Deep Stall?

[tiger26isfinals]

Hi

Just read a book and followed most of it(who am i kidding) apart from when it talked about deep stalls? Have not got a clue what this is...just wondered if anyone could help?

Thanks

Tiger

And thanks to Genghis for the last post

[BOAC]

Try Google?

[Genghis the Engineer]

A pleasure to have helped.

The term "deep stall" usually means an unrecoverable stall, where for whatever reason the aeroplane shows a complete disinclination to recover.

Speaking for myself, I've only ever seen it once, in a canard single seater with a very high thrustline. If you stalled it and left the throttle at idle, there was insufficient nose-down pitching moment to recover - I actually HAD to use thrust to unstall the canard - really quite disconcerting.

Probably the best known case of a deep-stall is the BAC 1-11 which killed a flight test crew when it stalled, but if memory serves correctly the mainplane blanked the tailplane so there was no elevator authority to pitch down. There's a nice explanation of this here (http://en.wikipedia.org/wiki/Deep_stall).

G

[Milt]

If you are flying a type which will deep stall, usually because of inadequate elevator effectiveness, try rolling inverted to recover.

Similarly if you get a mach tuck and full back stick becomes ineffective, let it carefully go under rather than continue the dive.

[Genghis the Engineer]

If you are flying a type which will deep stall, usually because of inadequate elevator effectiveness, try rolling inverted to recover.


Assuming that at such low speeds you have sufficient aileron authority to do so, and hoping that the transient sideslip during the roll doesn't put you into a spin.

G

[Hand Solo]

An additional factor in a deep stall with aircraft such as the BAC1-11 and DC-9 is that the turbulent airflow from the stalled wing prevents the engine developing adequate thrust to accelerate the aircraft out of the stall. Hence you end up in with a high angle of attack, no pitch authority to correct that and no thrust to accelerate out of it.

[tiger26isfinals]

Cheers folks

The wikipedia seems to have it all!

Thanks again

Tiger

[grusome]

Actually, tiger26isfinals, the wikipedia is fairly limited.

The prototype BAC1-11 had tab activated ailerons and elevators, so it not only had no elevator authority in deep stall, but no roll capacity either. Incidentally, the test crew (who knew their tenure on the planet was limited) continued a commentary on their attempts to recover all the way down. The ultimate professionals!
The solution for the production aircraft included not only powered controls, but modified wingtips and wing roots to alter airflow, much more efficient stall warning vanes, stick push and fuel dip. In theory, in the model 217 anyway, one could power out of a deep stall if all other measures failed to stop you reaching that condition.

I never tried!!!

Cheers
Gru

[m5dnd]

Grusome,

Good explanation but the 1-11 has NON powered ailerons..

[grusome]

M5,

Humble apologies, either poor expression or too many type ratings in the intervening 35 years, can't remember which!

Cheers
Gru

PS Can't quite recall whether the differential speed brake/spoilers were on the prototype, but have a vague recollection that these were to provide roll at high AoA.

edited for PS

[m5dnd]

Gru..

No problem... Just thought I would throw in my ounce of help!!..

Not sure re the Speed Brake/Spoilers but will find out in next couple of days.
If You check your PM's there will be a message for Yu later ..

TTFN

[Dave Gittins]

Was there not also a Trident lost as a result of the same deep stall (or locked-in condition) problem ) - G-ARPY I think. That being the reason why such aeroplanes have a stick shaker (or pusher) to initiate recovery before the condition becomes locked in.

DGG

[Swifty_N]

I belive a trident was lost due to this. One of my instructors at Cosford was talking to me about it sometime ago now and metioned a Trident being lost. Was a VC-10 too or is that my imagination?

NS

[barit1]

Trident deep stall (http://aviation-safety.net/database/record.php?id=19660603-1) accident

[m5dnd]

NS
"Was a VC-10 too or is that my imagination?"

Sadly it was Your imagination.. !! (sadly that is, for Your Imagination) please check Your PM's..

On 1-11's both Stick Shakers and Stick Pushers are fitted ..

DND

[ORAC]

Date of Accident: 26 July 1993
Airline: Bombardier
Aircraft: Bombardier Canadair CRJ-100
Location: Byers, Kansas, USA
Registration: C-FCRJ

Accident Description: The aircraft was on a test-flight out of Wichita, Kansas. While performing a side-slip maneuver at 12,000 feet, the crew lost control of the aircraft and it entered a deep stall. Descending through 8000 feet, the Captain ordered the anti-spin parachute deployed. Due to a system misconfiguration by the Co-pilot, however, the chute fell free of the aircraft. Control was never regained and the aircraft crashed into a cornfield.

[Conan the Librarian]

With the deep stall case as was made recently aware with the 111 (By the way - what was the Javelin like?) the B727 was operated in the States I believe without a shaker and pusher. The first ones on the UK register were by Dan Air and the CAA made them fit aforesaid shaker and pusher at not inconsiderable expense. Or so I am told... Anyone?

Conan

[barit1]

Conan, my recollection is spot on with yours.

You may recall that both AAL and UAL had high sink-rate, slow engine response accidents in one week (in Nov. 1965) with the 727-100. While not deep-stall events, they certainly increased the pucker factor with respect to T-tail transports.

(By sheer coincidence, that week was the 25th anniversary of another engineering slip-up: the Tacoma Narrows bridge collapse - "Galloping Gertie")
:oh:

[ORAC]

Javelin web site. (http://www.btinternet.com/~javelin/index.htm)

Didn´t realise the gate guard from Stanmore had been saved. It was in very poor shape and I thought it would have cut up. But if you look at the list of survivors, it´s now at Thunder City in SA. Anyone any information or photos of how she was moved and what work had to be done?

[Loose rivets]

Interesting thread.

The 1-11 would show auto-ignition first, then the shake, followed by the push. Nitrogen pushed the controls via a ram piston.

We routinely took the 1-11 through to the push on base training. In the days before sims of course. It was a fairly gentle change of pitch at stalling speeds.

An acquaintance of mine heard the tape and described their voices changing as they kept the report going. The crash footprint was not much longer than the aircraft.

The spoilers came out at an aileron angle of >4degrees I think. At 250 kts, the rate of roll was quite unbelievable for an airliner.

Even assuming that this system had been available on the prototype, the airflow would have been such that the spoilers would not have done much.

I think the push in Pappa India went off several times did it not?

[Shaggy Sheep Driver]

I think the push in Pappa India went off several times did it not?

It did, to the extent that the crew disabled it. This indicates that the system was prone to false alarms, as it's pushing did not alert them to the possibility of its cause - a configuration-induced stall (slats retracted at too low an airspeed).

SSD

[wileydog3]

With the deep stall case as was made recently aware with the 111 (By the way - what was the Javelin like?) the B727 was operated in the States I believe without a shaker and pusher. The first ones on the UK register were by Dan Air and the CAA made them fit aforesaid shaker and pusher at not inconsiderable expense. Or so I am told... Anyone?
Conan


The 727s in the States did operate with shakers. No pusher.

[Loose rivets]

Pappa India was a doubly tragic accident in a way. I'm sure I have mentioned this before, but one of the attending officers was a member and inspecting officer of our pistol club. He told me a bit about that day.

The emergency services were hampered by an unprecedented queue of folk, all stopping to look. Some of the people were still alive and there was just a feint possibility that some may have been saved could the services have got to them sooner.

[NutherA2]

[quote=Conan the Librarian]By the way - what was the Javelin like?]

If you fancied a deep stall, the Javelin was the jet for you, at least a couple were lost during flight test before any further stall research was cancelled. When the aircraft stalled the high-set tailplane was fully blanked, the angle of descent was thought to be as near vertical as made no difference.

The aircraft was released to service and throughout its life was limited to a minimum of 150 KIAS (except on approach to land) and a prohibition of looping aerobatic manoeuvres. If I remember Pilot's Notes correctly, recommended action in event of stalling was to persuade the aircraft to spin and try to recover from that by vigorous use of aileron; no-one was optimistic that this would work, but it was thought this would pass the time until the enormous rate of descent brought the contraption down to MSH for initiating a Martin Baker recovery.:rolleyes:

[henry crun]

NutherA2: You said "If I remember Pilot's Notes correctly, recommended action in event of stalling was to persuade the aircraft to spin".

As I recall it didn't need any persuasion, it almost inevitably would spin.
The quote from Pilots Notes re spin recovery is here.

http://www.pprune.org/forums/showthread.php?t=61378&page=7

[Conan the Librarian]

Thanks Nuther - Can't think of an aircraft with a more closely coupled wing and tail. Just looking at the Javelin side on makes me twitch... I wonder what it would have taken to dispense with the tailplane altogether? Presumably that would cure any deep stall proclivities at the same time.


Conan

[NutherA2]

[quote=Conan the Librarian] I wonder what it would have taken to dispense with the tailplane altogether?

:confused: I believe that the tailplane was essential because the Dragmaster needed flaps, which in turn were necessary to avoid giving the aircraft an unacceptably high nose attitude during landing; the alternative would presumably have been an immensely long nosewheel assembly. If anyone's got a better explanation, though, I'd defer to their expertise.

[Conan the Librarian]

I ask, because the Javelin always struck me as something of a Dogs' dinner, even as a layman. From what I understand the thing was decades ahead of its' time regarding relaxed stabiility, which is why they had to bolt that tail on, plus all those vortex generators too. Still, I digress, so forgive my idle thoughts :}

Conan

[Shaft109]

Did anyone ever test stall/spin a big delta type aircraft like the Vulcan, Concorde or the SR-71?

Just curious after reading this informative post as the Vulcan generally ressembles a Javelin but IIRC lots of programs give the impression the Vulcan (and Victor) were flown quite hard during service.

Cheers

[Genghis the Engineer]

Not quite a spin (but certainly post stall), some interesting things happened on the YB-49. Gen.Bob Cardenas (I think he was probably a Captain or Major at the time) found some very unpleasant things and recommended that it not be taken close to the stall as a result.

It's generally believed that Glen Edwards subsequently got a little further to Bob Cardenas' danger area than was wise, causing an in-flight breakup and loss of the aircraft and crew at around FL300.

General Cardenas put together a summary of his flight test reports a few years ago for a history session, and later was good enough to share them with me in support of some work I was doing into a similar problem. This is an excerpt from one of his reports:

“23 February YB-49 #368 one landing local Muroc-------- 0:35 mins.
Recommended no intentional stalls due to the fact that during the final phase of the stall entry maneuver it lurched over backwards into a tumble. Had to use asymmetric power to recover. Submitted a full report and thankful that the throttles were hanging down from the ceiling rather than in a normal position since G forces had my arms locked upwards and my rear off the seat. Flight test engineers told me later that I had encountered inertial coupling”

“the results of my one Stall Test during which the aircraft had assumed a very high angle of attack without a stall warning and then pitched over backwards…. The rotation was severe and made it difficult to keep my hands and feet on the controls. The engineers called it a lateral roll but I was experiencing a tumble! I was lucky that the designers had put two throttles hanging down from the upper surfaces, each connected to four engines.I applied full power with the left throttle and resolved the "tumble" with asymmetric power and elevon control.”



G

[rvator]

Try this on a Falcon 10/100.......

assuming you are flying an approach with full flaps and outboard slats only (ie in case of emergency extension of slats with #2 HYD generation....)....permit the outboard slats to retract (loss of #2 HYD...bad day !..).......& you will experience a deep stall....rather impressive and dangerous one by the way !...all the most that you will continue with nose up approach-like attitude, wings level.....but huge sink rate !!!!.......

That's why Dassault call for "No Slats - No Flaps"...........

(....however, that one will recover by simply retracting some flap......and applying TOGA of course..if you feel it and react promptly !!!)