Incident Overview
On January 5, 2021, a Tecnam P2006T aircraft, operated by Sevenair Academy, initiated a local training flight from Cascais Aerodrome (LPCS) in dual command at 08:45 UTC. The flight proceeded to the Sintra area. After approximately three hours of flight, the crew observed a reduction in oil pressure on the critical engine #1. Following checklist procedures, the crew visually confirmed an oil leak and shut down the engine. Declaring urgency with a "PAN-PAN" call, they returned to LPCS using only engine #2 and performed a successful landing at 11:45 UTC without further issues. No injuries were reported, and the aircraft sustained no damage.
Maintenance Findings
The contracted Part 145 maintenance provider investigated the oil leak. During an engine run-up, a leak was detected around the ignition housing. After disassembly, a damaged crankshaft oil seal was found. The probable cause identified was failure of the crankshaft oil seal retainer due to wear caused by contact with the flywheel hub. This contact resulted from defective installation of the retainer during a recent engine overhaul, which had occurred less than 10 flight hours prior.
Contributing Factors
The maintenance provider identified several contributing factors:
- The engine manual's maintenance instructions lacked proper detail for component installation, including warnings or attention-getter notes regarding dimensions and off-centre checks.
- The retainer installation requires a special tool (P/N 877270), but the manual process allowed possible misalignments without validation points.
- The Rotax 912 engine type overhaul training accessible to the maintenance provider did not include details on the component installation.
Actions Taken
The operator and maintenance providers implemented corrective actions:
- Evaluated the oil seal retainer installation and condition in all overhauled engines currently in service.
- The engine maintenance provider revised maintenance protocols to specify and detail the oil seal retainer installation procedure and add a double-check inspection after installation.
- The provider will contact the engine manufacturer with the findings to obtain information and advice to prevent recurrence.
Investigation Scope
The GPIAAF was notified at 12:39 UTC and opened an evaluation process. Based on data provided by the maintenance provider's quality department, the GPIAAF decided not to proceed beyond the immediate findings, deeming disclosure via this Information Notice relevant due to the high number of Rotax 912 series engines operating in Portugal.