Philsquares From , joined Dec 1969, posts, RR: Reply 1, posted (9 years 8 months 4 days 20 hours ago) and read 2348 times:
I guess I'm not too sure quite what you're asking. But, I will try to answer what I think is your question.
When a/c are deiced on the ground there are several types of deicing fluid that can be used. Generally Type IV provides the best "holdover" time. Holdover time is basically the length of time the a/c can sit in the conditions before it has to be deiced again. There are charts in the a/c that you can refer to that will determine holdover time. It is based on temp and type of precipitation.
As far as taking off in icing conditions, this is all for the 747-400. It is nothing really too special. There is engine anti icing which would be on, that takes bleed air and heats the cowling to prevent the formation of ice. On the -400 there is also wing heat for deicing of the wing leading. However with flaps out of the up position, the bleed air used for the wing heat is vented overboard. Once the flaps are retracted, you have wing heat available. However, the way the wing on the -400 is designed build up on the leading edge almost never occurs. You will find on the classic and the -400 the application of wing heat almost never occurs.
AUAE From United States of America, joined Apr 2004, 296 posts, RR: 4 Reply 4, posted (9 years 8 months 4 days 19 hours ago) and read 2292 times:
Most big commercial jets (ie B737-B777) use bleed air ducted along the wing and stabilizer (Ver and Horz) leading edges to combat ice during flight. Most can operate this sys with the leading edge clean or deployed. Smaller aircraft (ie RJs and props) usually employ bladders or electric heating blankets.
For clarification, bleed air is compressed air bled from the compressor section of an engine, not exhaust gases.
I am not aware of any commercial or other aircraft that excrete deicing fluid. Someone correct me if I am wrong, but I think there are a lot of negatives to a sys like that.
Friction warming probably does help at cruise speed, but at cruise altitudes icing should not be a problem.
Air transport is just a glorified bus operation. -Michael O'Leary, Ryanair's chief executive
Philsquares From , joined Dec 1969, posts, RR: Reply 5, posted (9 years 8 months 4 days 18 hours ago) and read 2263 times:
Not to quibble, but according to my AOM Vol II, it indicates the valves are open with the flaps up, nothing about when the flaps are out of the up position. But looking elsewhere, it would indicate that the EICAS indicates the valve being open regardless of the flap position and the correct epr/n1 correction is made to the thrust ref.
Not a real big deal, in either case when the flaps are out of the up position there is no wing heat.
Aviopic From Netherlands, joined Mar 2004, 2681 posts, RR: 44 Reply 7, posted (9 years 8 months 4 days 18 hours ago) and read 2250 times:
Don't know the exact data but icing can only be a problem up to a certain height, above that the air is very cold and there very dry as well.
Guess every body knows freeze dried food !
There are many different anti icing systems: electric, bleed air and pneumatic to name a few.
As far as I know only used during take off and climb, decent and landing all if required by the circumstances of course.
The truth lives in one’s mind, it doesn’t really exist
Philsquares From , joined Dec 1969, posts, RR: Reply 10, posted (9 years 8 months 3 days 22 hours ago) and read 2081 times:
Just checked my Vol II. Don't have that at all. In fact, our a/c are only the on/off switch. I was in the sim yesterday and it appears as though the FMS takes the bleed correction off based on the switch position. So, I really don't know if the valve is closed or if it is dumped overboard. Either way, the end result is the same, no wing heat with the flaps out of the up position.