Wet-Runway Takeoff and Alternate Fuel at Plaisance
You are preparing a scheduled IFR departure from Plaisance (FIMP), runway 14, TORA 3,040 m, TODA 3,040 m, ASDA 3,040 m. OAT is 31°C, QNH 1012 hPa, wind 140/08 kt, runway wet. Take-off mass is 21,200 kg; performance software gives a dry-runway ground roll of 1,950 m and a dry TODA requirement of 2,550 m. The operator's wet-runway correction is +12% on ground roll and +8% on TODA. A displaced obstacle requires a TODA of 3,100 m. The left thrust reverser is inoperative under MEL; the MEL applies a 6% take-off performance penalty. Destination FMEE has TEMPO TSRA; the filed alternate is FIMP. Fuel on board is 2,500 kg; trip 1,200 kg, contingency 300 kg, alternate 450 kg, final reserve 600 kg, taxi 80 kg. The dispatcher's release shows no additional alternate fuel.
1. Assess the takeoff performance and decide.
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The takeoff must be assessed on the wet runway, with the MEL penalty and the obstacle.
- Wet ground roll: 1,950 × 1.12 = 2,184 m. This is below TORA 3,040 m, so the ground roll alone is not limiting.
- Wet TODA requirement: 2,550 × 1.08 = 2,754 m.
- Apply the 6% reverser MEL penalty: 2,754 × 1.06 = 2,919 m.
- The obstacle requires a TODA of 3,100 m.
The controlling requirement is therefore 3,100 m against an available TODA of 3,040 m. The takeoff is not performance-limited by the ground roll but by the obstacle after the wet-runway and MEL corrections. The correct decision is to reject the takeoff as planned. The crew should not accept the dispatcher's figure without checking the obstacle and wet corrections. Options include reducing take-off mass, waiting for a lower OAT or different wind, or using a runway/intersection with better obstacle clearance if one exists.
2. Check fuel and alternate planning.
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The required fuel is the sum of trip, contingency, alternate, final reserve and taxi:
1,200 + 300 + 450 + 600 + 80 = 2,630 kg.
Fuel on board is 2,500 kg, so the aircraft is 130 kg below the required figure before any holding. The final reserve of 600 kg cannot be used to make up the difference. In addition, destination FMEE has TEMPO TSRA, which makes the alternate more likely to be used, and no additional holding fuel is shown. The release is therefore invalid on fuel as well as on performance.
The crew should request additional fuel or a revised alternate plan. If the destination forecast remains TEMPO TSRA, the alternate fuel should be based on the actual alternate weather and the possibility of a diversion. The crew must not depart with a fuel plan that relies on the final reserve.
3. What would you require to make the flight legal and safe?
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The flight can only proceed if both the performance and fuel deficiencies are resolved. The crew should require:
- A recomputed takeoff performance using the actual wet runway, OAT, QNH, wind and MEL penalty, showing that the obstacle TODA requirement is met with a clear margin.
- A reduction in take-off mass, a change in departure time to a lower OAT, or a different runway/intersection if the obstacle cannot be cleared.
- Additional fuel to meet the required 2,630 kg plus any holding and alternate contingency, or a change of destination/alternate to reduce the fuel requirement.
- A revised dispatch release reflecting the actual conditions.
If these cannot be achieved, the correct decision is to delay or cancel. The captain should not accept a release that is short of fuel and does not meet the obstacle clearance requirement, even if the destination weather is currently acceptable. The decision should be documented and communicated to the operator.