ASN Wikibase Occurrence # 294231
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| Date: | Wednesday 11 May 2011 |
| Time: | |
| Type: |  Diamond DA42 Twin Star |
| Owner/operator: | Epag |
| Registration: | F-GOKD |
| MSN: | 42.226 |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | None |
| Category: | Incident |
| Location: | Merville Calonne Airport -
 France
|
| Phase: | Approach |
| Nature: | Training |
| Departure airport: | Hazebrouck-Merville/Calonne Airport (HZB/LFQT) |
| Hazebrouck-Merville/Calonne Airport (HZB/LFQT) | |
| Investigating agency: | BEA |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
The student was performing a dual IFR instructional flight between Calais Dunkerque and Merville Calonne airfields. At the end of the flight, during the instrument approach procedure, the instructor and the student noticed the "L ECU B FAIL" alarm, without any power variation. The instructor applied the abnormal procedure "L/R ECU B FAIL" but was unable to clear the alarm. He completed the procedure and landed without further problems.
The aircraft was equipped with two Thielert TAE 125-02-99 engines. On the ground, a rivet of the friction disk of the torque and vibration damper of the left engine was found broken.
A piece of this rivet damaged the engine speed sensor of ECU B, which generated the alarm. This newly designed torque and vibration damper was recently developed by the engine manufacturer. It has a potential of 600 hours, which is higher than the old model's 300 hours. The damaged friction disc had been installed new on the left engine on February 2, 2011. At the time of the incident, it had a total of 265 hours of operation.
The friction disc was examined by the engine manufacturer. The engine manufacturer explained that the rivet failed due to overload because of misalignment of the friction disc during installation. They also identified that the installation tool did not meet the alignment tolerances. The engine manufacturer says it had previously identified this problem, which led to the development of a new friction disc design, in which rivets are replaced with bolts, making the new design less susceptible to potential alignment problems. The design of the installation tool has also been revised.
Service Bulletin TM TAE 125-1013, issued on May 10, 2011, the day before the incident, called for the replacement of the friction discs with this new design. It was made mandatory by EASA Urgent Airworthiness Directive 2011-0087-E, issued on May 12, 2011. The aircraft was within the tolerances defined by the service bulletin for the application times.
Conclusion
The incident was due to an incorrect design of the friction disc installation tool, which led to misalignment and overload failure of a rivet.
Sources:
https://bea.aero/en/investigation-reports/notified-events/detail/defaillance-dun-accessoire-dun-moteur-lors-de-lapproche-fausse-alarme-atterrissage-en-instruction/
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 10-Oct-2022 19:43 | harro | Added |
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