Definition
A device fitted to the airspeed indicator or air data system of high-speed aircraft that automatically corrects the indicated airspeed for compressibility errors as the airplane approaches the speed of sound, and warns the pilot when the airplane is nearing its maximum operating Mach number.
Plain English
A built-in correction system that keeps the airspeed reading accurate at high speeds and alerts the pilot before the airplane gets too close to the speed of sound.
Context Anchor
Seen in high-speed airplane systems, especially when studying control feel, trim, and handling changes at higher Mach numbers.
Derivation
Named after Ernst Mach, the Austrian physicist who studied the behavior of objects moving near the speed of sound. 'Compensating' here means correcting or adjusting — the device compensates for errors that appear as airspeed approaches Mach 1.
Why Pilots Care
Without compensation, control forces can become heavy or the aircraft can enter an uncommanded dive; the device reduces pilot workload and helps maintain stable flight through the transonic region.
Intuition Check
Do not think of this as a device that increases speed or changes the Mach limit. It compensates for control and trim changes that happen as Mach number increases.
Example Sentence 1
As the jet climbed into the flight levels, the Mach compensating device kept the airspeed indicator accurate and warned the crew when they neared the airplane's Mach limit.
Example Sentence 2
The checklist required verification that the Mach compensating device was armed before the high-speed test flight.