Continental TurboProp crash inbound for Buffalo
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Ah yes the venerable DC-9. As a newly minted F/O in '78 you just had to love an airplane that had a "push for tail" switch. Did it work? That will cost you a nice single malt. 7000 hours in both seats....what a hoot.
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okfine
I flew that thing forever and never thought of that switch in that way. but we sure had pretty FA's...especially Boston.
Hey guys , lets get this thread to 2000 replies!!!!
I flew that thing forever and never thought of that switch in that way. but we sure had pretty FA's...especially Boston.
Hey guys , lets get this thread to 2000 replies!!!!
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protectthehornet -
your little brother , the DC9 was a darn good plane...sometimes it is called, ''the last pilot's airliner''.
your little brother , the DC9 was a darn good plane...sometimes it is called, ''the last pilot's airliner''.
PTH is right. If the pilot wants something he should have it, the computer should not intervene. Pilots should have final control and manufacturers that take that away have removed the final survival tactic a pilot has.
To get the thread back on the issue at hand, a crash, and control inputs near the critical angle of attack ...
As I understand it, stick and rudder shakers are an alert, but don't change the control surfaces. In the plane I flew that had them, that was their sole function. Is that any different in commercial transport aircraft?
A stick pusher, on the other hand, is an uncommanded (by the pilot flying) control input that represents a robot's attempt to out-think the pilot at the controls, with the result being that the plane flies the pilot, at least for a moment or two. Granted, it seems to have been designed for corners of the flight envelope, and conditions that warrant nose down to prevent something bad from happening next ...
I think I understand why it was considered a good idea. For a UAV, it might be a brilliant piece of design work. What I don't understand is why, having two pilots, one at the controls and one able to make control inputs, there is a need for a stick pusher in any aircraft. How many accidents have been averted by a stick pusher? Is there data (FOQA or other programs ) to demonstrate/support this?
Some of the pilots who have posted here fly with stick pushers and are comfortable with them.
Can you explain why you like it?
Or, do you simply accept it and fly the plane anyway? This thread has caused me to think that the stick pusher was a solution in search of a problem, but I'd be happy to understand better, and learn from pilots who work with them on a daily basis.
Hmm, now that I think of it, maybe making sure you don't have to deal with it is part of flying the aircraft.
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Stick pushers are normally fitted if when an aircraft reaches a critical AoA the tailplane/elevator ability to unstall the wing is compromised. The classic example is the 'T-Tail' design where tailplane/elevator blanking occurs at high AoA and the aircraft cannot be recovered from the stall. It is essential on those aircraft and PREVENTS the pilot getting into the 'deep stall' by forcing the stick forwards and thus reducing the AoA. I'm not sure when they first flew, but I think it was following the BAC 1-11 crash in 1963 which killed Mike Lithgow and crew which was, I think, when the tail-blanking event was first recognised..
Would it be good not to have it interfere with a pilot's death wish? It should only work when the pilot has screwed up - as per your last sentence! As for how many push events there have actually been, I know not.
Would it be good not to have it interfere with a pilot's death wish? It should only work when the pilot has screwed up - as per your last sentence! As for how many push events there have actually been, I know not.
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BOAC, as far as I'm aware the only maneouvres Airbus FBW actively prevents the pilot from executing are a roll to inverted/spiral dive (stopping at 60 degrees bank) and an angle of attack that would induce stall without commensurate thrust increase (i.e. it increases the thrust to compensate if a pilot yanks back on the sidestick as a panic response).
Bubbers44, I'm not sure pilots should be doing either of those - final control be damned!
Bubbers44, I'm not sure pilots should be doing either of those - final control be damned!
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Apologies if I'm wrong, but bubbers44's comment seemed pretty pointed to me.
As an aside for all the "big red button" advocates, stick pushers could be overridden, but it didn't help the poor sods on G-ARPI.
As an aside for all the "big red button" advocates, stick pushers could be overridden, but it didn't help the poor sods on G-ARPI.
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but it didn't help the poor sods on G-ARPI.
Regarding the Buffalo crash we seem to be concentrating on a single issue here when there were multiple reasons for this crash. Certainly the ultimate reason was that the crew (both of them) mishandled the stall but then they had mishandled (or neglected) the aircraft all the way to that point so is that not surprising? Other factors to come into play were fatigue and poor knowledge of the aircraft (either due to poor type endorsement or lack of inquiry on the part of the crew).
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Actually, PL, one of the criticisms raised on the crew actions was that by inhibiting the stick pusher they allowed the a/c to pitch up into a deep or 'locked' stall after three push events. Whether allowing the stick pusher to continue operate would have prevented the crash is debatable, of course!
......................since we have diverged now from turboprop stalls into Buffalo, naturally............
......................since we have diverged now from turboprop stalls into Buffalo, naturally............
Stick pushers are normally fitted if when an aircraft reaches a critical AoA the tailplane/elevator ability to unstall the wing is compromised. The classic example is the 'T-Tail' design where tailplane/elevator blanking occurs at high AoA and the aircraft cannot be recovered from the stall.
Thanks!
As to turbo props crashing near Buffalo: the matter of what looks to be a compound error
1. not avoiding the stall
2. flaps up during stall recovery possibly making that recovery harder
looks like the antithesis of having two pilots fulfilling their roles (PF/PNF) during terminal area procedures.
A lesson for all multi place crews, no matter the platform.
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Ref 2) - I believe the recommendation when encountering a tailplane stall caused by tailplane icing in a T-Tail a/c following flap selection is to return the flaps to the previous position and I think the suggestion was the Captain (and possibly F/O?) thought they were experiencing such?
Yes, but earlier in the thread, a number of folks experienced in this aircraft indicated that it isn't susceptible to tail plane icing stall ... I was under the impression that this was agreed, but may be wrong about that.
With that in mind, if both crew misdiagnose a malfunction/condition, things can go downhill quickly. (Spent some time finding crew points of failure as an instructor, very enlightening to see how different crews handled the same series of incrementally challenging emergencies.
With that in mind, if both crew misdiagnose a malfunction/condition, things can go downhill quickly. (Spent some time finding crew points of failure as an instructor, very enlightening to see how different crews handled the same series of incrementally challenging emergencies.
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Lonewolf_50 - You're right about the Q400 not being susceptible to tailplane stall. Where tailplane stall came into this accident was because the Captain's previous type, the Saab, *was* known for suffering tailplane stall and the question was over whether he reverted to his previous training under pressure.
stepwilk - The last 707 commercial flight in the US was in 1985, but it continued in service abroad until the mid-1990s. BA retired their VC-10s from commercial operations in 1981, which brought the airline career of the type to an end.
The question of the G-ARPI stick pusher dump. From what I've read on the incident, the first push did succeed in raising the airspeed to where the wings were no longer stalled, but the assumption (due to no CVR) had to be that the crew, who were likely dealing with a major pilot incapacitation as well, thought that it was a false push, pulled back on the yoke and dumped the stick push, sealing their fate. While it's not the same incident in many ways I think it's quite relevant here because it was an inexperienced crew* dealing with a suddenly frightening situation and making bad choices as a result.
* - with the exception of the incapacitated Captain
stepwilk - The last 707 commercial flight in the US was in 1985, but it continued in service abroad until the mid-1990s. BA retired their VC-10s from commercial operations in 1981, which brought the airline career of the type to an end.
The question of the G-ARPI stick pusher dump. From what I've read on the incident, the first push did succeed in raising the airspeed to where the wings were no longer stalled, but the assumption (due to no CVR) had to be that the crew, who were likely dealing with a major pilot incapacitation as well, thought that it was a false push, pulled back on the yoke and dumped the stick push, sealing their fate. While it's not the same incident in many ways I think it's quite relevant here because it was an inexperienced crew* dealing with a suddenly frightening situation and making bad choices as a result.
* - with the exception of the incapacitated Captain
Lonewolf_50 - You're right about the Q400 not being susceptible to tailplane stall. Where tailplane stall came into this accident was because the Captain's previous type, the Saab, *was* known for suffering tailplane stall and the question was over whether he reverted to his previous training under pressure.
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DW, I didn't direct the comment about computers overriding pilot inputs to you. Your post saying automation has made flying safer is true if the pilot can override it if necessary. Also the pilot should never trust it. Recent accidents indicate automation has caused several situations where pilots did not intervene when automation failed. If automation goes to full power approaching a stall and you are not trimmed for full power, intervene. If the aircraft thinks it is flare mode at 2,000 ft, intervene. Don't let automation kill you.
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Not necessarily - sometimes leaving it alone is precisely the correct thing to do. Examples I can think of off the top of my head are the aforementioned G-ARPI Trident crash, the Aeroflot A310 where the pilot's son partially disengaged the AP, and the German A310 departure from control over Moscow.
In fact these days automation is incredibly reliable and it should be trusted in most cases. However it relies on the same instrument/sensor readings as pilots do, and as such pilots do need to be trained in recognising when things have gone south and how to remedy such situations.
In fact these days automation is incredibly reliable and it should be trusted in most cases. However it relies on the same instrument/sensor readings as pilots do, and as such pilots do need to be trained in recognising when things have gone south and how to remedy such situations.
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BOAC and others:
The captain applied power (eventually) and pulled back on the control column thus overriding the stick push. These actions are incorect for both a normal stall and the tail stall. As for the FO knowing what was going on I doubt it - she panicked and undid her last action by raising the flaps without any order from the captain.
I think that the captain wanted the speed to decrease towards his selected vref. He knew that with flap 15 the plane would fly at that speed. Unfortunatly he forgot / did not apreciate the consequences of the increase ref switch being on.
The rising red tape was in his mind somthing that should not be there and was not in his mental model. As a consequence the stick shake and push were things that were also not in his mental model and beyond his understanding at that time. In his world the plane should still be flying unstalled as he was above his vref. He therefore did not react corectly to the shake and push.
Stike Shake and push do not go off at the stall but during the aproach to the stall - the plane did not stall until he made it.
The lessons are that you should fly the plane you are currently in, have a thourough knowlage of the aircraft systems and be adequatly trained on type to react instinctivly and correctly when devices like stick shake / push go off.
Lets face it you do not fly at the edge of the stall envolope anticipating a stall intentially so when it does activate it will be a surprise - you should react to the stick shake the once recovered corectly figure out what you have done wrong.
The captain applied power (eventually) and pulled back on the control column thus overriding the stick push. These actions are incorect for both a normal stall and the tail stall. As for the FO knowing what was going on I doubt it - she panicked and undid her last action by raising the flaps without any order from the captain.
I think that the captain wanted the speed to decrease towards his selected vref. He knew that with flap 15 the plane would fly at that speed. Unfortunatly he forgot / did not apreciate the consequences of the increase ref switch being on.
The rising red tape was in his mind somthing that should not be there and was not in his mental model. As a consequence the stick shake and push were things that were also not in his mental model and beyond his understanding at that time. In his world the plane should still be flying unstalled as he was above his vref. He therefore did not react corectly to the shake and push.
Stike Shake and push do not go off at the stall but during the aproach to the stall - the plane did not stall until he made it.
The lessons are that you should fly the plane you are currently in, have a thourough knowlage of the aircraft systems and be adequatly trained on type to react instinctivly and correctly when devices like stick shake / push go off.
Lets face it you do not fly at the edge of the stall envolope anticipating a stall intentially so when it does activate it will be a surprise - you should react to the stick shake the once recovered corectly figure out what you have done wrong.