|Quoting Tb727 (Reply 1):|
I've been told the design and sweep of the wing makes it difficult for ice to form unless it is bad icing.
No ice protection on the jet that I fly either, and I have seen considerable ice build-up on the horizontal stab during the post-flight. I observed no significant adverse handling characteristics with ice accumulation on the tail. I am always cautious in icing since flying turboprops in severe icing conditions in the Great Lakes region, but I find it interesting that on a turboprop, tail icing can be fatal, while in a jet, this seems to be irrelevant. (Ice on a supercritical airfoil or in the engines, is, however a major concern.) I have read that tail design must meet be able to withstand a certain amount of ice accretion with no adverse handling characteristics, otherwise ice protection must be integrated into the design. Can anybody verify or correct this?
|Quoting Jetlagged (Reply 2):|
Jet aircraft tend to use thermal anti-ice because they fly quickly through the weather and cruise above it so don't suffer from the same continuous exposure to icing. They also have hot bleed air readily available, and rubber boots would tend to spoil the high speed aerodynamics
True, jets tend to climb through icing more quickly, while turboprops are stuck in the weather longer. But, I don't think this would explain the logic behind systems selection during the design of an aircraft. And yes, rubber boots would spoil high speed aerodynamics. Jets have utilized boots though, such as the G200, Dornier 328Jet, and certain Citations, to name a few. Typically at altitudes where the airfoil is transonic, icing isn't as much of an issue.
But, I am not impressed with pneumatic de-icing boots. They are old technology, dating back to the 1940's or so. I always thought that they were used since too much bleed air would be robbed from the engines for effective use of a "hot wing" system for a turbo-prop. Even pneumatic boots rob alot of bleed air from a turboprop, necessitating lower power settings for climb and cruise. Ironic since you need the extra power during periods of ice accumulation more, but instead need to reduce power. Often, I have needed to descend to lower altitudes during moderate and greater icing above 10,000ft or so because the aircraft didn't have the power to climb above, with the robbed power for engine anti-ice and wing de-icing boots, combined with performance hits from ice accumulation. I have held onto ice accumulated on the wings during climbout all the way through landing, post-fight, and the next flight's de-icing spray-down, even while cruising above the clouds with direct noon sunlight (although cold temps). Boots aren't always effective.
Jet wing anti-ice also robs the engine of thrust when you most need it, but I have never once seen ice build on the wings during proper usage. Only unheated surfaces see ice build-ups, such as winglets, nose, and tail. Operational limitations for jet anti-ice usage typically dictate usage before even a fraction of a millimeter of ice begins to build on critical surfaces, but this video shows a trace amount of ice being shed from a jet wing moments after wing anti-ice is selected on. http://www.youtube.com/watch?v=Rczi0TJ05YA
Only during abnormal situations would the system be used in the de-icing capacity shown in the video, but this illustrates the effectiveness of the system.
I would much rather have a "hot wing" over a wing with a boot. As far as I know, no jet with "hot wings" has ever crashed as a result of ice accumulation except for improper anti-ice usage and those aircraft that took off with contaminated wings, such as the Challenger at Montrose, the Air Florida aircraft at DCA