Originally Posted by
Piltdown Man
Are you sure you are correct? Firstly, we are talking about tail surfaces, secondly we are hearing that aircraft are appearing to be flying quite nicely when contaminated and lastly, nobody, absolutely nobody is suggesting that we shouldn't de-ice in the way that we are instructed. What is being discussed is "does the tailplane need to be de-iced?" and "if not why not?" and the fact that some of us have flown aircraft that have been contaminated in flight without the aircraft exhibiting any unpleasant flying characteristics.
Personally, I have been bitten (but not too badly) by a contaminated aerofoil. But to say that "ice will always kill" is patently wrong. All of us would be better off if we understood why some aerofoils were susceptible to suffering from ice and others were not. Until we have more knowledge though, we'll continue to piss away our company's cash being de-iced.
PM
Yes, the tailplane needs to be de-iced, and indeed anti-iced if necessary. It is defined as a "critical surface" for every type in existence, so it's a binding, regulatory, requirement that the tailplane, as for the wing and everything else declared "critical", be clean for takeoff.
Don't assume that because you have successfully flown an aircraft which has iced up, on an aircraft with no tailplane de-icing, that this means that tailplane contamination is not a concern for takeoff.
During certification, safe flight and acceptable handling is demonstrated for ice on the tailplane, as I mentioned above. The same is in fact shown for ice on ALL the unprotected surface, and even for failure cases for the protected areas. BUT there is one major exception - all of these demonstrations are conducted on an aircraft which is ALREADY AIRBORNE. There are no certification tests undertaken to demonstrate that you can safely takeoff - and in fact when we do the takeoffs with artifical ice to do the in-flight tests, we go to great lengths to mitigate the takeoff risks, which are considerable.
Yes, we do get airborne. But not at limiting speeds, weights or cgs. We make damned sure we don't overrotate, or rotate early. We do all kinds of things to try to make that takeoff safe. We certainly don't do things like mistrim the aircraft - something we DO do for the normal takeoff cert.
In short, takeoff certification, and thus the safety of the takeoff, is predicated on the CLEAN
AIRCRAFT CONCEPT - and if you don't get the aircraft into the condition that was assumed for certification, you just became a test pilot, because you're pushing the envelope.