Colgan 3407 Down in Buffalo

[surplus1]

Can anyone that flies the Q-400 please answer this question for me: Do the spoilers play any role in roll control of this a/c type, or is it strictly ailerons?

Some reasearch that I've been doing indicates that on earlier versions of the Dash-8 series they do - but so far I can't find anything about that related to the Q-400 specifically that confirms this.

 

[Captzaahlie]

They do on the 100,200,300's...
don't know about the 400's but thats an interesting point that you bring up.... I'd love to see that FDR report on the control surfaces.

 

[ReverseSensing]

Can anyone that flies the Q-400 please answer this question for me: Do the spoilers play any role in roll control of this a/c type, or is it strictly ailerons?

"In flight, the spoilers extend in proportion to the up going aileron to provide roll control. .... To reduce roll sensitivity, outboard spoiler operation is deactivated at speeds greater than 170 kias."

BTW, inboard spoilers powered by #1 hyd and outboard powered by #2 hyd. Only have a roll control function in flight -- though it'd be nice to have an in flight speed brake/lift dump function. On the ground, they deploy on landing with dual WOWs.

 

[surplus1]

Thanks very much. Later on I will talk about what I've found and possible relevance.

 

[surplus1]

This is cut and pasted from another thread. It seemed more relavant here. I posted it here because much of it agrees with my own hypothetical related to autopilot induced nose-up trim as the cause of the initial pitch-up to +31 degrees. I still do not buy the NTSB idea that the pilot intentionally applied back pressure to cause the initial pitch up.

From pprune. This sounds very realistic. Time will tell.

M

Autopilot level-off from a descent in an aircraft without autothrottles is a bit of a trap. Although I don’t know of any similar accidents, there’s beginning to emerge a story of a catalogue of similar frightening incidents on the Q400 where pilots have become preoccupied with resetting (or setting up ) the FMS and not noticing, whilst heads down, the body angle changing rapidly to nose-up (once below about 180kts the Q400 reputedly does this slowdown rather fast, iced up or not). The normal speeds for intermediate level-offs are 200 to 210 knots. It’s believed that Colgan 3407 slowed to as little as 134kts. Some of the anecdotes have both pilots heads down trying to resolve an FMS button-punching glitch and/or looking back at the special “wing inspection” lights illuminating the Q400 wingtips - to see if the ice is actually being dislodged.

Does the Q400 simply level off and start bleeding airspeed without any indications at all? Is setting this trap something that should be happening during high pilot workload on approach?

Should the autopilot instead be set to a descent rate and the altitude alerter set to clue the flight crew to do the level off manually - instead of the autopilot just capturing the altitude and slowing whilst awaiting the pilots setting of an appropriate thrust? At least then there would be an expected alerting chime or suchlike.

So did the "low time on type" Colgan Flt 3407 pilot respond to a sudden stick-shaker [and rapidly following stick-pusher] by raising the nose, cleaning up the gear and flap and attempting a go-round from a dangerously low speed (instead of taking the correct stall recovery action of adding power and lowering the nose?). At first glance, that possibility exists. Surprise can be quite a mind-numbing wake-up call. It’s called Instant Overload. It results from fatigue or loss of Situational Awareness (SA)

But why and how would he achieve 31 degrees nose up before the aircraft stalled and started spinning? Did he mean to? The logical response is “no, of course he didn’t”.

The simple answer is that that extreme nose-up pitch-up tendency would be the autopilot’s legacy to him after it kicked itself out due to reaching full nose-up auto-trim in pitch (in its attempt to maintain the set capture altitude against the added drag of ice, gear and flap - likely with something near idle power inadvertently LEFT set).

Once the autopilot kicked out and the panicky pilot added max power, the full noseup trim would be conducive to the aircraft looping the loop of its own accord. The pilot would be flummoxed by this setup and, after a confused pause, fighting hard against powerful nose-up trim forces to lower the nose. Adding max power at low IAS itself produces a powerful nose-up trim change. Add that to the already full nose-up trim state and they didn’t have a chance…… of avoiding a deadly stall/spin outcome.

I couldn’t imagine a nastier surprise. Fancy building in such a death-trap as an autopilot without autothrottle and an FMS that needs lots of head-down two-pilot trouble-shooting and reprogramming? His available solutions were:

a. Not to add full power, but just enough to keep it flying and, as per my flight school's SOP technique (see below)

b. Roll sufficiently (about 50 degrees bank) so that the fully back-trimmed airplane only pitched mostly into the turn - giving him a chance to wind the trim nose forward whilst minimizing the speed loss..

I had a similar situation (but not unexpected) tonight after a night take-off. The EFATO drill for a practice (or real) engine failure after take-off is for the front-seat student to raise the nose, simulate putting the throttle to “stop”, call Mayday on intercom and then he releases the stick after having run the pitch trim to full nose up (for his optimal survival seat-vector), places both hands on his left knee and calls “abandoning now” (simulating an ejection). The rear-seat instructor then takes over, banks into the circuit direction (turns “crosswind” essentially), to help the nose drop from around 25 to 30 degrees nose-up - all whilst running the elevator trim nose-down towards neutral and adding near to max power. It’s a silly drill (it’s like practising dying) but meant to be very realistic for the trainee - and it’s a requirement for him to do it prior to his NF3 night solo sortie. You wouldn’t want it to happen suddenly without warning however. It’d be a quite difficult recovery (particularly at night or in IMC).

Prima facie, and in light of all the similar anecdotes now emerging about turboprops with this cheap option (i.e.no autothrottles and a heads down FMS keypad), this would have been the scenario surrounding Flt 3407’s fate. For that Colgan pilot it would have all happened very fast. It’s a nasty setup just begging for a tech remedy.

Automation can be a half-baked bitch.

 

[Minimaniac]

FWIW... the Captain came from flying a turboprop with altitude capture but no auto-throttles (he was on the SAAB, I believe). And every pilot who has trained in something other than a highly automated jet (aka ALL OF US) has always had to add power to level off. Adding power is a natural course of action. There is no "trap". The only trap would be for an auto-throttle spoiled pilot who suddenly finds himself in a non-autothrottle situation. IF this accident comes down to BOTH pilots not noticing a decay in airspeed and no one thinking to add power in a level off, then there needs to be a serious review in who is allowed in the cockpit and how they are trained.

To me the big kicker is the 30 degree nose up pitch, and the (relatively) high positive G load that was recorded. It takes a lot to get a slow, heavy airliner rotated up to that pitch. Time will tell whether that 30 degree pitch was initiated by the pilot or the autopilot, but I suspect the autopilot made the first stab at that sky-high pitch chasing the glideslope...

 

[Kaman]

Finding it difficult to believe that the AP, if functioning normally would initiate a 31.5 degree nose-up pitch command to capture the GS. It's basic aerodynamics, if the AP is set to maintain altitude it will use trim to maintain altitude, correct? If this is the case, if you get into a situation where the AP is disconnected by the stall warning system and you "firewall" the power, doesn't the airplane seek it's trimmed airspeed? Adding power when altitude is constant would induce a nose-up pitching moment to find that trimmed airspeed (just like any airplane will that isn't fly-by-wire) Further aggravating the scenario would be a rapid programming of the yoke aft, which would have two very undesirable effects. First, you will load the wing (increase G=increase AoA) and secondary stall. I am just throwing that out there for anyone to comment that might know the Q and aerodymanics than I do.

Regards,

ex-Navy Rotorhead

 

[ultrarunner]

Finding it difficult to believe that the AP, if functioning normally would initiate a 31.5 degree nose-up pitch command to capture the GS.

The AP didn't. It was off the moment the stick shaker activated.

It's basic aerodynamics, if the AP is set to maintain altitude it will use trim to maintain altitude, correct? If this is the case, if you get into a situation where the AP is disconnected by the stall warning system and you "firewall" the power, doesn't the airplane seek it's trimmed airspeed?

Yes, to the extent possible. I believe the investigation will show that the 31 degree ANU was achieved in combination by the Captain reacting to the stick pusher as well as putting 10000 shaft horse power to an elevator that was trimmed for 100 kts.

I don't find it hard to believe at all that 31 degrees ANU was achieved. As it's already been mentioned here by Q drivers the 400's nose-up tendency to power application.

Keep in mind that the captains attempt to recover began at darn near 100 kts IAS. I truly believe we woudln't be talking about this had the ANU not reached the level it did. And I'm sure it's already be tested in the sim.

I think the focus of the investigation will be the reasons both pilots became so preoccupied with looking out the frigging window....worrying about ice..etc...and no one minding the flying of the plane.

 

[surplus1]

The autopilot didn't do anything - except trim the elevator to hold altitude at the corresponding airspeed (which was steadily decreasing). It is designed to do that.

When the shaker went off the autopilot simply disconnected. But, that does not remove the elevator trim that was already there - nearly full nose up trim.

As soon as the pilot added full power - you get the full combination of the high power + the already present nose up trim - and the nose immediately pitches up to +31 degrees. [At this point the pilot hasn't applied any back pressure at all. In fact he is probably applying forward pressure in an effort to stop the pitch up.]

During the pitch up - the wing stalls - activating the pusher.

The roll to the left (46 degrees) is caused by two things 1) torque from the power addition, 2) the left wing stalling more than the right wing ( more ice?).

Auto-throttles, which we don't have are not really a factor. The only thing they could have done (if they were there) is prevent the loss of airspeed by adding more power when the aircraft leveled at 2300 ft. In turn, that would have prevented all the up-elevator trim that was added by the autopilot - before the shaker went off.

The shaker would never have gone off if enough power to hold the airspeed (in level flight) had been added by the pilots - when the aircraft initially reached 2300 ft. [assumption]

It really isn't complicated at all. All that we have to prove is that insufficient power to maintain airspeed - above shaker activation - was not added as the a/c leveled off at 2300 ft.

In this case, we know that the pilots had activated the system that increases the margin of AOA before stall. In other words it went off a lot sooner (20 kts) than it would have if that switch had not been turned on. At that point the wing was NOT stalled - it was 20 kts above normal shaker activation (approach to stall) - more or less.

Thus the ficticious increment in shaker activation - a feature designed to PROTECT against a higher than normal stall angle - caused by ice - most likely accomplished the opposite by triggering the whole process. They might have caught the low airspeed in time - if it had not been artificially increased.

That's the theory - don't get confused by the mention of auto-throttles - we know this a/c is not equipped with those. Therefore the pilot has to take their place. For some reason, unknown at this point, apparently that never happened - until AFTER the shaker activated disconnecting the autopilot.

By that time the aircraft was already set up to respond - to full power + nearly full nose-up trim - exactly as it did.

 

[Icelandair]

though it'd be nice to have an in flight speed brake/lift dump function.

You already can land at any point you can see out of the front windshield in the 400. Add any more drag to that thing to try to get down faster you might even be able to land at a runway behind you!