I posted some photos of flight in known icing conditions,that were taken between 1969-73,in Canada,in Sea-king,Wessex,Wasp and Gazelle icing trials.They`re on P 15 of `R/heads around the World,28 Nov `03. Trials were done in stratiform sub-0 cloud,with a good cloudbase,and heavily instrumented aircraft.
A Gazelle we did icing-trials with in Ottawa, 1976 Feb-Mar. We flew in everything from heavy snow to freezing rain, Spray-rig, and freezing fog. I see from my log book that I also spent most of the time with the hyd. off for control force measurements.
Ice-damage to a Wx/S-K engine(T-58/Gnome), which also illustrates why an axial-flow compressor with VIGV`s is not an ideal engine to use in a helo, without adequate intake protection.
A WX blade with ice :we used a max rise in Tq. of about 20-25 %, before you quit, IF you were not getting ice shedding naturally. That would still give you an acceptable rotor performance if both motors quit/or a trans. failure. Which did happen in a S-King-- Everyone had their chutes on, but they got back before the g/b seized.
AH-56A Cheyenne on an early rig-run.
Front shot of a Wasp blade, showing the stagnation-point at the L/E, and ice growing out above/below the blade; very dangerous as the rise in drag/ torque is very rapid.