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Continental TurboProp crash inbound for Buffalo

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Continental TurboProp crash inbound for Buffalo

Old 22nd Feb 2009, 08:05
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I guess the Saab 340 does have a tailplane stall problem...Ready to fight the wrong war.
At least it had until the leading edges of the horizontal stab were modified to the version it has today, i.e. pointing upwards.

Last edited by Tjosan; 23rd Feb 2009 at 18:18.
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Old 22nd Feb 2009, 08:40
  #802 (permalink)  
 
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The latest scenarios discussing extreme trim settings, except protectthehornet's, seem to assume power was increased immediately at stall shaker/pusher activation and AP disconnect, thereby aggravating the nose-up condition. Do we have NTSB-supplied facts supporting that? I only remember Chealander saying power was increased, without mentioning at which point in the chain of events. Please correct me if I'm wrong.
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Old 22nd Feb 2009, 15:47
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I only remember Chealander saying power was increased, without mentioning at which point in the chain of events
I was pretty sure he said the power was increased immediately following the stick shaker (in a news conference 3 days after the accident). Applying full power at the stick shaker (especially if the low speed situation was realized at the same time) would be a very natural reaction.
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Old 22nd Feb 2009, 16:04
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I have seen the NASA tail-stall video, although not as part of official training for any aircraft I have flown (not even the DHC6!). I have NEVER heard of anyone having a tail-stall scenario in a simulator session...in fact I highly doubt that simulators are even programed to simulate them. I just find it way too hard to believe that in the heat of the situation that the pilots would decide to try to recover from a tail-staill when so much of their training would point them to other more appropriate recoveries.

I think this is the only time that people actually practice tail-stalls: YouTube - Learning how to tail stall in stour-ramparts
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Old 22nd Feb 2009, 19:32
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Originally Posted by DHC6tropics
I have seen the NASA tail-stall video, although not as part of official training for any aircraft I have flown (not even the DHC6!). I have NEVER heard of anyone having a tail-stall scenario in a simulator session...in fact I highly doubt that simulators are even programed to simulate them. I just find it way too hard to believe that in the heat of the situation that the pilots would decide to try to recover from a tail-staill when so much of their training would point them to other more appropriate recoveries.
AFAIK there is one (and only one) training device which does simulate a tailplane stall - it's a portable device developed by NASA and Buerle Applied Research, as part of the same programme that had the Twin Otter tests and which produced the video referred to.

It's a portable, fixed base, device, which the NASA icing guys have taken "on the road" to various places and which they give you a one hour or so "icing scenarios" session. There's a link somewhere in this thread to an "Aviation News Network" report which is basically about the device.

Obviously you wouldn't mistake this for a normal simulator session (as part of normal training/conversion).
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Old 22nd Feb 2009, 20:19
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when I read the bit about the Lear 60 being so powerful, the brakes wouldn't hold

it sounds to me like that plane has weak brakes, not strong engines.
So would you say the Harrier has weak brakes, because when you put full power on with the brakes on, it moves .... Up

NoD
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Old 22nd Feb 2009, 20:32
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It ain't necessarily so; it ain't necessaril...........

In any case, the early ones didn't move in any direction.
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Old 22nd Feb 2009, 21:18
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I must admit I put the power on very slowly most days. the performance of the Q400 is so good, it puts a strain on your neck at moderate weights, even at fully reduced T/O power. Besides, your bag goes flying backwards to the door if you get energetic on the levers.

Unless you are familiar with the Q400, you'd be surprised at how the power comes in- lots of pitch change, yaw and acceleration. Must be Canadian humour- compared to all other commercial equivalent types, it's a beast.

When you get used to it, it's no problem, but for newly qualified crew, it can bite.

with a flap 5 dep, 3000fpm is pretty normal.....
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Old 23rd Feb 2009, 09:27
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Prop Nursing

Robert Campbell is onto it. Haven't flown the 400, but from time on 100 series, on strips with loose gravel, composite blades need to be nursed. Damage on rear of blades was evidence of standing take-offs, while damage on front of blades showed evidence of too much reverse thrust. Power application with aircraft stationary can result in strong vortices reaching to ground level, even with a high wing aircraft.
Trick was rolling starts, and careful with reverse on landing, back to ground idle before aircraft slowed down too much.
Sorry about the thread drift, no bearing on Buffalo accident.

Last edited by Norm Sanson; 23rd Feb 2009 at 10:09.
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Old 23rd Feb 2009, 11:22
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I can understand how the 31-deg pitch-up occured, but how did the following 76-deg nose-down pitch movement (to 45-deg aircraft nose down) occur? Surely a stall at 31-deg but with full power on a powerful aircraft would not need such a large nose-down movement, or for the aircraft to pitched down so far to accelerate back out of the stall.

Last edited by dangrey; 23rd Feb 2009 at 16:21.
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Old 23rd Feb 2009, 12:31
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I seem to recall that Chealander stated in a briefing that full power was applied 6 seconds after the upset began. What the aircraft's pitch atitiude was at the time of power increase, and how pitch atitude was effected by the power increase, I don't know.

It would really be nice to have DFDR traces available.
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Old 23rd Feb 2009, 12:49
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This just in...

Received from colleague in US of A.
I cannot vouch for its accuracy or authenticity
This was circulated by Intam to Southwest Airlines Pilots:


"There is a potentially significant hazard concerning the ILS to runway 23 in BUF.
Information has been received indicating it is possible to obtain a significant nose pitch up, in some cases as much as 30 degrees, if the glide slope is allowed to capture before established on centerline. Pilots who are preparing to configure and land have the potential to experience abrupt pitch up, slow airspeed, and approach to stall if conditions present themselves in a certain manner.
This effect is the result of an earthen obstruction close enough to the ILS to affect the integrity of the glide slope signal. This has resulted in the issuance of an advisory given on ATIS which states that "the ILS Glide Slope for runway 23 is unusable beyond 5 degrees right of course." When attempting to intercept the runway 23 ILS from right traffic, the ILS glide slope indication may read full deflection down. Just prior to intercept it may then move up in such as manner as to enable approach mode to capture in such a way as to result in a nose up pitch and loss of airspeed. Southwest Airlines has issued a notice reading: "Until further notice, when executing the KBUF ILS/LOC Runway 23, DO NOT select Approach Mode until established on the localizer inbound."
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Old 23rd Feb 2009, 12:56
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Flight Article WK 24th Feb-2 March

Thumbing through Flight International this morning I came across an article on the Buffalo disaster, page 11.

It was interesting to note that the major focus of the investigation has swung from a severe icing encounter, to one of "a complex chain of events".

I dont become a Q400 driver until later this year, but reviewing the data quoted in the article, the speeds flown and the Vref quoted all seem sensible. As do the configuration changes for the impending landing.

However, the quoted sequence of events following the stick shaker is confusing, maybe a current Q400 driver could clarify.

The stick shaker activated 34s after selection of flap to 15 followed by the stick pusher. Just after the pusher activated, the aircraft pitched UP 31 and the AP disengaged. The crew then selected gear and flap up. The aircraft then entered high rate, left and right roll excursions and pitched 45 nose down. It wasnt until 6s after the upset that the crew applied max power.

Additionally, the crew had activated the icing switch to increment the shaker/pusher speeds by 20kts. I understand this to mean they had a significant buffer between stall warning, and actual aerodynamic stall.
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Old 23rd Feb 2009, 12:59
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I can how the 31-deg pitch-up occured, but how did the following 76-deg nose-down pitch movement (to 45-deg aircraft nose down) occur? Surely a stall at 31-deg but with full power on a powerful aircraft would not need such a large nose-down movement, or for the aircraft to pitched down so far to accelerate back out of the stall.
Put yourself in the position of the 2 pilots. How much of a shock do you think it would be to suddenly find yourself in a highly unusual attitude in poor weather, at night, and at low speed?

Even on departure, 18degs nose up is a 'normal' maximum. It is planned and expected, but still feels steeper than it is. I'm sure 31degs felt more like a vertical climb and perhaps led to an extreme recovery manoeuver. Big a/c, powerful engines, lots of inertia - very easy to see how it could happen once a crew becomes scared and disoriented.

Very few operators have an unusual attitudes recovery training programme, yet accident investigators have identified loss of control incidents (presumably resulting from UAs) as the major factor in fatal commercial accidents in recent years.
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Old 23rd Feb 2009, 13:34
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Can the -400 autopilot be lightly overpowered without causing an automatic disengagement of the auotpilot? If so at what point would the autotrim run?
Hypothetical scenario: early capture of GS; autopilot demands climb. Crew overpowers autos to maintain altitude causing the trim to run nose up; subsequently autopilot disengages / is disengaged, resulting in a large nose up pitch change. Trim change accentuated by speed reduction / flap deployment.
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Old 23rd Feb 2009, 13:48
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This just in...

--------------------------------------------------------------------------------

Received from colleague in US of A.
I cannot vouch for its accuracy or authenticity
This was circulated by Intam to Southwest Airlines Pilots:
Old news, already been posted here. Learn to use the Pprune search function so you don't embarrass yourself.
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Old 23rd Feb 2009, 16:40
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Why would anyone want to arm the G/S before joining the LOC? Too much risk of departing cleared altitude too early. G/S capture takes you down (or up!) when you may not want that to happen. Seems a daft SOP to allow arming of the APP mode early....lots of altitude restrictions/CFIT issues etc to comply with...I think SWA just made themselves look a bit silly...this is a red herring IRTO the accident.......
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Old 23rd Feb 2009, 17:42
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Baritone

Baritone - sorry, but it takes more than that to embarrass me! I'd just received the article, I didn't have time to search for any previous posting of same, and I thought it might have been of importance, or at least interest, to the Pprune readership.
My heartfelt apologies if I have transgressed and spoiled your otherwise perfect day.
I imagine you are probably more of a castrato than a baritone.
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Old 23rd Feb 2009, 18:05
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Old Lizzy....

When cleared for an approach, and within the distance/angle parameters, it is commonplace to arm the approach, so I don't think it was an embarrassment (SWA) nor was it an inappropriate post.
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Old 23rd Feb 2009, 22:54
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Originally Posted by cojones
I'd just received the article, I didn't have time to search for any previous posting of same, and I thought it might have been of importance, or at least interest, to the Pprune readership.
Well, it IS kind of annoying when people post something "new!" to a thread when it's already been posted several times before. It's on a par with those who say "I haven't read the previous 600 posts but thought you'd find this interesting" and then repeat something already posted on the first page. If the thread is important enough for you to contribute to, perhaps it's important enough to read first?
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