Full Throttle Altitude

Full throttle altitude is the altitude above which the throttle must be fully open to maintain a specified manifold pressure (typically the rated manifold pressure for take-off power). For normally aspirated engines, full throttle altitude is sea level — the throttle must be wide open immediately to maintain rated power at sea level in non-standard conditions. For turbocharged engines, full throttle altitude is their critical altitude.

Practical Meaning

As altitude increases, air density decreases. To maintain a given manifold pressure (and therefore engine power), the throttle must be progressively opened. On a normally-aspirated engine, the throttle may be at full open before the aircraft has even left the ground on a hot day at a high-elevation airport. On a turbocharged engine, the turbocharger maintains manifold pressure automatically up to the critical altitude, above which the engine behaves normally-aspirated.

Related Terms

See also: Critical Altitude, Manifold Pressure, Density Altitude.