Ancillary controls

Ancillary Controls lesson

Carburetor Heat

Mixture Control


Carburetor Heat: Icing

ice can form in the induction system:
  • Moist atmospheric condition.
  • -5°C to +30°C .
  • Caused by the absorption of heat from the air during vaporization of the fuel.
  • Also caused by venturi effect.
Indication of icing:
  • Loss of RPM with a fixed piched controller
  • Loss of manifold pressure with a constant speed controler.
What to do:
  • Immediately use: full carburetor heat .
  • In general carburetor heat should not be used while taxiing because in the “on” position the intake air usually bypasses the carburetor.
  • Avoid using carburetor heat during take-off, except during special procedures (very low temperature), since it may cause detonation and engine damage.

Carburetor Heat: system

Mixture Control

Mixture too rich:
  • Lower power
  • Uneven running of engine
  • Engine too cool
  • Fuel is wasted
  • Possible spark plug fouling
  • Range is reduced
Mixture too lean:
  • Power will be lost
  • Engine may run rough and vibrate
  • Engine too hot
  • Engine damage due to detonation

   Review questions

  • What effect does too rich a mixture have on the aircraft ?
  • What effect does too lean a mixture have on the aircraft ?
  • What is the first indication of icing to the pilot ?
  • Why don’t we use carb heat during taxiing?
Study flight
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