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The vital importance of high altitude stall recovery training in simulators

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The vital importance of high altitude stall recovery training in simulators

Old 5th Oct 2014, 14:19
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The vital importance of high altitude stall recovery training in simulators



A picture is worth a thousand words...
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Old 5th Oct 2014, 14:23
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And the importance of IR enhanced vision systems!
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Old 5th Oct 2014, 16:43
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The manufacturers say the current simulators DO NOT model the characteristics of the actual aircraft in high altitude stall conditions.




Boeing and Airbus have agreed on a simulator flight simulation software that generically models narrow body jetliners in post stall conditions. There's talk of making that a mandatory familiarization event in the future.
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Old 5th Oct 2014, 18:30
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Prevention, then recovry?

Centur
All for it.
How do You figure it shall work ?
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Old 5th Oct 2014, 19:05
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Isn't that a normal part of any typerating? Well, within the confines of current simulator specs of course as none can simulate a real stall yet. Anyway, stall recovery both low and high altitude have been normal parts in any typeratings I've done, just last night i had that once again. And then of course in regular intervals during normal simulatior training.
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Old 5th Oct 2014, 19:48
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FAA have in recent years moved away from the demo of stall recovery with minimum height loss, and in my view this is a good decision. So often previously many in the sim would add full thrust, allow the nose to drop a fraction, and upon seeing speed increase would then pull up to reduce the loss of height ....often then hitting the buffet again, or worse stalling. Sometimes they would scrape away to regain the lost height, but in a state that was right on the edge and hardly capable of dealing with the consequences of turbulence that would start the whole scenario again.

I'm brave enough to admit that I did manage to stall a jet aircraft at FL410 once, but thanks to the revised training I was not stupid enough to try and recover with minimum height loss. Instead I used up plenty of the sky that was below me, and at those levels (for those of you who are not stupid enough to make the mistake I made), that is what it does take - especially when stall and over speed are close to each other.
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Old 5th Oct 2014, 19:54
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no need for simulators, just everyone read, "STICK AND RUDDER"> STALL? PUSH FORWARD until you are flying again.

windshear recovery should be a sep maneuver.
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Old 5th Oct 2014, 20:36
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Denti

A simulator can simulate anything ,a stall in particulare.
As it is the yardstik for any flght test and performance.
High alltitude test flights at full stall are not needed for sertificatiion and not always recovered. Thereby not required, and not documented by test data.

Have fully stalled a Jar25 aircraft many times at say 8000 feet, but no medium or large jet.
Computer says NO.
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Old 6th Oct 2014, 01:48
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The manufacturers say the current simulators DO NOT model the characteristics of the actual aircraft in high altitude stall conditions.
Simply not true. The TDMs state that their FSTDs will meet approved data, no more, no less.

The issue is that the major airframe manufacturers are reluctant to either release or produce the required data for the TDMs to model.
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Old 6th Oct 2014, 03:00
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How about an unmanned full scale FBW airliner, flown over the ocean, via satellite, like a drone?
An aircraft at end of life cycle can be reused for this kind of training. Maybe not cheaper, but very accurate.
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Old 6th Oct 2014, 03:17
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How do You figure it shall work ?
The 737 FCOM/QRH doesn't say what minimum speed should be attained during stall recovery at high altitude before attempting to return to level flight.

However, a handy guide to what minimum IAS you should attain before levelling out after a stall recovery process lies in the Boeing 737 Classic FCTM under Chapter 4 - Climb, Cruise, Descent, Holding. Sub heading: Holding Airspeeds Not Available from the FMC. It states among other information: Above FL250, use VREF40 +100 knots to provide adequate buffet margin.

Depending on actual weight of course, then for want of a better figure it works out at close to 230 knots IAS before attempting to level out after stall recovery. If nothing else, in the heat of the moment it is a quick figure to work on since it is high unlikely the crew will have the time and inclination to go heads down into the FMC during a stall at high altitude simply to locate a suitable level out airspeed.

By keeping the body angle between zero to minus two below the horizon until reaching at least 230 knots IAS, you can should count on (IMHO) losing at least 3000 ft of altitude before reaching that speed. That assumes high power used in the process. That figure was from observations in a full flight 737-300 simulator
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Old 6th Oct 2014, 04:19
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Quote:
The manufacturers say the current simulators DO NOT model the characteristics of the actual aircraft in high altitude stall conditions. Simply not true. The TDMs state that their FSTDs will meet approved data, no more, no less.

The issue is that the major airframe manufacturers are reluctant to either release or produce the required data for the TDMs to model.








"Simply not true"? So if the airframe manufacturers don't release, or produce the data, exactly what data are the simulator manufacturers using to generate their simulation model?


Since you state that my statement is "simply not true" what Airbus or Boeing a/c have actual, and accurate, simulator modeling for post stall flight characteristics and which simulators can provide that training?


AW&ST has had several articles on this subject of high altitude upset in the last two years. That is the source I'm using. Interested readers could review those articles to find out what the simulators can and can't replicate. The articles discuss how Boeing and Airbus test pilots have agree to a generic software model that does a reasonable job replicating the flight characteristics of a generic n/b aircraft in the post stall regime.

Last edited by misd-agin; 6th Oct 2014 at 04:21. Reason: added "That is the source I'm using."
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Old 6th Oct 2014, 07:39
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A picture is worth a thousand words...

Pity the poor MPL or P2F in the right hand seat in that weather and the captain becomes incapacitated. Pity the passengers too..
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Old 6th Oct 2014, 07:59
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As an instrument tech at BZN I was involved in recalibrating the stall warning systems speeds on the Belfast, in order to increase the margin between the warning and the actual stall. A Belfast had encountered ice over the Alps along with tail de-icing failure and the stall warning system had not operated as required with the aircraft at a high nose-up angle. We did the adjustments by trial and error, with the crew holding the nose until the actual stall occurred for each tweak of the setting until we got the target margin of [30 knots?]. We covered all flap settings and I recall that the aircraft lost some 5.000 feet in the "clean" stall condition - producing some interesting comments during the first try, as we wondered if it ever would recover!

For civil certification the CAA predictably insisted on having a stick pusher installed.
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Old 6th Oct 2014, 08:21
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A picture is worth a thousand words...
I wouldn't typically associate that picture with stall recovery.

It seems to me that jetsteams are common cause of high altitude low speed events.
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Old 6th Oct 2014, 08:46
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I wouldn't typically associate that picture with stall recovery.
I would. Air Algerie MD80 apparently stalled at high altitude in cloud during storm penetration. The accident appears to have developed as a loss of airspeed awareness leading to a fully developed stall and roll off departure to the port side with post stall gyrations. The nose then became planted way nose down, left wing down as the stall broke, but they never recovered from the nose down-wing down attitude
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Old 6th Oct 2014, 09:07
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misd-agin

"Simply not true"? So if the airframe manufacturers don't release, or produce the data, exactly what data are the simulator manufacturers using to generate their simulation model?
That's exactly the point. The TDMs do not have the data to generate a realistic/accurate model. It isn't that the TDMs DO NOT model, it's that they CAN'T model the stalls correctly.

I don't know of any current Airbus datapacks with adaquate data to produce an FFS with accurate modeling for post stall flight characteristics. Can't comment on Boeings but there are some other manufacturers that have produced accurate data that has allowed for realistic post stall flight characteristics.
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Old 6th Oct 2014, 10:03
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Centaurus

By keeping the body angle between zero to minus two below the horizon until reaching at least 230 knots IAS, you can should count on (IMHO) losing at least 3000 ft of altitude before reaching that speed. That assumes high power used in the process. That figure was from observations in a full flight 737-300 simulator
That might work at the early stage of a low stall AOA, it would not have worked for AF447. Attitude is not relevant for stall recovery (which is the phase from stall entry until recovery completed), AOA and speed are the key elements. If those are in the ballpark, then attitude is the next step. Sure we reduce AOA by reducing pitch, but not until a given amount of degree nose down, but until AOA is below stall AOA, then we maintain that AOA until enough speed for attitude correction is available. Sure we take care of the bank angle in order to not exceed safe aircraft parameters, but for reducing AOA as fast as possible it has no relevance. Bank angle might even help in reducing AOA, think about it like in a nose high unusual attitude recovery, where the reduction of lift due to bankangle helps to bring the nose down faster than by a pure push over.

Underslung engines can create a pitch up moment, thus hindering the attempts to reduce the AOA, while the speed increase by the power output might be minimal due to the high AOA high drag flight path. To power out of a stall is not the correct thing to do when enough altitude is available. AF447 is again a good example for the lack of positive influence of TOGA at the wrong moment. Sure it is vital to have enough power available after the AOA has been reduced enough for aceleration and following attitude and altitude correction maneuvers.

If i misunderstood your post, then please explain.
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Old 6th Oct 2014, 10:24
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If i misunderstood your post, then please explain.
Thank you F4 for your reply. Of course you are quite right about recovering from the stall by what ever means necessary and that means no restriction on the nose down angle to get out of the actual stalled state. Without the benefit of an angle of attack indicator the crew have no choice except to lower the nose and thus reduce the angle of attack, to a speed where it is obvious the aircraft is unstalled (no buffet/stick shaker)

From simulator experience it takes very little nose down attitude below the horizon before it is obvious you are out of the stall and the next thing is to decide when to level out. Due to the loss of thrust at high altitude and slow engine acceleration, full throttle does not give the marked pitch up one would experience during a low altitude go-around in the landing configuration and is easily countered by appropriate elevator and stab trim use. In other words no problem for a competent pilot; especially as some stabiliser trim is needed to keep the aircraft in trim during the dive until a specific safe airspeed is reached. .

Although once attaining VREF 40 +100 knots should hopefully get you out of immediate trouble in good weather conditions, perhaps I should have mentioned that in the context of the original post (inadvertent stall in severe storm weather at high altitude) that the descent should be continued without delay until reaching severe turbulence penetration speed. Especially as the aircraft may well still be in severe turbulence in cloud. There may be significant height loss before reaching a typical severe turbulence speed.

Last edited by Centaurus; 6th Oct 2014 at 11:10.
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Old 6th Oct 2014, 10:44
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I would. Air Algerie MD80 apparently stalled at high altitude in cloud during storm penetration. The accident appears to have developed as a loss of airspeed awareness leading to a fully developed stall and roll off departure to the port side with post stall gyrations. The nose then became planted way nose down, left wing down as the stall broke, but they never recovered from the nose down-wing down attitude
And unbelievably it was flown by a TRE with 10,000 hours on type. Presumably he had flown approaches to stalls in the simulator, and taught others the correct (??) recovery technique as well.

All of which leads me to conclude that Centaurus is absolutely correct; either simulators do not accurately replicate high altitude stalls, or there are experienced pilots out there with woefully inadequate knowledge of the correct stall avoidance and recovery techniques.
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