Airbus crash/training flight

[jb5000]

In my opinion this much loved contempt of new technology by some of the more 'senior' members on PPruNe is because all they are basing their views of FBW and Airbus 'laws' on is what they can pick up from this very site.

If you complete an A320 TR the laws, protections, management and handling of these aeroplanes really are quite straightforward and intuitive.

Trying to understand them when you have 3 or 4 'conversations' on the go on any one thread, with the odd flight simmer popping up to give duff info makes it sound like we are all sitting there with no clue as to what is happening, completely 'out of the loop' and relying utterly on all of the automation so we can actually make it from A to B.

On the line out of probably hundreds(?) of different captains I have had only one who preferred being on an older type.

I am pleased that I fly the A320, I have taken the time and care to ensure that I understand all of the systems and protections.

Granted this means I can't stand around in smoking jackets with my cigar reminiscing of the 'good old days' when 'pilots actually controlled their aircraft rather than damn computers'. What a shame.

Aircraft technology moves on. Get over it.

Rant over.

Let's get back to one of the most interesting threads on PPruNe for quite some time, and let's see if we can actually learn something from this terrible accident.

[J.O.]

I think there is some misunderstanding of the information in the BEA report pertaining to the FACs. It is being suggested that the FACs failed, but when I read the following;

At 15 h 36 min 47 s, when the airplane was stable at flight level 120, the Captain asked “you want alternate law” and the New Zealand pilot answered “okay alternate law”.

At 15 h 37 min 08 s, the autopilot was disengaged. Nine seconds later, the callout « FAC 1, and FAC 2 is coming now »

I read it as saying that they purposely selected the FACs to OFF in order to get into alternate law. As I have never flown the test flight profile, I don't know if this is part of the test or not, but when I asked someone who has done it, he stated that turning the FACs off was not part of the test requirement.

[S.F.L.Y]

Had you studied the events without any prejudice, you would have noticed that the auto-trim did its job as the maneuver demanded : Back stick and a decreasing airspeed.
At that moment, they went into a stall warning and probably because the system sensed both FACs failed, it went - correctly - into direct law, because of the extended gear.

It's because I studied the report that I can say that the auto trim didn't do its job when it was supposed to. After it trimmed the aircraft for low speed, the trim was blocked into that configuration even when not in direct law and while the stick was fully forward (have a closer look to the report).

Explaining that laws and systems worked correctly according to the wrong AoA info is not satisfying. The fact is that the aircraft was set in a wrong trim configuration without giving any proper feedback to the crew and that this configuration was kept while this auto trim should have worked on returning to a normal setting. Please tell me where is the benefit of having sidesticks without force feedback because this is the only reason while this auto trim is required in "manual" flying.

[jb5000]

I do agree there is some automation complacency in the cockpit today, as well as various other technological and CRM concepts and challenges that affect our lives as pilots.

However........

This thread is centred around Airbus FBW envelope protections - an entirely different concept. An Airbus (320 at least) is designed to be flown in the same manner as any other aircraft, these almost 'hidden' protections are there to ***help*** the pilots should they find themselves in a highly unusual and uncommon situation.

Airbus FBW control laws are also important in this investigation, again.... nothing really to do with pilots becoming reliant on automation.

[Dysag]

Lemurian

Is that CPA's John Bent you're referring to? Great guy, understands Airbus philosophy better than almost anyone.

[ZeBedie]

In support of DC-ATE: I've flown the A320 a lot and believe it to be a good, safe aeroplane and better than the 737. However, I think the autotrim function is a mistake, in that, if I want to stall a Boeing/DC, I have to pull like mad, but this thing helps me by trimming into the stall.

I've not read the full report, but I expect autotrim helped the Bangalore (OPEN DES into the approach lights) accident to happen.

[Rananim]

Lemurian's answer to SFLY is evasive and unsatisfactory.It reads like a French accident report.ie.the pilots were stupid for not understanding the brilliantly convoluted design.Can someone with a little more honesty have a go at answering SFLY's embarassing question?

What a shame it crashed In French waters.No chance of an honest appraisal.

Yes,I'm biased.Yes,Im old-fashioned.I know.Back to lurking.

[ZeBedie]

Maybe the other faults, which let the stab run to full nose up,where it never normally goes, allowed a mechanical jam to happen? Rusty, unused screwjack, old, dirty grease/deicing fluid/fell off the end of its travel???

[MerzNorton]

conventional aircraft

DC-ATE

"My only 'complaint', if you will, from the beginning of THIS particular accident was.....that had it been a 'conventional' aircraft, there would not have been a need to check this system."

I am also from the "classic" era. I was able to participate in the twilight of the round engine days in the DC6 and finished my career in the B747-200F.

During my flying career I conducted a number of test flights of aircraft coming out of maintenance C and D checks. The aircraft were DC9-30, DC8-62, and DC8-73. In each case we were required to conduct inflight checks of the stall warning systems (stick shaker). We would pre-compute the appropriate stall speed and stick shaker speed for each configuration. We would initiate the stall recovery either at the shaker or the computed shaker speed which ever came first. It appears to me that the crew in this accident was conducting the equivalent system check in the A320.

One note I will make here is that the procedure for this test required that we would stop nose up stabilizer trim at 20 kts above the computed Vs. This then allowed the recovery without the requirement to override an inordinate pitch up. It appears in this incident the A320 autotrim presented the crew with a situation they were not expecting or not aware of.

[Smilin_Ed]

Wild Excursions

Would any pilot of an FBW aircraft, while conducting such a test (with proper authorization and at an appropriate altitude) expect the wild excursions from normal flight that this crew experienced? I hope not. If so, the test should not be conducted at ANY altitude.

[TripleBravo]

DC-8, you made your points, some of them I could follow, but over time your repetitions get a bit boring, sorry to say.

Several posters here have stated that in Direct Law, the plane flies just like it's non-FBW predecessors but obviously the pilots of this aircraft were unable to do so.

I think that's the main point. No reversion back from "auto" thinking to "manual" action.

• They entered a stage where they expected to see the kick-in of several protections.
• I assume they did never realise the completely back trimmed elevator - as this is no item to care for during normal ops, which they were used to.
• I assume the complete lack of protections and automation struck them in a situation they were unable to break that barrier of mind because of the huge workload kept them occupied (see sidestick action).
• They obviously never used the trim wheel manually during that flight, which seems to could have saved the flight.

The preliminary report suggests that 9 minutes before impact there was deliberate manipulation on the flight laws, not covered by the test procedure. Then the crew expected at that "stall test" in 3000' a fully functioning A/C, which it wasn't. The broken AOA disabled some auto functions. They could not break that and didn't make use of all items the A/C provided them to regain control.

Never make any "quick and dirty testing"... And that's exactly what the high altitude serves for in a "real" test flight: gain reaction time.

[Safety Concerns]

smilin ed you are showing your ignorance of air data systems.

Even analogue aircraft use AOA position for error correction of the air data system. So an analogue aircraft flying with 2 u/s AOA's would be in as much danger as any other aircraft.

It could affect more than just stall warning (depending on installation) and could become critical at low speed low altitude depending on the error induced.

I can't remember the exact figures but the MD11 used to cause problems in the early days during testing. If the AOA's were not all in the same position on the ground the air data readings would show huge differences between systems 1+2

[TripleBravo]

departed normal flight essentially because of a couple of seized AoA vanes

Normal flight being an idle power stall test in 3000' ? Interesting...

By the way, your stall warning horn on every Cessna or Piper is in fact as well an AOA sensor. Would you test that at traffic pattern height?

[Smilin_Ed]

No Independent Backup Flight Controls

Even analogue aircraft use AOA position for error correction of the air data system. So an analogue aircraft flying with 2 u/s AOA's would be in as much danger as any other aircraft.

But, in a totally analog aircraft, or an FBW aircraft with a viable alternative system totally unrelated to the primary system, you could kick out the offending system with the punch of one button and fly out of danger. Obviously, they didn't have that option and my contention is they should.

[Smilin_Ed]

Normal flight being an idle power stall test in 3000' ? Interesting..

By the way, your stall warning horn on every Cessna or Piper is in fact as well an AOA sensor. Would you test that at traffic pattern height?

Normal for what they were trying to do which is apparently an authorized test under some circumstances. Just at the wrong altitude. There's no argument that they shouldn't have tried it where they did..

[Smilin_Ed]

I think we're beating a dead horse here, Smilin_Ed. These 'new age' pilots are just as hard to convince of 'our way' as we are of theirs. Don't know 'bout you, but I'm glad I'm away from these flying machines. I'll leave you to carry the banner!

I don't object to FBW per se. It certainly can provide a smooth flight which translates not only to passenger comfort but also to fuel efficiency and accurate IMC approaches, to name a couple. But the attitude that "Nothing can go wrong," is dangerous and is certainly borne out by this accident. Things do go wrong and there need to be alternatives, not just redundancy. There are redundant AoA vanes, and at least two out of three failed in this case. I've never flown any FBW aircraft but I'm aware of other AirBus redundancies based on my reading of postings on this site. I spent 14 years evaluating the flying qualities and performance of aircraft. I also investigated several accidents in which colleagues died. With the data we have so far, I believe that there needs to be an alternative to back up FBW systems.

[lomapaseo]

I was sick and tired of reading argumentive posts about Boeing vs Airbus in an accident thread.

I'm just as sick now reading about the parsing of the argument in to FBW vs steam gage operation in accident threads.

All these arguments detract from the reasoning necessary to come up with prevetive measures (not causes) to prevent the next accident.

We have to face reality in that a preventive measure is not to ground all Boeings or FBW etc. aircraft.

Take these kinds of discussions to a tech forum where you can better band together in hate clubs.

[Hardcore]

The issue that intrigues me, is that every aviation regulatory body for every country in the world which allows Airbus to fly into it's airspace subscribes to the infallibility and redundancy of the Airbus Alpha floor protection system.
Otherwise the performance figures based on 1.12Vs (versus 1.3Vs of all standard flight control variants) wouldn't be accepted as the basis for the certified flight manual performance figures.
If it is a requirement for an Airbus rating to fly the alpha floor recovery, and the terrain avoidance maneuver actually by default calls one to fly into alpha floor, how could the integrity of the system be called into question?
The pilot's very probably had done hundreds of Alpha floor recoveries in the simulator and known at what stage of the deceleration the autotrim should have locked out and when alpha floor / TOGA lock kicks in. Why did they continue to decelerate below the paper VLS?

Surely the FAC's would have a comparator logic to cross reference other flight parameters with the AoA vanes and not just rely on a single similar sensor cross check?

If it's proven that the stall protection system is deficient in it's certified abilities, does Airbus and all the operators of airbus variants have to amend the performance figures (read weights) of the aircraft?

The problem as I see it isn't that the maneuver was carried out at less than the described altitude, but that the system has proven to be fallible.

[S.F.L.Y]

At 15:45:50 the plane did recover an horizontal attitude with horizontal wings, a 120kts IAS and under alternate law (meaning the auto trim was supposed to work). Because the trim remained stuck at -11 while the stick was fully forward, the plane stalled again. If the trim had work as it was supposed to, they may had recovered at 2500ft...

[PJ2]

S.F.L.Y.;

Because the trim remained stuck at -11 while the stick was fully forward, the plane stalled again.

No, the trim did not remain "stuck", the trim did exactly what it was designed to do in Pitch Direct Law - it stayed put but was movable by the crew. The aircraft provides an amber warning on both PFD's (Primary Flight Displays) to "Use Manual Pitch Trim" when in Direct Law. In this configuration, the 320 is no different than any other aircraft - it requires conventional crew action to trim and that the trim wheel should be rotated by the crew to achieve correct trim. Such system characteristics and crew responses are trained for in the simulator.

I am wildly guessing, but I have the thought that if they had rolled the trim wheel forward rapidly, they may have recovered a bit earlier in the subsequent dive or at least avoided the secondary stall - perhaps the final report may deal with this conjecture.

The airplane is certified controllable by elevator if the trim is within the green band beside the trim-wheel indicator on the pedestal. But bunting over from a very high pitch angle would have made such a recovery difficult especially with the reduced, (and possibly partially blocked) airflow over the elevators. In Direct Law, the elevators would be in their full down position in accordance with the stick position.

I reiterate that this last minute test action at low altitude resembles the less-than-ideal planning that occured prior to the Toulouse A330 test flight accident.