AHRS/AHARS Issues

Editorial Staff

Wednesday, April 20, 2022 at 07:07 PM ET

Verified

Key Takeaways:

AHRS failures are a common issue across various aircraft types, leading to loss of critical flight data (e.g., airspeed, altitude, attitude, heading) and frequent autopilot disengagement.
These failures can be intermittent, condition-dependent (e.g., cold weather, severe turbulence), or involve recently installed/overhauled units, highlighting reliability concerns.
Troubleshooting often fails to identify a definitive cause for these failures, even when they recur, posing challenges for diagnosis and resolution.

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Beech 58 Baron

Cold-Weather Failure

While at cruise altitude of 14,000 feet on a very cold day, the G500 panel flagged the airspeed, altitude, AIS, OAT, heading and horizon all “x” out with big red x’s. Loss of all data from the AHARS. Pilot used the backup instruments to complete the flight. Whenever cold, the unit would fault.

Part total time: Unknown

Beech B200 Super King Air

In-Flight Failure In IMC

While flying in IMC en route from JVY to OWB, the attitude, heading, reference system and autopilot failed in flight. At the time of the failure, the aircraft was level at 6000 feet, at 220 KIAS and coupled to the autopilot in nav mode and altitude hold. Pilot declared an emergency, descended to VMC and returned to JVY. Troubleshooting did not find any discrepancies.

Part total time: Unknown

Beech 400A

Defective AHRS

The flight crew reported the #1 and #2 AHRS disagreed and kicked off the autopilot. Troubleshooting found AHRS p/n 622-9336-400 defective. This unit was an overhauled item installed 17 flight hours earlier. Unit was removed from service and an OE unit was installed.

Part total time: 17.0 hours

Diamond DA40NG

In-Flight Failure In VMC

In level cruise flight in VMC, the G1000 NXi Phase II AHRS displayed a red x and the autopilot disengaged. The PFD showed failed attitude and heading with the message, “AHRS Align: Keep Wings Level.” The GPS continued to operate normally. After 32 seconds, the AHRS came back on-line. Maintenenace is unable to explain the cause or what would trigger the AHRS failure.

Part total time: 285.0 hours.

Learjet 45

AHRS Took Out The Rudder Boost

The flight crew reported that the CAS system indicated that the rudder boost was inoperative. Troubleshooting identified that the #2 AHRS had failed. The failed unit (p/n HG2010AC02) was removed and a tested unit was installed.

Part total time: Unknown

Pilatus PC-12/45

Turbulence-Related Failure

The pilot was cruising in bad weather when he experienced severe turbulence. Shortly thereafter, the #1 AHRS failed, indicating a red x across the screen. The pilot declared an emergency and diverted. On approach, the #1 AHRS energized and operated normally throughout approach and landing. Subsequent ground tests of the system were all normal. Maintenance determined no faults could be found.

Part total time: 642.0 hours