Flight Performance and Planning
Flight Performance and Planning tests mass and balance, take-off, landing and en-route performance, and fuel planning to CAR-OPS 1. Expect calculations using the Aircraft Flight Manual and the operational flight plan, plus judgement about regulated weights, performance-limited masses and reserve fuel.
Mass and balance
- Know MTOM, MLW, MZFW and the performance-limited take-off weight, which is the lowest of field-length, obstacle, climb, tyre-speed and brake-energy limits.
- Minimum climb gradients in the second segment are 2.4% for twins, 2.7% for three engines and 3.0% for four engines.
- Centre of gravity must stay inside the certified range: too far forward gives heavy rotation and stick forces, too far aft degrades stability and stall recovery.
Fuel planning
- Block fuel is built from taxi fuel, trip fuel, contingency fuel (normally 5% of trip, reducible to 3% in defined cases), alternate fuel, final reserve, additional fuel and extra fuel at the commander's discretion.
- Final reserve for a turbine aeroplane is 30 minutes holding at 1,500 ft above the destination aerodrome in ISA conditions - computed at holding flow, not cruise flow.
Performance
- Take-off distance available must exceed the required distance; density altitude, runway slope, wind and contamination all change the result.
- Convert gradients: 1 NM = 6,076 ft, so 3.3% is about 200 ft/NM.
Worked example
Trip fuel 800 kg, taxi 40 kg, alternate 200 kg, final reserve 30 minutes at a holding flow of 1,000 kg/h = 500 kg, contingency 5% of trip = 40 kg. Total before extra fuel: 40 + 800 + 40 + 200 + 500 = 1,580 kg. If the commander adds 150 kg for expected delays, block fuel becomes 1,730 kg. Note that using cruise flow for the reserve would understate it.
Traps
- Computing the final reserve with cruise consumption.
- Omitting taxi fuel or double-counting the alternate as an extra 30 minutes.
- Using pressure altitude where density altitude is required.
- Forgetting that a contaminated runway increases both take-off and landing distances.