Monday, February 16, 2009

Colgan Flight 3407 Crash (Continental Airlines Connector Flight 2/12/2009)

(The following are pull-quotes from AVSIG discussion on this crash. Full thread found here).

The crew was cleared to descend to 11,000 feet, and shortly afterward noticed "significant ice buildup" on the windshield and the leading edge of the wings, Chealander said. The flight- data recorder indicated a system that helps to de-ice the plane had been activated shortly before those comments were made, he said "Landing Gear Activated."

The landing gear was activated one minute before the end of the recording, and 20 seconds later the wing flaps were lowered, Chealander said. Within seconds, "severe pitch and roll" movements were recorded, he said. The crew tried to raise the gear and the flaps just before the recording ended.

I am VERY SURPRISED that the NTSB is already discussing the CVR and the indications of what seem to be a tailplane stall with the config change.

I think the NTSB has at least one outstanding recommendation concerning ice problems with this type turbo prop. -from a prior accident some years ago (Roselawn?).

Of course it's way too soon to even make a "cause" statement.
However, it seems like the initial data shows the crew was indeed using whatever deicing stuff was installed.

I was part of an accident investigation team at a turbo prop accident in Minnesota some years ago. Killed all on board around Christmas time.

We all thought it was a potential ice situation -but after some investigation and the CVR, it turned out to be a pilot problem -too low on the non ILS approach. (Well, there were a lot of other factors but I'll not go into those).
Sorry about this current tragic accident. Hope we can get some valid recommendations to prevent this in the future.
Part of the NTSB investigation will to review any previous "incidents" that could be related. I've always noted that most accident investigators would rather spend more time on investigation of incidents (the so called "close calls") and focus on prevention.

I'm just a humble Cessna pilot who has never encountered icing, but I thought the rule was: "Don't deploy flaps if your wings are iced up".
This is a plane certified for known icing. De-icing boots are on every control surface (which, BTW, is not typical on a jet... the tail feathers are usually without de-ice). Assuming the de-ice equipment was doing its job effectively, I would ordinarily not fail to use flaps. Certainly, don't use flaps 30 miles out, or in holding, since the flaps themselves have no de-icing capability.
The crew recognized the problem, and took what on the surface appears to be the proper corrective action... return the flaps to the previous configuration; in this case up.
Did they pull back on the yoke also? Don't know yet, but we will.

This accident does remind me a lot of the the Roselawn accident. The "pitch AND roll oscillations suggest more than tailplane seems to me that would principally cause only pitch oscillations. The "aileron snatch", such as what happened at Roselawn, will cause loss of both pitch and roll control. Only the FDR data will tell the tale.
This is the first fatal accident in the U.S. involving a large (>30 seat) turboprop aircraft (other than ramp accidents) since Roselawn, and the first in the U.S. involving the Dash-8, and only the second ever. Dash-8s and ATRs remain two of the safest aircraft around, even after this accident. Convincing the public of that will be an uphill battle. This is the first fatal accident in the U.S. since Comair in 2006. 28,000 flights departed yesterday, one crashed. We are now going some 20 million+ departures between fatal accidents.

Two things got my attention quickly. One was the crash site was a very tight area indicating a very steep path to the ground.
Second, later in the day a witness said when he say the airplane it was pointed northeast and he went on to describe the belly of the airplane, the left wing down and other detailed observations. Not your usual 'witness'. With the left wing down and facing northeast, the airplane would have rolled, nose down and wound up facing the opposite direction from the approach final course.
This fits the 'severe pitch and roll' comments from the NTSB and that has really surprised me that the NTSB is releasing information so quickly from the CVR and FDR.
At any rate, it was an event from which there was insufficient time and altitude to recover.
Now saying the airplane essentially hit FLAT.. 'all four points of the airplane, wing tips, tail and nose section' have been identified.
Autopilot was being used until a/c departed. Shaker and pusher activated.

More particular to this crash, the plane that the Dash-8 "Q-400" shares its fuselage with, the CRJ, does not have de-ice on the tail. Just like a Boeing 777.

All the Hawker jets I have flown have tail de-ice as do all the Cessna jets. Airbus' also have tail de-ice.
The only civilian jets I have flown that do not have tail de-ice are Boeings and the CRJ.
A few months ago I was talking to an Avantair crew at Atlantic in BNA and they mentioned that the P-180 didn't have any tail de-ice. That surprised me, being that it's a turboprop, but perhaps it's because of the unusual bi-wing design? The main wing may be far enough after that the tail is producing upward lift instead of downward.

The Boeing 747 (-100, -200, -300) does NOT have any system to de-ice or anti-ice the tailfeathers.
Nor does the Gulfstream IV.
Nor the Eclipse

As you know, I'm just a humble, low-time, Cessna pilot, but the C-172's I rent have 3-axis autopilots. There have been a few times in VFR conditions when the autopilot would have stalled the aircraft, had I let it.
Caught in a downdraft, the AP tries to hold altitude and doesn't give a hoot about airspeed. If you're watching, you can see the trim wheel spinning up and the airspeed bleeding off. Eventually you get a message 'trim in motion'.
I'm sure none of this probably applies to the loss of Cogan Air, but APs are dumb.

Some are smarter than others. Not sure how "smart" the A/P is on the Q400, though. It has a relatively advanced autoflight system, however. Speed loss due to flying through a downdraft wouldn't normally be much of a concern as the airplane has lots of power but it could certainly result in a stall if the crew doesn't use the available power or auto-throttles (if installed).
Generally you'd want to use more automation in high-workload situations but icing conditions are an exception as the autopilot can mask the signs of developing control problems from ice accretion.
Worse, they don't tell you when stuff happens. Ice can come on slowly,
necessitating constant slight pitch and power increases. A pilot hand flying
will notice that rather early. An AP covers it up until some mechanical
limit is reached, which can be mighty late for real corrective action.

From what I've seen posted, John, the carrier's procedures were not to use the AP in icing conditions for the reason you point out. One can't get a feel for how the plane''s handling when the AP is engaged. It if reaches the limit of it's control and lets loose close to the ground, there may not be time to recover if it's due to ice accumulation.
The FAA has come out with recent guidance on this issue.
Even in my P-Baron, I don't use the AP in icing conditions on an approach. I might use it in light ice higher up for short periods, but hand fly it frequently too get a feel for how the plane's handling.
These folks had a lot going on. Night descent in icing conditions is always busy. John discussed using APs to land in low ceiling and visibility environments on CNN. Who knows, one investigator said the AP was engaged, but the investigation isn't over.
I am a bit surprised that the crew was not specifically trained to avoid lowering the flaps and using the AP in these conditions given the Roselawn accident. FlightSafety and Simcom instructed me not use the AP or lower flaps unless absolutely needed in icing conditions. And even if you lowered flaps you should be prepared to immediately raise them if control issues arose.For those that fly for the airlines are similar warnings provided?

The flaps did not reach what is suspected as the commanded position, flaps 15. They started down, reached 10deg and the crew attempted to retract them.
Also, there appears to be some confusion about the pitch and thus the conjecture about a flat spin. Now we are hearing pitch varied between 30deg nose up and about 40deg nose low with bank angles of 105deg. That is enough to put the airplane on its back and with that pitch variation, possibly no spin.
I believe what they meant to say is the airplane did not impact nose down rather than say the airplane did not dive. I could be wrong.
We have not been instructed not to use the flaps when needed for landing, even in icing conditions. We are PROHIBITED from using them while holding in any conditions. In Roselawn, the extention of the flaps in icing while holding allowed ice to accrete behind the boot, which, when the flaps were raised, and subsequently a higher angle of attack was required to maintain level flight, a loss of roll control occured because of disrupted flow over the ailerons.We are instructed to not use the autopilot while making approaches in icing conditions. Not so in cruise flight, at least on the regional jets we now fly. On the ATRs, IIRC, it was recommended that we disengage the AP in cruise from time to time if in ice, to see if there was an alteration in the handling, and to be prepared for large control forces to be present when we disconnected. Jets have "hot wings", and ice does not accrete on them if the anti-ice (not "deice") systems are working properly. Turboprops have "deice" systems, like boots. Ice accretes, then is removed. A turboprop engine simply does not provide enough bleed air to heat a wing.This accident is still a mystery in my mind. Tailplane icing does not explain the 31 deg pitch up they experienced. A tailplane stall would cause a pitch down, wouldn't it? Something new happened here, heretofore unexpected, I'll bet. The fact that flaps were being extended at that moment is a clue...this is an aerodynamic icident I am not familiar with, and it may be characteristic of the Q400. All the autopilot use would have done is mask the onset of ice trouble. How that pitch up occured appears to me to be the key to the whole thing. What would cause such a thing?The investigation will tell.