Power Plant Instruments & AvionicsAir Navigation — DGCA CPL practice questions
Question 1 of 10
EGT (Exhaust Gas Temperature) gauge monitors engine health by measuring:
All 10 questions — Power Plant Instruments & Avionics
Air Navigation · DGCA CPL. The correct option is marked on each.
Q1. EGT (Exhaust Gas Temperature) gauge monitors engine health by measuring:
- A.Carburetor inlet temperature
- B.Turbine/exhaust temperature to prevent overheating and optimise fuel/air mixture✓
- C.Oil temperature at the sump
- D.Cylinder head temperature at the exhaust valve only
Why: EGT helps set the fuel/air mixture: peak EGT corresponds to stoichiometric mixture. Leaning past peak EGT without care can overheat cylinders. It also detects exhaust system faults.
Q2. CHT (Cylinder Head Temperature) is used to:
- A.Measure intake air temperature for density altitude
- B.Monitor engine cooling and ensure CHT remains within limits to prevent detonation and preignition✓
- C.Control the carburettor heat
- D.Trigger the fire warning system
Why: CHT monitors how well the engine is being cooled. Excessive CHT causes detonation, pre-ignition, and engine damage. Normal cooling is managed by airspeed, power setting, and cowl flaps.
Q3. Oil pressure gauge reads zero in flight. The correct action is:
- A.Continue — it may be an instrument fault
- B.Reduce power, prepare for engine failure, land at the nearest suitable aerodrome✓
- C.Increase engine RPM to restore oil circulation
- D.Check oil temperature only — pressure loss is secondary
Why: Zero oil pressure is a critical emergency — indicates imminent or actual oil starvation. Reduce power immediately to reduce bearing loads, declare emergency, and land as soon as possible.
Q4. A transponder squawking 7700 indicates:
- A.Radio failure
- B.Unlawful interference (hijack)
- C.General emergency✓
- D.VFR flight
Why: Transponder codes: 7700 = General Emergency, 7600 = Radio Failure (NORDO), 7500 = Unlawful Interference. 1200 is used for VFR in the USA; India uses allocated codes for VFR.
Q5. Mode C transponder provides ATC with:
- A.Aircraft identification only
- B.Aircraft identification and pressure altitude✓
- C.GPS position
- D.Groundspeed and track
Why: Mode A provides a 4-digit squawk code (identification). Mode C adds pressure altitude information encoded in the reply. Mode S provides selective interrogation and enhanced data including identity and altitude.
Q6. The manifold pressure (MAP) gauge in a piston aircraft measures:
- A.Total engine pressure ratio
- B.Absolute pressure in the engine intake manifold✓
- C.Boost pressure above ambient only
- D.Fuel pressure at the carburettor
Why: MAP gauge measures absolute pressure in the induction manifold (inches of mercury or hPa). It is the primary power setting indicator for non-constant-speed propeller and some constant-speed piston engines.
Q7. TCAS II (Traffic Collision Avoidance System) provides:
- A.Traffic Advisory (TA) only
- B.Traffic Advisory (TA) and Resolution Advisory (RA) with vertical escape manoeuvre guidance✓
- C.Lateral avoidance manoeuvres
- D.ATC-coordinated conflict alerts only
Why: TCAS II provides both TAs (traffic within ~40 sec) and RAs (resolution advisories — CLIMB or DESCEND commands 20–35 sec before predicted collision). RAs must be followed immediately, overriding ATC instructions.
Q8. The purpose of the fuel flowmeter in a piston aircraft is to:
- A.Measure fuel quantity in each tank
- B.Indicate fuel consumption rate to allow fuel management and cross-check tank contents✓
- C.Control the mixture automatically
- D.Trigger the fuel pump warning
Why: The fuel flowmeter shows instantaneous fuel burn rate (litres/hour or lb/hr). Used with fuel quantity gauges, it allows pilots to predict remaining endurance and detect abnormal consumption.
Q9. ADS-B (Automatic Dependent Surveillance – Broadcast) differs from transponder-based Mode C in that it:
- A.Requires active interrogation from a ground radar
- B.Broadcasts GPS position, identity, and velocity without interrogation✓
- C.Only works below FL180
- D.Provides ground proximity warning
Why: ADS-B Out continuously broadcasts GPS-derived position, altitude, velocity, and identity without needing radar interrogation. ADS-B In receives broadcasts from other aircraft for CDTI situational awareness.
Q10. An aircraft experiences a sudden rise in oil temperature with normal oil pressure. The likely cause is:
- A.Oil starvation
- B.Partially blocked oil cooler or excessive engine load✓
- C.Fuel contamination
- D.EGT sensor failure
Why: High oil temperature with normal pressure typically indicates inadequate cooling — blocked oil cooler, low airspeed (taxiing in hot weather), or high power setting. Reduce power and increase airspeed; check cowl flaps.