flyingturtle
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AF447 And Airbus Flight Testing

Sat Jun 15, 2013 7:14 am

Hiho dear a.nutters,


The 350 flight testing and the air-to-air-shots from the chase plane reminded me of something.

In the final report on Air France flight 447, BEA wrote that Airbus sent a similarly loaded 330 on a test flight in order to investigate the kind of nose-up descent that happened in June 2009.

Is there any technical report or even a video of this flight?


Curiously,


David
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wingscrubber
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RE: AF447 And Airbus Flight Testing

Thu Jun 20, 2013 6:58 pm

I don't imagine Airbus would let flight testing footage of that nature get out into public domain, the whole point of 'envelope protection' is supposed to be that they're unstallable. But I did find this-

http://www.youtube.com/watch?v=wvHzvZJnqS4
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roseflyer
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RE: AF447 And Airbus Flight Testing

Thu Jun 20, 2013 8:24 pm

Quoting flyingturtle (Thread starter):

Is there any technical report or even a video of this flight?

I doubt that is public. Flight test data is rarely shared unless it is used for marketing purpose. Doing stall recover maneuvers rarely falls into that domain, although there are some videos of 777s stalling that were part of a PBS documentary during 777 certification.

I am sure Airbus has videos of stalling A330s. Although envelope protection exists in the real world, stall recovery is a required part of flight testing, so they do have experience stalling the airplane even if they had to use “red label” flight controls software that overrode envelope protections.
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Tom_EDDF
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RE: AF447 And Airbus Flight Testing

Sun Jun 23, 2013 10:37 am

Quoting wingscrubber (Reply 1):

I don't imagine Airbus would let flight testing footage of that nature get out into public domain, the whole point of 'envelope protection' is supposed to be that they're unstallable. But I did find this-

http://www.youtube.com/watch?v=wvHzv...JnqS4

I agree such footage, if available, would not be released. The point about envelope protection is irrelevant though, as it should be known that AF447 reverted to "Alternate Law", therefore both bank and high AoA protection were lost. It is commonly known that an FBW Airbus for sure can be stalled, for sure in Alternate Law/Direct Law.

[Edited 2013-06-23 03:38:45]
 
flyingturtle
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RE: AF447 And Airbus Flight Testing

Sun Jun 23, 2013 3:45 pm

Quoting wingscrubber (Reply 1):
Quoting Roseflyer (Reply 2):

Thank you - I've already watched that video. But Airbus could publish that video, with the message that their test pilots are not shy about recreating a flight that cost hundreds of lives, and that an A330 can be saved in a AF447-like situation.


David
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Klaus
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RE: AF447 And Airbus Flight Testing

Mon Jun 24, 2013 11:35 am

Quoting flyingturtle (Reply 4):
Thank you - I've already watched that video. But Airbus could publish that video, with the message that their test pilots are not shy about recreating a flight that cost hundreds of lives, and that an A330 can be saved in a AF447-like situation.

As far as I'm aware they've stalled all the FBW aircraft models during regular flight testing (not fully into the stall, but far enough to know where the boundary really is and whether it matches simulations). So additional test flights would probably just have been for additional validation.

The problem with AF447 was not that the aircraft exhibited any surprising stall behaviours, as far as I'm aware, but the problematic reactions of the crew to the generally predictable and expected behaviour under the circumstances.

The aircraft remained controllable to the end – it just wasn't controlled properly.

Whether and if so how much even a confused crew could have been helped by technical modifications while not jeopardizing other accident-free flights can be a question, but it's definitely not a simple one.
 
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Starlionblue
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RE: AF447 And Airbus Flight Testing

Mon Jun 24, 2013 12:19 pm

Quoting Klaus (Reply 5):
The problem with AF447 was not that the aircraft exhibited any surprising stall behaviours, as far as I'm aware, but the problematic reactions of the crew to the generally predictable and expected behaviour under the circumstances.

The aircraft remained controllable to the end – it just wasn't controlled properly.


        

Indeed. Flight testing by Airbus seems redundant for this situation.
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7BOEING7
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RE: AF447 And Airbus Flight Testing

Mon Jun 24, 2013 3:26 pm

Quoting Klaus (Reply 5):
As far as I'm aware they've stalled all the FBW aircraft models during regular flight testing (not fully into the stall, but far enough to know where the boundary really is and whether it matches simulations).

For certification even on FBW airplanes you need to do full stalls not just nibble at the edge to insure there are no unexpected results.
 
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zeke
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RE: AF447 And Airbus Flight Testing

Mon Jun 24, 2013 3:41 pm

Quoting flyingturtle (Thread starter):

There will be a report, and it would have a lot of data, and more than likely footage. Probably the BEA has access to it, however it would be commercially sensitive.

The aircraft is first stalled in direct law, then retested in the various laws until normal law is active. This was a requirement for the A330 to be certified in the first place.

Flight testing does not attempt to cover every conceivable combination of attitude, airspeed, and altitude the aircraft will ever experience. Any pilot can with some effort can place an aircraft in a situation for which it is not designed, that aircraft could be a simple C172 or a complex aircraft like the A330.
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Starlionblue
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RE: AF447 And Airbus Flight Testing

Mon Jun 24, 2013 3:47 pm

Quoting zeke (Reply 8):
Flight testing does not attempt to cover every conceivable combination of attitude, airspeed, and altitude the aircraft will ever experience. Any pilot can with some effort can place an aircraft in a situation for which it is not designed, that aircraft could be a simple C172 or a complex aircraft like the A330.

Well put.

I like to put it thus: A determined pilot can crash the safest airplane in the world. This is why I trust CX, SQ and QF way beyond Airbus or Boeing. The vast majority of accidents are "caused" by the pilots so why do we talk about types being unsafe.
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KarelXWB
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RE: AF447 And Airbus Flight Testing

Tue Jun 25, 2013 9:03 pm

Quoting Klaus (Reply 5):
The problem with AF447 was not that the aircraft exhibited any surprising stall behaviours, as far as I'm aware, but the problematic reactions of the crew to the generally predictable and expected behaviour under the circumstances.

In fact, if the PF had released the joystick, the aircraft would have leveled itself. Even in alternate law.
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Chaostheory
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RE: AF447 And Airbus Flight Testing

Wed Oct 30, 2013 1:28 am

Quoting flyingturtle (Thread starter):
Is there any technical report or even a video of this flight?

During the joint Airbus and Boeing stall testing lecture at the Royal Aero Society in London, a number of stall test videos were shown. The videos included the 787, 777, A380 and A330 models.

I seem to recall that the A330 stall was characterised as "benign", and apart from cockpit vibration (which could make instruments unreadable), the stall tests were uneventful (similar to the 787).

It was interesting to see the A380 and 777 exhibit rapid roll tendencies under certain conditions. On one occasion during the 777 stall testing, it swung into a bank in excess of 80 degrees before John Cashmann managed to regain wings level.

There is a video of the lecture on youtube. Unfortunately however, the stall test videos have been edited out.

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bueb0g
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RE: AF447 And Airbus Flight Testing

Wed Oct 30, 2013 9:52 am

Quoting KarelXWB (Reply 10):
In fact, if the PF had released the joystick, the aircraft would have leveled itself. Even in alternate law.

Oft quoted bit of information with no evidence whatsoever to support it. Note that the PF was not pulling fully back on the stick - he only hit he aft stop once or twice. For most of the stall, the stick was quite near centred and on two occasions was in a nose down position. Nowhere in the report does it state that the aircraft would have recovered had the pilots left the stick in the neutral position - even had the aircraft "levelled" itself, that would not have been enough to un-stall. Once through 33,000 feet a full and maintained stall recovery was required to save the aircraft.
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nomadd22
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RE: AF447 And Airbus Flight Testing

Wed Oct 30, 2013 11:37 am

Quoting Starlionblue (Reply 9):
I like to put it thus: A determined pilot can crash the safest airplane in the world.

You should read the final report on John Denver's last flight. He found a way to stall an unstallable LongEze that I'm pretty sure nobody could have ever predicted.
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flyingturtle
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RE: AF447 And Airbus Flight Testing

Wed Oct 30, 2013 4:29 pm

Quoting ChaosTheory (Reply 11):

Thank you, I'll watch that lecture soon!


David
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KarelXWB
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RE: AF447 And Airbus Flight Testing

Wed Oct 30, 2013 6:10 pm

Quoting bueb0g (Reply 12):
Oft quoted bit of information with no evidence whatsoever to support it. Note that the PF was not pulling fully back on the stick - he only hit he aft stop once or twice. For most of the stall, the stick was quite near centred and on two occasions was in a nose down position. Nowhere in the report does it state that the aircraft would have recovered had the pilots left the stick in the neutral position - even had the aircraft "levelled" itself, that would not have been enough to un-stall. Once through 33,000 feet a full and maintained stall recovery was required to save the aircraft.

I did not say the aircraft would recover, they have a stall recovery procedure for that. But the A330 can level off when you leave the stick alone.
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WingedMigrator
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RE: AF447 And Airbus Flight Testing

Sat Nov 02, 2013 5:53 am

Quoting flyingturtle (Reply 4):
with the message that their test pilots are not shy about recreating a flight that cost hundreds of lives

Nobody is going to re-create that flight, at least nobody who cares about surviving.

Quoting 7BOEING7 (Reply 7):
For certification even on FBW airplanes you need to do full stalls not just nibble at the edge to insure there are no unexpected results.

There is a wide margin between a "full stall" and flying the airplane at 45-60 degree AoA for several minutes.
 
ferpe
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RE: AF447 And Airbus Flight Testing

Sat Nov 02, 2013 7:44 am

Quoting WingedMigrator (Reply 16):
There is a wide margin between a "full stall" and flying the airplane at 45-60 degree AoA for several minutes.

Indeed there is, once into the deep stall the risk of getting into rotation scenarios ie spin (which is more difficult to get out of if not sometimes damn hard ) is there. Noone goes into spin without having prepared that very well. For test flights of the spin domain you have a anti spin chute on the tailcone, should the fin and rudder turn out to not be effective  Wow! .
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Chaostheory
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RE: AF447 And Airbus Flight Testing

Sat Nov 02, 2013 4:35 pm

Quoting ferpe (Reply 17):
For test flights of the spin domain you have a anti spin chute on the tailcone, should the fin and rudder turn out to not be effective

Or, in the case of the A400M, a rocket!
 
jollo
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RE: AF447 And Airbus Flight Testing

Tue Nov 05, 2013 5:55 pm

Quoting KarelXWB (Reply 15):
But the A330 can level off when you leave the stick alone.

Genuine question: is this also true when in Alternate Law? And would it be a FBW action of just the effect of dynamic longitudinal stability?
 
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KarelXWB
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RE: AF447 And Airbus Flight Testing

Tue Nov 05, 2013 6:13 pm

Quoting jollo (Reply 19):
Genuine question: is this also true when in Alternate Law?

As far as I know, yes. Per pilot comments, the airplane react about the same as in Normal Law; you basically lose the flight envelope protections in Alternate Law.

http://www.airbusdriver.net/airbus_fltlaws.htm
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jollo
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RE: AF447 And Airbus Flight Testing

Wed Nov 06, 2013 3:44 pm

Quoting KarelXWB (Reply 20):
the airplane react about the same as in Normal Law; you basically lose the flight envelope protections in Alternate Law

http://www.airbusdriver.net/airbus_f...s.htm

Very useful summary, thanks a lot.

Quote:
In pitch alternate law the flight mode is a load factor demand law similar to the Normal Law flight mode, with reduced protections.

So if you leave the stick alone you're basically demanding 1 g, and that (barring peculiar parabolic trajectories) will eventually bring the a/c back to level flight. Right?

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