Fuel at Destination with a Marginal Alternate
Planned landing mass at destination is 62 000 kg. Trip fuel is 8500 kg, taxi fuel 250 kg, contingency 425 kg, alternate fuel 2100 kg, final reserve 30 min at 1500 ft, and additional fuel 0 kg. The aircraft's maximum landing mass is 66 000 kg and maximum take-off mass is 79 000 kg. Take-off fuel is 11 300 kg. En route the crew learns that the destination runway is closed for 40 min after their ETA, and the alternate is now forecast at the limit of its planning minima. The crew holds for 25 min at 1500 ft burning 1200 kg/h before the runway reopens.
1. Verify the planned fuel figures are internally consistent and state the landing mass before the hold.
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Fuel components: taxi 250 + trip 8500 + contingency 425 + alternate 2100 + final reserve (30 min at 1200 kg/h = 600 kg) + additional 0 = 11 875 kg. The stated take-off fuel of 11 300 kg is 575 kg short of this sum, so the plan is inconsistent and must be corrected before dispatch. Using the stated take-off fuel, landing fuel before the hold = 11 300 - 8500 = 2800 kg, which is below contingency + alternate + final reserve (425 + 2100 + 600 = 3125 kg). The aircraft would land with less than the required reserves even without the hold. Landing mass = 62 000 kg, within the 66 000 kg limit, so mass is not the constraint; fuel quantity is.
2. After the 25 min hold, can the flight still land at the destination with final reserve intact?
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Hold burn = 1200 x 25/60 = 500 kg. Fuel remaining at landing = 2800 - 500 = 2300 kg. Required final reserve is 600 kg, so 2300 kg is above 600 kg, but the alternate fuel of 2100 kg is now partly consumed: only 2300 - 600 = 1700 kg is available for a diversion, against a planned requirement of 2100 kg. Since the alternate is at the limit of its planning minima, the diversion may not be available at all. The correct judgement is to declare a fuel situation early, consider diverting before the hold is complete, and not to assume the alternate remains usable. Landing with 2300 kg is legal only if the destination is assured; with the alternate marginal, the safer decision is to divert while fuel permits.