reason I was never, ever allowed to dial anything lower than FAF or initial G/A altitude on any aeroplane, not just Airbus. Allegedly, practice was developed soon after altitude selectors made inroads in my country's aerospace and that was quite some time before I was born.

which is clearly indicated as IDLE on the thrust FMAYes, but despite the name, Airbus is aeroplane, not bus. It is even more obvious on the thrust display, be it EPR or N1. Woe to the any powered aeroplane pilot who doesn't pay attention to his power gauges.

.. as should be a protection !

If Airbus could once for all acknowledge this, they would nicely integrate somewhere in the instruments panel that single guarded switch the pilot could sensibly push to allow him to regain control in the shortest time when protections go wild.

Find me a case of protection gone wild that is not QF72 or MH124.

There are recorded cases of stickpushers trying to prevent the stall but confused and panicked pilot overriding them with fatal results. So both soft and hard protections have their good and bad sides, as (in the real life, outside of PPRuNe's Gedankenexprimenten) everything technical has. I wonder whether the locked groove track of "we want the override" would change if someone kills himself while overriding the functioning protection.

Triple sevens are very expensive widebodies. They are not abundant with less than scrupulous operators.

Mark my words, it will come out that you can't ground an Airbus enough to with stand a direct 100,000 volt lighting strike and not fry something. Airbi get lightningstruck regularly for last 20-odd year without dire consequences. Your words are marked. Not for the reasons you'd find agreeable, though.

Air France went down because those guys lost situational awareness at night in the soup. They didn't know if up was up, down was down, if the plane had air going over the wings or not because the screen weren't given them the information. The CVR conversation confirms this. Three guys looking at the panels and none of them knew what to make of it. Correct.... nothing to do with the machine.

Toga is for go around. Everybody knows that.Well then airline pilots just don't fit your definition of "everybody". There is more to TOGA then just go-around, however it is indeed not particularly applicable at FL330 over the ocean.

Let's ask the pilots who fly them... They just don't care about some loud, arrogant and largely ignorant group pretending to be the voice of the silent majority.

Others here have chuntered on about training, procedures blah blah....yes, they are vital but it has to start with the actual piece of kit in the first place!No, it abso:mad:ly must not! Training has to start with basics, type rating is no place to be learning them and do-whatever-you-need-just-control-your-attitude is very basic stuff! RTF Airbus manual! Disclaimer is on page two or thereabout!

1000 T7s is not a minuscule fleet but only 12,6% of total boeing FWB and airbii FBW combined. What about Embraers, 7x, Tu-204 and SSJ? Are we discussing just civilian FBWs or perhaps it is indeed not about FBW but rather another A vs B treadmill?

Interconnection is not objectively better no matter how much you and others claim it to be so.Exactly. It has good sides and bad sides with no controls configuration decisively proven to be better.

I think isolating sidesticks from view and from feedback, PLUS NO Connectivity, is a terrible idea.Did you tell FAA about this?
No conclusions. Not yet.FAA's current conclusion is that Airbus FBW is fine as it is.

you're supposed to trust your colleague, no? It's not just your significant-cockpit-other, it is ATCO, mechanic, weatherman, dispatcher and many more folks dealing with your flight that you have to trust enough to put your life in their hands but not enough to let anything they do and say go unchecked.

Does Air Bus acknowledge that its machinery is flown by PILOTS, or are they SYSTEM MONITORS:
I have no idea what Air Bus is but Airbus does. Preface of their manuals says it explicitly so.

In my opinion A/B is ignorant of HUMAN FACTORS:EASA should be informed of your opinion immediately. If you are right, then safety is seriously compromised. We must not allow this to continue, must we?

it is quite disturbing: Entertaining, too.

Flying the A320, Flight International 6. July 1985Wow. Some things never change.

Did you know that about-face in some cultures is viewed as sign of weakness, even if it would make one's opinion more aligned with the freshly available facts?

In a crew of two, you do indeed have to keep aware of what the other pilot is doingIn a crew of trainer and trainee during basic training it is indeed important to know what the trainee does with controls. Airliner pilots usually get formally trained when and how to take over the controls and learn to watch the aeroplane's behaviour, not what yoke or stick does. That some of them are going against their training (or they weren't given it at all) could be a leftover from their instructor days or lack of confidence in their copilots - mind you, it needs not be paranoid but pretty justified, depending on the operator.

Makes me wonder how anyone ever got rated on Airbus if "tactile feedback" from other side is indeed so important.

[RetiredF4]

Clandestino
Did you know that about-face in some cultures is viewed as sign of weakness, even if it would make one's opinion more aligned with the freshly available facts?


Now it´s time to leave this thread, as the BS hits the fan.

[DozyWannabe]

A few additions...

Major points of Strasbourg investigation are: know where you are, know where you need to go and don't trust the autopilot blindly

Or the ATCO - he gave an incorrect radar vector that put them significantly left of centreline.

Find me a case of protection gone wild that is not QF72 or MH124.

Both of which were recovered and landed safely, the latter of which was in fact a T7, not an Airbus.

There are recorded cases of stickpushers trying to prevent the stall but confused and panicked pilot overriding them with fatal results.

D.P. Davies explicitly lamented the knee-jerk reaction of a minority of pilots that condemned the introduction of the stick pushers in HTBJ.

[@RF4 - Clandestino may be too pugnacious for your taste, but if you fact-check him, he's rarely misinformed!]

[Lonewolf_50]

Reading comprehension time, Clandestino.
In a crew of two, you do indeed have to keep aware of what the other pilot is doing
I didn't say you have to ride the controls, did I? No.

"Trust Him!" is a good way to die, which is one of the reasons that CRM was developed. What the other pilot is doing when you aren't flying is usually shown to you on the flight instruments, by aircraft performance, etcetera. Of course, there are times when what the other pilot is doing is just what you are doing: monitoring what the robot is doing for you both. ;)

Nice to see you back in the scrum. :cool:

[Clandestino]

Reading comprehension time, Clandestino.

(...)

I didn't say you have to ride the controls, did I? No.

Did you just admit that non-linked controls are indeed fine for airline flying?

PNF checking what PF is doing is standard CRM. Performing it by looking at the yoke (or feeling it) instead of at the instruments is someone's very wrong idea of how it is done in airlines.

[Lonewolf_50]

Did you just admit that non-linked controls are indeed fine for airline flying?
When did I ever say it wasn't? Make sure you know what conversation you are having, and with whom, before you toss out wisecracks, OK? ;) There is more to this discussion than "must link yokes" "sidestick fine" and you may note that I was pointing out -- in the post of mine that you excerpted - to a non pilot (Dozy) that he was wrong about how that flying thing works in multi place aircraft.
PNF checking what PF is doing is standard CRM.
No kidding.

Thank you for returning my own comment back to me. We are in violent agreement. :cool:

Happy New Year, and glad to "see" you again.

[DozyWannabe]

@LW_50 - With respect, Clandestino seems to understand what I was driving at even if I phrased it badly (note I attempted to re-phrase above) - namely that you're not generally supposed to constantly monitor the PF through linked controls, rather more usually through monitoring the aircraft and by communicating with them.

By "trust them" I certainly wouldn't expect that to mean trusting them blindly - if you think they're doing something wrong then of course doing something about it is paramount.

[Lyman]

In an emergent abnormal, it would be nice for PNF to check the controls, both of them, since the aircraft is climbing, the PF swears he is commanding ND, the aircraft keeps climbing, at a higher rate, the airraft keeps climbing, it STALLS, and ten seconds before ending up as millions of pieces on the sea floor, he admits: "I have been holding aft stick for some time..."

Most of the time connected or visible SS are not needed.

"why bother? It hardly ever fouls up...." Or, "even with connected yokes, planes crash..."

Stop talking standard, and start addressing abnormal, please....

:ok:

[DozyWannabe]

the PF swears he is commanding ND

Where did he do that? I don't think he did, at least given the CVR and FDR evidence. No discrepancy between input and the aircraft's behaviour in that case ever existed, and there's no evidence to suggest any instruments other than ASI were malfunctioning. There were plenty of ways to see that the PF wasn't doing as he should have been.

[Lyman]

Yes, except the most obvious one, look at his hands.

You constantly try to distract from every question. They knew they had instrument issues; in an abnormal, everything is on the table, or should be.

"Yes, we go down..." how prophetic.... PNF had no choice but believe in PF. There is not necessarily something wrong with that, but after Stalling, the other two had no chance to cross check attitude with inputs. it is obvious that if the a/c had not been subject to invisible inputs, there is a strong chance the flight would not have been lost.

Cue "But other aircraft have crashed with visible controls..."

Over to you

But you rebut BEA as well... "The lack of Sidestick visibility may have been a factor..."

[DozyWannabe]

Yes, except the most obvious one, look at his hands.

It wouldn't be the "most obvious" to pilots (such as those we're discussing) whose main familiarity was with Airbus FBW types because they know that option is difficult and are trained to monitor using other methods.

An anomalous footnote (and I'm not rebutting BEA - "may have been a factor" does not mean they're recommending significant changes to the PFC implementation) to an accident which raised far more pressing technical and HF concerns is not going to be sufficient to compel a manufacturer to alter their entire control philosophy - one which has proven successful and as safe as any other (remember, yoke position has been ignored by PNFs several times in other accidents where the crew pulled up into a stall). I'm guessing this is why the "rumble" compromise has been put forward for the A350 (in response to the BEA's phrasing on the subject).

In this case it seems that the PNF allowed himself to become distracted from properly monitoring the aircraft and, by extension, the PF, by focusing on waiting for the Captain to return - that should be a far bigger worry.

[CONF iture]

Technically, the speed will get to Vfe (flap 3/full) and then the aircraft will pitch up...
No - High speed protection applies to VMO not Vfe.

[CONF iture]

Find me a case of protection gone wild that is not QF72 or MH124Eva air seems to be the most recent one.
And the MH 777 does not qualify for the 'wild' definition as the crew could always have control over the protection.

I wonder whether the locked groove track of "we want the override" would change if someone kills himself while overriding the functioning protection.
I don't know about that 'someone' I know about my airplane which is able to give full priority to a wild protection and blind fully ignoring my more reasonable command.

[Lyman]

Why has no one mentioned the uncommanded excursions of Airbii that prompted OEB: "do not reactivate AP, "uncommanded climb can result..." "?

Air Caraibes?

[DozyWannabe]

And the MH 777 does not qualify for the 'wild' definition as the crew could always have control over the protection.

Not in that instance. Check the article I posted in the other (T7 AoA) thread. According to the article (which quotes the ATSB report) the 777's systems re-engaged autothrottle uncommanded at least once after the crew had disengaged it.

[CONF iture]

According to the article (which quotes the ATSB report) the 777's systems re-engaged autothrottle uncommanded at least once after the crew had disengaged it.
Where does it say the crew could not have control over the protection ... ?
Quote from the ATSB report will do just fine. Leave the article to Clandestino.

[Lyman]

Praise God that 'articles' are different from "reports". Can you imagine if, like the uncommanded climb that can happen on A330, the AF:447 succumbed to same?

Now that inspires confidence....

[DozyWannabe]

From http://www.atsb.gov.au/media/24550/aair200503722_001.pdf

The pilot in command reported that he then disconnected the autopilot and lowered the nose of the aircraft. The aircraft autothrottle then commanded an increase in thrust, which the pilot in command countered by manually moving the thrust levers to the idle position. The aircraft nose pitched up again and the aircraft climbed 2,000 ft. The flight crew notified air traffic control (ATC) that they could not maintain altitude and requested a descent and radar assistance for a return to Perth.

The pilot in command reported that he attempted to disconnect the autothrottle by pressing the thrust lever autothrottle disconnect switches and pushing the autothrottle engage switch. The autothrottle arm switches had remained in the ‘ARMED’ position during the occurrence.

With the autothrottle armed it would automatically activate if the autopilot was not engaged and the airspeed was less than a flight management computer calculated value for 1 second, or the thrust was below that required for the mode of flight at the time.

The article (which I found after Clandestino clued me in to the incident - don't hold him responsible for the content) appears substantially correct.

It seems that the crew were unaware that disconnecting autothrottle was insufficient, and even with AP disengaged, the protections would order a thrust increase if the autothrottle system was still set to "ARMED".

Note that I'm not disputing that the T7 system can be disengaged more thoroughly than the Airbus equivalent, but it can be seen - even with that ability - the T7's functions can and do catch crews unaware if there is a problem with the air data.

Lyman, we're talking about FBW here, not autoflight. Can we at least keep the discussion vaguely on track?

[Lonewolf_50]

Dozy

"... namely that you're not generally supposed to constantly monitor the PF through linked controls ... "

you are right, you said that badly. Monitoring is mostly an SA and mental function if you are not the pilot flying. Once again, I never implied that the monitoring was being done via linked controls.

The monitoring begins with performance: is it (he) doing what we expect it (him) to be doing, or are we in a

'what's he doing now?'
'what's it doing now?'

condition?

Enough. Been over this exact point time and again in the 447 thread. With you.

[Lyman]

Lonewolf50

Have a nice rest. I will not let go of this purposeful obfuscation of the issues.

I am not the best one to persist, but if Dozy is the last one standing, the world will be a bit less safe.

No offense Doze, it is possible you do actually misunderstand the safety issues.

But to abandon the safety issues in favor of the status quo is ungentlemanly.

[DozyWannabe]

Once again, I never implied that the monitoring was being done via linked controls.

Nor did I imply that you did - my intent was that the context of the discussion at the time (which related to monitoring inexperienced pilots by "following through" on the controls) should have made my meaning more plain. Taken out of context it looks like a more prescriptive statement than was intended.

I don't want to argue with you - it's just a basic misunderstanding that I could have avoided by being clearer. Hope we can leave it there.

[Chris Scott]

Hello again, Clandestino, ¡Feliz año nuevo! *

After your 5 years or so on Airbus, you certainly cannot be accused of under-confidence... Anyway, glad you like the aircraft as much as I did.

Decisiveness and single-mindedness are laudable attributes in a pilot, but in a multi-crew environment they need to be tempered by a willingness to listen attentively, time permitting, before rubbishing the opinion or advice of other crew members. Dismissing reasoned arguments with sarcastic one-liners is not the way to win people round to your point of view.

To someone who forty years ago was flying big jets at present-day speeds and cruise altitudes with no FMS or A/THR; with AP/FD systems that needed to be told what (changing) pitch attitude to fly in the climb and descent, and could barely lock on to an ILS - let alone perform an autoland; it’s faintly amusing to have one’s careful explanation of the mis-selection of an FMGS mode dismissed with:

“know where you are, know where you need to go and don't trust the autopilot blindly or basically: Flight order says you are a pilot, so act like one for ******’s sake!”


* (Carefuly preserved the ~ for you...)

[Clandestino]

Awwwww, folks, don't take it personally. Despite increasing numbers of participants in our chat getting (auto)biographical, this thread is still about technical (and somewhat HF) subject and what we are discussing is a part of objective reality that doesn't care much (if at all) about someone's opinions.

I know about my airplane which is able to give full priority to a wild protection and blind fully ignoring my more reasonable command. If one is not seriously involved in the business of confirmation bias (http://en.wikipedia.org/wiki/Confirmation_bias) then one is obliged to recognize that not only such a system can counter unreasonable command but that it was a main reason why it was developed in the first place.

Or the ATCO - he gave an incorrect radar vector that put them significantly left of centreline.Yup. Couple of seconds or couple of degrees difference might mean we'd still operate old, flawed FCUs nowadays. Makes me wonder whether we'd have EGPWS today if B757 had speedbrake autostow like 320. Effing blood priority.

Now watch usual suspect rise to the bait. :E

[CONF iture]

If one is not seriously involved in the business of confirmation bias then one is obliged to recognize that not only such a system can counter unreasonable command but that it was a main reason why it was developed in the first place.
Works just great as long as data in are sane.

If one + the Manufacturer are not seriously involved in the business of confirmation bias then one + the same Manufacturer are obliged to recognize that such a system can produce nonsense that reasonable command could not counter ... but such eventuality was simply not foreseen in the first place.

If the aroplane's attitude doesn't follow your sustained input, you are in much, much bigger trouble than simple FC mode change.
But nice to see we do finally agree ... Time now to tell Airbus how to minimize the risk.

[DozyWannabe]

... but such eventuality was simply not foreseen in the first place.

So you assume, but I've been told differently - more than once.

[A33Zab]

Found following article in my archive folder, I don know the source nor date published.



5. ENHANCED DUAL INPUT AWARENESS

All Airbus FBW aircraft are fitted with uncoupled sidesticks. This choice of the sidestick was taken prior to the launch of the A320 due to the obvious benefits it provided for the operation of a Fly-by-Wire aircraft. The choice of non-coupled sticks, also taken at that time, was dictated by the available technology. With the technology of the eighties the only real choice was to couple both sidesticks mechanically; this would have unduly increased the complexity of the system and would have left the aircraft prone to failure cases (stick jamming) and common point typical of (and unavoidable) "mechanical" aircraft. With over 10 million FH of the AI FBW aircraft and over 15000 pilots qualified the initial debate on the merits and drawbacks of non-coupled sidesticks has ceased because flight crews have learnt to appreciate the advantages brought by the current system.

The feed-back received at Airbus from operators and pilot unions and the routinely analysis of in-service events indicate that there are still two areas where some pilots would appreciate some enhanced feed-back of "what the other pilot is doing".


These areas are:

Training flights.
In a high stress environment there have been prolonged and undetected dual input situations.
Airbus Industrie continues to explore all possible features available which might provide a reply to these concerns. Research activities have been conducted over the past months in the following areas:
Evaluation of electronically coupled sidesticks
Evaluation of features which may prevent prolonged dual input situations
5.1. Electronically coupled sidesticks

Electronically coupled sidesticks (so called active sidesticks) offered by various aerospace equipment manufacturers have been evaluated and analyzed by Airbus Industrie. Despite the diversity of the proposed solutions, all the systems rely on high speed torque motors to move one sidestick to the same position of the other sidestick. All suppliers provide adjustment capabilities (forces, thresholds, displacements...) to match the sidestick characteristics and feel to the current Airbus sidesticks.
The evaluations of electronically-coupled sidesticks covered the following issues: System safety analysis, integration to the AI FBW/AUTOPILOT architecture, pilot interface and simulator tests in normal/abnormal/emergency scenarios.
Our underlying premise during this evaluation was that the coupled sidesticks should not degrade the reliability, the feel, the consequences of failure cases and the pilot interface of the current non-coupled sidesticks.

The main items identified during this activity were:

a) The increased complexity of the coupled sidestick makes it very difficult to closely match the current feel of the Airbus sidestick which is appreciated by flight crews.
The "copy" function of the active sidestick is accurate.
The implementation of coupled sidestick would require a modification of the current simple principle of "algebraical addition of both sidesticks orders".

c) The current capability for the PNF to instinctively take control of the a/c, with or without the use of the priority pushbutton, must be kept.
The identification of the sidestick movements of a trainee under normal circumstances is improved. There is a clear benefit for the training scenario.

e) Due to the small deflections of the Airbus sidestick in high stress situations it is difficult to clearly identify what the PF is doing with the sidestick, namely if the motions are small and rapid.

f) When the PNF makes a small correction to the PF, here again in abnormal or emergency situations, the input from the PNF will, in most of these cases, go undetected.

g) Motion of the PNF sidestick can be distractive and in most circumstances can drive the attention away from the most important parameters or cues to be monitored.

h) There is a clear risk for injury if the sidestick hits the hand of either pilot following any runaway of the control system.

i) The active sidesticks introduce a number of new failure situations (runaway, jam...) and a common point which are significantly more severe than with the current AI system. To minimize the impact of these failure cases major modifications to the current flight control system architecture would be required.

Based on the analysis of these results it was concluded that:

a) The current technology for active sidesticks provides a marked improvement relative to that available at the time of launch of the A320: it improves the PNF awareness of the PF actions during training flights.

b) With characteristics of the AI sidestick, dual input situations can remain undetected with coupled sidesticks specially under stress situations (which is where the dual inputs tend to occur).

c) The increased complexity of the sidestick assembly and of the integration to the AI FBW architecture will unavoidably reduce the overall reliability of the system.

d) Work should be launched to develop alternative means to improve the detection of dual inputs situations since it was demonstrated that the coupled sidestick cannot provide a 100% detection rate.

5.2. Dual input detection enhancements

5.2.1. Description
As a complement to the active sidestick evaluations, various new features have been developed to improve the crew awareness of dual input situations on the FBW aircraft. The main objective of these features is to provide warnings which will prevent long duration dual input situations.
The following visual, aural and tactile cues have been tested with the active participation of pilots from Airbus, airlines (Cathay, DLH, Sabena), unions (ALPA, SNPL, German Cockpit) and Airworthiness Authorities (CEV, CAA, FAA, Transport Canada).

VISUAL CUE

When both sidesticks are deflected simultaneously (for more than 0.5 sec), the CAPT and F/O captions of the Sidestick Priority Light on both glareshields are illuminated flashing in green. As soon as the priority p/b is pressed on either sidestick, the glareshield lights revert to the classical priority configuration (CAPT and arrow or F/O and arrow). The principles of this visual indicator are identical for all FBW aircraft.

AURAL CUE

A "DUAL INPUT" audio message is triggered when both sidesticks have been simultaneously deflected for a certain time. The timing of the audio message has been adapted on the A320/A321/A31 and A330/A340 families due to the different systems architecture such that, on all cases, the message is triggered after the illumination of the glareshield lights. In this way, there is a degree of sequencing such that the aural warning will only be triggered if the dual input situation is prolonged.
The "DUAL INPUT" audio is repeated every 5 sec. It has the lowest priority of all the audio (voice) messages but can be generated simultaneously with any other non-voice audio warnings.
When the priority p/b is pressed on either sidestick the warning is canceled except if it has already started (i.e. it cannot be interrupted).

TACTILE CUE (BUZZER)

The sidestick is fitted with a small electrical motor which rotates an unbalanced weight and thus generates a vibration of the sidestick. The level of vibration depends on the rotation speed and on the weight of the rotating mass.
When both sidesticks are deflected for a certain time, the buzzer on both sidesticks are activated to produce a series of intermittent vibrations. Since the level of buzzer vibration could not be increased at will due to various reasons (e.g. rattling noise on the lateral console) the principle of intermittent "shots" was selected to improve the detection of the buzzer activation.
The timing of the buzzer activation has been adapted on all the FBW aircraft such that the buzzer is activated simultaneously or slightly after the illumination of the glareshield lights.
When the priority p/b is pressed on either sidestick the buzzer is stopped immediately.

5.2.2. In-flight evaluation campaign

The in-flight evaluation process was split into two phases: An initial period devoted to the definition of the various features and a demonstration phase where the visual, aural and tactile cues were presented to non-AI pilots in various scenarios. The tests were conducted on the in-house test A340 and A330-200 aircraft.

The initial development and definition phase concentrated on:

a) Adjustment of the activation thresholds

b) Relative timing of the three features

c) Adjustment of the buzzer vibration levels and frequencies

d) Adjustment of the quality and level of the audio message

c) Simulator and in-flight evaluation in various normal, abnormal and emergency scenarios

d) Definition of an evaluation program for non-AI pilots (airlines, unions, Authorities)


During the demonstration phase the modifications were presented to pilots from airlines, Airworthiness Authorities and Unions. In each flight the guest pilot flew the aircraft and the AI pilot made unannounced dual inputs. The dual inputs were performed in the following scenarios:

Precise tracking tasks in the normal flight envelope (tight turns, manual ILS approach)
Take-off rotation
Flare for landing and GA
High speed dives entering the HSP and triggering the Overspeed Warning
Stall Warning in Alternate law
Low speed maneuvering during approach
Maneuvering in the AOA-prot range (Avoidance maneuvers and GPWS pull-ups).
At the end of the flight the guest pilot debriefed the flight and gave his overall opinion of the different features presented; the AI pilot indicated the number of cases where the dual input situation went undetected.

5.2.3. Results of the in-flight evaluation campaign


There was a clear consensus of the evaluating pilots on the following issues:

The sidestick buzzer does not interfere in the normal piloting tasks
The illumination of the glareshield lights may go unnoticed specially in daylight conditions
The sidestick buzzer is probably the only useful cue in high stress situations
All of the features improve the dual input detection capability
There was also a general consensus that these features, even if frequently requested by the pilot community, are not really mandatory since nothing, other than crew discipline, can prevent dual input situations. The proposed features will reduce the likelihood that these situations last while remaining undetected but will not prevent them.

5.2.4. Conclusion

a) The definition and inflight evaluation of the aural and tactile warnings is completed.

b) These features will be presented for Certification.

c) The visual, aural and tactile cues will enhance the detection of dual input situations. These features will not prevent dual inputs, but the likelihood of having prolonged dual input situations will be greatly reduced.

d) These features may be proposed as Standard Options grouped as follows:


Light only (option already available)
Light + Audio
Light + Buzzer

[mm43]

Thanks A33Zab.

The above is part of a larger article found at www.oavia.com (http://www.oaviao.com/pesquisa_codigo_empresas/manuais_voo/performance_airbus/FBW.html), and appears to have been published circa 2000.

[CONF iture]

So you assume, but I've been told differently - more than once.
And your source is ?
or is it another case of 'tied hands' ... ?

Show me the meat DOZY.

[Gretchenfrage]

A33Zab:

I remember this pamphlet. It had been dicussed ad nauseam.

Basically it turned out to be biased and sometimes outright silly.

1. The statement that flight crews learnt to appreciate the advantages of the system shows the bias. There is no proven advantage to take away tactile feedback. The crews simply got used to its absence and some even liked it (mostly the lesser gifted pilots ….) To claim that pilots appreciated non existing advantages mainly serves to cover up the fact that many disapproved of its apparent and admitted disadvantages. It’s like eternally reiterating that pilots were involved in the design, as to enhance its credibility. Most linepilots do not really think big of management- or factory-pilots, because they wear one hat too many.

2. Stating that control interconnection would increase chances of injury is silly. The conventional layout is still predominant in modern aviation and that would mean all other aircraft than Airbus would be exposed to such danger. As I said: Silly.

3. The most silly statement however is the following:
“Motion of the PNF sidestick can be distractive and in most circumstances can drive the attention away from the most important parameters or cues to be monitored”.
How about the movement of the conventional dual commands? What about the capability of humans to process visual and tactile inputs in parallel (as opposed to two visual inputs)?
Really no comment needed.

4. The argument that incorporating electronic interconnection would increase the chances of malfunction, due to increased complexity, is equally flawed. Why would we allow all the new gimmicks into our cockpits then? TCAS, EGPWS, Smart Landing System with all their interconnections, warnings and protections surely increase complexity. Just because every now and then one of these systems goes hayward was never cited or accepted as a reason not to implement them. Why should that now suddenly apply for a safety enhancement in flight controls?? That's a double standard.



PS @ Dozy: If you write your unavoidable spin to this, draft it to the community, no answer to me, I can no longer read your contributions.

[jcjeant]

Hi,

Gretchenfrage
Basically it turned out to be biased and sometimes outright silly.
Beautiful argumentation
This is what I call "turning a pancake without dropping from the pan" :ok:

[flash2002]

For those who think that the protections are gentle or gradual and that time is available... Thats especially for you dozywannabe. I just received some more info regarding the incident from my company:

In the recent event, all three probes became frozen and the aircraft erroneously detected an ‘incorrect angle of attack’ scenario which triggers Alpha Prot. As the AOA probes are frozen Alpha Floor will not be activated as the triggering AOA limit is not reached . As designed, the aircraft protection activated and a nose down input was introduced.
Unfortunately, as the probes were frozen (and continually sensing the incorrect alpha), the AOA did not reduce and the flight controls continued to demand a pitch nose down. Within 10 seconds, the aircraft had achieved 12 degrees nose down pitch and a rate of descent of 9400 fpm.
Aft sidestick input had no effect and the aircraft continued to pitch nose down.


And had that A330 been fitted with BUSS:
• Back Up Speed Scale (BUSS), which is fitted onto newer aircraft relies upon AoA inputs. It must not be used, so DO NOT switch off more than 2 ADR’s.

Switching off those 3 ADR's could have been a major problem, making things worse. So there goes the theory that they followed an established procedure.
These guys were badly caught out by the FBW protection in a rapidly developing situation.
Luckily they managed to get everything under control. But if there was ever an argument for a button to deactivate normal law, this is it.

[BOAC]

That to me is absolutely terrifying, particularly the total loss of 'normal' flight control function.

[Chris Scott]

Hi A33Zab,

Thanks for all that. Don’t know how you reproduced it here, but can you confirm that the actual text of Para 5.1.(b) has not been omitted?

It looks familiar to me, which is not surprising if it’s from the 20th century. Even wrinklies like me are now using domestic electronic devices far more complex and reliable than we were in the year 2000, so perhaps AI is revisiting this design area. If they are, they wouldn’t be shouting about it from the rooftops, for obvious reasons.

[Lyman]

I have mentioned the dichotomy in the discussion prior. A very few adherents have interpreted the topic masthead as "how safe is Airbus"?

The opinion displayed becomes: "Quite safe". But that is not the question.

As I read it, it is: "How safe is AB flight control system when compromised?"

How is it doing in failure?

Gretchenfrage's analysis of the shiny pamphlet is instructive. He describes how prose can dazzle, and convince, to accomplish subtle goals.

One can only guess how the incident turns out if Roll Direct had challenged the crew.

Twelve degrees ND, and 9400 fpm descent. Without (commanded) elevator effect.

Charming.

[A33Zab]

so perhaps AI is revisiting this design area.


Perhaps, even the absolute zero (0 K) is less absolute (http://www.nature.com/news/quantum-gas-goes-below-absolute-zero-1.12146)nowadays:confused:

Checked it with the link provided by mm43, it is also missing on the site.

IMO the ref b) starts with "The implementation of coupled sidestick..."
and the ref d) with "The identification......."

[Chris Scott]

A33Zab,

What next...? Thanks.

Just wondering if flash2002's post should be duplicated on the A330/A340 EAD (AoA PROBES) thread, which is currently moribund.

And I remain curious as to if and how the respective probes seem to pack up (due icing) more-or-less simultaneously. Unless it’s something to do with this (http://www.pprune.org/rumours-news/502079-a330-a340-ead-aoa-probes-7.html#post7605319):

“...I sometimes used to ponder, during my walkrounds, on the pros and cons of locating Pitots 1 & 2 at precisely symmetrically-opposite positions on the fuselage (Pitot 3 being the odd one out). Then I would remind myself that the same applied to the AoA probes. It seemed to me that this might be a recipe for (roughly) simultaneous ice accretion of numbers 1 & 2.”

[Lyman]

Would it not have more to do with simultaneous ice pack of 1 and 3?

One and three have more in common in asymmetric airflow. No?

From a statistical point of view, cruise flight would generally represent most of the aircraft's exposure to symmetric airflow. In areas where particulate water Ice is present, a very small portion of total time in cruise, Ice is associated with turbulence, hence a higher chance that Ice would hobble vanes and pitots when unstable air is encountered. This suggests a higher probability that pitots located in close proximity would fail simultaneously.

Chris Scott:

"Can anyone cite an accident prior to AF447 that was related to the icing of a properly-heated pitot probe or AoA probe? Right now, I can't think of one, nor of a type that regularly experienced UAS problems in any flight-phase."

Not an accident, no. Incidents? Of course.... The AD is a place to start, re Thales.

[Lyman]

I do not mean to disrespect your walkarounds. Just after 447, i found a 300 and a 330 to stare at for extended periods. After marvelling at the exquisite look of the engines and general fit and finish of these beautiful birds, i focused on the pitot and AoA arrangement.

One conclusion was that the three appeared to be fit arbitrarily....more to accomodate plumbing than interface with airflow....

Were I Thales I would invest serious money in a statistical analysis of the turbulence encountered by AF447, up to and through the 'event'. To include sensory malfunction re: TCAS and W/S.

Cheers

[Chris Scott]

Lyman,

I think we are looking at this from different perspectives. You make some interesting points, but you may have read too much into my simplistic observation. I well remember getting very seriously iced-up in strato-cumulus on an (empty) C-47 in my misspent youth. We ended up with ice about an inch thick over the whole of both unheated windshields, and - when that had later melted enough for us to see through a hole in same - there was a stalagmite-like horn sticking forward about 6 inches from the frame between the two. The ice seemed to have propagated gradually backwards along both sides of the nose (I don’t recall noticing any ASI problems). When we eventually landed, there was still a circular area of glaze ice about 3 ft in diameter below the centre of the nose.

Now the characteristics of ice in strato-cumulus at an IAS of 120kts and TAT of just below freezing may be very different from those in cirrus or Cb at, say, IAS 280kts and TAT MS30C. And I don’t know how much research has been done into how much accretion there is on the nose in the latter circumstances. Although the heated windshields usually remain fairly clear (in my experience), except in heavy precipitation, you can see very little of the fuselage skin from the cockpit. It may be that the heated pitots and, usually further back, the AoA vanes can ice up before the unheated nose skin. But I doubt it.

When I ask if it’s a good idea for numbers 1 and 2 in each case to be positioned exactly symmetrically on the left and right sides respectively, I’m assuming that aircraft are normally flown with zero sideslip. Therefore, if both installations are serviceable and identical, they are likely to accumulate any ice in unison (unless the sun is shining from the side). You say that turbulence is required, but I presume that would even out in zero sideslip?

You suggest that the positioning of probes is arbitrary, which I doubt. But I’m sure you have noticed that the positions of numbers 1 and 2 mirror one another? And, when I ask about pre-AF447 accidents related to probes (heated as designed, and not damaged or blocked by any foreign object), I’m not limiting the question to Airbuses.

N.B.
Once again: are we discussing this on the wrong thread?


[EDIT]
Have reposted this (http://www.pprune.org/rumours-news/502079-a330-a340-ead-aoa-probes-8.html#post7615003)on the Rumours & News A330/A340 EAD (AoA PROBES) thread. Thanks Turbine_D.

[Turbine D]

Chris Scott,

I am going to repost my latest on the other thread and remove the posting on this thread.

[Lyman]

The nose does not describe a lateral in sideslip, necessarily. Since relative airstream can emanate from a 360 circle from in front, there are vertical slippages to account for (Probe2?). That 1 and 2 are opposite and co-planar, we can assume the airflow position in stable air is a design consideration. So why a placement of Standby below the 1, 2 plane? 'Anomalous design' imo..

From BA 038, I have pointed out common mode as an enemy of redundant design. This suggests that anomalous design can counter mere "redundancy" design.

I have been discussing micro granular water Ice, not "accreted" water Ice.

I don't say that turbulence is a requisite for ice packing of probes, only that it is statistically more likely to be present in these events.

A working theory is that micro granular water Ice is less responsive to Pitot heat solutions than is accreted water ice, to include supercooled water as the progenitor...

In BA038 thread, I proposed: one engine RRTrent700, and one GE90. Since it turned out that the RR had designed insufficiencies in its ability to melt Ice in fuel, the supposition is available that 038 may have made the runway, and prevented hull loss if utilising a GE90 as one of two engines.

Only a what if. It strikes me that pitot or vane design is not germane to the discussion of Airbus 'system design' problems.

Systems fail, Ice is only one possible bubble in the cheese. What is of critical import is what the systems do when facing a failure.

Apparently, there are bubbles installed at the factory. And flight test continues....With occupants.

[DozyWannabe]

For those who think that the protections are gentle or gradual and that time is available... Thats especially for you dozywannabe. I just received some more info regarding the incident from my company:

Thanks - I'm going to wait for the report, but at the same time I don't think it's fair to pin this on the protections - there's something screwy with the AoA probes, and despite not being prepared for it - and in the climb phase, where any false Alpha Prot trigger would be most problematic - the crew managed to resolve the situation.

[flash2002]

Pin it on the protections? What brought the aircraft in a 12 degree nose down pitch with 9400fpm within 10 seconds of the AOA probes becoming faulty?

Wait dont answer that.... the protections.

If this airbus a330 would have been equipped with BUSS, switching off those ADR's would have put the aircraft under manual control with AOA information displayed on the PFD's... What would have happened in that case???

dozy you need to get your pink glasses off, this type of aircraft needs a normal control switch to turn off the protections when they are clearly not controlling the aircraft in an acceptable manner.

12 degrees nosedown is NOT ACCEPTABLE! Havimg to switch of ADR's to regain control over some renegade computers is not acceptable.
Boeing might have problems on their aircraft that need resolving, but this needs to be resolved on airbus!

[DozyWannabe]

As I said, I want to wait for the report before drawing conclusions - the fact is that this is but one incident, apparently caused primarily by faulty AoA vanes. Mandating a sweeping change of the kind you're describing to a system that has worked more-or-less faultlessly for 24 years and heaven knows how many flight hours is overkill.

This is not about "pink" glasses, this is about wanting all the facts to be known before letting the usual suspects argue for a single incident to settle old vendettas.

[CONF iture]

dozy you need to get your pink glasses off, this type of aircraft needs a normal control switch to turn off the protections when they are clearly not controlling the aircraft in an acceptable manner.
I simply think that's the most reasonable step the manufacturer should take, for the good of all.

Mandating a sweeping change of the kind you're describing to a system that has worked more-or-less faultlessly for 24 years and heaven knows how many flight hours is overkill.
The sweeping change has to be mental more than anything. Airbus simply needs to admit that the protections can make a mess too and a simple tool should be provided to the crew to help them to stop the possible mess to go too far.

[CONF iture]

I just received some more info regarding the incident from my company
Do you have any written document on the event, or is it more informal information, do you think you could get more info soon ... What you report here for sure matches the seriousness of the published EMERGENCY AD + AIRBUS AFM TEMPORARY REVISION but I find it very annoying still no one has publicly stated its intention to investigate the event ...

[jcjeant]

but I find it very annoying still no one has publicly stated its intention to investigate the event ... Just a reminder ..
http://www.pprune.org/7591225-post91.html