In this example, there is no wind therefore, true airspeed (TAS) is also 100 knots, the same as GS. If an aircraft consumes 5 gallons of fuel per hour, the total fuel consumption is 20 gallons (4 hours times 5 gallons). For example, a flight of 400 NM at 100 knots GS takes 4 hours to complete. The amount of fuel needed for a given flight can be calculated by multiplying the estimated flight time by the rate of consumption. GS determines the time the flight will take. When planning a flight, you must determine how much fuel is needed to reach your destination by calculating the distance the aircraft can travel (with winds considered) at a known rate of fuel consumption (gal/hr or lbs/hr) for the expected groundspeed (GS) and ensure this amount, plus an adequate reserve, is available on board. Preflight planning should be supported by proper monitoring of past fuel consumption as well as use of specified fuel management and mixture adjustment procedures in flight.įor simple aircraft with reciprocating engines, the Aircraft Flight Manual/Pilot’s Operating Handbook (AFM/POH) supplied by the aircraft manufacturer provides gallons-per-hour values to assist with preflight planning. The typical label for specific range is NM per pound of fuel, or often NM per 1,000 pounds of fuel. This standard industry convention yields a pounds-of-fuel-per-hour value which, when divided into the nautical miles (NM) per hour of travel (TAS ± winds) value, results in a specific range value. For this reason, jet fuel is generally quantified by its density and volume. In contrast, density (weight) is less affected by temperature and therefore, provides a more uniform and repeatable measurement. When determining these large fuel quantities, using a volume measurement such as gallons presents a problem because the volume of fuel varies greatly in relation to temperature. Since turbine engines consume much more fuel than reciprocating engines, turbine-powered aircraft require much more fuel, and thus much larger fuel tanks. Typically, fuel consumption in gasoline-fueled aircraft is measured in gallons per hour. Another quick method of conversion is to use the scales of NM and SM at the bottom of aeronautical charts.įuel ConsumptionTo ensure that sufficient fuel is available for your intended flight, you must be able to accurately compute aircraft fuel consumption during preflight planning. Most flight computers or electronic calculators have a means of making this conversion. For example: a wind speed of 20 knots is equivalent to 23 mph. ![]() To convert knots to mph, multiply speed in knots by 1.15. Because there are 6,076.1 feet in 1 NM and 5,280 feet in 1 SM, the conversion factor is 1.15. Pilots, therefore, should learn to convert wind speeds that are reported in knots to mph.Ī knot is 1 nautical mile per hour (NMPH). ![]() However, airspeed indicators in some aircraft are calibrated in mph (although many are now calibrated in both mph and knots). The NWS reports both surface winds and winds aloft in knots. The aviation industry is using knots more frequently than mph, but is important to understand the conversion for those that use mph when working with speed problems. Converting Knots to Miles Per HourAnother conversion is that of changing knots to miles per hour (mph).
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