bubbers44

AOA above stall doesn't matter much. No it wasn't 90 degrees but it was held above stall by the PF for over 3 minutes. That is what caused the crash and the PNF not intervening. 1 G is a constant like going down an elevator, descent rate doesn't matter once established. The only way they had to save themselves once in the descent was to lower the nose if possible so they could be unstalled to generate the G's to recover. No one did that.

Why? You learn that in the first 5 hrs of flt training.

Lonewolf_50

Pitch and power isn't the only thing one is trained in (granted, it's a core fundemantal)

Was what his training?
What was his currency?
What else was he trained to do?
Did he receive any negative training?
Why did his instrument scan break down to soon?
What element of his training, or lack of it, or lack of recency in training, factored into that?
(I am making an assumption that the PF's instrument scan broke down early in the event, as evidenced by his climbing 3K or so without ample correction well before alt change went that far. If my assumption is off, so be it.)

DozyWannabe

Stall protections (in fact all hard protections) were gone as soon as the speed went unreliable. Alternate 2 (NO PROT) means just that.

jjeppson

My last 777 sim session in July, I specifically requested we experience a high altitude stall. In my 33 years of commercial flying and 12 years of US Navy aviation, I could not remember ever seeing a high altitude stall demonstration.

We ran the sim up to 37,000 and disabled the automation (auto throttles, auto pilot). Pulled the power off and waited. When the aircraft stalled it entered into a rapid descent, nose up attitude with some wing rocking. We first applied max power without lowering the nose; no recovery. Aircraft did not exit a stalled condition until we agressively shoved the yoke forward, reduced AOA, and regained flying speed.

It sure made a believer out of me. If you stall at higher altitudes (above 30,000), it will take an agressive push over to recover.

We all practice stalls at lower altitudes in training where all it takes is the addition of power and a slight lowering of the nose to recover.

Next time you are in the sim, make your instructor demonstrate this.

PaleBlueDot

Clear explanation why accurate air speed indication was essential. According to this, margin of error was only ~ 25 knots.

"As the speed of sound depends on the temperature of the air, which decreases with altitude up to the tropopause at around 17,000 metres, the maximum speed an aircraft can fly at safely (before running into speed-of-sound effects) likewise decreases with altitude. Thus, on a chart of altitude (vertical) versus speed (horizontal), there is a point where the positively sloping plot of the plane’s stall speed crosses the negatively sloping line of its maximum safe speed below the speed of sound (Mach 0.86, in the case of an Airbus 330). The apex where the two lines intersect—where the minimum and maximum safe speeds are the same—is known euphemistically as "coffin corner". At 10,600 metres, a fully loaded Airbus 330 cruises (for reasons of fuel economy) just below this critical point in its flight envelope—with probably no more than 25 knots (46 kph) between stalling (through flying too slow) and breaking up in a shockwave-induced dive (through flying too fast).
....
With the plane buffeted violently by the turbulent updrafts, the first thing the pilot would have done would have been to reduce speed to ride out the storm. But with no clear idea of what the actual airspeed was—and with no automatic systems to prevent manual inputs from making the aircraft fly too slowly or too fast when operating so close to its coffin corner—the pilot could have unwittingly pitched the plane into an uncontrollable stall."

Aviation accidents: The Difference Engine: Wild blue coffin corner | The Economist

overthewing

Jjeppson, can I ask at what altitude you were when you managed to exit the stall in the sim?

MGifos

"We all practice stalls at lower altitudes in training where all it takes is the addition of power and a slight lowering of the nose to recover."

More likely this is, stall warning practice or 'approach to stall'.
1. Stall warning = Approaching stall - Actions are required to avoid stall.
2. Stalled = Stalled - Actions are required to recover from stall.
3. Deep Stall = Stalled and no Pitch Authority - Recovery unlikely, at least by using elevator.

Some have suggested, or implied, that 'Deep Stall' may be defined as 'very much stalled', but this offers very little additional information than 'Stalled'. Which is why we refer to a Stall which has also removed normal pitch authority as a Deep Stall.

SLFinAZ

I'm curious if there is any thought that the PF felt that his SS input would have the effect of having the computer fly "pitch & power"? That he was still somehow "protected"? In the absence of such a train of thought I can't comprehend how he would fly "up"...knowing that every meter of altitude gained reduced his margin of error with regard to speed. It would seem that if anything the natural response would be to move lower to widen the speed envelope.

Mike X

Psychologically, I agree. However, law change should have alerted him to lost protections.

The PNF, once again features, based on CVR audio. HE appears to have sussed the situation out, but did not assert his observations.

This is going 'round in circles. However, the PNF took control for a few seconds and the PF re-assumed control in an unethical manner.

This, to me, smacks of an ego clash - remember, the PF's wife was onboard.

I agree (from what we know) that the captain did not assign authority accurately.

Octane

I suspect that when the aircraft initially stalled, the 1g acceleration earthwards would have created a "falling sensation". However once the aircraft reached terminal velocity downwards there is no further acceleration just a downwards velocity vector. Then there is no acceleration hence no "falling" sensation anymore. How long it took to reach terminal velocity, no idea. Someone cleverer than me can probably calculate it with the right data. I'm guessing the Captain rushed back up front when he felt the vertical acceleration before terminal velocity....

Brian Abraham

From a blog.

Lyman

They did not know the a/c had Stalled. They did not have Atttitude displays on the panel. Had there been any attitude displayed, anywhere, there would gave been a reaction on the part of this crew . This is so blindingly obvious, one cannot fathom the continuation of all the drivel re: PPL, ab initio, etc.

caveat. If they had an attitude display, it provoked no comment, no reaction, and no solution, nor discussion of same. In other words, it fit their conversation; it was roughly level, or slightly descending. To assume these guys had any provocation of the STALL shows only the ignorance of the critique. As Brian's quote above, if these guys did this, and the posters here are correct, we'd all best be not flying, anywhere.

To continue with the incredulity shows how eager are some to have a quick solution, a reason, a soothing, of the Fear. In the face of common sense, can you not see this? Their behaviour is readily explained, and if one took the time, carrying an open mind, the evidence fits.

Play it any way you like, there are no rational explanations except these: these gents were trained, they were alert, and they were together.

They had no clue, because there WERE NO CLUES. Resting one's lazy arse on data that got pulled out of the drink, data that they had no access to, To condemn, is not just lazy, it is a mockery of itself. It is right in front of you, it is not mysterious. More, much more than they had.

Stop leaving unsaid that which you pretend not to know: Look at the reasons, the logical ones, not the snarky gossippy drivel about how the training must be at fault.

You are looking at data that did not exist in a real way for this flight. It is a time capsule, and unfortunately it is being believed, and used, as if its purpose alone is to lend credence to a slander.

KAG

Final "conversation", and we all read it, comment it, teach our little lesson...

Zorin_75

1 g earthwards is what you're feeling right now.
Or he could look at page 106 of interim report #3.

BOAC

Oozlum time again. - which does NOT apply to AF447, and as far as we know only applies to T-tailed a/c (OK - or perhaps one with excessive tailplane icing) - just to make sure we do not set off yet again on one of our circles. Are we clear?

PS Forget these red herrings like the NASA Schweizer in #431 - two minutes reading up on the project would show it to be interesting but irrelevant.

AlphaZuluRomeo

[quibbling]Not exactly. g protection remained; which is a good thing IMO, should a recovery attempt have been made after the stall. [/quibbling]


jjeppson:
Thanks, that shows (at least) the A330 & 777 sims perform the same. Until proved incorrect, I'll assume the planes themselves do that too.

Lyman:
Until proven incorrect, I'll believe they had three or (at last) one attitude display. They are mentionned in the CVR. "Selon les trois tu montes" could be about the 3 attitude displays or the 3 V/S or a combination of attitude+V/S+altimeter. Later, "l'horizon secours" is mentionned by the captain...

BOAC

While we are going over old ground - can anyone give me a link to an explanation of why PF's 'instruments' were placed in ATT by PNF (2:10:39) and what it means? Why would it have been done - is it a QRH action, and if so for what?

My contribution to the Oozlum flying display

TurboTomato

My apologies, I stand corrected. I think the PF could have made the same mistake as me!

Slickster

I'm neither a newbie, nor a greybeard, but have only experienced Boeings, and admit to healthy distrust, due to my Luddite tendencies, of Airbus.

What astounds me is that this pilot held the stick back for three minutes, almost as if he'd lost hope, and that was all he could think to do. It smacks of someone continually pushing the lift button, harder and harder, even though the lift has been called.

I find it very difficult to believe that any pilot of my 737 would sit there, for three minutes, with the yoke in his stomach, the stick shaker rattling, and the altimeter unwinding. Boeings have their faults, and all automation has its traps, but this accident does nothing to quell my Luddite fears of Airbus.

It's all very well saying that you can fly an Airbus, it's just like any other aircraft, but it patently isn't. It's been designed to be flown through the autopilot, and seems to do that very well, and provide a lovely working environment. However, the downside is the pilot-machine interface. The sidestick and stationary thrust levers offer no tactile feedback to the pilot, as to what his aircraft is attempting to do, nor even any clue to his colleague when flying manually.

The Airbus sounds lovely on a normal at the office, but seems to turn into a nightmare when things go wrong, and the very things that make it work so well on a normal day, seem to make the pilots even less well equipped to deal with problems when they arise.

The pilots were not linked in. They were sat there scratching their heads, basically. All they had to do was fly the bloody thing, but it didn't seem to occur to them.

Aileron Drag

Slickster, that is all so true. Modern aircraft seem to be full of nasty technological traps.

The 777 has a Thrust Asymmetry Compensator (TAC), which puts the rudder in for you with an engine failure. While I was there, every other Base Check was performed with the TAC working. Easy peasy. But you only had one go per year of feeding in the rudder manually.

I don't recall who the operator was, but one of the first real engine failures on the 777 sent a big chunk of metal through the cowling, and straight into the TAC, taking it out!

The PH coped ok, but then he was probably (in those days) an old stick n' rudder guy.

Here's a case where the one day you need stall protection, it ain't working!