ACS Fuel Systems & Aircraft Plumbing 1 — Questions and Answers
Question 1: What is the primary purpose of a fuel strainer (gascolator) in a reciprocating aircraft engine fuel system?
- To measure fuel flow rate
- To remove water and sediment from fuel before it reaches the carburetor or fuel injector (Correct answer)
- To regulate fuel pressure to the engine
- To prevent vapor lock in the fuel lines
Correct answer: To remove water and sediment from fuel before it reaches the carburetor or fuel injector
A fuel strainer (gascolator) filters water and particulate contamination from the fuel before it enters the engine fuel metering system.
Question 2: Why must aircraft fuel tanks be vented to atmosphere?
- To allow fuel vapors to escape for fire prevention
- To prevent tank collapse or pressure differential as fuel is consumed and altitude changes (Correct answer)
- To equalize pressure between wing tanks
- To enable fuel cross-feed between tanks
Correct answer: To prevent tank collapse or pressure differential as fuel is consumed and altitude changes
Tank venting prevents vacuum buildup as fuel is consumed and compensates for atmospheric pressure changes with altitude, preventing tank deformation and fuel flow interruption.
Question 3: What type of fuel is used in most turbine-powered aircraft operated in the United States?
- 100LL AVGAS
- Jet-A (kerosene-based turbine fuel) (Correct answer)
- MOGAS (automotive gasoline)
- Jet-B wide-cut turbine fuel
Correct answer: Jet-A (kerosene-based turbine fuel)
Jet-A is the standard turbine fuel used in most US turbine aircraft, with a flash point above 100°F and freeze point around -40°C.
Question 4: What color is 100LL aviation gasoline (AVGAS) dyed, and why?
- Red, to distinguish it from Jet-A
- Blue, to identify it as 100 octane low lead and prevent misfueling with other grades (Correct answer)
- Green, per FAA standard
- Clear/colorless, undyed for purity
Correct answer: Blue, to identify it as 100 octane low lead and prevent misfueling with other grades
100LL AVGAS is dyed blue to identify it as 100 octane low lead fuel and prevent misfueling with Jet-A or other grades.
Question 5: During a preflight fuel check, a pilot/mechanic finds a small amount of water in the fuel sample. The correct action is:
- Continue sampling and draining until no water is found, verifying the sample is clear (Correct answer)
- Add fuel system icing inhibitor and return to service
- Drain only the affected sump and continue
- Ground the aircraft indefinitely until the tank is removed
Correct answer: Continue sampling and draining until no water is found, verifying the sample is clear
When water is found in a fuel sample, continue draining and sampling from all sumps until all samples are consistently clear and free of water, then verify the quantity before flight.
Question 6: What is the function of a boost pump in an aircraft fuel system?
- It replaces the engine-driven fuel pump as the primary pump
- It provides positive fuel pressure for starting, backup fuel pressure, and transfer between tanks (Correct answer)
- It filters fuel before delivery to the engine
- It controls the fuel-air mixture ratio
Correct answer: It provides positive fuel pressure for starting, backup fuel pressure, and transfer between tanks
Electric boost pumps provide fuel pressure for engine starting, serve as backup if the engine-driven pump fails, and assist in fuel transfer between tanks.
ACS Fuel Systems & Aircraft Plumbing 1
What is the primary purpose of a fuel strainer (gascolator) in a reciprocating aircraft engine fuel system?