A diversion changes time as well as distance
A pilot plans a cross-country leg to an aerodrome east of the departure point. The route calculation is complete, and fuel consumption has been estimated from the aircraft’s actual usable fuel and the planned operating condition. Partway along the route, new information makes the destination unsuitable. A nearby alternative lies west of the aircraft and looks attractive because it is geographically closer. The updated wind, however, would be a substantial headwind on that diversion. A second alternative lies farther away but in a direction with a better groundspeed. The pilot is in safe visual conditions, has confirmed the current position and has time to compare the alternatives without rushing.
1. How should the pilot compare the alternatives?
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Calculate distance, groundspeed, time and fuel for each new route, retaining the applicable reserve and allowances. Check terrain, airspace, weather, runway availability and aircraft performance as well. A closer aerodrome is not automatically the quickest or most fuel-efficient option in different winds.
2. Why does confirming position matter before the calculation?
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Every diversion estimate depends on the actual starting point. A plausible-looking but incorrect position can corrupt distance, track, time and fuel estimates simultaneously. Maintain aircraft control and confirm the fix using independent information before committing to a new heading.