Commercial VFR Charter Fuel and Alternate Decision
You are the pilot-in-command of a Cessna 206 on a commercial VFR charter from Lakeview Aerodrome to Pine Ridge, a 2.0-hour flight at normal cruise. Usable fuel is 180 L and the engine burns 50 L/h. The destination forecast is visibility 6 SM, broken cloud at 4,000 ft AGL, with a TEMPO period of 2 SM in light rain and broken cloud at 2,000 ft. The nearest suitable alternate, Cedar Strip, is 30 minutes away. The aircraft has no fuel at Pine Ridge. A front is forecast to bring a 20-kt headwind on the route. The operator's manual requires day VFR reserves of 30 minutes. The pilot has three passengers and 40 kg of baggage; weight and balance are within limits. Dispatch asks whether the flight can depart with 180 L and no alternate fuel.
1. Compute the minimum fuel required for the planned trip under the stated reserve and compare it with 180 L. Is the flight legal on fuel alone?
Read the worked answer
Fuel required = trip fuel + reserve. Trip = 2.0 h × 50 L/h = 100 L. Reserve = 30 min × 50 L/h = 25 L. Minimum = 125 L. With 180 L, the flight has 55 L (1.1 h) extra, so it is legal on fuel alone.
Allow for the forecast headwind: if 2.0 h is still-air time at 120 kt TAS, a 20-kt headwind gives 100 kt groundspeed and 2.4 h enroute. Trip fuel becomes 120 L; minimum = 145 L, still below 180 L. The decision is not automatic, however: the TEMPO forecast, not just the fuel arithmetic, governs whether an alternate plan is needed.
2. Given the TEMPO forecast, what alternate and fuel plan should be made before departure?
Read the worked answer
The TEMPO 2 SM is below the 3 SM VFR minimum in controlled airspace, so a VFR arrival at Pine Ridge is not assured. Before departure, carry enough fuel to fly the trip, divert to Cedar Strip, and still hold the 30-minute reserve. With the headwind: trip 120 L + alternate 25 L + reserve 25 L = 170 L. With 180 L, the margin is only 10 L (12 minutes), which is thin for an unforecast headwind or a second diversion. Without the headwind the requirement is 150 L, leaving 30 L.
A prudent decision is to delay until the TEMPO clears, add fuel, or nominate a closer alternate. Simply departing with 180 L and no alternate fuel is not a sound commercial decision even though the basic reserve is legal.