A British Aerospace Plc 3201 Jetstream (VH-OAE) was operating a scheduled passenger flight between Mt, Gambier to Adelaide both in Southern Australia. At approximately 50 miles (93 kilometers) from the destination, while in a shallow turn (during the cruise phase of the flight) the right engine surged twice, and then flamed out.
The incident aircraft on another flight (© Brian Wilkes)
The crew completed the “ ENGINE FAILURE IN FLIGHT “ memory items in accordance with the operator’s procedures. Once the Memory Items were completed the QRH (Quick Reference Handbook) was used to shut down and secure the engine in accordance with the relevant checklists.
ATC was informed about the engine shutdown and requested a Direct to Adelaide, additionally, they requested a descent to 10.000 feet (3000 meters) to prevent cabin pressurisation issues with only one engine operative. A company pilot, who was deadheading on the flight, took it upon him to inform the passengers about the issue with the engine and the plans the crew had, this pilot’s actions helped for a great deal to overcome anxiety among the passengers Just prior to reaching the Top of Decedent they attempted Automatic and manual restart of the engine, following the procedures as given in the QRH. This would result in the engine rotating, the propellor would unfeather, but the engine would not start. The descend, approach and landing (at 18.50 lt) were completed without further trouble. After passengers and crew had disembarked maintenance crew started investigating the issue. This investigation led to the removal of the TPE331-12UHR-702H engine, after which it was shipped to the manufacturer for failure analysis under the supervision of an NTSB member at the request of the Australian Transportation Safety Board. Some facts and figures on the engine;
· Purchased by the airline from the manufacturer in November 2005
· The engine was fitted to VH-OAE on the 20th of December 2005
· TSN was 6242 hours when fitted to VH-OAE
· CSN was 7987 cycles when fitted to VH-OAE
· Since installation the engine ran for 15.65 hours and completed 17 cycles
Prior to delivery to the airline, the engine had undergone an inspection at its facility and during which some parts on the reduction gearbox were replaced. More specifically a Gear (marked yellow in the diagram below and Bearing this due to wear on the gear teeth. Another gear in the reduction gearbox (marked green in the diagram below) was inspected and refitted.
Part of the reduction gearbox Illustrated Parts Catalog (source atsb.gov.au)
When the engine was inspected by the manufacturer several gear teeth were found to be missing from the gear that was driven by the newly installed gear. It is likely that the P/N 3103590-2 gear teeth (marked green in the diagram above) separated as a result of accelerated tooth wear due to the mating of new and worn components leading to fatigue failure and the subsequent loss of one or more teeth from that gear. However, the possibility of the damage occurring from a foreign object could not be excluded. So either interaction between the new and the old gear or a Foreign Object in the reduction gearbox caused the engine failure. The full investigation report can be found by clicking here