Engine Fuel Metering Systems Flashcards
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Read the first 7 Engine Fuel Metering Systems flashcards as text
An aircraft fuel injection system is described as 'continuous flow.' This means:
Answer: Fuel flows continuously to each injector nozzle and is metered by restrictor orifice size and pressure differential
In a continuous-flow system, fuel is constantly delivered to each nozzle at a metered rate, unlike pulsed or timed systems used in automotive engines.
What is the correct procedure when the engine-driven fuel pump fails in flight on an aircraft with an electric boost pump?
Answer: Turn on the electric boost pump; it can sustain normal operation at reduced power levels
The electric boost pump is designed to provide sufficient pressure to sustain flight if the engine-driven pump fails, though the pilot should follow the AFM and land as soon as practicable.
A float carburetor's main metering jet is primarily responsible for:
Answer: Controlling the maximum fuel flow rate at cruise and high-power settings
The main metering jet is a calibrated orifice that controls the rate of fuel flow through the main discharge nozzle during cruise and high-power operation.
When performing a fuel flow check on a fuel injection system using a flow meter, uneven fuel flow between cylinders may indicate:
Answer: Worn or partially clogged injector nozzles or differences in nozzle orifice size
Uneven fuel flow between cylinders in a continuous-flow system most commonly results from partially clogged, worn, or mismatched injector nozzles.
What aviation regulation requires that the fuel system be capable of delivering fuel to the engine at a flow rate of at least 150% of the takeoff fuel consumption?
Answer: 14 CFR Part 23 / 25 fuel system design requirements
14 CFR Part 23 (and Part 25 for transport category) specifies that fuel system flow must be at least 150% of takeoff consumption to ensure a safety margin.
The function of the air bleed in the main discharge circuit of a float carburetor is to:
Answer: Emulsify (aerate) the fuel to improve atomization and prevent siphoning
The main air bleed introduces air bubbles into the fuel stream before it exits the discharge nozzle, improving atomization and preventing fuel from siphoning out when the engine is stopped.
After reinstalling a carburetor following overhaul, the idle mixture should be adjusted by:
Answer: Running the engine to normal operating temperature and adjusting for a slight RPM rise when the mixture is slowly moved to cut-off
Correct idle mixture is confirmed by slowly moving the mixture toward cut-off and observing a 25–50 RPM rise before the engine stumbles, indicating the mixture was slightly rich at idle.