Report on air accident at Nordnestjønn, east of Arendal Airport Gullknapp on 14 August 2019 involving Pipistrel Alpha Electro, LN-ELA

On Wednesday 14 August 2019, a Pipistrel Alpha Electro suffered motor failure during its approach to Arendal Airport Gullknapp (ENGK). The probable cause of the motor failure was the power controller interrupting power to the motor. The reason for this was most likely overheating due to low fluid level and air pockets in the cooling system.

According to the flight manual, the coolant level should be checked prior to each flight. However, this is not possible without removing the top cowling. The investigation has shown that this is so impractical and time-consuming that pilots often chose not to perform this item on the checklist.

The Norwegian Safety Investigation Authority recommends that Pipistrel modifies the Alpha Electro model to make it easier to check the coolant level.

On Wednesday 14 August 2019, a Pipistrel Alpha Electro experienced motor failure during its approach to Arendal Airport Gullknapp (ENGK). The probable cause of the motor failure was the power controller interrupting power to the motor.

The investigation has shown that there was no complete and easily identifiable checklist for regaining motor power in situations like these. The relevant checklists are on different pages of the flight manual, and do not have unambiguous headings.

The Norwegian Safety Investigation Authority recommends that Pipistrel prepares a complete and easily recognizable checklist for regaining motor power should the aircraft's power controller cut power to the motor. This work should include an overall review of the flight manual to make it more unambiguous and easier to read in an emergency.

On Wednesday 14 August 2019, a Pipistrel Alpha Electro experienced motor failure during its approach to Arendal Airport Gullknapp (ENGK). The probable cause of the motor failure was the power controller interrupting power to the motor. The reason for this was most likely overheating due to low fluid level and air pockets in the cooling system.

In connection with a motor replacement, coolant was not optimally replenished. The procedure for this is not described in the maintenance manual. An insufficient amount of coolant was therefore replenished, and air was trapped in the system.

The Norwegian Safety Investigation Authority recommends that Pipistrel review the Aircraft Maintenance Manual with a view to improve the work description for replenishing coolant. The work description should also contain a cross-reference to the table for fluid quantity, which is in another section of the manual.

On Wednesday 14 August 2019, a Pipistrel Alpha Electro experienced motor failure during its approach to Arendal Airport Gullknapp (ENGK). The commander performed a successful emergency landing.

When the motor failure occurred, use of the ballistic rescue parachute was an alternative. The flight manual does not contain information about the minimum altitude for safe deployment of such a rescue parachute. Such information can be important when a pilot in an emergency situation has to decide whether to deploy the rescue parachute or not.

The Norwegian Safety Investigation Authority recommends that Pipistrel adds information about minimum altitude for safe deployment of the rescue parachute to its flight manual.