C-FRSO, a Boeing 787-9 aircraft operated by Air Canada, was conducting flight ACA844 from Calgary Intl, AB (CYYC) to Frankfurt/Rhein-Main, Germany (EDDF) with 11 crew members and
196 passengers on board. During cruise flight at position N5940/W4626, approximately 550 nm North East of Goose Bay, NL (CYYR), the flight crew noted a loss of oil in the number 1 engine.
The flight crew declared a PAN PAN and requested a diversion to CYYR. The power on the engine was reduced to idle where it remained until the aircraft landed without further incident.
The operator’s maintenance determined that the L2 Variable Frequency Starter Generator (VFSG) was leaking oil due to O rings damage on the shaft and the carbon seal. After the VFSG and the carbon seal were replaced, a successful leak check was carried out.
Subsequently, the aircraft was released back to service.