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FAA Flight Engineer Reciprocating Engine (Added Rating) Knowledge Test Practice Test

The FEX added-rating knowledge test concerns reciprocating-engine systems and the flight engineer’s understanding of their operation. Practice-bank questions address engine components and maintenance indications, including accessory drives, cylinder compression, lubrication flow, turbocharging, valve clearance, crankshaft counterweights, and propeller controls. These subjects connect component functions with the effects of faults or restrictions on engine performance.

Exam overview

Exam providerFederal Aviation Administration
Exam codeFEX
CategoryAviation

About the FAA Flight Engineer Reciprocating Engine (Added Rating) Knowledge Test Exam

Engine-system knowledge includes tracing how mechanical, lubrication, ignition, and induction components support reliable operation. A flight engineer must distinguish the functions of an accessory gearbox, reduction gear, and crankshaft counterweights, and understand why valve clearance is specified. Questions also call for interpreting symptoms: leakage heard at an exhaust outlet during a compression check points toward the exhaust-valve path, while a restricted oil cooler can affect oil temperature. Other concepts include the role of an oil-filter bypass valve when flow is restricted, how turbocharging supports induction, and how a constant-speed propeller governor adjusts blade pitch. Relating these mechanisms to observable indications helps with system monitoring and fault recognition aboard aircraft powered by reciprocating engines.

Sample Practice Questions

Review a selection from this exam's published US Practice Tests practice bank.

Question 1

What is the primary purpose of the accessory gearbox on many aircraft reciprocating engines?

  1. ATo drive engine-mounted accessories from the engine
  2. BTo regulate the fuel-air ratio in each cylinder
  3. CTo reduce combustion-chamber temperature by circulating oil
  4. DTo alter propeller blade pitch directly
Show answerCorrect answer: A

The accessory gearbox transmits power from the engine, commonly through the crankshaft or drive train, to accessories such as pumps and generators. It does not directly control mixture or propeller blade pitch.

Question 2

During a compression check, a cylinder shows low pressure and air is heard escaping at the exhaust outlet. Which condition is most directly indicated?

  1. AAn exhaust valve is not sealing properly
  2. BThe piston rings are sealing too tightly
  3. CThe intake valve is opening too early
  4. DThe oil pump is producing excessive pressure
Show answerCorrect answer: A

Air escaping through the exhaust system during a cylinder leak check points to leakage past the exhaust valve or its seat. The location of escaping air helps identify the likely leakage path.

Question 3

In a pressure-fed lubrication system, what is the purpose of an oil filter bypass valve?

  1. ATo maintain oil flow if the filter becomes excessively restricted
  2. BTo stop all oil flow whenever the engine is cold
  3. CTo route fuel around the carburetor during takeoff
  4. DTo increase crankcase pressure when oil pressure is low
Show answerCorrect answer: A

If a filter is blocked or oil is too viscous to pass through it readily, a bypass valve can allow oil to continue to the engine rather than interrupting lubrication. The bypass may permit unfiltered oil to pass.

Question 4

What is a common purpose of a turbocharger in an aircraft reciprocating engine?

  1. ATo compress intake air so the engine can maintain greater power at altitude than it could without that boost
  2. BTo cool engine oil by spraying it into the exhaust
  3. CTo reduce the engine's displacement during climb
  4. DTo drive the aircraft's landing gear
Show answerCorrect answer: A

A turbocharger uses exhaust energy to drive a compressor that raises intake-air pressure. This can help an engine retain power as ambient air density decreases with altitude, subject to system limits.

Question 5

Why is valve clearance specified for many reciprocating engines?

  1. ATo allow for thermal expansion and ensure valves can seat as designed
  2. BTo keep the crankshaft from rotating during operation
  3. CTo determine the fuel grade required by the engine
  4. DTo prevent the starter from engaging the flywheel
Show answerCorrect answer: A

Valve clearance provides the specified relationship between valve-train parts when the engine is cold or at the measurement condition. Proper clearance accommodates thermal expansion and supports correct valve opening and seating.

Question 6

What is the principal function of a propeller reduction gear on an engine installation designed with one?

  1. ATo allow the engine to turn faster than the propeller
  2. BTo increase fuel pressure supplied to the engine
  3. CTo convert a fixed-pitch propeller into a constant-speed propeller
  4. DTo reduce cylinder compression at high engine speed
Show answerCorrect answer: A

A reduction gear lowers propeller speed relative to engine speed. This allows an engine to operate in a suitable speed range while the propeller turns more slowly, as intended by the design.

Question 7

What can a restricted engine-oil cooler cause during operation?

  1. AHigher-than-normal oil temperature
  2. BA permanently higher compression ratio
  3. CReduced cylinder displacement
  4. DAn increase in fuel octane rating
Show answerCorrect answer: A

A restricted oil cooler reduces heat transfer from the oil to the cooling airflow. This can lead to elevated oil temperature, subject to the specific system and operating conditions.

How to use this practice test

The free FEX practice bank contains 50 published questions. Each session presents up to 20 random questions, with results shown after the session. Use a session to check whether you can connect a component’s function with its operating effect, then revisit missed concepts such as compression leakage, oil flow, or propeller-governor action.

Preparation tips

  • For compression-check questions, trace where escaping air is heard and connect the outlet to the likely cylinder sealing fault.
  • Sketch the pressure-fed lubrication path, including the filter, bypass valve, and oil cooler; note what changes when a passage or cooler is restricted.
  • Compare the functions of an accessory gearbox, propeller reduction gear, and constant-speed propeller governor.
  • Review how turbocharging affects induction and how ignition booster devices assist starting in applicable magneto installations.
  • For each component, state its purpose and one operational indication that could suggest malfunction.
Official sourceOfficial exam page ↗