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Reserve fuel is built up from separate blocks: fuel to fly to the alternate, a final reserve to hold at 1,500 ft over the alternate (30 minutes is the usual figure for turbine aircraft), and a contingency percentage on trip fuel to cover forecast error. All three are converted from time to quantity using the cruise burn rate.
Reserve fuel
Reserve = burn x (alternate min + final reserve min)/60 + contingency% x trip fuel
Aviation results are planning estimates only. Always verify take-off, landing, fuel, weight and balance figures against the certified Aircraft Flight Manual, current performance charts and applicable aviation regulations before flight.
It is the common turbine figure at holding speed. Piston aircraft VFR rules often require 30 minutes day and 45 minutes night; always check the applicable regulation.
No. Contingency is a percentage of trip fuel only, and it is the block most commonly reduced by in-flight re-planning.