Hi Clandestino,

A320%20321%20FCTM%20Flight%20Crew%20Training%20Manual.pdf OP-020. P 15/16 FCTM 08 JUL 08

It appears to Airbus themselves who made the statement.

JAR 25
 

The A330 was certificated to JAR 25 Change 13, which should have been virtually identical to FAR 25 as written at that time (1980s?) I'm not sure how the FAR 25 you quote (2012?) relates to that earlier standard.

Anyway, the differences seem to be: [The emphasis and selections are mine]

Maybe marginal, but the A330 seems to meet this requirement also

Since the demonstration is supposed to be ended as soon as the aeroplane is stalled the designers would not have been expected to maintain the warning throughout 54 seconds of stall. With hindsight this requirement should be up for review.

PS. On checking, the current CS25 has removed the reference to the demonstration, which fits the bill:

The AF447 pilots probably mistook it for an indication of overspeed. At high altitude there isn't any appreciable difference between high-speed and low-speed buffet as both are caused by the same aerodynamic phenomenon (an oscillatory interaction between local shock waves and airflow separation).

The certification pilots probably considered the buffeting to be "a strong and effective deterrent to further speed reduction". BEA says as much in a note on page 54 of IR#2: "The stall manifests itself particularly through vibrations." (I take it that "vibrations" is franglais for "buffet").

In the video of a TV emission that was posted a little while ago on the other thread, the AB Chief Test Pilot also seems to talk about "deterrent buffet" (at 34:50), but my understanding of spoken french is not good enough to understand what he says. Maybe one of our french contributors could help?

What you posted is First Choice Airways Flight training manual.

It is possible "Airbus themselves" made the statement, which was then copypasted into the FTM, yet it is equally possible someone at FCA was the source of the (mis)statement.

While I think Airbus pilots have to be trained to deal with unusual attitudes and approach to stall recovery in laws other than normal, this has no bearing on AF447 accident. Failure to recover did not result from lack of skills but inability to understand what is going on and consequently apply the correct procedure.

Hi Clandestino,

Thanks for the decode of FCA. I only noticed the Airbus logo on the top of the page, however my airline's FCTM has exactly the same words so I conclude they are Airbus recommendations.

I agree.

On previous type conversion courses, we stalled the simulator to the nose drop and then recovered. When we had stopped using the manual pitch trim, the elevator feel was incredibly heavy, buffet could be mistaken for turbulence, controls became sloppy. It was impossible to prevent the nose dropping below the horizon using elevator control alone.

I've never stalled the A320 sim. I've flown at Alpha max & seen TOGA Lock, and heard "Stall Stall" briefly. etc.

The AF447 crew presumably had never been exposed to a full stall in the sim and hence they failed to recognise the symptoms.

Hi

@ rudderrudderrat & Clandestino, re:
(my bold)
In Alternate (or Direct) law, an A320 (or other FBW Airbus) is no more a protected aircraft.

I admit this is a bit far fetched... and would prefer this sentence to be removed or, at last, better explained.

AFAIK, no such sentence is in the A330/A340 FCTMs :)

Is there a consensus yet as to the altitude needed to effect a recovery by a typical crew (ie not the optimum with hindsight type of recovery), say from the dynamics AF447 had at 30k ft ? I believe the law they were in retained over-g protection but with no visible horizon or AoA meter would recovery rely on watching speed and pitching up to the stall warner when flying again ?

As I recall, the Colgan crew had just been discussing tail stall which may have primed them for their wrong reactions.

When you are the one flying and something grabs your stick, it is a natural human tendency to fight back. What we need is something that leads us to the correct action.(Even at 4:00 AM :})

Does anyone have any thoughts along that line? Perhaps a Sim routine combined with a standardized stall warning device that creates an almost Pavlovian response.:confused:

I say almost Pavlovian, because I remember the Abidjan A-310 accident where dropping the nose in the face of a false stall warning on takeoff caused an accident. Obviously the stall warning reaction has to be tempered with some common sense.

Before the hamster wheel started turning, it was becoming clear that the actual pull out of the resulting dive would create less altitude loss than the recovery from the stall.

It seems that the Basic Fighter Maneuvering (BFM) turn strategy was relevant to the pullout altitude loss.
From Hazelnuts last cut at the problem, it seems that the pullout could benefit still more from a little more power during the recovery to level flight. Maximum structural g was not being reached (probably due to induced drag at the higher AOA recovery).

Mach:

I'd be real careful with advocating this.

You're not looking for a sustained QTT (quickest tightest turn) here.

Just something approaching a minimum radius maneuver. Turn rate is irrelevant.

Thanks for the caution OK465.
In that turn rate is pointing your velocity vector away from the down direction, it isn't irrelevant.

I'm actually interested in identifying some generic simple to use guidelines that pilots could use. Obviously you will not want to be adding power above your cornering velocity, but the concept of adding power while having your nose pointed down to improve your pull out is a bit counter-intuitive to most pilots.

It looks like cornering velocity for a particular aircraft might be a good thing to know. No one plans on having to recover from a dive, so no one seems to be teaching it.

I am not advocating anything but a look to see if we could do a better job in performing dive recovery should the need arise. How/when/what to teach would raise a host of other issues that would probably be premature to discuss.

Man machine interface (Pavlov approach)
 

Hi,

Machinbird:

For example:

A "vibrating (modulated, AM and FM)" pilots seat special cushion (integrated or stand alone as a retrofit).

:8

PS

Differentiating CLEARLY low speed and overmach by "sophisticated (and reliable) "multiple input parameters data processing".

Something like "seat of the pants" Mk II :}

Thanks. I recall Hazelnut's post and the relatively limited loss of altitude (well to my non-pilot eyes) anyway. A really interesting recent post mentioned 20k feet(thanks Dozy great post !) perhaps based on sim. Figured there must have been other attempts so wondered what the consensus was and what the best strategy is. knowing how much nu can be attempted when time is really pressing doesn't look that obvious when in an unusual attitude.

It depends. When you have plenty of altitude you would play it safe to avoid secondary stalls.

When the ground is approaching fast, my strategy as a non-pilot engineer would be (I've been shot down earlier mentioning this): Push the sidestick fully forward until the stall warning stops. Then immediately SS to neutral, slowly start pulling, carefully increasing the pull force until stall warning is encountered, then immediately SS to neutral until stall warning stops, then start pulling again, etc.

For the reasons you mentioned I wouldn't add power.

P.S.
Depending on how fast autotrim moves the THS, manual trim should be considered.

In the A320 sim it was actually relatively speedy. You could probably physically move the wheel faster manually, but I suspect the servos moving the THS would take roughly the same amount of time in any case.

Hazelnut, will potential recovery options be part of the accident investigation and reported eventually ?

No, I don't expect that will be the case. We are engaging in an academic discussion that is only remotely relevant to AF447 whose pilots apparently never realized they were in a stalled situation.

The first priority is and should remain staying out of a stall. In that spirit BEA has made a number of recommendations, for example "that EASA and the FAA evaluate the relevance of requiring the presence of an angle of attack indicator directly accessible to pilots on board airplanes."

To further this academic discussion I would venture this in general...

(edit: in response to the use of the esoteric term 'corner velocity' :))

IIRC 'Va' for a 330 varies from around 320k at around 28,000 down to around 260 at sea level. This encompasses quite a wide range of TAS, all 'limited' to 2.5 g.

From a practical standpoint, I'm not sure how likely it is that anyone who put themselves, or was put into a dive situation would be able to deftly modulate thrust to maintain a speed (let alone mental concentration on it), whose value was varying nearly as rapidly as the requirement to modulate the T-levers, on the way down.

Dive recoveries have been taught in every heavy I checked out in. The recovery procedures are recommended by the manufacturer and worked fine in all the aircraft I'm familiar with.

In this same vein, as CONF says, the manufacturer established stall procedures that involve extending the slats (Flaps 1) below 20,000 if clean. Were one to have a chance to practice this, one might see the decidedly positive benefits of following the manufacturer's guidance.

One first has to recognize that the guidance is applicable.

That G limitation only applies in Normal Law however. Once you're in Alternate, roll is direct and the calculations can no longer be applied to limit the maneouvre.

@HN39

While you're right that preventing a stall in the first place must remain a priority, I believe that Airbus and Boeing collaborated on providing proper stall recovery training for airliner crews. What bothers me about the AoA indicator is that while it would certainly be a help in a situation where the pilot knows how to use it, we're dealing with a situation here where at least one pilot was unable to use the basic panel to diagnose and recover from a stall.

3,300 ft stall recovery
 

@ Mr Optimistic

I am very glad to see how many answers you have had.

A Tech & physical view is my first answer but, instead of a fastidious (and probably wrong explanation) I have better to give you a short report:

Quote:

---

...in good weather conditions, the aircraft suddenly started to climb adopting a steep pitch attitude and stalled. The crew managed to recover control of the aircraft and came round to land.
...
The throttle levers were then quickly brought back to the idle position. At the same time, the trimmable horizontal stabilizer started to move in a nose-up direction.

As the aircraft descended through 1,700 feet, at 10 h 43 m 22 s, with a speed of about 195 knots, the Captain asked for flap extension to 20°. The VFE, the speed limit authorized for this new configuration, is 195 knots. When the flap control was set to 20°, the thrust levers advanced and engine thrust increased.
The flight crew countered the nose-up effect resulting from the increase in thrust by using the pitch controls, with the auto-throttle (ATHR) remaining in automatic mode.
The throttle levers were then quickly brought back to the idle position. At the same time, the trimmable horizontal stabilizer started to move in a nose-up direction.
The nose up effect that resulted was countered by the flight crew through gradual nose-down action on the elevators. When the trimmable horizontal stabilizer reached its maximum nose-up value and the elevators also reached their maximum nose down value, the throttle levers, according to the FDR readout, moved rapidly to their stops.
In a few seconds, the flight path started to rise and the pitch attitude went to 60°. Witnesses saw the aircraft climb. It banked sharply to the left and the right and stalled before adopting a strongly negative pitch attitude ( .33 degrees) towards the ground.
The maximum altitude reached was 4,100 feet, while a minimum indicated speed of 35 knots was recorded. The stall and ground proximity warnings sounded during the descent.
The flight crew managed to regain control of the aircraft, with the lowest point being around a height of 800 feet, that is 240 meters from the ground.
In a few seconds, the flight path started to rise and the pitch attitude went to 60°. Witnesses saw the aircraft climb. It banked sharply to the left and the right and stalled before adopting a strongly negative pitch attitude ( .33 degrees) towards the ground. The maximum altitude reached was 4,100 feet, while a minimum indicated speed of 35 knots was recorded. The stall and ground proximity warnings sounded during the descent. The flight crew managed to regain control of the aircraft, with the lowest point being around a height of 800 feet, that is 240 meters from the ground.

---

4,100 minus 800 equal 3,300 ft stall recovery
(of course, air density is more important near the ground)

Doze:

The 2.5 g limit applies in all laws, including Boyle's, Charles's, and Burke's (Gene Barry) law and the law of supply and demand. :)

In one particular law you can actually exceed it. Starts with a 'D'. :}

You know what I meant - the aircraft's systems will no longer prevent a pilot from exceeding it outside of Normal Law. ;)

Neofit , thanks. some ride.

Still with significant nd and thrust at idle ? Think 20k ft was intimated in an earlier post which is what caught my eye. With a startled crew in poor conditions one minute isn't very long to interpret and initiate a course of action.

Post disappeared.

@PJ2 - not sure where your post's gone, but...

Going back to my notes, it took about 16-18,000ft to recover the way we did it. My writeups are on the last page of thread 6 and the first page of this thread.

We did not reenable ADR or FPV during the recovery, so I don't have the numbers available that you do. This was purely seat-of-the-pants stuff, applying ND until the THS returned more-or-less to the centre and holding the dive to gain speed, correcting the adverse roll with rudder inputs and gently pulling out of the dive once we figured we were going fast enough to be flying again.

Our experiment was purely qualitative - proving that the aircraft could be recovered if the situation was correctly diagnosed in time and that the aircraft's systems would in no way impede the recovery.

Re altitude loss and other data, Dozy, what was your experience in the sim? Our sim exercises usually took about 20,000+ ft. for recovery.

Dozy, edited/re-posted for clarity.

With weights, CG, SAT mirroring AF447 and a bit of turbulence, following loss of airspeed (all 3 ADRs out), the sim was pitched up at FL350 and held in the climb until stalled, (THS reached 13.6deg). Shortly after the stall we returned the ADRs for use during the balance of the exercise, (to see the FPV during the stall).

Post-apogee (approx FL360), full forward stick was applied and held.

At FL330 the pitch was 8deg ND.

At FL310 the AoA (using FPV) was approx 40deg and the VSI was 18000fpm +. Pitch was about 14deg ND which was all the pitch that could be obtained.

Pitch slowly reduced to about 10degND still with full forward stick. As it was held the THS unwound and returned to normal settings.

We could watch the AoA reducing as the FPV slowly climbed "up" the PFD from past the red ND warning arrows below 30deg pitch marks.

Thirty seconds after the first Stall Warning passing through FL270 the AoA had reduced to 30deg, descent rate was 16000fpm.

Ten seconds later at FL255 the AoA was 12deg, CAS was 250kts, VSI was 7400fpm.

At FL245 the stall warning stopped 40 seconds after it began, the AoA was 10degND, M0.658, VSI 7000fpm down, CAS 278kts.

From an AoA of 40deg to 10deg took 24 seconds and about 6000ft. This exercise took about 22000ft; some were less.

Overspeed was never a problem nor was a secondary stall if one was gentle, (took about another 6000ft IIRC)

Sorry to butt in but can i ask how you judged how much pitch up to apply?
:rolleyes: Hmm post back again...

The unfolding sequence over 2 years has given the profession plenty of time to consider how one would have dealt with this situation so in a sense you must have figured out what you hope you would have done. if not 'primed' for action allow a minute to stabilize the brain and that must add another 10k ft at the rod experienced. i realise the issue was how not to get to that situation in the first place but understanding the option space does inform any potential mitigations .

Mr. Optimistic;

Normal cruise pitch attitude is between 2.3 and 3deg depending mostly upon weight. A pitch up to 5deg pitch attitude (+2.5deg) results in about an 800 to 1500fpm climb and a gradual loss of energy if held long enough. The UAS QRH checklist and the FCTM cautions strongly against holding such pitch attitudes for long and advises to get the QRH out quickly and set pitch and power. The FCTM also states that the Memory Items are not to be done if the immediate safety of the aircraft is not impacted.

For the purposes of the exercise there was no "judging" of how much to pitch up. We pitched up high enough to stall the aircraft. Fifteen degrees would do it, sometimes we were higher.

The overriding impression of these sessions was how quickly things occurred and how fast was the altitude loss.

Sorry Pj2, cross posted. Thank you.

Mr. Optimistic;

Does "option space" refer to the time available to assess a situation, decide upon a course of action, assess the response and secure the airplane? I hadn't heard of the term but likely it applies!

The danger of subtlely being taken in by hindsight bias is always there even when one really tries to avoid it; - we simply know what happened beforehand. The best that can be hoped for in these practical experiments is some sense of possible recovery time. "What would one do?" is not part of the exercise because we already really, really know what we would do!, and we weren't there... ;-)

But two questions remain unanswered: "Why the initial pitch-up?", and "Why wasn't the stall warning heeded post-apogee?". We've all seen various explanations as to why and are waiting to see how the BEA HF people come to terms with these two inexplicable matters and how such compares with our own thoughts and suggestions.

Yep that is what i had in mind about option space, the time and actions available to the people required to act. I understand that the lhs did the wrong thing, and the rhs should have spoken and acted, but the safety of the industry cannot rely on people always being on top form or of analysing to the degree bystanders like us can.
If you are going to design a clever aircraft, need to help the crew in situations like t
his.

Mr. Optimistic:

Other way round - the PF was in the RHS on this occasion. I'm not fully understanding your point either - the aircraft's systems told them that they were approaching stall, and continued to warn them as they went into the stall regime itself. It warned them that they were in Alternate Law 2 without protections. The ADI told them that they were too nose-high, the speed indications (when they came back) indicated they were too slow and the altimeter was unwinding at an alarming rate.

How much more help can you expect the aircraft to give?

Recovery altitude and "touch"
 

Salute!

If I recall, we determined that the jet was not in a "deep stall" such as the Viper had or the T-tail jets. In other words, the cee gee and center of aero pressure was much like most airplanes.

So I have a hard time thinking it would take more than 10,000 feet to recover.

Granted, I was used to flying at the limits and sometimes over the limits, but I can forgive the basic heavy pilots in that regard.

As PJ has asserted, being smooth and getting the nose back up after reducing the AoA is the key to minimum altitude loss. You can't do this as a "mechanic". You have to have "touch" and be in "touch" with the jet ( I can just see Doze snorting, heh heh). I don't see any way to do this in a sim.

A reliable AoA indication seems a great thing to help you get back to acceptable flight conditions. The FBW implementation on the 'bus appears to have a flaw with regards to AoA. In other words, you can override the "system" and get into the situation that AF447 did. I don't get it. I lost one friend over the desert that buried the nose too far on an attack pass and the gee/AoA limiter gave him the best aero possible but he was just too low/steep. Sierra happens.

I also speak from personal experience in straight wing jets and bent wing ones and deltas. The mach buffet feels different than the stall buffet. One is more of a buzz and the other is more of a "shake". Then there's aileron reversal if it's a mach problem as others have described here about the shock waves.

Go read about Yeager's experience and his use of the horizontal stab. Once supersonic his elevators didn't work, so he manually cranked the stab. Seems an engineer warned him about that possibility( I heard the story directly from Yeager one day in 1979 at the 16th Sqd, First in the F-16) So all the USAF jets after that had the solid horizontal stab that worked for elevator and kept working in the transonic/supersonic regime.

I have to admit that this is a sad story, and I pray that I fly as a SLF with a crew that does more than drag us from DFW to DEN without flying a Citabria every now and then.

Gums

I guess like me that you are an engineer. yes we all discuss the evidence available but look at the outcome. The 'system' failed. Sorry about the lhs/rhs issues, it has been discussed so often i forget where the pendulum stopped.

How do you train aoa instrumentation if it is never to be used unless in upset!

The warnings they had didn't tally with the situation they thought they were in so the significance of the warnings was lost. The stall warnings in their minds were erroneous and had to be filtered out.

Re, "How do you train aoa instrumentation if it is never to be used unless in upset!"

Precisely.

There is far more to this suggestion than just installing the guage.

If you are responding to my post #1084, I suspect we are talking about different things. The airplane encountered "low speed" buffet at 02:10:53 at Mach 0.68. I believe that buffet was caused by "an oscillatory interaction between local shock waves and airflow separation", rather than the stall buffet as you describe it..

Or, a combination of Center of Lift [max] and roll angle causing the lift separation and 5 second pitching, which persisted for about 15 seconds before pitch and AoA parted company.

Sim Stalls
 

PJ2 Sim Stalls #1107
I assume that these were reproducing 447's performance using TOGA. A lower power ( Flight Idle ?) might have helped in the earlier stages.
How in the limited time (which WE now know was very limited) could PF have explained what he was having to do, to PNF. There was no further Drill to be actioned.
Of course he should not have stalled... But having got there, someone had to try to get out of it.
The Captain might have come to the Flight Deck without being called, due to the change of apparent gravity with the change of pitch of the aircraft - not I think, noticeable on a simulator.
( None of my Training or being checked was done on a simulator - we just had to use the real thing, with four fans and a Flight Engineer.)
LT

With all respect, how do you train someone to use an oil pressure gage?

When necessary, you assess whether or not it is in the marked proper range and note whether it is increasing, decreasing or steady. You're trained.

What you do then is up to you.

Why do you say that? I don't scoff at the idea that pilots should have a feel for the aircraft in the slightest, I just don't agree with the idea that the Airbus FBW control design makes that impossible. In fact all jetliners have had artificial feel of some sort from the DH Comet onwards.

No-one "overrode" anything - the system dropped into a failure mode without protections because the airspeed sensors temporarily failed, and the evidence points strongly towards departure from controlled flight as being pilot-induced due to escalating misreading of the situation.

The point is that from the moment the UAS indication appeared, the PF did not in fact immediately have to do anything. They were at cruise, their speed was OK, they had a little bump from turbulence, but that wasn't going to send them into a significant dive. The correct thing to do according to CRM would have been to let the aircraft ride itself out of the turbulence and then discuss what to do with each other while monitoring the aircraft's response. Instead, the PF seems to have instinctively yanked the aircraft into a climb and developed a near death-grip on the sidestick until they hit the water, without telling anyone that he was doing so.