AME Gas Turbine Engine Theory 5

Question 1

What happens to gas velocity and pressure as subsonic gas flows through a convergent exhaust nozzle?

Accepted Answer

Velocity increases, pressure decreases

Answer

Per Bernoulli's principle, subsonic flow in a convergent duct accelerates while static pressure drops.

Question 2

A choked exhaust nozzle produces which type of additional thrust?

Accepted Answer

Pressure thrust

Answer

When the nozzle is choked, exit pressure exceeds ambient, and the pressure difference across the exit area adds pressure thrust.

Question 3

Using F = M x (V2 - V1), what happens to net thrust as aircraft forward speed increases, assuming constant exhaust velocity and mass flow?

Accepted Answer

Net thrust decreases

Answer

Higher forward speed increases inlet velocity V1, reducing the velocity change and thus net thrust.

Question 4

What is the purpose of a convergent-divergent exhaust nozzle on supersonic aircraft?

Accepted Answer

Allow exhaust gases to expand to supersonic velocity for added thrust

Answer

Flow reaches Mach 1 at the throat and accelerates supersonically in the divergent section.

Question 5

Which engine parameter is generally used as the primary thrust-setting indication on many turbofan engines?

Accepted Answer

EPR or N1

Answer

EPR (exhaust pressure ratio) or fan speed N1 directly relates to thrust and is used for power setting.

AME - Aircraft Maintenance Engineer Practice Test