Hot petrol

[Tony Griffiths]

Carburettor icing I have encountered once only, [first starts of the day, inland North Island NZ Winter, prob 1-2 deg C] but that was down to the factory water passages in the intake manifold of the vehicle being blocked by gunge.

Carburettor icing is not at the first start of the day. The scenario is that it starts at first start of the day, then maybe 20 miles down the road the air flow through the carb is reduced to zero by the formation of a large chunk of ice. Of course by the time the AA man (me) arrives the ice has melted and the engine starts.  I found it mainly occurred in damp foggy weather at just over freezing temperature.

He's the griff on carb icing. As it shows, it's possible for it to occur even at relatively high temperatures when combined with high humidity. P.S. In a light aircraft when the engine starts misfiring and the carb ice-warning light comes on, you select "Hot Air". As the ice melts, the misfire will often worsen; unfortunately, a number of pilots have then concluded that the hot-air setting must be making the problem worse and switched back to cold - whereupon their engine stopped.....and would not restart.