1.8 Performance Ceilings.

Service Ceiling

This is defined as the altitude at which the rate of climb of an aircraft falls to a specified figure, usually 100 ft per minute.

Absolute Ceiling

The absolute ceiling is the altitude at which the rate of climb of an aircraft falls to zero.

Piston-Engined Aircraft

For such aircraft, operating under 26,000 ft, then the improved atmospheric density found in winter in high Altitudes will give the highest ceiling.

Jet-Engined Aircraft

As most jet-engined aircraft operate above 26,000 ft, then the best performance ceiling will be found at the highest tropopause and lowest temperature, i.e. in summer, and at low Altitudes.