Piston Engine Fuel Systems Flashcards
Avgas density/specific gravity?
0.72kg per litre
What can lead to fuel detonation?
Feel with poor anti-knock qualities
Indirect mixture
Anything which unduly causes increased temp or pressure pre-detonation
High engine temps
What causes vapour lock?
Fuel vaporising in fuel lines or pumps
What is pre-ignition?
Fuel igniting before the spark plug has sparked caused by cylinder hot spots
What colours are 100LL and 100 avgas?
100LL is blue, 100 is green
What is the stoichiometric ratio of air to fuel?
15:1. This cannot be used though as the engine would overheat
What mixture ratios are ideal for lean and high power/rich settings?
Lean:20:1
High power:8:1
What do over and under rich mixture settings lead to?
Excessively rich leads to black exhaust smoke, excessively lean leads to high engine temps
What temp reading can be used to adjust mixture in the cruise?
EGT (Exhaust Gas Temp)
What is the purpose of the carburettor?
Mix air and fuel via an air intake and an engine driven pump
What is the purpose of the Venturi in the carb?
Drops the air pressure which sucks in the fuel to the throat
What is the purpose of the accelerator pump?
Provides additional fuel during acceleration of the throttle
What prevents excessively weak and excessively rich mixture at high flow rates?
Pressure balance duct and diffuser respectively
When is carburettor icing most likely?
18-24C at low power settings (butterfly valve closed, max’ venturi effect)
What other system replaces the carburettor?
Fuel injection (no carb icing)
