ACS Powerplant Systems & Engine Overhaul 3

Question 1

What is the function of an intercooler in a turbocharged aircraft engine installation?

Accepted Answer

Cool compressed induction air between the turbocharger compressor and the engine intake

Answer

An intercooler (also called aftercooler) cools the hot compressed air from the turbocharger before it enters the engine, increasing air density and preventing detonation.

Question 2

Which FAA document provides the official time between overhaul (TBO) limits for an aircraft engine?

Accepted Answer

The engine manufacturer's Type Certificate Data Sheet or service manual

Answer

TBO limits for certified engines are established by the manufacturer and listed in the Type Certificate Data Sheet or the engine service/overhaul manual, not in FARs.

Question 3

During engine assembly, what is the correct procedure for installing a new oil seal on a crankshaft?

Accepted Answer

Lubricate the seal lip with clean engine oil and press it in squarely to the specified depth

Answer

Oil seals should be lubricated on the sealing lip with clean engine oil to prevent lip damage during installation and initial start-up, and pressed squarely to the correct depth.

Question 4

What condition does a 'hung start' describe in a turbine engine?

Accepted Answer

The engine lights off and runs but stabilizes at an RPM below idle due to insufficient power from the starter

Answer

A hung start occurs when the turbine engine lights and reaches a self-sustaining condition but RPM stabilizes below normal idle because the starter cannot supply enough energy to accelerate the engine further.

Question 5

In reciprocating engine ignition timing, what does 'BTDC' mean and why is it used?

Accepted Answer

Before Top Dead Center; spark is fired early so combustion pressure peaks as the piston passes TDC

Answer

BTDC means Before Top Dead Center; the spark fires early because combustion takes time, allowing peak pressure to build just after TDC for maximum mechanical advantage on the piston.

(ACS) Airman Certification Standard Certified Mechanic Practice Test

(ACS) Airman Certification Standard Certified Mechanic Practice Test

ACS Powerplant Systems & Engine Overhaul 3