Hawaiian A332 at Los Angeles on Sep 22nd 2022, trim motor failure causes erratic movements of trim wheel

Last Update: September 20, 2024 / 01:37:28 GMT/Zulu time

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Incident Facts

Date of incident
Sep 22, 2022

Classification
Incident

Airline
Hawaiian Airlines

Flight number
HA-3

Departure
Los Angeles, United States

Destination
Honolulu, United States

Aircraft Registration
N393HA

Aircraft Type
Airbus A330-200

ICAO Type Designator
A332

A Hawaiian Airlines Airbus A330-200, registration N393HA performing flight HA-3 from Los Angeles,CA to Honolulu,HI (USA) with 278 passengers and 12 crew, was climbing out of Los Angeles' runway 24L when the trim wheel started to move erratically. The crew disengaged the autopilot, worked the related checklists and decided to return to Los Angeles for a safe landing on runway 24L about 90 minutes after departure.

The NTSB reported the primary trim motor failed causing the erratic movements of the trim wheel. No notification of any faults were displayed on the ECAM. The crew returned to Los Angeles.

The aircraft returned to service after about 2 days on the ground.

On Oct 27th 2022 the NTSB released their preliminary report reporting the sequence of events:

As the airplane was climbing through Flight Level (FL) 360 after departure from LAX, the flight crew reported that the trimmable horizontal stabilizer (THS) pitch trim wheel began a rapid uncommanded nose up/nose down movement while autopilot 2 was engaged. The first officer, who was the pilot flying, disconnected autopilot 2 and took manual control of the aircraft. The trim wheel continued the uncommanded movement with the autopilot disengaged; however, the crew stated the airplane was controllable during manual flight. No messages regarding the pitch trim anomaly were generated on the electronic centralized aircraft monitor (ECAM).

The captain declared an emergency and notified air traffic control that they would be returning to LAX and would need to jettison fuel. He then requested a non-revenue A330 captain seated in the cabin to assist in the cockpit. The captain stated he used this additional crew member, plus an A330 first officer that was jumpseating, to distribute workload in the cockpit: assisting the primary crew in troubleshooting the pitch trim, jettisoning fuel, and preparing for the airplane’s arrival back to LAX.

Before landing, the crew assessed the aircraft handling qualities in the landing configuration and remained vigilant to the continued movement of the manual trim wheel. The landing was uneventful, and the aircraft was taxied to a remote parking area where the passengers deplaned.

On Sep 20th 2024 the NTSB released their final report and investigation docket concluding the probable cause of the incident was:

Uncommanded movement of the trimmable horizontal stabilizer control wheel for reasons that could not be determined based on the available evidence.

The NTSB wrote:

The flight crew reported that, when the airplane climbed through flight level 360, the trimmable horizontal stabilizer (THS) trim wheel began to move “very quickly” forward and aft, creating small pitching oscillations. No message appeared on the airplane’s electronic centralized aircraft monitor, and no flight deck alerts annunciated. The crew decided to turn off the autopilot to isolate the malfunction. However, when the autopilot was off, the trim wheel continued to move erratically. The crew then reengaged the autopilot, and small pitch oscillations resumed. These oscillations, which were below the threshold to trigger a fault, were partially countered by flight control system inputs, but the trim wheel continued its uncommanded movement. The first officer (the pilot flying) then turned off the autopilot and manually flew the airplane for the rest of the flight while the captain (the pilot monitoring) managed the situation.

The flight crew contacted air traffic control to declare an emergency and advise that fuel would need to be jettisoned before the airplane returned to the airport. Afterward, fuel was jettisoned until the airplane reached its maximum landing weight. The airplane landed uneventfully, and the emergency was terminated after landing. The airplane’s Post Flight Report information showed the “PITCH TRIM ACTR [actuator] OVERRIDE SWITCH” fault message.The maintenance crew at the airport replaced the pitch trim actuator (a subcomponent of the THS actuator), and an operational test of the THS actuator was successful.

One possible scenario for the uncommanded pitch trim wheel movement involved a failure or malfunction of a subcomponent of the THS actuator (the No. 1 digital electronic module, which digitizes the analog signals from THS position sensors. Extensive testing of the THS actuator and its subcomponents, including the incident pitch trim actuator and the No. 1 digital electronic module, was conducted at the manufacturers’ facilities. However, the testing did not identify the specific reason for the uncommanded pitch trim wheel movements during the incident flight. As a result, the investigation was unable to determine the cause of the anomaly based on the available evidence. It is important to note that this investigation found that the anomaly appeared to be isolated to components that were either removed and repaired or replaced on the incident airplane. Further, the incident airplane had no pitch or pitch trim flight control faults related to the circumstances of this incident since the THS actuator was removed and replaced in November 2022.
Aircraft Registration Data
Registration mark
N393HA
Country of Registration
United States
Date of Registration
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TCDS Ident. No.
Fijnl Subscribe to unlock
Manufacturer
AIRBUS
Aircraft Model / Type
A330-243
Number of Seats
Enc Subscribe to unlock
ICAO Aircraft Type
A332
Year of Manufacture
AqAh Subscribe to unlock
Serial Number
IAkh Subscribe to unlock
Aircraft Address / Mode S Code (HEX)
Iqjlfn Subscribe to unlock
Engine Count
H Subscribe to unlock
Engine Manufacturer
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Engine Model
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Engine Type
PfngA dmi Subscribe to unlock
Pounds of Thrust
Imqme Subscribe to unlock
Main Owner
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Incident Facts

Date of incident
Sep 22, 2022

Classification
Incident

Airline
Hawaiian Airlines

Flight number
HA-3

Departure
Los Angeles, United States

Destination
Honolulu, United States

Aircraft Registration
N393HA

Aircraft Type
Airbus A330-200

ICAO Type Designator
A332

This article is published under license from Avherald.com. © of text by Avherald.com.
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