View Full Version : stalling behaviour with large airliner
lynn789
18th Sep 2010, 21:28
it it true that if a large airliner stalls, it will flip over on its back and head straignt down nose first?
is there any simulator program that simulates this? Ive heard that on a sim the stall can be approached but not actually experienced
Bealzebub
18th Sep 2010, 21:35
No it isn't.
No because this doesn't happen. A simulator will simulate a stall.
captjns
18th Sep 2010, 22:29
Deep stall demonstrations in large jet aircraft produce a good deal of an onset buffet to let you know you better get your head out of your butt and do someting about it.
If you ignore the stick shaker, and the onset buffet, it just gets more pronounced and the jet just starts to lose altitude while the nose is still above the horizion. When you unload the jet by releasing the back pressure on the control column, and allow the nose to come through the horizion it recovers very nicely. I've stalled the 727, 737, and 757. I have to tell you these aircraft recover alot better than the Bellenca Viking or the old Cessna 310.
Caution... deep stalls in jets cause white caps in the coffee.
Denti
19th Sep 2010, 00:11
When you unload the jet by releasing the back pressure on the control column, and allow the nose to come through the horizion it recovers very nicely.
Provided you have not trimmed all the way backwards, which is what the automatics will do if you let them.
MarkerInbound
19th Sep 2010, 04:27
it it true that if a large airliner stalls, it will flip over on its back and head straignt down nose first?
Why would it do that? Aerodynamics is aerodynamics, it's do the same as a Piper Cub. Disclaimer for the PhD Aeronautical Engineers - yes, I have some grasp of the swept wing Mach tuck T tail high speed buffet issues, but in this case I'd say, "Just fly the plane."
...it true that if a large airliner stalls, it will flip over on its back and head straignt down nose first?
Only if the flying pilot stomps on the rudder just as the airplane stalls...:yuk::ugh:
MarkerInbound
19th Sep 2010, 06:19
Good point.
STBYRUD
19th Sep 2010, 07:09
My 737 does the opposite if I remember the function of the speed trim system correctly - tries to create speed stability at low speed thus making it more difficult to enter the condition in the first place.
Well, lynn, if you look at the bank angles achieved in the case of the Perpignan airbus accident, yes, it is true for a medium airliner - if mishandled.
If not wings levelled, it will fall into a spiral-like dive, not like a real spin (like in aerobatics planes), like a corkscrew. If wings-levelled, as mentioned, it will increase sink rate with a nose down tendency, depending on trim setting.
hth,
Dani
Daysleeper
19th Sep 2010, 09:13
A simulator will simulate a stall.
Actually most of them won't. They will simulate to the "stall" as in the first point of a stall break.... but beyond that what you get is a sim developers best guess of what the stall characteristics will be like coupled with the limitations of the motion platform and visuals.
Post stall behaviour is generally not modelled for transport category aircraft even in engineering sims and as such it is difficult to program with any degree of accuracy.
lynn789
19th Sep 2010, 23:47
thanks everyone
we previously established that a sim cant be used to simulate ditching so perhaps sims have more limitations than some expect
HarryMann
20th Sep 2010, 01:21
Even PC sims like X-Plane can simulate post-stall behaviour reasonably sensibly. It's just another set of equations to solve, sometimes the inertial components aren't represented that well, but if its modelled well the behaviour is often quite surprisingly realistic...
Agree with the bootfull of rudder comment... likewise a handful of underslung turbofan thrust, rather than two symmetric handfulls?
Even PC sims like X-Plane can simulate post-stall behaviour reasonably sensibly.
The aerodynamicists involved in designing large commercial jets emphatically do not agree.
It's just another set of equations to solve
No it's not. It's a set of wind tunnel tests to perform, without a tailplane installation, and a set of guesses as to what will happen when the object (a) has a tailplane, and (b) is no longer fixed in relation to the relative wind, but moves about freely in it. It is all about extrapolation from limited data sets.
PBL
XPMorten
20th Sep 2010, 13:59
Anyone know of any NTSB or other reports containing FDR data with a stall?
XPM
Leodis737
20th Sep 2010, 14:25
Two I can think of - recent West Caribbean MD82 report, does have FDR data: available at avherald, search using 'West MD 82'.
Northwest Airlines 727 accident due to pitot freezing (heating off), NTSB report AAR-75-13 (google it), descended from 24,800ft to impact in 83 seconds, report states FDR data was retrieved and used, and suggests it may have been available for the public hearing, but is NOT actually shown in report.
Those both T-tails however.
Type1106
20th Sep 2010, 15:47
In the late 80s, early 90s, I carried out a number of post major inspection air tests in the RAF's VC10s.
In most configurations she stalled like any aeroplane, with aerodynamic as well as stick shake to announce the on coming stall, wings level and don't touch the rudders and at the stall the nose dropped away and standard recovery unload, apply power and recover. How anyone could not recognise what was about to happen is beyond me - it required strength and determination to get there!
However, the 10 had a 'stick pusher' fitted to prevent a true deep stall (the reason why this was fitted only to T tail aircraft on the British register is a long story). The pusher speed was calculated and you used a lot of muscle power to keep the IAS coming back to that figure. In addition an AoA indicator was temporarily installed on top of the coaming in front of the captain and if you got to the magic figure (+14 degrees seems to ring a bell) before the push you got out of it quickly by unloading etc. Try again and if still no push then the system was u/s and needed recalibration.
Contrary to some comments above, the flight simulator did a good job (and still does) of reflecting the whole stall and recovery process - not absolutely the same but good enough to train before the air test.
1106
HarryMann: Even PC sims like X-Plane can simulate post-stall behaviour reasonably sensibly.
PBL:The aerodynamicists involved in designing large commercial jets emphatically do not agree.
Type1106:Contrary to some comments above, the flight simulator [of the VC-10] did a good job (and still does) of reflecting the whole stall and recovery process - not absolutely the same but good enough to train before the air test.
Point taken. I really wasn't thinking of 45-year-old jets that are no longer in commercial service, but of what Boeing used to call "third generation" aircraft. I was thinking in the present, and immediate past, tense and should have made it clear, say by saying "modern".
PBL
N7242G
20th Sep 2010, 20:55
...it true that if a large airliner stalls, it will flip over on its back and head straignt down nose first?Only if the flying pilot stomps on the rudder just as the airplane stalls...:yuk::ugh:
isn't that the proper way to do stall recovery in any and all aircraft?! That's how I've been doing it! :}
dwshimoda
1st Oct 2010, 23:59
isn't that the proper way to do stall recovery in any and all aircraft?! That's how I've been doing it!
Then I'm amazed you are still alive.
Pitch & Power was what I was taught and works very well on everything from a C-150 to a B-752. I'm aware some people do power then pitch, which may be equally effective.
Stamping on the rudder - life would have to be pretty bad before I was resorting to that!