Instrument Flight: Flight Performance and Planning
What the exam tests
Flight Performance and Planning tests mass and balance, take-off and landing data, climb gradient, fuel policy and alternate planning for an IFR flight. Mauritius conditions, with warm humid air, a sea-level airport and limited alternates, make density altitude and fuel reserve questions common.
Core rules
- W&B: compute zero-fuel mass, take-off mass, landing mass and CG; keep all within the envelope.
- Take-off and landing distances are corrected for pressure altitude, temperature, wind, slope and contaminants.
- Climb gradient: required gradient = height gain divided by ground distance, multiplied by 100; convert to ft/NM.
- Fuel plan: taxi, trip, contingency, alternate, final reserve and additional or extra fuel.
- An alternate is required unless destination weather and runway criteria are assured under the operator and AIP rules.
- An IFR departure may need a minimum climb gradient to clear obstacles or airspace.
Worked example
Trip fuel 120 kg, taxi 10 kg, contingency 5% of trip = 6 kg, alternate 20 kg, final reserve 30 kg, extra 15 kg. Minimum fuel = 10 + 120 + 6 + 20 + 30 + 15 = 201 kg. Planning 190 kg makes the flight illegal before engine start. The largest single error is omitting contingency or final reserve.
Traps
- Using QNH instead of QFE for runway performance.
- Mixing Celsius and Fahrenheit in density altitude.
- Confusing landing mass with zero-fuel mass.
- Assuming a nearby island is always a usable alternate.