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Tail Stalls-EXCELLENT discussion worth reading

Talian

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Although it's really early on in the investigation, I can't help but wonder about tail icing considering that the CVR shows pitch and roll upset immediately after flaps we set .
I remember the Washington state crash of a Jetstream 31 operated by United Express in 89 or 90.
This specific accident was directy related to tail icing. In this case the aircraft stalled over the threshold when elevator was applied to transition from the descent into the flare.
This should be very interesting to see what the conclusion of this one reveals.

My thoughts and prayers are with all those directly involved.
 

Oakum_Boy

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What's astonishing is that tailplane icing was only a brief mention in ground school a decade ago. Never saw it in the sim.
 

spudskier

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What's astonishing is that tailplane icing was only a brief mention in ground school a decade ago. Never saw it in the sim.

Guessing that'll change.. maybe even a new ops spec that says no more than flaps 15 in icing?
 

JettBoii

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The NTSB stating that the crew was concerned over "significant ice on the windows". Was the accretion rate so high that the window heat could not clear it? SLD? No idea. Very very scary indeed. As heartbreaking as this accident is I hope this investigation helps all of us no matter what we fly operate safer in icing conditions.
 

Metrojet

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100-1/2

OVER-N-DUN!
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NASA had an awesome article in one of the Pro Mags detailing the lengths they went in a Twin Otter to research Tail Ice and adverse flight regimes. Seem to recall T-tail aircraft were extremely susceptible to Tail Stalls after introduction of 20' or more of flaps. Don't know Colgan SOP's but speculate with most that landing configurations of Gear and final flaps would be elected just outside the marker or GS intercept where this Q4 lost it. I also could swear following NASA's research in the late 90's an AC was issued recommending minimal flaps for moderate/extreme Ice encounters to assure sufficient boundary layer flow across the tail. Anyone with any time or experience in the Q4 or strait -2's know they kind of fly like they are dragging their arse through the air. With that huge fuse out in front of the C(enter)P(ressure) on the Q4, if they were not anticipating the potential for atail stall, they would not have settled in their heads that when the extra flaps were thrown out that the tail stall would require pushing the nose forward to break the stall rather than fighting the tail stall through the nose dive.

Amazingly, Flightaware's ground track shows they actually spent little time in the arrival and feeder segments where they could have picked up a bunch of ice and the ATC tapes seem to reflect Colgan's sequence to be in the front of the pack, turning final about 5m(2-3 out of the marker) from the airport. That had to be some nasty stuff, particularly the way NWA alarmed of their concerns. Obviously, saturated with the events, ATC didn't quite pick-up the first pirep from NWA.

Nasa's otter conducted its exercises over 10k if my memory serves. Wouldn't beleive these poor souls had a chance <2k AGL.

prayers ya'll.

100-1/2
 

clr4theapch

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As dispatchers do... I was looking at the weather during that time.. some of the graphics I have show that the area was ripe with liquid moisture from 12k down to 4K.. just north of BUF where is was light snow the waether was actually freezing rain and warmer than at the BUF airport.. so It seems to me that it may have been warmer in that 12k down to 4 k areas that they just decended thru.. once they got below 4K the air got colder and possibly run back water froze and the leading edges were fully contaiminated.. of course we know that they where using the autopilot for the apch so they would not have had any feel of impending control issues, once they got low and slow, and the auto pilot was kicked off when they lowered the flaps, the control forces where HUGH and maynot have been able to recover, they certainly were up against it being that they were low on the aproach.. prob no time to do much but try to fly out of the tail stall, thus the nose up, or Flat belly crash on that House....
 

surplus1

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As dispatchers do... I was looking at the weather during that time.. some of the graphics I have show that the area was ripe with liquid moisture from 12k down to 4K.. just north of BUF where is was light snow the waether was actually freezing rain and warmer than at the BUF airport.. so It seems to me that it may have been warmer in that 12k down to 4 k areas that they just decended thru.. once they got below 4K the air got colder and possibly run back water froze and the leading edges were fully contaiminated.. of course we know that they where using the autopilot for the apch so they would not have had any feel of impending control issues, once they got low and slow, and the auto pilot was kicked off when they lowered the flaps, the control forces where HUGH and maynot have been able to recover, they certainly were up against it being that they were low on the aproach.. prob no time to do much but try to fly out of the tail stall, thus the nose up, or Flat belly crash on that House....

Excellent observations.

In my opinion, unfortunately airline pilots in the "regional" category more often than not do not have available adequate weather analysis information.

There is often little time available between turns. The 'release' is focused on the destination airport only (for the most part) and doesn't show the "big picture" of the region into which operating. Pilots don't have available to them what may be available to their dispatchers and rarely speak directly with dispatch - unless something really goes wrong.

Dispatchers for the most part do an excellent job but it takes two to tango and often they are not consulted. Even if they are, a great many are very inexperienced. They would like to help but don't know how. Many may even be unlicensed individuals crunching out paper work under the supervision of a single licensed individual.

Rarely do weather reports contain the phrase 'severe incing' or 'heavy icing' - regardless of their origin. You may see 'moderate to severe' pridictions but that still permits the aircraft to depart. Predictions of 'severe' or 'heavy' icing (by themselves) would shut down the system - an economic penalty that is studiously avoided where possible.

We can easily justify that with a simple explanation - weather forecasting, at its best, is not an exact science.

Of course I don't know, but I would educatedly guess that the crew of the accident aircraft did not have any consultations with dispatch (regarding weather) while enroute to BUF. If I am right, they never saw the graphics that you did and were most likely completely unaware of the potential for severe icing in the general area of their destination. They just did what 99% of us do. The result is greatly diminished situational awareness - when the chips are down.

For instance - can you imagine LGA shutting down every time birds are reported in the vicinity of the airport? Likewise, how many flights to BUF would have been canceled that night if the weather report read "severe icing in clouds" in the BUF area?

That is NOT a critique of the flight crew, it's just 'standard procedure'. Unfortunately it is also hazardous procedure and this time it apparently turned out to be fatal procedure.

Of course it is possible that had they been aware before the fact - events may have turned out differently. It is equally possible that nothing at all would have changed. We can only conjecture about that - reality is we'll never know.

As with all accidents a single event is seldom the true cause. Instead a chain of little things progressively accumulate and reduce the margain for error. Sometimes the chain breaks suddenly - and the result is catastrophic.

Hindsight is always 20/20 and Fate is the Hunter.
 
Last edited:

belchfire

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clr4thepch...your analysis makes sense but there are several other things that could have contributed. The current guidance is to turn on anti/deicing systems as soon as any icing conditions are encountered.

This is exactly correct for anti-icing systems-on a turboprop these would be inlet and propeller systems. Deicing systems, namely boots need to be treated differently.

My experience-admittedly outside NASA's controlled experiments-in real conditions in booted turboprop aircraft proved that you should let ice build up somewhat before blowing the boots. I had several new FO's fresh out of their 172's absolutely concerned about some impact snow less than .125 inch thick right on the leading edge...yeah, that white stripe is in stark contrast to the black of the boot, but WTF. I'd humor them and pop the boots. No Change! There was no tube right on the leading edge and with that little ice there were no tubes in the boots to break the accumulation off.

Then we would have a discussion of where the tubes that were in the boot existed and how much ice it would take to get into an area where the boots would do some good. Then I would demonstrate-we had no auto pilot-the little changes in pitch that could be felt as first the wing then the tail boots cycled.

Bridging has been mentioned in a couple of threads. Let me assure you that we are not dealing in this case with boots that were powered off the back side of a vacuum pump at about 5psi! The typical turboprop has better than ten and more likely 20+ psi fed onto the boots to inflate the tubes within the boot.

My current turbojet machine, well, we turn on the inlet anti-ice when the book calls for it. It has no defense against icing on the tail surfaces and in the last three years the wing de/anti-icing heat has never been turned on...even heavy we get through icing layers too quickly to see an accumulation or we are going so fast that the TAT is precluding the formation of ice on leading edges.

As for the Q400-I've read that the anti-ice was turned on. I don't know if that turn on just the prop and inlet anti-ice or if the boots go into some sort of automatic cycle...IMHO boots (de-icing) should be cycled as needed and anti-icing systems should be on in visible moisture and within the required temperature specification-either OAT or TAT as required.

Regardless, airframe and engine icing are highly unpredictable, change rapidly and are difficult to predict. These factors make icing one of the most difficult situations to deal with in an airplane-especially during the takeoff and approach phases.

Follow your GOM/AOMs, use your icing airspeed additives for landing and be really careful out there. Summer's coming and we will get faced again with yet another set of challenges!
 
Last edited:

poorpilot83

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I have a couple of thousand hours in a dash 8 200, we always landed with flaps 15, never full. Does the 400 do the same or land with full flaps?
 

Captainzero1

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Excellent observations.

In my opinion, unfortunately airline pilots in the "regional" category more often than not do not have available adequate weather analysis information.

There is often little time available between turns. The 'release' is focused on the destination airport only (for the most part) and doesn't show the "big picture" of the region into which operating. Pilots don't have available to them what may be available to their dispatchers and rarely speak directly with dispatch - unless something really goes wrong.

Dispatchers for the most part do an excellent job but it takes two to tango and often they are not consulted. Even if they are, a great many are very inexperienced. They would like to help but don't know how. Many may even be unlicensed individuals crunching out paper work under the supervision of a single licensed individual.

Rarely do weather reports contain the phrase 'severe incing' or 'heavy icing' - regardless of their origin. You may see 'moderate to severe' pridictions but that still permits the aircraft to depart. Predictions of 'severe' or 'heavy' icing (by themselves) would shut down the system - an economic penalty that is studiously avoided where possible.

We can easily justify that with a simple explanation - weather forecasting, at its best, is not an exact science.

Of course I don't know, but I would educatedly guess that the crew of the accident aircraft did not have any consultations with dispatch (regarding weather) while enroute to BUF. If I am right, they never saw the graphics that you did and were most likely completely unaware of the potential for severe icing in the general area of their destination. They just did what 99% of us do. The result is greatly diminished situational awareness - when the chips are down.

For instance - can you imagine LGA shutting down every time birds are reported in the vicinity of the airport? Likewise, how many flights to BUF would have been canceled that night if the weather report read "severe icing in clouds" in the BUF area?

That is NOT a critique of the flight crew, it's just 'standard procedure'. Unfortunately it is also hazardous procedure and this time it apparently turned out to be fatal procedure.

Of course it is possible that had they been aware before the fact - events may have turned out differently. It is equally possible that nothing at all would have changed. We can only conjecture about that - reality is we'll never know.

As with all accidents a single event is seldom the true cause. Instead a chain of little things progressively accumulate and reduce the margain for error. Sometimes the chain breaks suddenly - and the result is catastrophic.

Hindsight is always 20/20 and Fate is the Hunter.

You hit the nail on the head brother!
 

atpcliff

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Total Time
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Hi!

I've done a lot of DC-9 training lately.

We were told not to use the autopilot when there is a lot of ice. We were also warned if we hear the autopilot trimming a lot, to puch off the autopilot and check the trim situation.

Also, we were told to land with 25 flaps (40 is normal) if there are any problems: High crosswinds, thrust problems, problems with the aircraft flyability, etc.

They also talked about tailplane icing, and how to work the wing vs. tailplane icing system. Before we are allowed to go to flaps 40 (the final setting) in an icing situation, the tail needs to have been just de-iced, or, after ANY use of the icing system anytime, the tail needs to be de-iced at the end of the sequence.

We did NOT practice tail stalls in the sim, just regular ones. I do think that NO ONE is required by the FAA to do anything other than the standard stall series. Our instructor told us how the stall series is not like in real life, and had us do some wing stalls in real-world situations (but still no tail-stall scenarios).

cliff
GRB
 
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