Engine Cooling SystemsAircraft & Engines — DGCA CPL practice questions

All 5 questions — Engine Cooling Systems

Aircraft & Engines · DGCA CPL. The correct option is marked on each.

1. Q1. Cowl flaps are normally opened during:

   • A.Cruise
   • B.Descent
   • C.High-power, low-airspeed conditions such as takeoff and climb✓
   • D.Engine shutdown only

   Why: Open cowl flaps maximise cooling airflow when power is high and airspeed low; they are closed in cruise/descent to reduce drag and avoid over-cooling.

2. Q2. The CHT gauge sensor is a:

   • A.Thermistor
   • B.Thermocouple✓
   • C.Capacitive probe
   • D.Bourdon tube

   Why: A thermocouple generates a voltage proportional to temperature; if only one is fitted, it goes on the hottest-running (usually a rear) cylinder.

3. Q3. Air cooling is preferred over liquid cooling for most aircraft piston engines because it is:

   • A.More effective in the climb
   • B.Simpler and lighter✓
   • C.Quieter
   • D.Immune to over-cooling

   Why: Liquid systems cool well but are heavy; air cooling with fins, baffles and cowl flaps is simple and light.

4. Q4. Cooling fins on a cylinder serve to:

   • A.Strengthen the cylinder
   • B.Greatly increase the surface area for heat dissipation✓
   • C.Direct the fuel spray
   • D.Reduce exhaust back pressure

   Why: Fins multiply the surface exposed to cooling air; baffles distribute the air evenly over all cylinders.

5. Q5. Over-cooling an engine is undesirable because it:

   • A.Increases detonation
   • B.Reduces available BHP and impairs fuel vaporisation✓
   • C.Raises oil pressure
   • D.Causes valve bounce

   Why: An engine below its working temperature loses power and vaporises fuel poorly — cooling must be controlled, not maximised.