Canadians all know of a device called a Herman-nelson.Loved if it starts , hated when it does'nt. I'ts a large space heater, powered by a gasoline engine. Newer ones have Honda engines and start first pull at -40. Heat is then applied to all the important areas of the helicopter. In the case of logging S-61's this can take up to 2 hours to remove snow and ice. The batteries will have spent the night in the drying room of the camp and will be installed nice and warm.
On S-61 's ice can be found in the oddest of places:in the corners of the inlet shield, inside the NFG spring, which will cause jammed yaw pedals.Blade pockets can fill with ice and the upper cargo door rail will collect it in flight.
The start-up limits for a CT-58 are -25 below , and for good reason.If you ever check the oil level at such temps the dipstick will appear to have oil on it with the viscosity and appearance of treacle. Starting with the oil in such a state will overstress the accessory drive.
Winter flying takes a lot more effort on the ground.