Similar set-up on the Yak-52 where the external air scoop retracts into the cowling for warm air. The Yak is more prone to carb-ice on the ground than in the air, but I got a touch of it the other day, in a spinning exercise, so it's still possible.
We have a long running debate in our group regarding the Yak 52 carb heat (or not). Can you operate yours in flight? We have to back off the speed to about 170kph before we can move the lever !
The Russian flight manual only states that "at temperatures of +10c or more the carb heat may be left out", whatever that means. That tends to suggest at less than +10c carb heat should be left hot. Apparently some Yak 50's did not have a carb heat flap at all, the mechanics took them off!
Whatever the answer I have picked up icing whilst taxying at temps of +5c or less, but never in flight so long as you have a power setting above 'economy cruise'
As the carb intake temp should remain between +10 and +45 the lever seems to be more use as a carb cooler on summer days and a carb heater in winter
