Definition
A malfunction or loss of the Attitude and Heading Reference System, the solid-state sensor unit that supplies pitch, roll, and heading information to the electronic flight displays. When the AHRS fails, the affected display can no longer show valid attitude or heading data, and the system typically annunciates the failure with a warning flag, red X, or removal of the attitude and heading indications.
Plain English
The box that tells your glass-cockpit screens which way the airplane is pointing has stopped working. The attitude and heading shown on that display can no longer be trusted, and the system will usually flag it clearly so the pilot knows.
Context Anchor
Seen in glass-cockpit instrument flying, especially when discussing unusual-attitude protection, display warnings, and backup instrument use.
Derivation
AHRS stands for Attitude and Heading Reference System. 'Attitude' here means the airplane's orientation in space (pitch and roll), not a mood. 'Reference' signals that the unit is the source the displays look to for that information. When that reference fails, the displays lose their truth source for which way the aircraft is pointing.
Why Pilots Care
Loss of AHRS data forces immediate transition to backup instruments or partial-panel techniques to avoid loss of control.
Analogy
It is like a phone’s compass and motion sensing failing at the same time: the screen may no longer know which way it is facing or how it is tilted.
Grounding Statement
In flight, an AHRS unit failure means the pilot may need to stop using the main electronic attitude or heading display and shift to backup instruments.
Intuition Check
Do not read attitude here as a mental state; in AHRS, attitude means the aircraft’s pitch and bank. A failure also does not always mean the display goes blank; it may show a warning, remove the indication, or present information that must not be trusted.
Example Sentence 1
After the AHRS unit failure, the attitude indicator on the PFD showed a red X, so the pilot transitioned to the standby attitude indicator and continued the approach.
Example Sentence 2
After the AHRS unit failure the autopilot disconnected and the pilot flew the approach using the standby attitude indicator.