The standard plan of the previous lesson assumes a destination with an alternate behind it and a contingency priced on the whole trip. Operations exist where that shape wastes payload or simply cannot be flown, and the operational requirements provide procedures that bend the plan for them: a decision point that shrinks the contingency, a predetermined point that restructures the reserves, the isolated aerodrome that has no alternate to plan for, and the purely commercial choice of carrying cheap fuel into an expensive port.
The reduced contingency fuel procedure
Contingency at 5 per cent of a long trip is a lot of mass that usually lands unburned. The reduced contingency fuel (RCF) procedure recovers most of it by naming a decision point along the route and a destination 2, a refuelling aerodrome, alongside the commercial destination 1. The fuel loaded is the greater of two sums:
To destination 1 via the decision point — with contingency of only 5 per cent of the fuel from the decision point to destination 1, plus the usual alternate fuel, final reserve and additional components.
To destination 2 — with the standard contingency for that flight, plus its own alternate, final reserve and additional.
Passing the decision point, the crew checks the tanks: enough for the first sum's remainder and the flight continues; not enough and it diverts to destination 2 to refuel. The unforeseen is only being insured from the decision point onward, which is why the insurance premium shrinks.
The predetermined point procedure
Where the destination and its alternate lie far apart, the predetermined point (PDP) procedure restructures the back end of the plan. A point is fixed from which the flight can still reach either aerodrome, and the fuel loaded is again the greater of two sums:
Via the PDP to the destination — with additional fuel of not less than 2 hours at normal cruise consumption overhead the destination for a turbine aeroplane; for pistons, 45 minutes plus 15 per cent of the planned cruising time, or 2 hours, whichever is less.
Via the PDP to the destination alternate — with a floor of 30 minutes at holding speed at 1,500 ft for a turbine; 45 minutes for a piston.
The 2-hour block on the destination leg (the rules reuse the name additional fuel for it, though it is a different quantity from the failure-case supplement of the previous lesson) is doing the work of the alternate and final-reserve components combined: past the PDP there is no diversion left to price, so the protection is banked overhead the destination instead.
The isolated aerodrome
Some destinations have no alternate to plan for at all. An isolated aerodrome is one whose nearest adequate destination alternate lies beyond that same threshold: more fuel than 2 hours at normal cruise consumption overhead the destination for a turbine (the piston formula above), final reserve included. A flight there is planned without a destination alternate, under a specific approval, using the predetermined-point machinery: the PDP is placed at the last possible point of diversion to an available en-route alternate. In flight the crew monitors a point of no return computed from the actual conditions of the day: before it, the en-route alternate is still reachable; beyond it, the flight is committed to landing at the isolated destination, which is exactly why the plan banked 2 hours of protection overhead it.