Continental TurboProp crash inbound for Buffalo
Join Date: Feb 2000
Location: asia
Posts: 542
Likes: 0
Received 0 Likes
on
0 Posts
has anyone watched the animated reconstruction mentioned earlier on liveleak?
It doesn't seem to me to tie in with the facts as already presented - i thought there was a 180 and flat crash, not the nosedive this appears to show.
It doesn't seem to me to tie in with the facts as already presented - i thought there was a 180 and flat crash, not the nosedive this appears to show.
Guest
Posts: n/a
stickyb
I thought it fairly accurate, given the published and official info. One thing missing was the re-roll to 105 degrees. the last half second showed a partial nose drop from level, not a "nose-dive". On the whole, I thought it was helpful, and welcome from an agency that seemingly seems connected to its mission, NTSB.
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
jimclearsky,
"Deep Stall" or "Superstall" is a condition only encountered by T-Tail jets.
Propeller aircraft are not susceptible to deep stall, since the propwash will provide sufficient airflow over the elevators. (The exception might be for rear-mounted props, but these are very rare.)
In addition, non-swept wings have much more benign stall characteristics; generally they pitch down after the onset of stall, swept wings, unless specifically designed otherwise, will expose pitch-up tendencies when stalled.
The chapter about stall in "Handling the Big Jets" is very enlightening, if you can get hold of a copy. (The book is primarily about the differences between jets and props.)
Bernd
"Deep Stall" or "Superstall" is a condition only encountered by T-Tail jets.
Propeller aircraft are not susceptible to deep stall, since the propwash will provide sufficient airflow over the elevators. (The exception might be for rear-mounted props, but these are very rare.)
In addition, non-swept wings have much more benign stall characteristics; generally they pitch down after the onset of stall, swept wings, unless specifically designed otherwise, will expose pitch-up tendencies when stalled.
The chapter about stall in "Handling the Big Jets" is very enlightening, if you can get hold of a copy. (The book is primarily about the differences between jets and props.)
Bernd
Last edited by bsieker; 17th Feb 2009 at 17:51.
Join Date: Jan 2008
Location: Denmark
Age: 79
Posts: 158
Likes: 0
Received 0 Likes
on
0 Posts
Conan The Barber
I agree fully with the points you are bringing forward in #538.
Actually acc. #520 speed was 134 kts when flaps AND gear were selected down (line 3 in the text) - i.e. the aircraft flew in a clean configuration with 134 kts, (if the info in #508 is correct).
I am puzzled!
And I miss another important information: Where were the throttles positioned at the time of flaps and gear selections?
At idle? or?
brgds
Actually acc. #520 speed was 134 kts when flaps AND gear were selected down (line 3 in the text) - i.e. the aircraft flew in a clean configuration with 134 kts, (if the info in #508 is correct).
I am puzzled!
And I miss another important information: Where were the throttles positioned at the time of flaps and gear selections?
At idle? or?
brgds
Last edited by grebllaw123d; 17th Feb 2009 at 21:11.
Gender Faculty Specialist
Just reading the report in the Aviation Herald link.
It says that the gear was selected down and then Flap 15 was selected, 20 seconds later Flap 10 was reached.
To me this implies that the flaps were selected from ZERO to 15 after the gear was selected down, it certainly doesn't take 20 seconds for the flaps to travel from 10 to 15. My company SOP is Flap 5 then gear down, Flap 10, Flap 15, Flap 35 (If using 35 for landing).
Does anyone else read it like that? And does anyone know the SOP's for Colgan?
Bsieker, if the Q400 wasn't prone to deep stalls then would it still be fitted with a stick pusher?
It says that the gear was selected down and then Flap 15 was selected, 20 seconds later Flap 10 was reached.
To me this implies that the flaps were selected from ZERO to 15 after the gear was selected down, it certainly doesn't take 20 seconds for the flaps to travel from 10 to 15. My company SOP is Flap 5 then gear down, Flap 10, Flap 15, Flap 35 (If using 35 for landing).
Does anyone else read it like that? And does anyone know the SOP's for Colgan?
Bsieker, if the Q400 wasn't prone to deep stalls then would it still be fitted with a stick pusher?
Join Date: Jul 2007
Location: Germany
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
Chesty Morgan
Bsieker, if the Q400 wasn't prone to deep stalls then would it still be fitted with a stick pusher?
Bsieker, if the Q400 wasn't prone to deep stalls then would it still be fitted with a stick pusher?
I recommend again "Handling the Big Jets" to understand "Stall" vs. "Deep Stall":
Amazon.com: Handling the Big Jets: An Explanation of the Significant Difference in Flying Qualities Between Jet Transport Aeroplanes and Piston Engined Transpor: David P. Davies: Books
[EDIT: nonsense deleted.]
Bernd
Last edited by bsieker; 17th Feb 2009 at 22:12.
stickyb;
The "animation" is strictly from someone's imagination and basic animation skills, and nothing more.
While such animations can be done by anyone with sufficient skill in the standard programs (3D Studio, Corel, Flash, etc), for an animation to be useful and not misleading, it must be driven by the flight data. Nobody beyond the NTSB will have that data. Even if they had, it isn't just anybody who would have the kind of proprietary software that is capable of turning digital data into an accurate representation/animation.
This illustrates the very significant problem with cartoons vs data-driven accident investigation tools. Because it looks "real", it is taken as such by most viewers, when in fact it is just a figment of someone's imagination using the information made available from the NTSB briefings.
So you are right - the animation, a poor one at that, does not tie in with the known facts and should be dismissed out-of-hand. The sound-track is your first clue...
PJ2
has anyone watched the animated reconstruction mentioned earlier on liveleak?
It doesn't seem to me to tie in with the facts as already presented - i thought there was a 180 and flat crash, not the nosedive this appears to show.
It doesn't seem to me to tie in with the facts as already presented - i thought there was a 180 and flat crash, not the nosedive this appears to show.
While such animations can be done by anyone with sufficient skill in the standard programs (3D Studio, Corel, Flash, etc), for an animation to be useful and not misleading, it must be driven by the flight data. Nobody beyond the NTSB will have that data. Even if they had, it isn't just anybody who would have the kind of proprietary software that is capable of turning digital data into an accurate representation/animation.
This illustrates the very significant problem with cartoons vs data-driven accident investigation tools. Because it looks "real", it is taken as such by most viewers, when in fact it is just a figment of someone's imagination using the information made available from the NTSB briefings.
So you are right - the animation, a poor one at that, does not tie in with the known facts and should be dismissed out-of-hand. The sound-track is your first clue...
PJ2
While such animations can be done by anyone with sufficient skill in the standard programs (3D Studio, Corel, Flash, etc), for an animation to be useful and not misleading, it must be driven by the flight data. Nobody beyond the NTSB will have that data. Even if they had, it isn't just anybody who would have the kind of proprietary software that is capable of turning digital data into an accurate representation/animation.
This illustrates the very significant problem with cartoons vs data-driven accident investigation tools. Because it looks "real", it is taken as such by most viewers, when in fact it is just a figment of someone's imagination using the information made available from the NTSB briefings.
So you are right - the animation, a poor one at that, does not tie in with the known facts and should be dismissed out-of-hand. The sound-track is your first clue...
PJ2
This illustrates the very significant problem with cartoons vs data-driven accident investigation tools. Because it looks "real", it is taken as such by most viewers, when in fact it is just a figment of someone's imagination using the information made available from the NTSB briefings.
So you are right - the animation, a poor one at that, does not tie in with the known facts and should be dismissed out-of-hand. The sound-track is your first clue...
PJ2
Join Date: Jan 2001
Location: Dallas, TX USA
Posts: 739
Likes: 0
Received 0 Likes
on
0 Posts
To all,
A stick pusher is normally added to an aircraft if it displays some behavior during the stall, that deviates from the benign behavior of consistently dropping the nose wings level. It's not uncommon to add it to an upgraded version of an aircraft, when more powerful turboprop engines (more powerful than the original design) cause some new disruption of airflow over the wing during a stall, resulting in one wing dropping more that the other in the stall. So the need for a stick pusher may not be related to deep stall at all, however since a wing drop during a stall could result in a spin, the stick pusher is used to prevent the stall in the first place.
I don't know why the stick pusher is used on the Q400, but again, it's normally used to mitigate some less than benign stall characteristic.
Edited to add:
I found this old article from Flight Global in 2000 (a pdf photocopy of the then magazine article), explaining the stall characteristics of the Q400, and the need for the stick pusher. The aircraft indeed has some "propeller effect" from the new engines. In fact this link has an entire flight test article for the Q400. Just click on the magazine pages to the left, to see the other pages.
stick pusher | roll control | stall | 2000 | 1351 | Flight Archive
A stick pusher is normally added to an aircraft if it displays some behavior during the stall, that deviates from the benign behavior of consistently dropping the nose wings level. It's not uncommon to add it to an upgraded version of an aircraft, when more powerful turboprop engines (more powerful than the original design) cause some new disruption of airflow over the wing during a stall, resulting in one wing dropping more that the other in the stall. So the need for a stick pusher may not be related to deep stall at all, however since a wing drop during a stall could result in a spin, the stick pusher is used to prevent the stall in the first place.
I don't know why the stick pusher is used on the Q400, but again, it's normally used to mitigate some less than benign stall characteristic.
Edited to add:
I found this old article from Flight Global in 2000 (a pdf photocopy of the then magazine article), explaining the stall characteristics of the Q400, and the need for the stick pusher. The aircraft indeed has some "propeller effect" from the new engines. In fact this link has an entire flight test article for the Q400. Just click on the magazine pages to the left, to see the other pages.
stick pusher | roll control | stall | 2000 | 1351 | Flight Archive
Last edited by Flight Safety; 17th Feb 2009 at 18:50.
Gender Faculty Specialist
to understand "Stall" vs. "Deep Stall
The need for a stick pusher is because the aeroplane has failed to meet the stalling requirements by aerodynamic means. This could be due to several reasons.
1. The natural stall of the aeroplane is not acceptable.
2. The manufacturers are unwilling to test the aeroplane past Max CL.
3. The manufacturers have decided that the aircraft structure would not be strong enough to handle either the buffet and or the big nose down moment.
Number 1 implies that an aircraft that has benign handling characteristics in the stall regime does not require a stick pusher. It makes no mention of T-Tails, swept wings or jet engines.
Join Date: Sep 2008
Location: MI
Posts: 570
Likes: 0
Received 0 Likes
on
0 Posts
Folks, I hope you get a chance to read this before it's deleted. (My last one with this info disappeared ??) It was directed at "bsieker" for a remark of his:
"B737 is not a T-Tail and as such not susceptible to Deep Stalls. It still has a stick pusher, as do all airliners except the side-stick-operated FBW airbus."
No matter what "Wiki" or any other 'search engine' says, a 'deep stall' is possible in any airplane.
And, all airplanes do NOT have stick pushers.
Carry some extra knots, PLEASE!
"B737 is not a T-Tail and as such not susceptible to Deep Stalls. It still has a stick pusher, as do all airliners except the side-stick-operated FBW airbus."
No matter what "Wiki" or any other 'search engine' says, a 'deep stall' is possible in any airplane.
And, all airplanes do NOT have stick pushers.
Carry some extra knots, PLEASE!
Join Date: Jan 2008
Location: Sonoma, CA, USA
Age: 79
Posts: 143
Likes: 0
Received 0 Likes
on
0 Posts
134 Kts.?
Re: Post 508 --
How long was the aircraft flying at 134 kts? Consider the angle of attack at 134 kts.
In looking at photos of the Dash 8 400, the flaps look like a slotted Fowler or Semi-fowler type.
I'll bet that there was ice accumulation on the bottom of the wings behind the boots because of the slow airspeed and high angle of attack at 134 kts. There was probably ice buildup in the slot forward of the flaps.
That's why company sop was 190 kts in icing conditions. When the flaps were lowered, the leading edge airfoil of the Fowler flap which is supposed to provide added lift was spoiled because of ice accumulation.
We worried about this in the DC-3s though the 3 had a split trailing edge flap and no gap. But ice accumulation behind the boots was a worry. If the airspeed got too slow, we had no choice but to descend in order to keep the speed up.
certainly company sop to hold at 190 in icing conditions.
In looking at photos of the Dash 8 400, the flaps look like a slotted Fowler or Semi-fowler type.
I'll bet that there was ice accumulation on the bottom of the wings behind the boots because of the slow airspeed and high angle of attack at 134 kts. There was probably ice buildup in the slot forward of the flaps.
That's why company sop was 190 kts in icing conditions. When the flaps were lowered, the leading edge airfoil of the Fowler flap which is supposed to provide added lift was spoiled because of ice accumulation.
We worried about this in the DC-3s though the 3 had a split trailing edge flap and no gap. But ice accumulation behind the boots was a worry. If the airspeed got too slow, we had no choice but to descend in order to keep the speed up.
Join Date: Jan 2008
Location: Denmark
Age: 79
Posts: 158
Likes: 0
Received 0 Likes
on
0 Posts
nooluv
Just to clarify: An approach speed of 137 kts is the correct one (using flaps 15 for landing and corrected for icing conditions) according information given in #508.
But what looks strange and puzzling is the information given in the NTSB briefing that the aircraft - apparently - flew 134 kts without any flaps selected - an unusually low speed.
In any case ATC has no way of knowing what the actual minimum speed for an aircraft is, as the actual flaps setting is not known to them.
But what looks strange and puzzling is the information given in the NTSB briefing that the aircraft - apparently - flew 134 kts without any flaps selected - an unusually low speed.
In any case ATC has no way of knowing what the actual minimum speed for an aircraft is, as the actual flaps setting is not known to them.
Join Date: Jan 2009
Location: alameda
Posts: 1,053
Likes: 0
Received 0 Likes
on
0 Posts
Stick Pusher DEAR SIR ALL AIRLINERS DON'T HAVE PUSHERS!!!!
I can assure you that ALL AIRLINERS do NOT have pushers.
The DC9, which can get into a deep stall, which is why vortillions or chin strakes are fitted DOES NOT HAVE A PUSHER. (there is a unique hydraulic ram to ensure ''nose down'' elevator input in a deep stall, but it is not in any way a stick pusher)
It is T TAIL SWEPT WING JET.
IT has a very effective stall warning system with ligts, horns and SHAKER but NO PUSHER.
The warnings start at stall plus 10percent...sometimes more if accelerated.
There seems to be a lot of stuff being put out there.
ALSO, about GEAR UP and positive rate. ALL of our maneuvers at our airline require a positive rate of climb prior to gear retraction. For what it is worth, we don't even change configuration in a windshear encounter.
That broad statement about ALL AIRLINERS was so sure, that I even got out my manual to double check~!
I do hope all of you pilots out there in icing consider configuration changes at higher speeds and altitudes to allow for emergency recovery and keep your hand on the handle you are moving...IF THINGS GET WORSE WHEN YOU MOVE SOMETHING>>>MOVE IT BACK! (again, from the idiots guide to flying)
The DC9, which can get into a deep stall, which is why vortillions or chin strakes are fitted DOES NOT HAVE A PUSHER. (there is a unique hydraulic ram to ensure ''nose down'' elevator input in a deep stall, but it is not in any way a stick pusher)
It is T TAIL SWEPT WING JET.
IT has a very effective stall warning system with ligts, horns and SHAKER but NO PUSHER.
The warnings start at stall plus 10percent...sometimes more if accelerated.
There seems to be a lot of stuff being put out there.
ALSO, about GEAR UP and positive rate. ALL of our maneuvers at our airline require a positive rate of climb prior to gear retraction. For what it is worth, we don't even change configuration in a windshear encounter.
That broad statement about ALL AIRLINERS was so sure, that I even got out my manual to double check~!
I do hope all of you pilots out there in icing consider configuration changes at higher speeds and altitudes to allow for emergency recovery and keep your hand on the handle you are moving...IF THINGS GET WORSE WHEN YOU MOVE SOMETHING>>>MOVE IT BACK! (again, from the idiots guide to flying)
Join Date: Jan 2009
Location: alameda
Posts: 1,053
Likes: 0
Received 0 Likes
on
0 Posts
robert campbell
I too am wondering why the plane was at 134knots clean. I hope someone will clue us in.
while some find solace in slowing to the min speed to change flap settings, in ice I will change flaps at the max speed allowed.
In one turboprop I flew, many many many years ago, I got an invalid stall warning. It was a simple short circuit in the system...but both computers were involved.
I have to ask if the stall shaker and pusher could have been triggered by something other than a genuine stall. I do hope the NTSB will take a good look at that scenario.
I too am wondering why the plane was at 134knots clean. I hope someone will clue us in.
while some find solace in slowing to the min speed to change flap settings, in ice I will change flaps at the max speed allowed.
In one turboprop I flew, many many many years ago, I got an invalid stall warning. It was a simple short circuit in the system...but both computers were involved.
I have to ask if the stall shaker and pusher could have been triggered by something other than a genuine stall. I do hope the NTSB will take a good look at that scenario.
Join Date: Jan 2003
Location: Europe, Africa
Posts: 78
Likes: 0
Received 0 Likes
on
0 Posts
What puzzles me indeed as is with others is the low speed they where flying (134 kts.) Our company minimum speed for maneuvering is 135 kts. and that is at low weights. 
They where descending at low speed.
I was learned very early on to watch my speed especially when you where descending. This because if you stall while descending you lower wing would drop. Resulting in a uncontrolled roll into that lower wing.
This in contrast with a climbing turn where you high wing would drop and so leveling the airplane out.
They where descending at low speed.
I was learned very early on to watch my speed especially when you where descending. This because if you stall while descending you lower wing would drop. Resulting in a uncontrolled roll into that lower wing.
This in contrast with a climbing turn where you high wing would drop and so leveling the airplane out.
Last edited by D-OCHO; 17th Feb 2009 at 20:22. Reason: Stupidity :}
Sorry Bernd, I'll have to disagree on some of your points.
Deep stall is condition encountered by any aeroplane which elevators lose effectiveness when horizontal stabilizer gets into wake from stalled wing and there is no pronounced pitch-down in stall. Even F-104 and DC-6 can suffer from it if CoG is particularly unfavourable. T-tailed transport category aeroplanes are particularly vulnerable because of highly loaded wings and relatively inefficient elevator (relative to aerobatic aeroplanes, that is, it meets certification criteria and works well under normal circumstances) that gets behind the wing just as it's about to stall.
Sorry but propwash on twin turboprops does not affect the elevators, fortunately, I don't know if I could live through autopilotless days with yoke vibrating from propwash. One of the first things I found amusing when starting flying ATR was that there was no trim change with power change, but speed change did require quite a lot of trim, compared to small piston twins. Whether propwash would find its way to the elevators of ATR spinning flatly, I don't know and never had the intention of finding out. ATR was not keen on finding out either as the aeroplane was provided with stick pusher. IIRC shaker activated at 12.5° AoA normal condition and 8.5° icing conditions (shift was automatic, with turning the flight controls heat on) but pusher always fired at 15°.
If the swept wing's tip stalls first, center of pressure moves forward giving pitch-up as the wing stalls. Not good. Therefore to meet certification requirements, wing has to stall root first and considerable washout is required to achieve this. As for benign stall characteristics, turboprop's straight and thick wings do stall nicer than thin, swept ones but they still have more bite than the wings of Cessna 172.
IIRC, our B732s didn't have pushers and B727 do or don't have pushers depending on their reg i.e. local CAA's standards of airworthiness. I stand to be corrected on this, though.
Originally Posted by bsieker
"Deep Stall" or "Superstall" is a condition only encountered by T-Tail jets.
Originally Posted by bsieker
Propeller aircraft are not susceptible to deep stall, since the propwash will provide sufficient airflow over the elevators.
In addition, non-swept wings have much more benign stall characteristics; generally they pitch down after the onset of stall, swept wings, unless specifically designed otherwise, will expose pitch-up tendencies when stalled.
B737 is not a T-Tail and as such not susceptible to Deep Stalls. It still has a stick pusher, as do all airliners except the side-stick-operated FBW airbus.
Last edited by Clandestino; 17th Feb 2009 at 20:30. Reason: typo
protecthehornet
if I follow this presumption than I can't imagine what caused the oscillations in the aircraft.
Can you fill in the blanks. Just what should be found on the DFDR?
I have to ask if the stall shaker and pusher could have been triggered by something other than a genuine stall. I do hope the NTSB will take a good look at that scenario.
Can you fill in the blanks. Just what should be found on the DFDR?