How is contingency fuel generally calculated for flight planning?

Contingency fuel is an important aspect of flight planning that provides a buffer for unforeseen circumstances during a flight, such as unexpected weather changes or delays. The correct method for calculating contingency fuel involves adding a specific percentage of the planned trip fuel to a time allowance, which is intended to ensure that the aircraft has sufficient fuel to handle unplanned situations safely.

The most widely accepted practice is to calculate contingency fuel as 5% of the planned trip fuel plus an additional 20 minutes of flying time. This combination ensures that the aircraft is equipped to handle minor delays or diversions without risking a fuel shortage. The 5% contingency provides a buffer based on fuel consumption, while the extra flying time accounts for the possible need to circle or divert due to operational conditions.

Using this method allows flight planners to account for variations in fuel consumption that may arise during the trip, ensuring a higher level of safety and operational readiness. Thus, the correct approach to calculating contingency fuel under the given circumstances is consistent with standard aviation practices.