Aviation Gasoline (AVGAS) and CombustionAircraft & Engines — DGCA CPL practice questions
Question 1 of 5
AVGAS 100LL is coloured:
All 5 questions — Aviation Gasoline (AVGAS) and Combustion
Aircraft & Engines · DGCA CPL. The correct option is marked on each.
Q1. AVGAS 100LL is coloured:
- A.Green
- B.Blue✓
- C.Red
- D.Straw/clear
Why: 100LL (low lead) is blue; AVGAS 100 (high lead) is green.
Q2. The octane rating of a fuel is a measure of its:
- A.Energy content
- B.Resistance to detonation✓
- C.Volatility
- D.Specific gravity
Why: Octane rating compares the fuel's anti-knock quality against iso-octane (100) and normal heptane (0); it says nothing about energy content.
Q3. Detonation is:
- A.Ignition of the charge before the spark
- B.A violent uncontrolled explosion of the unburnt end-gas after normal ignition✓
- C.Normal rapid combustion
- D.Fuel boiling in the lines
Why: Detonation is the explosive combustion of the remaining 'end gas' due to excessive heat and pressure — causing knocking, power loss and engine damage.
Q4. Pre-ignition is typically caused by:
- A.Too low an octane rating
- B.A local hot spot such as a glowing carbon deposit✓
- C.Retarded ignition timing
- D.Closing the throttle quickly
Why: Pre-ignition is the charge lighting BEFORE the spark, usually from an incandescent hot spot — distinct from detonation.
Q5. Tetra-Ethyl Lead (TEL) is added to AVGAS to:
- A.Colour the fuel
- B.Increase its octane rating and resist detonation✓
- C.Lower its freezing point
- D.Lubricate the fuel pumps
Why: TEL raises the fuel's resistance to detonation, allowing higher compression ratios and power.