Carburettor Heater
Chapter 4.12
The Carburettor Icing
Carburettor icing is possible in high humidity and at temperatures ranging from 0°C to +20°C (sometimes also at higher temperatures).
Recognizing Carburettor Icing
Already existing carburettor icing may be recogized as follows:
- Decrease in RPM
- Despite an increase in power, the drop in RPM continues. (The drop in RPM can easily go unnoticed because it is so slow.)
- Irregular / rough running of the engine
- Engine failure
- If the following situation occurs after the carburettor heater has been switched on:
Initially a sharp decline in RPM, irregular engine run;
After about 3 seconds, constant rise in RPM
Recognizing Carburettor Icing
The icing of the carburettor can only be detected and counteracted if the heater can act long enough. A short use does not make sense.
Some aircraft have a thermometer in the carburettor that indicates the temperature range in which carburettor icing may occur. The range at risk is indicated by a yellow arc.
The Carburettor Heat Control
A device is installed in the cockpit, by which the carburettor heater can be switched on and off.
The Carburettor Heat Control
Using the Carburettor Heater
How to recognize carburettor icing
No carburettor icing
- When switching on the carburettor heater, a drop of 100 to 200 RPM will occur. It retains that value.
- When switching off the carburettor heater, the RPM resumes its original value.
Using the Carburettor Heater
How to recognize carburettor icing
Light carburettor icing
- When switching on the carburettor heater, the RPM will drop from 100 to 200 RPM. After 5-10 seconds, the RPM increases.
- When switching off the carburettor heater, the RPM increases above its initial value.
Using the Carburettor Heater
How to recognize carburettor icing
Severe carburettor icing
- When switching on the carburettor heater, a strong drop in RPM is observed. As the Ice melts, the engine may run roughly. Then the RPM increases to the initial value.
- When switching off the carburettor heater, the RPM increases remarkably above the initial value.
Using the Carburettor Heater
Deicing the carburettor / DEICING
Severe carburettor icing
- For checking, the carburettor heater is switched on from time to time for a few seconds.
- For checking, the carburettor heater is switched on frequently for a few seconds.
- The carburettor heater remain switched on. When flying with the carburettor heater on, available power is reduced.
- Since the air which is heated is less dense, consequently the mixture setting will be too rich. If you fly for a long period with the carburettor heater switched on, you have to lean the mixture accordingly.