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Engine Instrument Systems: Powerplant practice questions

Five original questions on engine instrument systems, each with the answer, an explanation and an FAA-H-8083-32B page reference.

1. Which gauge marking shows a range that may be passed through but in which the engine may not be operated?
  1. Red arc
  2. Yellow arc
  3. Green arc
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A. Red arc It generally marks an engine-propeller vibration range. A red line marks a point beyond which a dangerous condition exists.

Reference: FAA-H-8083-32B, Ch. 10, p. 10-21

2. On the handbook's example fuel pressure gauge, what range does the green arc cover?
  1. 0 to 2 psi
  2. 2 to 9 psi
  3. 9 to 10 psi
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B. 2 to 9 psi The red lines at 2 psi and 9 psi mark the minimum and maximum allowable fuel pressure.

Reference: FAA-H-8083-32B, Ch. 10, p. 10-22

3. What is the white radial "slippage mark" on an instrument with markings on the cover glass for?
  1. It marks takeoff power
  2. It shows whether the glass has moved relative to the case
  3. It marks the vibration range
Show answer

B. It shows whether the glass has moved relative to the case If the glass rotates, the range markings no longer line up with the dial, and the white mark shows it.

Reference: FAA-H-8083-32B, Ch. 10, p. 10-21

4. Why does an oil pressure gauge have a small restriction in its case or fitting?
  1. To keep pump pressure pulses from damaging the gauge or making the pointer oscillate
  2. To lower the reading for calibration
  3. To keep oil from freezing in the line
Show answer

A. To keep pump pressure pulses from damaging the gauge or making the pointer oscillate The restriction damps the pulsations from the oil pump.

Reference: FAA-H-8083-32B, Ch. 6, p. 6-8

5. What does a manifold pressure gauge measure?
  1. Oil pressure at the main bearings
  2. Pressure of the fuel/air mixture before it enters the cylinders
  3. Exhaust back pressure
Show answer

B. Pressure of the fuel/air mixture before it enters the cylinders It indicates the performance that can be expected of the engine.

Reference: FAA-H-8083-32B, Ch. 3, p. 3-6

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What does the Powerplant test cover on engine instrument systems?

The Aviation Mechanic Powerplant ACS lists engine instrument systems as one of its areas. The FAA reference for this material is FAA-H-8083-32B.