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DGCA Technical General · 29 questions

Engine Instruments: DGCA Technical General Questions and Answers

29 practice questions on Engine Instruments with answers and explanations, plus the key concepts and formulas, from the TrueHeading question bank.

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About this topic

Use this page to revise Engine Instruments for the DGCA Technical General paper. Below are the key ideas first, then 12 practice questions with answers and explanations, picked from the 29 questions in the TrueHeading bank for this topic.

In short: Piston: manifold pressure, RPM, oil pressure and temperature, CHT, EGT. Turbine: N1, N2, EPR, EGT/ITT, oil, vibration.

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Key concepts: Engine Instruments

2 ideas to know cold.

Piston and turbine engine instruments?

Piston: manifold pressure, RPM, oil pressure and temperature, CHT, EGT. Turbine: N1, N2, EPR, EGT/ITT, oil, vibration.

EPR=Pt7Pt2EPR=\frac{P_{t7}}{P_{t2}}
  • Tachometer: magnetic or tacho-generator
  • N1 is the low-pressure spool; N2 the high-pressure

What are the key engine parameters to monitor?

N1/N2 or rpm, EGT, EPR/torque, fuel flow, oil pressure and temperature.

  • EGT highest at start and max thrust
  • EPR measures thrust
  • Oil pressure drop = engine problem

Practice questions: Engine Instruments

Tap “Show answer” after you have tried each one.

Q1A tachometer in a piston engine aircraft indicates:

  1. the oil pressure
  2. the EGT
  3. the manifold pressure
  4. the crankshaft rpm
Show answer

Answer: D. the crankshaft rpm

Measured in revolutions per minute.

Q2The manifold pressure gauge measures:

  1. the oil pressure
  2. the fuel pressure
  3. the exhaust pressure
  4. the absolute pressure in the induction manifold
Show answer

Answer: D. the absolute pressure in the induction manifold

In inches of mercury (or hPa) absolute.

Q3At engine shutdown on the ground the manifold pressure gauge reads:

  1. the oil pressure
  2. zero
  3. approximately the ambient pressure
  4. 100 in Hg
Show answer

Answer: C. approximately the ambient pressure

It reads the field barometric pressure.

Q4N1 in a turbofan engine refers to:

  1. the fuel flow
  2. the high pressure rotor speed
  3. the low-pressure (fan) rotor speed
  4. the turbine temperature
Show answer

Answer: C. the low-pressure (fan) rotor speed

Expressed as a percentage of design rpm.

Q5N2 in a turbofan engine refers to:

  1. the oil pressure
  2. the fan speed
  3. the nozzle temperature
  4. the high-pressure compressor rotor speed
Show answer

Answer: D. the high-pressure compressor rotor speed

N2 is used to monitor engine start and core speed.

Q6EGT is measured by:

  1. pressure sensors
  2. mercury thermometers
  3. bimetallic strips
  4. thermocouples (chromel-alumel) in the exhaust gas stream
Show answer

Answer: D. thermocouples (chromel-alumel) in the exhaust gas stream

Chromel-alumel thermocouples are used for the exhaust.

Q7The oil pressure gauge generally reads:

  1. the oil quantity
  2. the fuel pressure
  3. the oil temperature
  4. the pressure of oil in the main oil gallery
Show answer

Answer: D. the pressure of oil in the main oil gallery

A drop in pressure may signal a leak or a failed pump.

Q8An engine pressure ratio (EPR) indicator measures:

  1. the ratio of turbine outlet to compressor inlet pressure
  2. exhaust temperature
  3. oil pressure to fuel pressure
  4. cabin altitude
Show answer

Answer: A. the ratio of turbine outlet to compressor inlet pressure

A thrust-setting parameter.

Q9The fuel flow meter measures:

  1. the flow rate of fuel to the engine, in kg/h or lb/h
  2. the fuel quantity
  3. the fuel temperature
  4. the fuel density
Show answer

Answer: A. the flow rate of fuel to the engine, in kg/h or lb/h

Transmitted by a flow transmitter.

Q10A vibration indicator on a turbofan monitors:

  1. oil quality
  2. fuel flow
  3. imbalance of the rotating components
  4. static pressure
Show answer

Answer: C. imbalance of the rotating components

High vibration needs investigation.

Q11Torque in a turboprop is measured to indicate:

  1. the fuel flow
  2. the airspeed
  3. the EGT
  4. the power output of the engine to the propeller
Show answer

Answer: D. the power output of the engine to the propeller

Torque is shown as % or psi.

Q12Cylinder head temperature (CHT) is measured by:

  1. a magnetometer
  2. a thermometer in the cabin
  3. a thermocouple attached to the hottest cylinder
  4. a pressure gauge
Show answer

Answer: C. a thermocouple attached to the hottest cylinder

An overheated engine may detonate.

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More DGCA Technical General topics

Aerodynamics & Performance181 QFlight Controls & Stability38 QAirframe & Structures25 QPowerplant79 QPropellers32 QAircraft Systems116 QPitot Statics35 QBarometric Altimeters61 QRadio Altimeters37 QVertical Speed Indicators (VSI)32 QAirspeed Indicators24 QAirspeeds41 QMach55 QGyroscope52 QAttitude Indicators20 QTurn and Slip50 QINS, IRS and FMS32 QEFIS24 QAutoflight23 QFlight Director21 QEICAS / ECAM24 QTemperature Indicators34 QFuel Systems35 QCompass54 QWarning & Recording Systems33 QTCAS39 Q
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