How much AvGas is required to fly 600 NM with a 15 knot headwind at 18,000 ft and -21 °C?

To determine how much AvGas is required for a flight of 600 nautical miles (NM) with the specified conditions, it is essential to consider the impact of wind on the flight's ground speed and fuel consumption.

First, calculate the true airspeed (TAS) of the aircraft at 18,000 feet and -21 °C. Generally, at this altitude and temperature, an aircraft might have a typical TAS around 150-180 knots, but the specific TAS can vary depending on the aircraft and its performance characteristics.

Next, account for the 15-knot headwind. If the aircraft has a TAS of, for instance, 160 knots, the ground speed (GS) would be reduced to 145 knots (160 knots TAS - 15 knots headwind). This reduction in ground speed results in longer time in the air, which consequently increases fuel consumption.

Next, the flight duration can be calculated by dividing the distance by the effective ground speed. For a distance of 600 NM with a ground speed of 145 knots, the flight duration would be approximately 4.14 hours (600 NM / 145 knots).

The fuel burn rate is crucial in this calculation. If the aircraft, under normal conditions, consumes fuel at