What happened
On June 7, 2015, an E1 Antares, registration HB-2414, was performing a self-launch from runway 25 at the Fricktal-Schupfart airfield (LSZI). Shortly after takeoff, the pilot noticed unusual noises coming from the engine. Within approximately 400 meters of the start of the takeoff roll, the electric motor ceased operation. Following the engine failure, the propeller could not be feathered. The pilot subsequently executed an emergency landing with the propeller in the extended position, following a downwind leg and communicating the situation via radio. There were no injuries to the pilot or any third parties.
The investigation
Investigators examined the electric motor and discovered that several windings had been damaged due to a local short circuit. The investigation traced the mechanical origin of the failure to a previous maintenance event in 201-4, during which motor seals had been replaced. While parts were replaced during that service, it was noted that a pre-existing damage to the electric drive (EA42) had left the rear bearing seat outside of permissible tolerances.
Technical analysis indicated that the excessive bearing play allowed the internal ball bearing to rotate and undergo significant axial displacement. This movement caused the spiral retaining ring to be pushed against the rotating sealing disc of the bearing. The resulting friction and force eventually caused the failure of the retaining ring component.
Findings
- The primary cause of the engine failure was a short circuit in the electric motor windings.
- This electrical failure was triggered by mechanical instability in the bearing assembly.
- Excessive play in the rear bearing seat allowed the spiral retaining ring to be displaced by the rotating sealing disc.
- The underlying issue stemmed from a previous maintenance error where a bearing seat out of tolerance was not identified during a 2014 seal replacement.