Air France jet crashed nose-up after 4 minute ordeal

Folks who might criticize the Airbus design might also want to equally harp on the F-16

Correct. It is usually arm-chair experts who think somehow that fly-by-wire is an "Airbus" thing (they think of themselves as defenders of the "American made Boeing" I suppose (they are not American made any longer). What they don't know is:

- Literally all airlines designed after 1985 are fly-by-wire.
- All major military aircraft designed after 1980 are fly-by-wire.
- And lastly, who in their right mind would trust cabled under thousands of pounds of tension going to all the extremities of an aircraft, versus redundant wiring harnesses? Sheesh.

So, should the focus be on the pitots (per another commentary on “freezing up”)? What would make the aircraft go into a stall on it’s own from previous level flight?

Pitot system. From the first hours after the accident, that has been the theory. It is supported by known incidents in A320, A330, and A340 aircraft with that series of pilot system.

That was a NWA flight NTSB Investigates Speed Data On Airbus A330s

However, the report shows they flew pitch and power and things worked out; within 5Kts of desired speed. The only thing that remained amiss was the alternate law condition for the remainder of the flight. The bottom line is they didn't crash.

Reading the details contained in today's BEA report (past the summary) one gleans that the stall warning only sounded twice during the ill-fated descent; first immediately after disconnection of the A/P and again 2 minutes later. Two stall warning amongst all whistles and bells going off, whereas in fact they were stalled the entire time.

Perhaps the PF was pitching up because he was losing altitude and was applying full power to regain it, not knowing he was stalled. It appears that below a certain threshold the data become NCD, i.e., NON COMPUTED DATA so it isnt even considered valid by the system, and that might be a cause for the stall warning to disappear completely. That has been observed in an incident investigated 2 months ago...

This actually is really surprising. It seems as though it's possible that the relative airflow at a pitot in a severe stall might be oblique enough to cause the sensed airspeed to drop below a threshold which means that the way the stall warning system is designed, if the stall progresses far enough, the computer will stop reporting the condition. This just seems horrible... Given that a stall has an entry point, and one hopes an exit as well, it seems as though it would make much more sense for the flight computers to set a flag when the stall is detected, and then clear that flag only when reliable air data indicates the plane is flying again. Until the flag is cleared, the stall warning continues.

SO, if you're nose-up, descending through FL100, w/100% N1, how is it possible to not know you're in a stall? Spatial Disorientation. It's dark, you can't see the horizon, the instruments are telling you things that don't make sense...

Since the PF progressively and slowly over 2-3 mins pitched the plane up, with high power, the speed bleed was in real life slow and small, and thus the trade off between AOA and pitch attitude happened slowly and discreetly, the further away the AOA grew from the actual pitch of the airplane, the more the THS trimmed up to keep the pilot input. This is one of those tricky areas in Airbus; trim being automatic. The pilot doesn't look at the trim wheel per say nor do they trim on the stick because there isn't a function like that. Since the aircraft was heavy, the actual pitch attitude didn't get to 40^o, but rather the aircraft was decending pitched up slightly and the angle between the direction descent and the wings was 40^o. The aircraft probably looked like it was in a slight climb attitude...it is a very very tricky situation in an airliner, and since they weren't in a sim - they were in it for real - add in the confusion, the panic, the high heartbeat, the callouts that they were getting near 10,000 feet and im sure the weather outside was lightning and turbulent...it became a soup of a situation.

British CAA recently released a document concerning stall recovery technique

Applicability: RETRE, TRIE, TRE, SFE, TRI, SFI
Effective: Immediate
STALL RECOVERY TECHNIQUE

Recent observations by CAA Training Inspectors have raised concerns that some instructors (both SFIs and TRIs) have been teaching inappropriate stall recovery techniques. It would appear that these instructors have been encouraging their trainees to maintain altitude during recovery from an approach to a stall. The technique that has been advised is to apply maximum power and allow the aircraft to accelerate out of this high alpha stall-warning regime. There is no mention of any requirement to reduce the angle of attack – indeed one trainee was briefed that “he may need to increase back pressure in order to maintain altitude”.
It could be argued that with all stall warning devices working correctly on an uncontaminated wing, such a recovery technique may well allow the aircraft to accelerate out of danger with no height loss at the lower to medium altitudes. The concern is that should a crew be faced with anything other than this idealised set of circumstances, they may apply this technique indiscriminately with potentially disastrous consequences.
The standard stall recovery technique should therefore always emphasise the requirement to reduce the angle of attack so as to ensure the prompt return of the wing to full controllability. The reduction in angle of attack (and consequential height loss) will be minimal when the approach to the stall is recognised early, and the correct recovery action is initiated without delay.
NOTE: Any manufacturer’s recommended stall recovery techniques must always be followed, and will take precedence over the technique described above should there be any conflicting advice.
Any queries as a result of this FCTN should be addressed to Head of Flight Crew Standards at the following e-mail address:
flightcrewstandards@caa.co.uk.
Captain David McCorquodale
Head of Flight Crew Standards
21 April 2010

Airbus subsequently released the following

For the A320 fleet:
As soon as any stall indication (could be aural warning, buffet...) is recognized, apply the immediate actions :
- NOSE DOWN PITCH CONTROL . . . . . . . . . . . . . . . . . . . . APPLY
This will reduce angle of attack
Note: In case of lack of pitch down authority, reducing thrust may be necessary
- BANK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . WINGS LEVEL
• When out of stall (no longer stall indications) :
- THRUST . . . . . . . . . . . INCREASE SMOOTHLY AS NEEDED
Note: In case of one engine inoperative, progressively compensate the thrust asymmetry with rudder
- SPEEDBRAKES . . . . . . . . . . . . . . . . . . . CHECK RETRACTED
- FLIGHT PATH . . . . . . . . . . . . . . . . . . . RECOVER SMOOTHLY
• If in clean configuration and below 20 000 feet : - FLAP 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SELECT
Note: If a risk of ground contact exists, once clearly out of stall (no longer stall indications), establish smoothly a positive climb gradient.

That notwithstanding, it seems to me that the BEA has put all the facts out there...they just aren't saying outright what the cause of the accident is. From where I'm sitting, this is pretty cut and dried:

the pilots were flying at .80 in slight turbulence
the pitots freeze up/fail
AP disconnects
AT disconnects
loss of reliable airspeed
they pitch up the airplane and it climbs to FL375
during the climb, the speed bleeds
Pilots push nose down and flatten trajectory
Stall warning goes off
Pilots apply nose up input
Plane climbs to FL380
Captain reenters cockpit
Plane enters full stall and begins falling rapidly
Pilots move thrust levers to idle detent (per new AB procedure)
AoA never recovers

The new airbus procedure allows for thrust reduction, in this case it helped by not aggrevating the nose up moment which is what essentially stopped them from getting out of the stall. Its suprising that the aircraft did not enter a spin. One can infer from this that the aircraft is inherently very stable actually.

I believe if one reads the report carefully, it is pretty clear what the problem was. The event that started everything were the crappy Pitot tubes failing/icing, but as a hobbyist with plenty of theoretical knowledge of commercial flight and the procedures and physics involved, I think it's pretty clear that the crew made some grave errors in this accident. We can debate whether other crews would have performed differently, better, worse, or the same, but I personally think that since this is the first outcome of its kind despite pitots having frozen/failed plenty of times before, it puts this event in a particular light.

I believe that there is certainly no design issue with the A330 that caused this issue. The faulty pitots have been replaced, but now it's time to teach pilots how to fly a plane so they can execute when feces hits the fan.

“# Stall warning goes off
# Pilots apply nose up input”

“The faulty pitots have been replaced, but now it’s time to teach pilots how to fly a plane so they can execute when feces hits the fan.”

Like learning to put the nose down when the stall horn goes off?

Hangar pilots ARE the best ya’ know ...

WRT fly-by-wire versus cable. It’s a LONG way from the front of a 747/7X7/A-X00 etc to the rear of the airframe and the tips of the wings.

WHY use mechanical and/or hydraulic systems that weigh perhaps tonnes more, AND introduce lag, slap and wobble from stretched cables and worn fittings? Think Stearman ;-)

I have more issues with different brands of engines than I do airframes. I don’t like the harmonic whine of RR engines on the big birds at take off power. It hurts my ears. Once in flight on cruise, no worries. But climb out is painful if I am sitting in front of the wing.

I don’t like the harmonic whine of RR engines on the big birds at take off power.

Same. Give me a GE/Snecma any day.

Like learning to put the nose down when the stall horn goes off?

No. Only an idiot teaches pilots a single response like that to stall warning. 1000' AFE, and your "put the nose down" response is certain death. Pilots need to be taught the pitch up effect of thrust in some aircraft (A330 in particular), as well as the need to reduce angle of attack. "Nose down" is not the same thing as a reduction in angle of attack. In most jet aircraft, max thrust could induce a pitch up moment and still reduce angle of attack.

We're not talking Cessna here. We are talking about 90,000# of thrust.

When you are in the area of reverse command only engines with super high thrust outputs are going to get you out of the situation they were in. F-15s yeah, A330, no.

Holiday Inn Express again?

So, the aircraft is at 35K and is falling at 10k FPM. Simple math states that even if they don’t try to correct the situation, it will take 3.5 minutes to auger in. Four minutes is not all that long in this situation. throw in spacial disorientation into the mix and it’s actually pretty quick.

If all you use is ground speed and wind direction, then I am assuming you are not flying IFR. These guys were. At night or in IFR conditions, airspeed, altitude, needle/ball and VSI are the only things that keep the aircraft in controlled flight. Three of the four indicators are pitot/static. How do you get your ground speed? How do you compute airspeed and stay above stall or fly proper AOA without a pitot static system? How do you figure out you are straight and level without an altimeter and VSI? If you are flying IFR with just ground speed and wind direction, then you are using a technique I have never heard of.

Very true about fly by wire, or even fly by hydraulics. That is why feedback is programmed into the systems.