Definition
An uncommanded nose-down pitching tendency that occurs when an aircraft approaches or exceeds its critical Mach number. As airflow over the wing reaches supersonic speed, shock waves form and disrupt the lift distribution, shifting the wing's center of lift rearward. This rearward shift creates a strong nose-down pitching moment that, if uncorrected, can drive the aircraft into a steeper dive and a further increase in Mach number, worsening the condition.
Plain English
When a fast jet gets close to the speed of sound, the airflow over the wing changes in a way that pushes the nose down on its own. If the pilot doesn't correct it, the aircraft tries to dive even faster, which makes the problem worse.
Context Anchor
Encountered in ground training for high-speed and high-altitude airplane operations, especially when discussing flight near Mach limits.
Derivation
Named after Ernst Mach, the Austrian physicist whose name is used for the ratio of an aircraft's speed to the speed of sound. 'Tuck' is everyday English for a sudden inward or downward fold — here it describes the way the nose tucks under as the aircraft pitches down on its own.
Why Pilots Care
Uncorrected Mach tuck can produce a rapid descent, exceed structural limits, or lead to loss of control if the pilot is unprepared.
Grounding Statement
Picture an airplane already moving very fast: as it nears its Mach limit, the nose may start dropping because of the airflow itself, not because the pilot pushed it down.
Intuition Check
Mach tuck is not a deliberate maneuver and it does not mean the pilot “tucked” the airplane into a dive. It is an aerodynamic nose-down tendency that can appear at very high Mach speeds.
Example Sentence 1
During high-altitude cruise, the crew monitored Mach number closely to stay well clear of the speed where Mach tuck could begin.
Example Sentence 2
During the descent the pilot recognized the light buffet and forward pressure as the start of Mach tuck and applied nose-up trim.