Been in too much natural ice, mostly in the NE US. Also flew interesting trials at the spray rig in Ottawa.
Lots of information, but here is how I see it (PPRUNE comments are welcomed!):
1) Ice Forecasts are not necessary. Ice is almost always available in clouds below feezing temp. If it is visible moisture, and it is below freezing, you will probably get ice if you fly in it.
2) The ice on your blades can form even if you have no ice on your airframe. The blades are in a different environment, and the speed and shape of them can allow ice to form on them while your windshield and wipers are completely clean. And vice-versa, your windshield can get glazed over with thick ice, and your blades can be completely free. (Go figure!)
3) Be aware of the torque your engines are producing for the cruise collective setting, that is your only predictable cue to the formation of ice. When the blades get "ice cholesterol" (a wise guy term for clogged with ice) they get a brand new airfoil, invented by the weather, and it is not the airfoil the designer wanted. the drag will be higher and the lift will be lower, so the torque (MP) will start to climb up all by itself, for the same collective setting. Best way to find out if you are getting ice is to leave the collective alone, and just watch the torque. In ice, with constant collective and altitude, the torque will creep up while you are watching. New airfoils (like those on all newer helos) are more susceptable to loss of performance because they have lower drag than the old 0012 airfoil everybody used in the 60's and earlier.
4) If you are in ice, you are coming down unless you get lucky. The ice will grow if you stay in the ice cloud (it is actually a cell inside the cloud that might end in 100 meters, or might be miles long). If you get lucky, the ice will stop growing, and even sublimate into the atmosphere as you continue to fly (the torque will magically go down to the original torque). A 180 degree turn is a very nice option, if ice is forming and you catch it in time.
5) If you break out into the clear, the ice will probably sublimate. I escaped an ice situation once by turning toward a bright patch, and when I popped from the side of the cumulus I had been in, the bright sunshine and clear air cleared the ice in about 30 seconds. I went from absolutely no climb at Vy to normal cruise speed at the same power.
6) Ice will shed if it gets thick enough, but your performance will be nil by that time. If your flight performance is nil (lots of power, but you are descending) then you can bet your autorotative performance is also nil, could be that you can''t even hold the rotor in the green in autorotation at bottom collective.
7) Breaking out over warm water is a nice option, if you know the clouds don't go to the water, and that the air over the water is warm. This works in the North Sea, and is near suicide anywhere else.
8) Keep the engine protected with anti-ice whenever there is visible moisture near freezing temps. Never let it go off. Most engine installations are fully ice protected even when the rest of the aircraft is not, at least for Part 29 helos. Ice will kill an engine very fast.
9) Best way to handle helicopter ice is stay out of clouds that are cold. Period. If you fly IMC and expect that only forceast icing is a problem, you will become a PIREP in a heart beat.
10) De-iced blades is a great thing. In most parts of the world, as important as being equipped for IMC, I think.
Last edited by NickLappos; 6th Oct 2003 at 01:57.