AMT Aircraft Fuel Systems 2 — Questions and Answers
Question 1: What is the purpose of a crossfeed system in a multi-engine aircraft?
- To transfer fuel between main and auxiliary tanks of the same engine
- To allow any engine to draw fuel from any onboard fuel tank (Correct answer)
- To pressurize all fuel tanks simultaneously for high-altitude operations
- To automatically balance fuel loads during refueling
Correct answer: To allow any engine to draw fuel from any onboard fuel tank
A crossfeed system allows any engine to draw fuel from any tank, providing fuel management flexibility and enabling continued flight if an engine-specific pump or tank develops a problem.
Question 2: What type of filter or strainer is most commonly used in aircraft fuel systems to remove particulate contamination?
- Pleated paper element filter
- Mesh screen or sintered bronze strainer (Correct answer)
- Activated charcoal filter element
- Magnetic particle separator
Correct answer: Mesh screen or sintered bronze strainer
Mesh screen or sintered bronze strainers are standard in aircraft fuel systems because they trap particles while allowing fuel to flow with minimal pressure drop, and can be cleaned and reused.
Question 3: What condition causes vapor lock in an aircraft fuel system?
- Fuel pressure becomes excessively high and ruptures the fuel line
- Fuel temperature rises and vaporizes in the lines, creating bubbles that disrupt flow (Correct answer)
- Water contamination freezes in the fuel lines during high-altitude cruise
- A clogged fuel filter causes suction that collapses the fuel pickup tube
Correct answer: Fuel temperature rises and vaporizes in the lines, creating bubbles that disrupt flow
Vapor lock occurs when fuel temperature rises sufficiently to vaporize fuel inside the fuel lines or pump, creating vapor bubbles that disrupt or completely block liquid fuel flow to the engine.
Question 4: What does a fuel pressure regulator do in a fuel-injected piston aircraft engine?
- Increases fuel pressure automatically for high-altitude operations
- Maintains a constant fuel pressure to the fuel injector manifold regardless of pump output variations (Correct answer)
- Regulates fuel temperature by controlling flow rate through a heat exchanger
- Controls total fuel quantity delivered from tanks to the distribution manifold
Correct answer: Maintains a constant fuel pressure to the fuel injector manifold regardless of pump output variations
The fuel pressure regulator maintains steady, constant pressure at the injector inlet, ensuring accurate and consistent fuel metering to each cylinder regardless of engine speed or pump output changes.
Question 5: What is the purpose of fuel tank sumps in aircraft fuel systems?
- To increase usable tank capacity by using otherwise dead space
- To collect water and sediment at the tank's lowest point so they can be drained during preflight (Correct answer)
- To provide structural reinforcement to the bottom of the fuel tank
- To house the capacitance probes used by the fuel quantity gauging system
Correct answer: To collect water and sediment at the tank's lowest point so they can be drained during preflight
Sumps are located at the lowest point of each tank; since water and sediment are denser than fuel, they settle into the sump where they can be detected and drained during preflight sump checks.
Question 6: What color is AVGAS 100LL dyed to prevent misfueling?
- Clear/colorless
- Straw yellow
- Blue (Correct answer)
- Red
Correct answer: Blue
AVGAS 100LL is dyed blue by industry standard to visually distinguish it from Jet-A (clear/straw) and AVGAS 80 (red), reducing the risk of misfueling a turbine aircraft with leaded gasoline.
Question 7: What is the primary purpose of a fuel jettison (dump) system installed on large transport-category aircraft?
- To purge contaminated or degraded fuel from tanks before landing
- To rapidly reduce aircraft gross weight to below maximum landing weight during an emergency return (Correct answer)
- To transfer fuel from center tanks to wing tanks during cruise for CG management
- To pressurize fuel tanks before descent to prevent vapor lock at low altitude
Correct answer: To rapidly reduce aircraft gross weight to below maximum landing weight during an emergency return
Fuel jettison systems allow the flight crew to rapidly dump fuel overboard to reduce gross weight to the maximum allowable landing weight when an emergency requires an immediate return to landing shortly after takeoff with a full fuel load.
AMT Aircraft Fuel Systems 2
What is the purpose of a crossfeed system in a multi-engine aircraft?