Factual Information
The aircraft involved was a Boeing 767-300, registered as JU-1021 (MSN 41519, manufactured 10 May 2013). It was powered by two GE CF6-80C2B7F engines. The incident occurred on 12 September 2022 at 03:13 UTC over Airway 575 near "Соснавка" (Sosnavka). The flight was a scheduled passenger service from Chinggis Khaan International Airport, Ulaanbaatar, to Frankfurt. On board were 10 crew and 252 passengers. No injuries were sustained.
Flight History
Before departure, the right engine Integrated Drive Generator (IDG) was inoperative. The aircraft was dispatched under the Minimum Equipment List (MEL). The flight departed Ulaanbaatar at 10:19 local time. At 11:13 local time, the cockpit display showed an APU oil low quantity message. The crew decided to return to Ulaanbaatar and landed without further incident.
Damage to Aircraft
Post-incident external inspection revealed damage to the APU generator. The head of a bolt on the cooling oil line for the APU generator was broken, and the bolt shank had fallen out. No other damage was noted.
Personnel
The captain, male, 53 years old, held an Air Transport Pilot Licence and had accumulated over 19,890 flight hours. The co-pilot, male, 34 years old, was undergoing command training. Both were qualified and current.
Investigation
The Aircraft Accident Investigation Bureau of Mongolia conducted the investigation. The probable cause was not stated in the available report.