What happened
On June 14, 2022, Qatar Airways Flight QTR-6J, operating a Boeing 777-3DZ(ER) with registration A7-BEA, was cruising at Flight Level 380 on a scheduled passenger flight from Lahore to Doha. The aircraft carried 197 people and was traversing Pakistani airspace via the Karachi FIR.
While in flight, the crew observed a progressive decline in oil pressure for Engine No. 2, which dropped below 10 PSI, accompanied by a rapid loss of oil quantity. In response, the crew executed an in-flight shutdown of the affected engine and declared a MAYDAY emergency. Air traffic control coordinated with Tehran ACC to vector the aircraft directly to Jinnah International Airport (JIAP) in Karachi. The aircraft landed safely on Runway 25L without injury to any persons on board or on the ground.
The investigation
A post-landing inspection revealed significant oil leakage around the Accessory Gearbox (AGB) of Engine No. 2. The engine module was sent to GE Aviation Wales for teardown and metallurgical analysis. Investigators found that the AGB oil nipple was misaligned with the oil supply tube, indicated by mismatched clamp witness marks.
Further examination identified two primary manufacturing defects: the thread engagement depth in the AGB housing was non-conforming (13 mm instead of the required 16 mm), and excessive weld rework on the nipple created uneven surfaces. These defects prevented the nipple from achieving proper torque preload during installation.
Findings
The investigation determined that the in-flight shutdown was caused by the axial displacement (push-out) of the AGB oil nipple. The lack of correct preload allowed micro-movements between mating threads during operation, leading to progressive wear and eventual seal failure. Contributing factors included the non-conforming thread depth, weld rework irregularities, inspection methods that failed to detect the lack of preload, and organizational delays in propagating corrective actions for this specific failure mode.
Safety action
GE Aviation issued a Service Bulletin mandating detailed inspections of GE90 AGB housings and oil-nipple assemblies for thread depth and weld conditions. The OEM also committed to developing improved verification methods to confirm proper conical seating and preload, as well as strict limits for weld rework on nipple components.