Colgan 3407 Down in Buffalo

[belchfire]

Do you train in a jet? Or something like an L-188, DC-6/7? If so your training is the same as mine has been.

My training experience in the smaller propeller airplanes has been the opposite. I didn't agree with it but I didn't get to make the rules.

Jet now, Jetstream before...

I double checked my current manual before I made my statement and it's clear on the point-don't change configuration of gear or flaps until stall recovery is complete.

I don't have my Jball manuals with me to check them-if I recall correctly it was the same thing-but that little bugger recovered so quickly with full power that it wasn't but a few seconds before the wing was flying again and one would be cleaning up. The little beast was also more stable with the gear out and had wild pitch changes between flaps 20 and 35.

 

[trainer8]

ABC News reported quoting the NTSB that the Captain had 110 hours total hours in Q400, having previously flown the Saab 340.

T8

 

[Flyin2low]

Hi Trainer,

I've only ridden in a Dash 8/200 once in my life. EYW-MIA many years ago. I've never even seen a live Q-400; just pics.

Your points 1 and 2 are important especially # 1. I think the time line here - the exact moment of auto pilot disconnect - is very important. If it is true that the autopilot did NOT disconnect until AFTER the shaker activated, then I would modify my hypothesis to something I have not wanted to say.

That would be that the aircraft reached 2300 ft, with insuffient power to sustain level flight. It slowed gradually - with the auto pilot trimming nose up - unobserved by the flight crew until the shaker activated disconnecting the auto pilot - followed by a stall.

This would mean that the stall speed - with the ice - [as re-programmed by the crew] had increased to somewhere around 130 kts. (given that NTSB says CAS was 134 kts on the FDR) and activated the shaker disconnecting the auto pilot. It would explain the pitch up - and cause the actual aerodynamic stall. But, it would also point to what none of us want to hear = PE.

The initial roll off would simply be a by-product of the stalled wing (1st stall) and the 2nd the product of the accelerated secondary stall. This would NOT be good for the crew.

On your point #2 - I know that if there's ice on the wings there is also ice on the tail. However, the manufacturer claims that flight test data indicates that the Q-400 is NOT susceptible to tailplane stall.

Personally I'm just not ready to buy into the tailplane stall theory, although I'm very much aware that the manufacturer will launch into full CYA mode if it believes that's necessary. Manufacturers never voluntarily admit design anomalies.

If you're right about #1, then I hope I am wrong about #2.

Good to see you.

I'll vote for point #1 and #2 and raise you point #3 (ABC News reported quoting the NTSB that the Captain had 110 hours total hours in Q400, having previously flown the Saab 340.)

NTSB Identification: DCA94MA027 .
The docket is stored on NTSB microfiche number 52866.
Scheduled 14 CFR
Accident occurred Friday, January 07, 1994 in COLUMBUS, OH
Probable Cause Approval Date: 4/12/1995
Aircraft: JETSTREAM 4101, registration: N304UE
Injuries: 5 Fatal, 2 Minor, 1 Uninjured.The airplane stalled and crashed 1.2 nautical miles east of runway 28L during an ILS approach. The captain initiated the approach at high speed & crossed the FAF at a high speed without first having the airplane properly configured for a stabilized approach. The airspeed was not monitored nor maintained by the flightcrew. The airline had no specified callouts for airspeed deviations during instrument approaches. The captain failed to apply full power & configure the airplane in a timely manner. Both pilots had low flight time and experience in in the airplane and in any EFIS-equipped airplane. Additionally, the captain had low time and experience as a captain. Inadequate consideration was given to the possible consequences of pairing a newly upgraded captain, on a new airplane, with a first officer who had no airline experience in air carrier operations, nor do current FAA regulations address this issue.
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
(1) An aerodynamic stall that occurred when the flightcrew allowed the airspeed to decay to stall speed following a very poorly planned and executed approach characterized by an absence of procedural discipline; (2) Improper pilot response to the stall warning, including failure to advance the power levers to maximum, and inappropriately raising the flaps; (3) Flightcrew inexperience in 'glass cockpit' automatic aircraft, aircraft type, and in seat position, a situation exacerbated by a side letter of agreement between the company and its pilots; (4) The company's failure to provide adequate crew resource management training, and the FAA's failure to require such training; (5) The company's failure to provide adequate stabilized approach criteria, and the FAA's failure to require such criteria; and (6) The unavailability of suitable training simulators that precluded fully effective flightcrew training. Note: Items 1, 2, and 3 were approved by a Board vote of 4-0. Item 5 was adopted 3-1, with the dissenting Member believing the item was a contributory cause. The Board was divided 2-2 on items 4 and 6, two Members believing them causal and two Members, contributory. (NTSB Report AAR-94/07)

 

[Singlecoil]

Another idea on why it rolled left first:

What happens when you go from idle to full power in a propeller-driven airplane that doesn't have counter-rotating props?

You need to stomp down on the right rudder hard, or the airplane will be uncoordinated. Remember departure stalls when you didn't use enough right rudder? Which way did the stall break?

 

[bailout]

As I see it, the key to your statement is in the first sentence: "The part i dont get, is if there were no pitch control input changes prior to the AP disconnect, why would it pitch up?"

Now put the autopilot back in the equation. You told it to hold 2300 ft, and it does. As the airspeed decreases how does it do that? It trims the elevator nose up, to hold the altitude.

If you do nothing else it will continue to trim nose up and the airspeed will continue to decrease - until one of the two reaches the level required to hold that altitude with that amount of power. In other words, if the power available matches the power required to hold altitude at that speed, the auto pilot will stop triming and you will be in level flight with x amount of nose up trim and y amount of power - stable. If the power available/used remains less than required - airspeed will continue to deteriorate slowly until the auto pilot runs out of available trim capability or you exceed the critical AOA and stall.

Everything is now stable and the auto pilot has stopped triming nose up -but - it has NOT removed much if any of the trim previously input. You're still at 2300 ft and headed for the localizer. Glide slope is not alive and has not captured.

As you approach the localizer the autopilot begins a turn to capture it. The auto pilot is still flying. What happens now?

As the bank increases more back pressure is required to hold the altitude. The auto pilot provides in by additional nose-up elevator trim. Something else also happens - the airspeed begins to deteriorate (slow) again. You decide to accept the slightly lower airspeed and you don't add more power - it's already where you think you want it.

Meanwhile bank angle is increasing and elevator is trimming nose-up (slowly). Bank angle tries to increase beyond 25 deg. (due to the ice) until the auto pilot exceeds its limit and kicks off. The nose pitches up and the wing stalls.

Instantly the bank increases from 25 to 45 degrees - further increasing the stall speed. What happens to stall speed as bank angle increases? Yep, its higher than in was before. It was already on the edge - you just didn't know it.

Just as you act to correct the bank the wing stalls. You call for full power and all that up elevator trim is still there. Where does the nose go before you can stop it? All the way to +31 degrees nose up and you have the yoke full forward. There's a lot of power there and some very big props.

Down goes the nose - very rapidly. Your control input has taken effect There is still too much elevator trim for that amount of power and you're pushing hard.

The instant you see 45 degrees nose down you reverse the pressure and pull like hell. You still have almost full aileron cranked in to pick up the left wing. You havent thought at all about trim. Who would?

Just as you apply that back pressure you now enter an accelerated secondary stall. The aircraft snaps to the right - exceeding the vertical bank angle. It is completely out of control - plus you just lost a thousand feet.

I understand everything you are saying here, except for this: are you saying the nose pitched up when AP disconnected or after they added full power?

I completely understand the nose up pitch change if they added full power after the disconnect with the trim at the limits, but if no power changes were made after the disconnect it should stay in whatever pitch it was at the time of disconnect, correct?

 

[surplus1]

Flyin2low,

I think I know where you're going with your #3 but I'm not quite ready (personally) to take that route - especially if your thinking is based on 'low time in type'.

From my perspective - if I were going at all to look at the 'experience' quotient, I would not be looking at time-in-type. The data we have so far do not appear, in my opinion, related to unfamiliarity with the specific type of aircraft.

Overall experience is a horse of a different color. I don't have any information on the overall experience of this flight crew.

I would add this thought:

"Experience is the exchange of the erros of youth for those of age." As it applies to pilots, a pilot may have 10K hours of 'experience' - or one hour of experience - repeated 10 thousand times.

Flying hours are a much too subjective measure of 'experience' for my gullet.

 

[Britpilot]

I understand everything you are saying here, except for this: are you saying the nose pitched up when AP disconnected or after they added full power?

I completely understand the nose up pitch change if they added full power after the disconnect with the trim at the limits, but if no power changes were made after the disconnect it should stay in whatever pitch it was at the time of disconnect, correct?

I think the point surplus1 was making was that the A/P would have trimmed more aft for the turn to intercept the LOC and that the stall occurred with this additional aft trim followed by power application and rapid pitch up moment then an accelerated stall while the airplane was in a bank.
In some aircraft the A/P will trim more than what is required for the given flight status, this is noticiable sometimes when you disconect the A/P to hand fly and you are given an airplane that is out of trim.

 

[surplus1]

Another idea on why it rolled left first:

What happens when you go from idle to full power in a propeller-driven airplane that doesn't have counter-rotating props?

You need to stomp down on the right rudder hard, or the airplane will be uncoordinated. Remember departure stalls when you didn't use enough right rudder? Which way did the stall break?

Points well made - in general true.

I'm not familiar with this aircraft type at all - haven't even seen one, other than in pictures.

That being said, I've been reading a lot about it since this accident occurred, and have learned a few basic things.

1. The propellers are quite large.
2. They are made by Dowty-Rotol.
3. The aircraft type has a history of propeller malfunctions that is way less than stellar.
4. A propeller malfunction, if not recognized correctly and handled correctly right away, can cause very severe controlability problems. It has happened more than once.

I don't know enough about the propeller control mechanism on this aircraft to be intelligent but there are generalities that are relevant.

A. In any propeller aircraft and especially one with such large propellers and so much available power - the torque factor you mention can be significant.

B. Most large propellers to not respond well to very large and abrupt power changes. I refer specifically to asymmetric 'spool up'. Very often, the two props (or the 4) do not respond equally (at the same time). Usually this is related to the particular governing mechanism. This can produce some control difficulties - although brief and transient in most cases.

C. A long time ago I was CA of another aircraft type (turbo prop) equipped with a Dowty-Rotol product. They may sue me, but the truth is that particular propeller was an accident looking for a place to happen. My pucker factor was orange for every hour in that thing. I know of at least one fatal accident (original Allegheny Airlines) on approach that was contributed to that propeller design. I know of another accident - I believe the only one ever in that different type - but equipped with essentially the same Dowty-Rotol propeller.

That was a long time ago (30 yrs +) and hopefull those anomalies have been corrected but it left a very bad taste - at least for me. Something akin to - Ill never buy another XXXX car. I have the same built in aversion to electrical systems by Lucas (the prince of darkness).

D. Much more recently I have flown another type that suffered from serious propeller control anomalies. That particular propeller caused at least 4 fatal accidents and its manufacturer fought tooth and nail to resist correcting the design flaw that was causal. Eventually they were forced (literally) to fix the problem.

We won't know until the NTSB is finished, but in this case I doubt that the props were a factor.

 

[atrdriver]

As I see it, the key to your statement is in the first sentence: "The part i dont get, is if there were no pitch control input changes prior to the AP disconnect, why would it pitch up?"

Actually there were lots of pitch input changes - all made by the auto pilot and unobserved by the crew. [If the darn airplane had a trim wheel they might have noticed it turning] Additionally, the autopilot was struggling to keep the wing from increasing the bank angle (due to the ice on that wing), which they also did not know.

The aircraft was in a descent - through 6000, 4000 to 2300. Power most likely retarded for the descent. Altitude is pre-selected to 2300.

As we reach 2300, altitude captures and is held by the autopilot. What happens now to airspeed? Unless power is added, airspeed will decrease.

If the autopilot was NOT engaged, and you didn't touch the yoke - what would happen to the nose as the airspeed decreases? It would drop off wouldn't it? If you did not want that to happen but you still wanted to slow down. what would you do? Trim nose up.

Now put the autopilot back in the equation. You told it to hold 2300 ft, and it does. As the airspeed decreases how does it do that? It trims the elevator nose up, to hold the altitude.

If you do nothing else it will continue to trim nose up and the airspeed will continue to decrease - until one of the two reaches the level required to hold that altitude with that amount of power. In other words, if the power available matches the power required to hold altitude at that speed, the auto pilot will stop triming and you will be in level flight with x amount of nose up trim and y amount of power - stable. If the power available/used remains less than required - airspeed will continue to deteriorate slowly until the auto pilot runs out of available trim capability or you exceed the critical AOA and stall.

I am only saying how it works - not what they did. I assume that they added enough power to hold the desired speed (or what they thought would hold it).

Everything is now stable and the auto pilot has stopped triming nose up -but - it has NOT removed much if any of the trim previously input. You're still at 2300 ft and headed for the localizer. Glide slope is not alive and has not captured.

As you approach the localizer the autopilot begins a turn to capture it. The auto pilot is still flying. What happens now?

As the bank increases more back pressure is required to hold the altitude. The auto pilot provides in by additional nose-up elevator trim. Something else also happens - the airspeed begins to deteriorate (slow) again. You decide to accept the slightly lower airspeed and you don't add more power - it's already where you think you want it.

Meanwhile bank angle is increasing and elevator is trimming nose-up (slowly). Bank angle tries to increase beyond 25 deg. (due to the ice) until the auto pilot exceeds its limit and kicks off. The nose pitches up and the wing stalls.

Instantly the bank increases from 25 to 45 degrees - further increasing the stall speed. What happens to stall speed as bank angle increases? Yep, its higher than in was before. It was already on the edge - you just didn't know it.

Just as you act to correct the bank the wing stalls. You call for full power and all that up elevator trim is still there. Where does the nose go before you can stop it? All the way to +31 degrees nose up and you have the yoke full forward. There's a lot of power there and some very big props.

Down goes the nose - very rapidly. Your control input has taken effect There is still too much elevator trim for that amount of power and you're pushing hard.

The instant you see 45 degrees nose down you reverse the pressure and pull like hell. You still have almost full aileron cranked in to pick up the left wing. You havent thought at all about trim. Who would?

Just as you apply that back pressure you now enter an accelerated secondary stall. The aircraft snaps to the right - exceeding the vertical bank angle. It is completely out of control - plus you just lost a thousand feet.

The rest ...............

It's all hypothetical ... just a theory.

I have never seen a turboprop autopilot that could adjust the aileron trim, and I doubt that the Q400's will either.

 

[q100]

Points well made - in general true.

I'm not familiar with this aircraft type at all - haven't even seen one, other than in pictures.

That being said, I've been reading a lot about it since this accident occurred, and have learned a few basic things.

1. The propellers are quite large.
2. They are made by Dowty-Rotol.
3. The aircraft type has a history of propeller malfunctions that is way less than stellar.
4. A propeller malfunction, if not recognized correctly and handled correctly right away, can cause very severe controlability problems. It has happened more than once.

I don't know enough about the propeller control mechanism on this aircraft to be intelligent but there are generalities that are relevant.


D. Much more recently I have flown another type that suffered from serious propeller control anomalies. That particular propeller caused at least 4 fatal accidents and its manufacturer fought tooth and nail to resist correcting the design flaw that was causal. Eventually they were forced (literally) to fix the problem.

We won't know until the NTSB is finished, but in this case I doubt that the props were a factor.

I agree with the last thing you said...

Dash8s do not have, at least not that I know of, a "less than stellar" history of prop problems. Not to say they've not happened, but they are rare and usually MX (and pilot) related. I know of at least one crew that took off with faulty torque indications, and, guess what, had an unscheduled autofeather on T/O, for example...

I believe the type you refer to in "D" was the Brasilia? Weren't they Hamilton Standard props that were shedding blades? At least one of those events was traced to MX.

Too many people, even Jim Hall (ex-NTSB chair who really oughta both a) know better than to think one accident, due to causes yet unknown, in an a/c type with no history of similar incidents is cause for grounding the fleet, and b) keep his yap shut) are in too much a rush to pin the blame for this crash on someone or something. How about we all wait for the facts?

Speculating is one thing - we all do it and it can produce some useful results. Rushing to judgement is another beast entirely, and it does no one any good while potentially damaging the innocent.