Induction System Flashcards
Throttle Knob
A throttle knob is the means by which the pilot
controls the amount of fuel/air (mixture) provided to
the cylinder of the engine.
Mixture Knob
Sets the amount of fuel added to the
intake airflow.
-At higher altitudes, the air density decreases so the fuel
volume must also be reduced to give the correct air–fuel
mixture
Fuel/Air ratio
Stoichiometric Ratio: 15:1. Ratio of air to fuel by weight
entering the cylinder
Benefits of properly leaned engines
- Better engine performance
- Better fuel efficiency
Leaning Process
Starting 3,000 ft and thereafter every 1000 ft of
altitude gain, rotate the mixture to the left (lean)
by one rotation until reaching the PEAK RPM
-Slightly enrich the mixture until it drops
slightly below the PEAK RPM
Rich of peak (Leaning type)
- Engine is slightly rich of maximum power
- Better engine cooling
Lean of peak (Leaning type)
- Mixture is slightly lean of maximum power
- Better efficiency
MIXTURE TOO RICH
- Lower engine Power output
- High fuel consumption
- Possible fouling of spark plugs
MIXTURE TOO LEAN
- Lower engine power output
- HIGH engine temperatures
- Rough engine and can cause
Detonation and Pre-Ignition
Carburetor icing formation
Outside Air Temperature below 70 deg F.
Or 21 deg C and Relative Humidity is
above 80%
Carburetor Icing
- Unexplained reduction or loss of engine
power - OAT at 20 deg. C or below, with high
humidity in the air
Carburetor icing detection on fixed pitch propellers
Reduction in RPM and leads to engine roughness
Carburetor icing detection on constant speed propellers
Reduction in manifold pressure but no reduction in RPM
Carburetor heat
Carburetor heat uses hot air drawn from the exhaust shroud to raise the temperature in the venturi section of the carburetor high enough to prevent or remove any ice
build-up
Note: introducing hot air makes the mixture richer
(since hot air is less dense)
Carburetor heat application
Expect a reduction in engine power. Usage below the Green Arc of Tachometer Only.
If carburetor ice was present, there will be a
slight INCREASE in RPM after you apply the Carb Heat
If carburetor ice was not present, RPM REMAIN
CONSTANT
Indication of a successful application of carb heat in fixed pitch propeller.
Increase in RPM after the carburetor ice
is melted
Indication of a successful application of carb heat in constant speed propeller.
Increase in manifold pressure after the
carburetor ice is melted.
