What is the MPG of a small airplane?

Answer 1

It is not practical to use "MPG" (miles per gallon) for an aircraft due to a lot of factors that make fuel use extremely variable, like how many times and how far a plane climbs or descends, gross weight of the aircraft, altitude it cruises at, weather conditions, etc - all these factors have more impact on an aircraft than on a car. A more practical value for flight planning is "GPH" (gallons per hour). A pilot's operating handbook (POH -- the plane's user manual) always includes performance tables showing expected fuel intake at specific altitudes and power settings for a desired speed, and this is used by the pilot to compute the required amount of fuel for a specific flight leg. Normally, the pilot must account for the expected wind, air pressure and temperature, altitude, and loading of the aircraft to make this computation. But as a crude estimate, a light, 4-seat single-engine aircraft equipped with a 150 HP engine, like a Cessna 172 or a Piper Cherokee, will use between 8 and 10 gallons of fuel per hour in cruise, for a true air speed of 100-110 knots. This gives us ~15 MPG. Some better-performing aircrafts, like the Mooney M20, are able to reach 20 MPG in cruise because of their higher speed for the same engine. Of course, as the plane gets more powerful, the fuel economy plummets. Each engine of an early Piper Apache (a small twin-engine aircraft, 4000 lbs gross takeoff weight) guzzle about 12 GPH, for a cruise speed of 150 knots; this comes to a dismal 7 MPG in cruise.