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Wing De-Icing Question
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 |
#12
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Wing De-Icing Question
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 |
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Wing De-Icing Question
Bertie the Bunyip wrote:
Note that this flight started its plunge right at or after the outer marker. The outer marker is where you normally lower gear and flaps. Lowering flaps is the thing that causes the tailplane stall if the tailplane is iced up. Rubbish. Uhh, which part of this is rubbish? As I recall from a news account of the FDR, the loss of control was immediately following gear / flap extension. If it was the "outer marker is where you normally lower gear and flaps", well yeah but I'm not sure that's the point. T |
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Wing De-Icing Question
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 |
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Wing De-Icing Question
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Wing De-Icing Question
On Feb 15, 4:23*pm, 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 Maybe a silly notion/question buuuut...if this (pitching/roll -this from new reports as of 2/16) had occurred at a higher altitude, 7000 ft say, would the plane have entered a 'flat' spin? Was the impact indicative of such? |
#18
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From OP Re Wing De-Icing Question - A Few More Questions
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! :-) |
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Wing De-Icing Question
wrote in message ... On Feb 15, 4:23 pm, Dudley Henriques wrote: Cool! Let's speculate on speculation. |
#20
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Wing De-Icing Question
On Feb 16, 8:01*am, wrote:
On Feb 15, 4:23*pm, 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 Maybe a silly notion/question buuuut...if this (pitching/roll -this from new reports as of 2/16) had occurred at a higher altitude, 7000 ft say, would the plane have entered a 'flat' spin? *Was the impact indicative of such? Difficult to say. I'm far from being the expert on transport aircraft. My understanding is that if, and that is still a big IF, tailplane icing was involved in the Buffalo accident, it was the lowering of the flaps and the cfg change to the wing increasing the aoa on the tail that was the factor actually taking them into stall. If that was the cause, the actual breaking of the stall caused by the ice on various leading edges could very well have taken them into uncontrolled auto rotation. For that to happen, yaw had to be present at the stall. The scenario above assumes low altitude due to the flap extension factor. At this stage in any accident investigation, it's always conjecture. Already however, the seldom discussed issue of tailplane icing is getting a lot of attention throughout the entire aviation community and that alone is good for flight safety. The NTSB investigation will provide the answer I'm sure. Dudley Henriques |
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