ACS Fuel Systems & Aircraft Plumbing

Question 1

What is the primary purpose of a fuel strainer (gascolator) in a reciprocating aircraft engine fuel system?

Accepted Answer

To remove water and sediment from fuel before it reaches the carburetor or fuel injector

Answer

To measure fuel flow rate

Answer

To regulate fuel pressure to the engine

Answer

To prevent vapor lock in the fuel lines

Question 2

Why must aircraft fuel tanks be vented to atmosphere?

Accepted Answer

To prevent tank collapse or pressure differential as fuel is consumed and altitude changes

Answer

To allow fuel vapors to escape for fire prevention

Answer

To equalize pressure between wing tanks

Answer

To enable fuel cross-feed between tanks

Question 3

What type of fuel is used in most turbine-powered aircraft operated in the United States?

Accepted Answer

Jet-A (kerosene-based turbine fuel)

Answer

100LL AVGAS

Answer

MOGAS (automotive gasoline)

Answer

Jet-B wide-cut turbine fuel

Question 4

What color is 100LL aviation gasoline (AVGAS) dyed, and why?

Accepted Answer

Blue, to identify it as 100 octane low lead and prevent misfueling with other grades

Answer

Red, to distinguish it from Jet-A

Answer

Green, per FAA standard

Answer

Clear/colorless, undyed for purity

Question 5

During a preflight fuel check, a pilot/mechanic finds a small amount of water in the fuel sample. The correct action is:

Accepted Answer

Continue sampling and draining until no water is found, verifying the sample is clear

Answer

Add fuel system icing inhibitor and return to service

Answer

Drain only the affected sump and continue

Answer

Ground the aircraft indefinitely until the tank is removed

Question 6

What is the function of a boost pump in an aircraft fuel system?

Accepted Answer

It provides positive fuel pressure for starting, backup fuel pressure, and transfer between tanks

Answer

It replaces the engine-driven fuel pump as the primary pump

Answer

It filters fuel before delivery to the engine

Answer

It controls the fuel-air mixture ratio