Lonewolf_50, TAT probe freezing.
This is (was) a ‘relatively’ common problem occurring on several aircraft types. It was most prevalent on the BAe146 which suffered engine roll back due to ice crystal icing in the compressor – all engines since modified.
The most usual erroneous TAT indications, as with the A330 incident, are where the temperature stabilises at zero (ice or water ice) due to the blockage. The temperature change is relatively slow in comparison to the assumed ‘near instantaneous’ pitot blocking.

“…seeing alt low a few hundred feet … prompts pilot to make what is initially a small correction to climb back to FL350?”
Yes, very much my point; this would provide a reason for the initial nose up input, but not answer the subsequent control actions.
Amongst this we should consider that the FDs had probably failed (cf VH-EBA), thus the crew might be looking for a cued parameter to follow. Also, consider what the VS might show after an ‘instantaneous’ 300 ft descent and attempted recovery (inertial / air data mix IIRC).
What happens to Mach No? cf VH-EBA.
What happens to MMO/VMO computation? It’s most likely to be independent of the airspeed display as the value is also used by the FWC for audio warning; would the warning still work?

As for IRU, I knew of one design which had an air data correction in the unit (I forget why), but during testing, a sharp pull up with a rapid loss of speed and quickly increasing altitude caused the ADC software to detect a ‘failed’ (out of tolerance) condition and shutdown both ADCs, which in turn shut down both IRUs. The system design was changed before certification!
The point is that ADC seems to get into many dark corners of modern systems, thus we might not be sure of what the effects of simultaneous ADC malfunction might be.

safetypee: much obliged.
Were such an anomaly to have the capacity to muck up a pitch and power response ... :eek:

FAA Proposes Airspeed-Sensor Fixes
 

FAA Proposes Airspeed-Sensor Fixes - WSJ.com

Hear ! Hear ! ( see also #1567 )

Yup to Speedbird. Just blurking here. AB (and Boeing) pilots will get something constructive out of the final reports, and as a very old SLF I will be grateful. The rest is dross.
My days ended with dinosaur blood. Cannot relate to all this FBW stuff, but judging from you guys, it mostly works. Think back, you aulde guys, to what a handful a DC-4 could be in rough wx.

Extract below from the BEA's report on the 2008 A320 Air New Zealand accident at Perpignan. Also an excerpt from the CVR transcript covering the last few minutes.

The BEA, on this occasion, seems to have concluded that the THS going to 'full up' made it impossible for the pilots to get out of the stall even with the sidestick fully forward; but that the pilots apparently simply didn't see the need to re-trim. It also says, rather poignantly, that they 'did not understand the behaviour of the aeroplane' - a point that is very clearly illustrated by the CVR transcript.

I wouldn't be at all surprised if the eventual report on AF447 says very similar things.

Full report available for download here.

http://www.bea.aero/docspa/2008/d-la...a081127.en.pdf

Quote:

---

15 h 44 min 46 Okay here we go
15 h 44 min 49 Und ich sag ihr jetzt dass wir im Moment in Dreitausend bleiben
The weight is fifty four
And I say now to her that we are maintaining three thousand at the moment
15 h 44 min 51 Golf X-ray Lima triple eight
Tango can you speed reduce speed again
15 h 44 min 56 We are reducing
15 h 44 min 57 Triple click
15 h 44 min 58 ��We are still reducing the speed Golf X-ray Lima triple eight Tango (*)
15 h 45 min 03 (*) I will say when the trim stops
The word “stops” is stronger than the rest of the phrase
15 h 45 min 05 SV: Stall ( x13)
Cricket (stall warning)
15 h 45 min 06 Stop ! Noise similar to thrust levers being moved forward to the stop
15 h 45 min 13 (oh oh oh)
15 h 45 min 18 (…)
15 h 45 min 19 End of stall warning
15 h 45 min 20 Single chime
15 h 45 min 24 Ich nehm die Speed noch mal hoch ja?
(I increase speed ) Yeah?
15 h 45 min 26 Ja it's pitching up all the time
15 h 45 min 27 (…) Stick forward (*)
15 h 45 min 29 Pitching up
15 h 45 min 30
15 h 45 min 31 It’s (*) alpha floor we’re in manual Single chime
15 h 45 min 33 It's pitching up this (…)
15 h 45 min 34 Kriegst du das geregelt? Are you able to handle this?
15 h 45 min 35 Nee No
15 h 45 min 36 Gear up SV: Stall (12 times)
15 h 45 min 37 Gear up Cricket (stall warning)
15 h 45 min 39 Gear up Gear up
15 h 45 min 40 (*)
15 h 45 min 42 (…)
15 h 45 min 44 (…)
15 h 45 min 45
15 h 45 min 47
15 h 45 min 48
Golf X-ray Lima triple eight
Tango contact tower one one eight decimal three bye
End of stall warning
Single chime
15 h 45 min 54 What’s wrong here
15 h 45 min 55 Flaps up
15 h 45 min 57 (*)
15 h 45 min 58 Flaps up
15 h 46 min 00 End of stall warning
15 h 46 min 00,5(*)
Continuous repetitive chime
15 h 46 min 02 Speedbrakes
15 h 46 min 02,5 End of CRC
15 h 46 min 03 C chord (Altitude alert)
15 h 46 min 04
SV: (*) terrain terrain
15 h 46 min 05 (…) (…)
15 h 46 min 06
15 h 46 min 07 End of recording

---

Also, the Perpignan A320 was, I think, being piloted by very highly experienced Type Rating Examiner; the guys who really know their aircraft inside out.
I agree with the assessment above, something not good about THS's that trim themselves full or nearly full NU and then remain there when it might be appropriate for them to auto-nose down to help overwhelmed pilots in the heat of battle with FBW systems..... not to mention stall warnings that shut down at slow speeds, then warn again as airspeed increases... brilliant.

I am not a fan of autotrim in the 777 either.

Not exactly the case. The flight crew were two XL line pilots asked to do an Alpha Protections test without full knowledge of how the aircraft would behave as it approached the stall. The test should have been carried out at above FL100 but commercial pressure resulted in the test being undertaken without ATC knowledge while being vectored on approach at about FL030. The third seat was occupied by the AirNZ check pilot tasked with overseeing the end of lease handover by XL to AirNZ.

A full read of the report will reveal all.

A lot of interesting reading and theories.

A quick and incomplete look at some stall accidents still bothers me.

Birgenair 757 stalled due to pitot problems and the pilots not proficient enough to recover, although the aircraft would have permitted. Reasons known and uncontested.

Cali AA 757 stalled due to the non self retracting speedbrakes and the pilots not realizing it. The aircraft would have permitted recovery. Reasons known and uncontested.

330 testflight in Toulouse stalled due to pilot mishandling leading to an unrecoverable stall. Two experienced pilots. Still some debate if the aircraft would have been able to save, still debates about the electronics/protections handling.

320 Perpignan stalled due to THS behavior. Normal pilots. Still some debate about the recovery possibility or not.

Qantas Perth. Aircraft apparently didn't obey pilot orders, recovery succeeded. Still debating about the real reason of the electronic/protections behavior.

AF 447. Enormous debate about the THS, crew performance. Unsure if the aircraft was recoverable.

The troubling questions are still looming, and they are all on AB.
Boeings might fail just as much, but it seems that they would be more easily recoverable in upsets. I can't dismiss the ugly feeling that in upsets the possibilities in AB are less and it would take almost IT trained astronauts to be able to realize and apply the multiple tasks, switchings or many and different procedures to recover.

Airbus needs to clean up their act. Even Joe bloggs like me should be able to apply and memorize a simple and uncomplicated task for upset recovery.
At the moment this seems unrealistic. Therefore all debates are basically futile, because any finding will lead to the perpetual "they should have known" which seems almost impossible.

Gretchenfrage

Where did you get this misinformation from? if it is the crash I think you were talking about they were simulating and engine failure and the due to a problem with Alt* the aircraft lost too much speed, they had almost recovered but did not have enough height. The Alt* programme was subsequently changed. More of a Vmca problem.

Again misinformation! The THS was a contributing factor, the pilots incorrectly carried out the low speed check at too low an altitude and without following the Flt Test procedure. A recovery could have been possible if the correct actions were taken / correct procedures followed.

Jury still out on that one, as the equipment tested correctly and there were other factors.

There is no enormous debate about the THS, it behaved correctly and if the correct actions had been taken I am sure the A/C would have been recoverable.

What an amazing statement to make! Perhaps you are not an average Joe Bloggs!:rolleyes:

Finally, some useful and relevant discussion on this thread during these last two pages.

The Perpignan Accident may well explain why the crew were unable to recover flight AF447.

However it doesn't explain the F/O's actions in response to the unreliable airpseed.

Was it...

A) He was applying (inappropriately) his memory items practised recently in the sim?

B) An attempt to "regain" altitude apparently lost during the event?

C) An attempt to climb above the weather they were experiencing i.e. turbulence, hail, st elmo's fire?

@SKS777Flyer

the 777 only auto trims for config changes as you know. It doesn't speed trim which is still a manual input.
May I ask why you are not a fan of this trim setup?
The only thing I have with the system is that there is no trim wheel so you are not very aware of what position the stab is at.

I think the THS has played a massive part in this incident but there is not enough information to deduce exactly what happened. A lack of visual cues I've always had issues with. It relies on an active scan (even in cruise) which as we all know is not something a human being is very good at in states of low physical demand. Combine that with a lack of training (cost/sim limitations) in unusual situation and we can see the holes in the cheese lining up.

Having had TAT probe icing in the cruise (without knowing what to look for!!) we thought it was static around the EECs that was causing the EPR indications and all Perf calcs in the FMC to blank (Also A/T disconnect) therefore never did the QRH drill.

Lesson learned...

The Duh in Aerodynamics
 

An airliner on departure, climb, cruise, descent, approach and landing is like a symphony orchestra, with all the components working in concert. The conductor can be the FMS, Fright Management System, or the aircraft commander.

It's all seamless and symphonic until a component hits a sour note. Then you really see the contribution of the other components and what is driving them.

It's basic to conventional airplane dynamics, as taught in Langewieche's "Stick and Rudder" and hundreds of other instructional manuals:

Pitch controls airspeed.
Power controls altitude.

The A330 Flight test accident in 1994 uncovered the flaw in Airbus logic. The plane was on autopilot in Altitude Capture mode when the pilot pulled the power on one engine. The AP responded to lack of power by pulling the pitch up to over 30 degrees. Instead, it should have kept the pitch at desired speed, and told the pilot, "We can't do that."

The TK951 B737 approach accident at AMS in 2007 revealed the same flaw. An undetected erroneous input to the A/T caused it to go to Flight Idle. The autopilot tried to stay on Glideslope by pulling the nose up and trimming to lower speed to make up for lack of power. Instead, it should have kept the desired speed, and let the plane sink below glidepath. If the pilot hadn't caught that, he would have heard, "TOO LOW! GLIDESLOPE." Firewalling the throttles would have stopped the sink, and not have caused such a pitchup, as the elevator would still have been trimmed for the correct speed. The pilot could have intentionally traded some airspeed for altitude, and without fighting full aft trim.

How does this apply to 447? We'll see. Trying to control altitude with pitch is a loser, regardless.

Hi,

Just a tought ... but for me if the tests were conducted at the altitude of 35.000 feet ... the result of Perpignan will be the same than AF447
I don't see that altitude will change the fate of the Perpignan event.
The scenario was set to finish in the sea .. from any altitude over the one of the day.
And indeed the pilots were very experimented on type.
Again .. the hours on type are not a reference for "experience" ... as seen in many accidents.

The memory items were innapropriate (reason why AF changed it after the AF447 crash and sended all their "experienced" pilots to the sim for play again the scenario)

I DON'T BELIEVE THIS..
Are you serious?...:ugh::ugh::ugh::ugh:

We are talking about jets here, it's the other way 'round

(And that makes it adamantly clear: you never flew one)

Its not "black and white", golfyankeesierra, it really depends on the circumstances: for example, when you're on an "open climb" in your A330 (at a fixed power), its pitch/attitude that controls your speed. The same for an open descent.
After more than 1600 posts here, where the main preoccupation was to understand why the AF447 PF didn't lower the nose of its A330 to reduce AoA and therefore to increase "speed", it seems pretty clear that not always "power" is enough to regain speed...

iceman you just proved my point.

QED

golfyahnkeesierra makes it plain why modern "airmen" sometimes know nothing about airmanship. Just because his electric airplane's power levers stay in the climb detent, he thinks "You pull back to go up and push forward to go down."

I'd rather fly with Wolfgang Langeweische (or his son William, which I have done) than GYS.

Pearpignan

Golf X-ray Lima triple eight
Tango contact tower one one eight decimal three bye
End of stall warning
Single chime
15 h 45 min 54 What’s wrong here
15 h 45 min 55 Flaps up
15 h 45 min 57 (*)
15 h 45 min 58 Flaps up
15 h 46 min 00 End of stall warning
15 h 46 min 00,5(*)
Continuous repetitive chime
15 h 46 min 02 Speedbrakes
15 h 46 min 02,5 End of CRC
15 h 46 min 03 C chord (Altitude alert)
15 h 46 min 04
SV: (*) terrain terrain
15 h 46 min 05 (…) (…)
15 h 46 min 06
15 h 46 min 07 End of recording

Someone unstalled the a/c. Unfortunately, it was pointed at the Ocean. Either the pilots started the Drill too low? (or not). Or the a/c would not allow NU? (what do the g traces say?). Both?

GYS I presume you are a Flight Sim wannabee if you don't understand how we can control airspeed with pitch (which you do everyday on an airliner, well any aircraft, in both climb and descent) :{