Colgan 3407 Down in Buffalo

[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.

 

[twighead]

I'd watch it before my next flight then.....

Don't worry I already did earlier. That's how I knew I had never seen it before.

 

[poydras]

Godspeed to you all

 

[GINCHBLASTER]

I've had two days worth of discussions, and a few instructional videos to help me think about this crash. These poor pilots had seconds. Fly safe guys!

 

[ReverseSensing]

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.

Pusher in the Q400 is inhibited below 500' AGL.

The Q400 has the squirreliest airspeed tape you've ever seen. Even in non-upset conditions, the tape swings wildly up and down (for example in windshear and/or turbulence). This makes for some fairly sporty times when you're recovering (in the sim) from upsets, etc.

Without ice, in the sim, I always thought the stall and recovery characteristics were pretty docile. But I never saw a tail stall in the sim. Not part of the curriculum.

 

[Singlecoil]

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 think you may be oversimplifying things a bit there.
Tail stall occurs when the horizontal stabilizer's critical angle of attack (negative angle of attack) is exceeded or there is airflow separation about the horizontal stabilizer due to ice on the leading edge. The horizontal stabilizer (tail) experiences the highest demand for negative lift (tail down force) and the most negative angle of attack when the wing's center of pressure (lift) is furthest aft of the center of gravity. This occurs at higher airpeeds and when the flaps are extended. If you think about it, when you accelerate or when you add flaps you need to push on the yoke, or add more tail down force to keep the nose from rising. This act of pushing is what increases the angle of attack on the tail (in the negative direction if you will) and can lead to a tail stall.

 

[Flightjock30]

As someone of a friend who works for the NTSB this is what REALLY happened.....
autopilot was engages, one of the wing's de-icing system was working, the other did not work (due to a mechanical failure that is still under investigation at this moment....). The crew lost control of the aircraft as it spiraled to the ground in a nose dive from loss of lift on one of the wings.
A lift imbalance due to one wing unable to melt the ice off caused this crash!
Godspeed to all!

 

[Captzaahlie]

bad link earlier sorry:

http://video.google.com/videoplay?docid=3493859021331008391

note what is said at 31 minutes...

 

[LowlyPropCapt]

As someone of a friend who works for the NTSB this is what REALLY happened.....
autopilot was engages, one of the wing's de-icing system was working, the other did not work (due to a mechanical failure that is still under investigation at this moment....). The crew lost control of the aircraft as it spiraled to the ground in a nose dive from loss of lift on one of the wings.
A lift imbalance due to one wing unable to melt the ice off caused this crash!
Godspeed to all!

So, boots melt ice? Damn. I have thinking wrong for the past 11 years...

Your "buddy" at the NTSB already has it figured out and released the information to you? Then you post your neat tidbit on a public internet forum? Uh huh.

I don't know what your adgenda is here, but this smells like bull$hit. The NTSB is normally tighter than that.

 

[satpak77]

I can guarantee you that the NTSB has not "released" information to any "buddies"

 

[Captzaahlie]

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

In a nut shell NASA test pilots say that NO Aircraft has ever been built to operate in "SLD" ICING CONDITIONS...... (super sized droplet freezing rain conditions)


You don't have to watch the full video, you can just drag the bar to that time position...

http://video.google.com/videoplay?docid=3493859021331008391

note what is said at 31 minutes...