A&P Aircraft Fuel Systems 1 — Questions and Answers
Question 1: What is the purpose of a fuel system boost pump on a reciprocating engine aircraft?
- To pressurize the fuel tanks to prevent fuel boil-off at altitude
- To provide fuel pressure for starting and as a backup if the engine-driven pump fails (Correct answer)
- To filter debris from the fuel before it reaches the carburetor
- To measure the quantity of fuel remaining in each tank
Correct answer: To provide fuel pressure for starting and as a backup if the engine-driven pump fails
Electric boost pumps prime the fuel system for starting and serve as an emergency backup if the engine-driven mechanical fuel pump fails in flight.
Question 2: Which grade of aviation gasoline (AVGAS) is dyed blue and used in most current general aviation piston aircraft?
- 100LL (Low Lead) (Correct answer)
- 80/87
- 100/130
- 115/145
Correct answer: 100LL (Low Lead)
100LL (100 Low Lead) AVGAS is dyed blue and is the standard fuel for most piston-powered general aviation aircraft in the United States.
Question 3: What is the primary reason fuel sumps must be drained during preflight inspection?
- To verify the fuel quantity gauge is calibrated correctly
- To check for and remove water and sediment that accumulate at the lowest points of the fuel system (Correct answer)
- To relieve pressure that builds up in sealed fuel tanks
- To sample fuel for octane rating verification
Correct answer: To check for and remove water and sediment that accumulate at the lowest points of the fuel system
Water and contaminants are denser than fuel and settle at the lowest points (sumps), so draining removes these before flight to prevent engine fuel starvation.
Question 4: What does a fuel crossfeed valve allow on a multi-engine aircraft?
- It allows fuel from one wing tank to feed the engine on the opposite wing (Correct answer)
- It automatically balances fuel between left and right tanks during cruise
- It prevents fuel siphoning when the aircraft is parked
- It bypasses the fuel filter in an emergency
Correct answer: It allows fuel from one wing tank to feed the engine on the opposite wing
A crossfeed valve allows either engine to draw fuel from either wing tank, enabling the crew to feed both engines from one tank or maintain fuel balance.
Question 5: What is the function of a fuel system vent?
- To vent fuel vapors overboard through a flame arrester as a fire prevention measure
- To equalize tank pressure with ambient air pressure, preventing collapse or structural damage during fuel consumption and temperature changes (Correct answer)
- To allow ground crews to pressure-fill the tanks more quickly
- To drain condensation from the fuel cap area
Correct answer: To equalize tank pressure with ambient air pressure, preventing collapse or structural damage during fuel consumption and temperature changes
Fuel tank vents prevent a vacuum or pressure differential from forming as fuel is consumed or temperature changes, which could collapse the tank walls or prevent fuel flow to the engine.
Question 6: What color is Jet-A turbine fuel, and how does its ignition temperature compare to AVGAS?
- Blue; Jet-A ignites at a lower temperature than 100LL AVGAS
- Clear to straw-yellow; Jet-A has a higher flash point (less volatile) than AVGAS (Correct answer)
- Red; Jet-A and AVGAS have identical flash points
- Green; Jet-A has the same volatility as AVGAS but higher energy density
Correct answer: Clear to straw-yellow; Jet-A has a higher flash point (less volatile) than AVGAS
Jet-A is colorless to straw-yellow and has a flash point of approximately 100°F (38°C), which is significantly higher than AVGAS's flash point of about −50°F (−46°C), making Jet-A less volatile.
A&P Aircraft Fuel Systems 1
What is the purpose of a fuel system boost pump on a reciprocating engine aircraft?