I spent 9 years flying in the Alaska bush. Planes like C172, C207, C208, SC7 and eventually a DC6.
I strongly advise against the use of carb heat on takeoff *unless* the manufacturer has a specific recommendation describing the procedure.
On the DC6, I once saw a letter on Pratt and Whitney letterhead describing the use of carb heat on takeoff at temps of -40C. And we performed the procedure a few times, but we had Carb Temp gauges with yellow bands to help us regulate the temp....but even so....it's a *very* workload intensive procedure for the flight engineer to manage the power reductions and related carb temp changes from takeoff power to METO power to climb power: Four throttles, one prop master lever, four cowl flap dials and four carb heat levers and only *two* hands! It's a CRM nightmare that usually calls for the FO to help manage the carb heat.
And by the way, we'd normally reduce the manifold pressure 1"hg for every 10 degrees below standard temp(+15C), while observing BMEP limits.
But, back to carb heat on smaller engines. The problem with using carb heat on say, a Lycoming, when it's so cold outside is that you may be actually warming the air in the throat of the carb to the *perfect* temperature for carb ice!!! (~-20C to 0C).
This is not a good idea without manufacturer recommendations and a Carb Temp gauge.
In fact, for most of the companies I work with in Alaska, we'd set -40C as a cutoff and stop flying the recip aircraft. Everything just gets too brittle at that temperature.
