How much horsepower does an engine lose with altitude?

A normally-aspirated piston engine loses power roughly in proportion to air density — about 3% per 1,000 ft of density altitude (Gagg-Ferrar). At 8,000 ft density altitude a 180 hp engine makes closer to 135 hp. Turbocharged engines hold rated power up to a critical altitude, then fall off the same way.

Do jet (turbine) engines lose power at altitude?

Yes. Jet engines produce thrust, not horsepower, and thrust falls as you climb because thinner air means less mass flow through the engine — roughly with the ambient pressure ratio, so a turbofan at FL400 may make only about a third of its sea-level static thrust. Turboprops produce shaft horsepower and are usually flat-rated to a critical altitude, then lose power as density falls.

Free aviation & aerospace calculators

Aircraft Horsepower at Altitude Calculator

Thin air, less power.

Thin air carries less oxygen for combustion, so a piston engine loses power as density altitude rises. Pick your aircraft and a density altitude — get yours from the density altitude calculator — to see the horsepower you actually have.

Aircraft Horsepower at Altitude Calculator

Thin air carries less oxygen for combustion, so a piston engine loses power as density altitude rises. Pick your aircraft and a density altitude to see the horsepower you actually have. ↑ use the density altitude from above

Educational estimates only — not for flight planning, dispatch, or weight-and-balance. Always fly the numbers in your POH and current official weather.

Aircraft

Density Altitude

Rated Power (sea level)

180 hp

% of Rated Power

76%

Power Available

137 hp