Density Altitude

Density altitude is formally defined as pressure altitude corrected for non-standard temperature variations. In practical aviation terms, it is the altitude at which the aircraft "feels" like it is flying. It is one of the most critical meteorological factors affecting aircraft performance during takeoff, climb, and landing phases.

When the air temperature is higher than the International Standard Atmosphere (ISA) standard (which is 15°C at sea level), the air becomes less dense. This reduction in air density means that wings generate less lift, engines produce less power (as there is less oxygen for combustion), and propellers generate less thrust.

For both fixed-wing aeroplanes and helicopters, high density altitude dramatically increases takeoff roll distances and decreases the rate of climb. In rotary-wing operations (like the Bell 206L-1), high density altitude can severely limit hover Out of Ground Effect (OGE) capabilities, often necessitating reduced payload or fuel loads.

Pilots must routinely calculate density altitude as part of their pre-flight performance and loading calculations. It is a frequent subject in both CASA CPL (Commercial Pilot Licence) and FAA exams.