Flight Planning and Monitoring
Flight Planning and Monitoring - what the exam tests
Planning questions check that you can turn a route, a forecast wind and a fuel burn into a legal, fuel-safe flight - and then monitor it in the air rather than flying the plan blindly.
Core rules
- Leg time = distance ÷ groundspeed. Groundspeed comes from TAS and the wind triangle; using TAS on a leg with a 20 kt headwind understates time and fuel.
- Typical VFR fuel plan: taxi fuel + trip fuel + contingency (often 5% of trip) + alternate fuel + final reserve (30 minutes by day VFR, 45 minutes by night VFR). The final reserve is not available for normal planning.
- Fuel mass = volume × density; 100LL is about 0.72 kg/L, so 100 L ≈ 72 kg. Check the volume available, the mass against MTOW, and the CG after burn-off.
- Altimetry: flying from high pressure to low pressure without resetting the subscale puts you lower than indicated - "high to low, look out below".
- In-flight monitoring: revise ETAs with actual groundspeed, log fuel at each waypoint, and re-plan the alternate and reserve when wind or burn differs from forecast.
Worked example
180 NM leg, TAS 110 kt, headwind component 20 kt. GS = 90 kt, so time = 180 ÷ 90 = 2.00 h. At 32 L/h the trip fuel is 64 L. Add taxi 5 L, contingency 3.2 L, alternate 20 min = 10.7 L and final reserve 30 min = 16 L, giving about 99 L required. With 130 L usable and MTOW satisfied, the flight may depart. If the headwind rose to 35 kt, GS falls to 75 kt, trip fuel rises to about 77 L and the whole plan must be reworked.
Traps
- Using TAS instead of groundspeed for time and fuel.
- Dropping contingency or final reserve to make the numbers fit.
- Mixing litres and kilograms within one calculation.
- Filing a flight plan and not amending it after a long departure delay.
- Forgetting that a change of level or route invalidates the SAR time.