Airframe Mechanic Certification Powerplant Systems & Maintenance 5

Question 1

What is the purpose of a fuel-air ratio enrichment system (or power enrichment valve) in a carburetor?

Accepted Answer

Enrich the mixture at full throttle to prevent detonation and provide cooling

Answer

The power enrichment system richens the mixture at high power settings to prevent detonation and provide additional cooling through excess fuel.

Question 2

What color is Jet-A turbine fuel, and what is its approximate flash point?

Accepted Answer

Colorless to straw-colored, approximately 100°F (38°C)

Answer

Jet-A is colorless to straw-colored with a minimum flash point of approximately 100°F (38°C), making it less volatile than avgas.

Question 3

What is the primary cause of hot section deterioration in a turbine engine?

Accepted Answer

Thermal cycling and oxidation from extreme combustion temperatures

Answer

Combustion temperatures far exceeding blade material limits cause oxidation, thermal fatigue cracking, and erosion in the turbine hot section.

Question 4

In a constant-speed propeller system, if the propeller control is moved to the INCREASE RPM position, the governor:

Accepted Answer

Releases oil from the propeller dome allowing springs/counterweights to decrease pitch

Answer

Moving toward higher RPM causes the governor to port oil away from the propeller piston, allowing centrifugal twisting moment or springs to decrease blade pitch and increase RPM.

Question 5

A turbine engine hung start is defined as:

Accepted Answer

An engine that lights off but does not accelerate to idle RPM

Answer

A hung start occurs when the engine ignites and sustains combustion but fails to accelerate to self-sustaining idle speed, requiring an abort.

Airframe Mechanic Certification Practice Test

Airframe Mechanic Certification Practice Test

Airframe Mechanic Certification Powerplant Systems & Maintenance 5