Synopsis
On 7 April 2022, a Boeing 767-322ER (registration N670UA) operated a scheduled passenger flight from Dulles International Airport to Zurich Airport. While cruising at Flight Level 360 off the south coast of Ireland, the crew observed decreasing No. 1 engine oil quantity. The oil quantity reached zero, and a low oil pressure warning prompted an emergency declaration and diversion to Shannon Airport. The No. 1 engine was shut down during descent. After landing, a fire developed on the left-hand undercarriage during taxi, which was extinguished by the Airport Fire and Rescue Service. The aircraft was subsequently towed to its stand, and passengers and crew disembarked normally.
History of the Flight
The aircraft departed Dulles at approximately 22:21 hrs on 6 April 2022. At about 02:08 hrs, while at Flight Level 340, a climb to FL360 was initiated. At FL360, the crew noticed the No. 1 engine oil quantity decreasing. Operations control advised monitoring. Oil quantity reached zero at 03:27 hrs, and oil pressure began to decrease 23 minutes later. At 04:13 hrs, a low oil pressure warning displayed, and the associated checklist required engine shutdown. The crew declared an emergency to Shannon ATC, reporting low oil pressure and need to shut down an engine. ATC cleared the diversion. The engine was shut down at 04:20 hrs during descent through FL295 overhead Cork, approximately 52 NM from Shannon. The aircraft landed on Runway 24 at 04:40 hrs and performed a 180-degree turn at the runway end.
While taxiing toward the parking area, the Airport Fire and Rescue Service (AFRS) observed a fire on the left main bogies. The aircraft was stopped, and fire-retardant foam was applied. The AFRS initially requested evacuation on the right side, but the fire was extinguished before evacuation commenced. The crew reported a brake temperature warning during the turn at the runway end. Following extinguishment, the aircraft remained stationary for 60 minutes to cool brakes, monitored by AFRS thermal imaging. After cooling, the aircraft was towed to its stand, and all 117 passengers and 9 crew disembarked without injury. No damage to the aircraft or engine occurred.
Notification and Response
The AAIU learned of the occurrence from a Safety Occurrence Report submitted by Shannon ATC. Two inspectors deployed to Shannon to commence an investigation.
Probable Cause
The probable cause of the brief fire at the left-hand undercarriage was heat from the brake units and the presence of lubrication grease or oil that had leaked from the No. 1 engine.