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Can airliners recover from a stall?

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Can airliners recover from a stall?

Old 2nd May 2005, 05:13
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Can airliners recover from a stall?

Or is it just impossible to stall an airliner as it's got some sort of stick-pusher mechanism........
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Old 2nd May 2005, 06:37
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All airliners have gizmos to prevent stall and pitch instability that could lead to stall - Boeing uses autoslats, stick pushers, stick nudgers and engine nacelle vortex vanes/chines.

The T-tail 727 configuration has an unrecoverable deep stall characteristic hence the stick pusher or nudger. Some 767 have a stick nudger because of pitch instability - but this was removed by adding nacelle vanes. Everything else Boeing is stick shaker & autoslats .. but these arent too new - Even the Tigermoth has these really cool spring loaded autoslats for stall

Ive heard that AIRBUS has better climb performance in windshear because the computer FBW is better able to nail the stall margins to the ragged edge - then a sweating Boeing pilot with pucker factor ..
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Old 2nd May 2005, 12:41
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Nacelle strakes

A lot of airliners have used nacelle strakes - the DC-10 for example. DC-8-70's likewise. They're generally used to improve deep stall characteristics.

One airline got annoyed with forgetful technicians leaving tools atop the thingies, and removed them. The manufacturer's rep got wind of this and saw to it they were reinstalled.
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Old 2nd May 2005, 13:28
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allwerp,

Airliners either can (A) recover normally from a fully developed stall, or (B) have on-board systems preventing stall entry, or (C) have fitted systems or aerodynamic assistance (such as strakes) to augment normal recovery from the stall. Without falling into one of these categories, the aircraft could not gain certification.

Don't confuse this issue with the deep stall discussion on another currently running thread. Having done a fair bit of testing work in endeavouring to take this category of aircraft beyond the normal stall into the "deep stall", the object of the testing was always to ascertain that recovery was possible. It always was. Not so for the poor souls who lost their lives during BAC-111 testing, but their legacy carried on to later generations of aircraft (and at the time caused Douglas to enlarge and redesign the Stabiliser/Elevator system on the DC9).

used2flyboeing, are you sure you're not confusing the DC9 with the B727? I flew both extensively, and clearly recall the very necessary hydraulic actuation of the elevators in a forward control push, but recall no such system on the B727. Maybe C.R.A.F.T's disease is catching up with me.

Regards,

Old Smokey
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Old 2nd May 2005, 14:13
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how about a spin ? any recovery possible?
may be someone tried in the sim..?
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Old 2nd May 2005, 14:16
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Are we sure he is not asking if they can be intentionally held to deep stall. If that is what he is asking, the answer is yes. Hold the stick back(Boeing) and you will eventually enter deep stall regardless of the backup systems. Is it recoverable at that point? Depends on the pilot. During certification of a 727 hushkit I went through 600+ stalls as the observer. Some were so deep that the indicated air speed was less than 80 kts. During one stall, the right wing broke early and we went about 95% of the way to inverted.

If you want to get real cute, lets start talking about wind up stalls.
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Old 2nd May 2005, 14:27
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During certification of a 727 hushkit I went through 600+ stalls as the observer. Some were so deep that the indicated air speed was less than 80 kts. During one stall, the right wing broke early and we went about 95% of the way to inverted.
Jeez, that must of been some ride!Whats it like experiencing a stall in an airliner and nearly rolling completely over?i know what its like in a light aircraft (stalls that is, not inverted flight!)
regards
(P.s what are wind up stalls?)
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Old 2nd May 2005, 15:21
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The odd-ball thing is that, having entered the deep stall (usually by 'wind-up), if the wing dropped to vertical, or you went inverted, you were 'out of the poo', because you now had normal airflow over the tail surfaces. If you mismanaged the ensuing rapid descent with increasing speed, you were back in the poo of a different type.

Normal 'full back stick' stall testing is done with idle thrust, and stabiliser trim trimmed for Vs+10, and a controlled deceleration at 1Kt/sec until stall occurs. 747FOCAL's and my definition of a 'wind up' stall may differ, but for deliberate efforts to enter the deep stall, large UP stabiliser trim was used with large thrust settings to gain high pitch attitudes just pre-stall, and then chopping the thrust and rapidly applying full UP elevator. Disneyland offers no more exciting ride.

corporal klinger, tried many fully developed spins in the simulator "just in case". Never recovered successfully from one of them.

Regards,

Old Smokey
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Old 2nd May 2005, 15:24
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All airliners that have been certified under JAR/FAR 25 (wouldn't know of a current type that isn't) can recover from a stall. On aircraft on the British register, this is even demonstrated during an air test each time the certificate of airworthiness is renewed.

It must be possible to recover (with our without assistance from devices such as a stick-pusher), but also to maintain lateral control by means of unreversed operation of the ailerons within 20 degrees of bank. Please note the difference to JAR/FAR 23 a/c where it is taught not to use ailerons in a stall and rudder is used instead.

Erik.
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Old 2nd May 2005, 16:26
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Remember the case of the Russian A300 that someone let his son fly? Reading the accident report, it seems that that aircraft stalled and spun. They recovered from autorotation into a dive, but too late to avoid making a crater.

Conf
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Old 2nd May 2005, 20:22
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There was one flap setting (5 If memory suits me) where the Boeing test pilots did the heavy aft cg inverted thing and ended up losing nearly 20,000 ft of altitude before getting it back at around 2500 ft.

Just had a friend go up in a learjet test flight where they entered stall and it would not push over and they fell for like 20 seconds with it kicking and bucking all over the place. Full redline power is the only thing that saved them.

For those of you that have been in actual stalls, question for you.... Granted its more pronounced in tail mounted engines, but what do the noises your hearing from the aircraft sound like to you?

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Old 3rd May 2005, 00:10
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A note of caution for those who might be tempted to generalise or extrapolate from the particular to the general and play test pilots with their light aircraft ...

Be aware that stall definitions and test protocols have varied over the years. In particular, some aircraft were tested only to the point of stall and to pull such animals into the stall might well involve some excitement ... like being upsidedown and/or spinning.

Be very wary of using rudder to do things in the stall.
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Old 3rd May 2005, 02:27
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john_tullamarine is right. Playing around with stalls is not for the amatuer pilot. I have never flown them accept in the sim. The only way I will go up and do anything like that is if the pilots flying have been doing it for years. There are only a few places on the planet you can find them boys and at $1000 USD per flight hour I think maybe Disneyland would be a better choice.

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Old 3rd May 2005, 14:41
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Notwitstanding that some T tail types may not recover due to deep stall, perhaps we ought to add that other types will recover providing there is sufficient height to recover before hitting the ground!
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Old 7th May 2005, 22:11
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"what do the noises your hearing from the aircraft sound like to you?"
-----------

At somewhere less than 80kts on a T-tail at FL290 it goes really quiet and its as if she's relaxing, a few joints creaking...
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Old 7th May 2005, 22:54
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BAD things can happen
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Old 9th May 2005, 03:07
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Robin stall

The initial stall characteristic in the Robin 2160 (although not a jet aircraft) is a very fast roll rate during the initial 3 to 4 spins (incipent stage), once you have developed into a stable spin the prop stops spinning and the only sound is the wind moving over the aircraft.

The recovery technique that I have been taught is the Beggs procedure 1) Throttle to iddle 2) identify direction of the spin 3) Take your hands off the stick, place on top of dash 4) Full opposite rudder until spinning stops 5) allow the speed to increase until the prop start starts spinning again 6) pull up out of the dive.
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Old 9th May 2005, 13:46
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barit1 describes a horrifying, but completely avoidable situation. As tha accident report indicates, the flight crew had received no training in recovery from the fully developed stall. Not their fault, and not the fault of probably most airline pilots who have never seen the stall characteristics of their aircraft.

The standard training syllabi indicate training for recovery from the stall warning only. In one sense that's a good thing, the aircraft is still fully controllable, and the onset of the stall warning is the appropriate time to IMMEDIATELY initiate stall recovery actions, there's no question about that. On the other hand, with high fidelity simulators available, I have always campaigned for additional simulator training demonstrating the fully developed (full back stick) stall, and have always given that exercise to my trainees as a bit of 'bonus' training. Control and recovery procedures differ considerably from their earlier full stall training on prop aircraft, and the application of the intuitive responses learned at this phase could be disastrous. Sadly, this seems to have been the case for the ill-fated DC8 crew, who might have benefited from such training.

I have done a lot of fully developed stalls during flight testing, but, with trainees in the aircraft whilst awaiting simulator certification, also did a lot of recoveries from the stall warning, NEVER to the fully developed stall. On one occasion, the student got such a fright as the overly assertive stall warning triggered, that he applied full BACK stick, precipitating the full stall. On that day, my own full stall exposure paid big dividends. It can, and does, happen.

Hopefully, one day, pilots will receive simulator training in recognition of and recovery from the full stall. Until that day, the title of this forum should perhaps have been amended from "Can airliners recover from a stall?" to "Can airline pilots recover from a stall?"

Regards,

Old Smokey
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Old 9th May 2005, 14:42
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There was one flap setting (5 If memory suits me) where the Boeing test pilots did the heavy aft cg inverted thing and ended up losing nearly 20,000 ft of altitude before getting it back at around 2500 ft.
Just had a friend go up in a learjet test flight where they entered stall and it would not push over and they fell for like 20 seconds with it kicking and bucking all over the place. Full redline power is the only thing that saved them.
i think thats enough to frighten the **** out of anybody!
how far do you reckon they will go with stall testing on the a380?surely they will only be incipient stalls.
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Old 9th May 2005, 15:32
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how far do you reckon they will go with stall testing on the a380?
All the way, certification requires it. And, as a special bonus, the Australian CAAS will want a little bit more because QANTAS have ordered the A380, just as they did for the TAA A300 so many years back.

Mind you, all the way might be a great big nothing, minimum 'Z' speed and all that.

Regards,

Old Smokey
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