Wing De-Icing Question

On Feb 16, 8:01*am, "Robert11" wrote:
Hello,

Not a Physicist, so please bear with me.

The posts here seem to imply that wing icing occurs (mainly), if not
exclusively, on the leading edges, and not on the upper or lower wing
surfaces.

Why ?

If it does occur on the upper surfaces in modern jet commercial aircraft, is
there also
hot bleed air available for this large surface, as there is for the leading
edges ?

If it does occur on modern turboprops, on the upper surface, there is
nothing they can do to remove it.
Right ?

Why did they say that a 180 degree turn "may" help break off ice ?

Thanks,
Bob
---------------------------------

"VOR-DME" wrote in message

...



In article
,
says...

On Feb 15, 5:41 pm, Tman wrote:
Dudley Henriques wrote:
There's a very good chance the Boston crash might have been tailplane
icing.

Did you mean BUF or did I miss something in Boston?
T

Yes. I've been dealing with a Boston issue most of the day and my
senior moment quota kicked in. It was Buffalo.
DH

Oh thanks! Spent two hours on the NTSB database trying to figure what
Boston crash we were talking about! :-)- Hide quoted text -

- Show quoted text -

Think for a moment about the airflow around thle wing. At one point
the air flows up and over, and a little lower on the leading edge if
flows down and under. There is a line then, the point where the flow
seperates, where there is little airflow at all. It's called the
stagnation point. If ice is going to form it will form where there's
not a lot of wind blowing the water away, that's why it forms on the
leading edges. You'll see, in icing conditions, ugly ice sticking out
from the leading edges first.

The magic of a 180 degree turn is, back where you came from there was
not ice forming -- go back there!

On Feb 16, 3:38*pm, VOR-DME wrote:
In article
,
says...



On Feb 15, 5:41*pm, Tman wrote:
Dudley Henriques wrote:
There's a very good chance the Boston crash might have been tailplane
icing.

Did you mean BUF or did I miss something in Boston?
T

Yes. I've been dealing with a Boston issue most of the day and my
senior moment quota kicked in. It was Buffalo.
DH

Oh thanks! Spent two hours on the NTSB database trying to figure what
Boston crash we were talking about! :-)

Sorry. Those "senior moments" can be annoying for sure. It's a shame
youth is wasted on such young people.
:-)))
-D

On Mon, 16 Feb 2009 05:58:24 -0800 (PST), a wrote:

The magic of a 180 degree turn is, back where you came from there was
not ice forming -- go back there!

??????????

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?

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.

On Feb 16, 9:18*am, 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?

Now they're looking at the pilot's possibly having the
autopilot on during the descent into and during the icing conditions,
against company policy. Anyone who has flown an autopilot will know
that it isn't the smartest beast and can cause problems. See
http://www.google.com/hostednews/ap/...BGCYgD96CNPN81

Dan

On Feb 16, 11:11*am, Gezellig wrote:
On Mon, 16 Feb 2009 05:58:24 -0800 (PST), a wrote:
The magic of a 180 degree turn is, back where you came from there was
not ice forming -- go back there!

??????????

I may not have been clear. If you find yourself in icing conditions,
retreating (do a 180) is often a good option.

On Mon, 16 Feb 2009 09:06:22 -0800 (PST), a wrote:

On Feb 16, 11:11*am, Gezellig wrote:
On Mon, 16 Feb 2009 05:58:24 -0800 (PST), a wrote:
The magic of a 180 degree turn is, back where you came from there was
not ice forming -- go back there!

??????????

I may not have been clear. If you find yourself in icing conditions,
retreating (do a 180) is often a good option.

Thx!

On Mon, 16 Feb 2009 08:35:08 -0800 (PST),
wrote:

Now they're looking at the pilot's possibly having the
autopilot on during the descent into and during the icing conditions,
against company policy. Anyone who has flown an autopilot will know
that it isn't the smartest beast and can cause problems. See
http://www.google.com/hostednews/ap/...BGCYgD96CNPN81

Dan

"The Dash 8 Q400 plane, operated by Colgan Air, was equipped with a
"stick shaker" and "stick pusher" mechanism that rattles the yoke to
warn the pilot if the plane is about to lose aerodynamic lift, a
condition called a stall. If not corrected in time, the mechanism
automatically pushes the stick forward to avert a stall.

Chealander said the plane was on autopilot until the "stick shaker" and
"stick pusher" kicked in, automatically putting the plane back in the
pilot's hands.

At some point, the pilot switched on an anti-stall device that increases
the speed of the plane by 20 knots and gives a pilot more margin to
recover from a stall if it occurs.

Asked whether the pilot might have overreacted by pulling the stick back
when it automatically went forward, Chealander said, "Yes, it's
possible."

================================================== =======================

Isn't this counter to pulling back on the yoke, cutting power and speed,
when you get nose pitch due to tail icing?

On Feb 16, 11:18*am, 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?

I would be hesitant to comment to that level not being current in type
or directly involved in the investigation. As the investigation
progresses there will be a deep look into the aircraft configuration
during the descent vs recommended procedures for conditions I'm sure.
-DH