Colgan 3407 Down in Buffalo

[The Prussian]

My sense of all of this is that this aircraft...similar to what happened post Roselawn incident, is going to be relegated to flying the southern-tier states until they get these issues ironed out.

 

[ackattacker]

I'm no where near being able to remotely call myself an aerospace engineer.........but here's my 2 cents...a common everyday stall is the norm
(therefore that's what you try to protect against, you can overpower a stick pusher). A tailplane only stall is a function of the a/c being redesigned by mother nature due to ice.... I wouldn't know how you could mechanically differentiate or detect between the two....
(and would it be cost effective for something so rare? I'm not being insensitive to the price of a human life, just saying that flight has some inherent risks involved....) that is why computers cannot fly a/c under all conditions. You obviously need a human mind calculating the best decision for a given event.​

Tail stall occurs when the angle of attack goes excessively negative.

Main wing stall occurs when the angle of attack goes excessively positive.

The pusher only fires at high angles of attack. The pusher should not fire during a tail stall... however if a tail stall leads to an upset it is understandable at some point during the attempted recovery the angle of attack could exceed the amount required to fire the pusher.

 

[clr4theapch]

Of course we dont know the second by second time frame of things that happened.. but I would think it is actually possible to get a stick shaker/pusher if the crew responded to the tail stall by puling back on the yoke (as is the procedure for tail stalls) Then assuming that the tail started flying again, at the point it's possible that the AOT was now nose high enough and the airspeed was dropping low enough to activate the shacker/pusher..for a full wing stall...of course all of this could have happend in a matter of seconds..

So I see where this could happen.. God bless them.

 

[Brody1]

I'm no aeronautical engineer either, and maybe I'm being ignorant here, but it would appear that the design of a stick pusher/shaker doesn't allow it to tell the difference betweent the two. I haven't had the pleasure of fighting the stick pusher (yet), so I have no idea how difficult it would be to fight in actual flying conditions- especially if it's made worse by icing. It may not have mattered in this case- but what if it did?

Andy, I hear what you're saying, but what are the parameters of the flying envelope when the a/c is covered with ice? Like Wsurf said, our first reaction is usually the one we practice the most. Unfortunately, and assuming the info in the video is correct, that reaction can be catastrophic, espcially at low altitudes. Regardless of whether this was a contributing factor in the crash the other night, it would seem to me that any flight training department (and the FAA) should look very closely at this.

 

[LowlyPropCapt]

Tail stall occurs when the angle of attack goes excessively negative.

Main wing stall occurs when the angle of attack goes excessively positive.

The pusher only fires at high angles of attack. The pusher should not fire during a tail stall... however if a tail stall leads to an upset it is understandable at some point during the attempted recovery the angle of attack could exceed the amount required to fire the pusher.

I am not so sure about this...

I agree that the stick shaker/pusher activates at and beyond the wing's critical (excessively positive) AOA. But here is the thing... Increased airspeed aggrevates the stalled condtion in the case of a tailplane stall, since it causes the AOA to become more "negative." Since the nose would have been headed downhill during a tailplane stall event, at what point would the critical AOA of the wing have been exceeded? Furthermore, the pusher is inhibited below a certain altitude I am sure (Q pilots help me here?) The aircraft was already at 1500ft AGL... How much time would they have had to have a tailplane stall event, then get the airplane excessively slow so that the stick shaker and pusher activated prior to impact? Maybe if the airplane rolled over... I suppose a high LF could induce a high enough AOA, maybe.

I guess I am just spit ballin' here, but obviously something is missing. I don't think I would have expected a stick pusher activation with a tailplane stall event...

I am really curious to see what the rest of you think.

 

[AV1ATRX]

It's not impossible at all.....

NOTE WHAT IS SAID AT 31 MINUTES AND ZERO SECONDS.......

http://video.google.com/videoplay?do...31008391&hl=en

I'm on dial-up. What does it say?

 

[bailout]

I am not so sure about this...

I agree that the stick shaker/pusher activates at and beyond the wing's critical (excessively positive) AOA. But here is the thing... Increased airspeed aggrevates the stalled condtion in the case of a tailplane stall, since it causes the AOA to become more "negative." Since the nose would have been headed downhill during a tailplane stall event, at what point would the critical AOA of the wing have been exceeded? Furthermore, the pusher is inhibited below a certain altitude I am sure (Q pilots help me here?) The aircraft was already at 1500ft AGL... How much time would they have had to have a tailplane stall event, then get the airplane excessively slow so that the stick shaker and pusher activated prior to impact? Maybe if the airplane rolled over... I suppose a high LF could induce a high enough AOA, maybe.

I guess I am just spit ballin' here, but obviously something is missing. I don't think I would have expected a stick pusher activation with a tailplane stall event...

I am really curious to see what the rest of you think.

The time lines should tell. They did say there were major pitch changes up and down, so..

My thinking, is you get the tail stall, the nose drops, auto disconnect, then the pilots pull agressively backwards on the yoke, the aircraft pitches up radically, stick shaker/pusher goes off, dropping nose again, pilot pulls back, you still have the tail stall going on but now too slow, wing over stall, plane either rolls over, or flat 'spins', or rolls one way or the other, and hits the ground flat.

 

[airplane wizard]

Why would the stick shaker activate if it was a tail stall, unless it was actually a wing stall? Or is it possible to have both at the same time?

Maybe they stalled the wing when they pitched up to recover from the tail stall.

 

[ackattacker]

I am not so sure about this...

I agree that the stick shaker/pusher activates at and beyond the wing's critical (excessively positive) AOA. But here is the thing... Increased airspeed aggrevates the stalled condtion in the case of a tailplane stall, since it causes the AOA to become more "negative." Since the nose would have been headed downhill during a tailplane stall event, at what point would the critical AOA of the wing have been exceeded? Furthermore, the pusher is inhibited below a certain altitude I am sure (Q pilots help me here?) The aircraft was already at 1500ft AGL... How much time would they have had to have a tailplane stall event, then get the airplane excessively slow so that the stick shaker and pusher activated prior to impact? Maybe if the airplane rolled over... I suppose a high LF could induce a high enough AOA, maybe.

I guess I am just spit ballin' here, but obviously something is missing. I don't think I would have expected a stick pusher activation with a tailplane stall event...

I am really curious to see what the rest of you think.

I don't know about the pusher on a Q-400, but on the ATR the pusher is not tied in with the radio altimeter and is never inhibited in flight except for 10 seconds after takeoff.

Also, low speed is not a prerequisite for a main-wing stall. Only high angle of attack. Large excursion in pitch can cause a stall at any speed.

 

[Raskal]

Maybe they stalled the wing when they pitched up to recover from the tail stall.

The AOA had to go beyond positive limits to get a pusher-it won't go otherwise, to get there with flaps would have required a considerable change in angle. A recovery from a tailplane stall involves not only back pressure on the yoke but flaps being retracted, everything I've been taught says back pressure alone won't be enough.

To get a pusher means something else or a major upset in attitude...I don't think we'll know for a while.