On Mon, 16 Feb 2009 11:18:45 -0500, Gezellig wrote:

On Sun, 15 Feb 2009 14:23:43 -0800 (PST), Dudley Henriques wrote:

On Feb 15, 11:59*am, Gezellig wrote:
On Sun, 15 Feb 2009 06:00:13 -0800 (PST), Dudley Henriques wrote:
On Feb 13, 4:44*pm, "Robert11" wrote:
Hello,

I guess de-icing is going to be a popular subject.

Question, please: *On commercial jet airliners like, e.g., a 767 or 757, is
there any in-flight deicing system for the wing and tail surfaces, other
than a leading edge pneumatic boot ?

What about the "main," large upper surfaces ?

How in general is wing de-icing accomplished on these new, modern jets ?

Thanks,
Bob

There's a very good chance the Boston crash might have been tailplane
icing.
DH

To explain the erratic flight behavior?

It's just a guess, but yes. I viewed a NASA film only this morning on
this issue. The key if correct would be that whatever happened
happened immediately after they went to 15 degrees of flaps. That
would have increased the aoa on the tail surface leading edge. That
leading edge is sharper than the wing leading edge and very
susceptible to icing. Assuming the boundary layer sep point was moving
aft on the stabilizer already, when they lowered the flaps they could
have easily exceeded the CLmax for the tail.
Even if this theory is correct, I'd be looking for additional factors
related to icing coupling to cause the autorotation they seemed to
have entered prior to impact.
It's all theory anyway. The NTSB will come up with something as they
progress with the investigation.
DH

Following the theory, for the sake of discussion, is this pilot error
and is it avoidable?

I realize they can't see the tail but icing on the windshield was
reported.

I have icing, weather, an aircraft with a history of tail icing (due to
its design)....even if they had no stick inputs, do you go to flaps
knowing that you could possibly cause a sever pitch down and the
inevitable results?

NTSB: Flight 3407 Was On Autopilot Before Accident

Mon, 16 Feb '09
Practice Violated Company Policy For Icing Conditions

A National Transportation Safety Board official confirmed Sunday that
downed Continental Express flight 3407 was being flown on autopilot at
the time of the crash, contrary to normal procedures.

In conjuction with FAA recommendations, NTSB spokesman Steve Chealander
said Colgan Air, the plane's operator, recommends that pilots manually
fly during all conditions... and requires them to do so when there's
evidence of severe icing.

"You may be able in a manual mode to sense something sooner than the
autopilot can sense it," Chealander told the Associated Press,
emphasizing the need to hand-fly the airplane to better feel how it's
really flying when conditions are critical.

An autopilot will trim out an aircraft, within its capabilities, to
compensate for changing conditions -- including airflow disturbances
caused by icing -- without the flight crew necessarily becoming aware of
any abnormalities.