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Accident investigation report completed and information captured
Narrative: AAIB investigation to DA 42 NG, G-HAKA: Loss of electrical power shortly after take-off, Leeds Bradford Airport, West Yorkshire, 8 December 2020. Although the aircraft sustained no damage, the AAIB considered it to be a "serious notifiable incident", and the following is an excerpt from the AAIB Final Report, published on 8 July 2021...
"The pilot and passenger intended to fly to Southampton Airport where the aircraft was required for aerial work. Neither engine would start, and the pilot reported no glow-plug indications and poor engine turnover when using the starter motors. Engineers from the operator’s maintenance provider eventually started the engines with the aid of a ground power unit. Engine ground runs and a download of the engine Electronic Control Units (ECUs) showed no anomalies. A maintenance release form was signed off on the basis that the main aircraft battery charge state was probably low, and the pilot and passenger reboarded the aircraft approximately 1 hour 45 minutes behind schedule
The pilot reported that the engines started, but the low volts cautionary alert was displayed shortly after the cockpit checks were complete. This was disregarded “as a likely result of the earlier problems and something that would clear with engine running”.
Following a normal takeoff there was an audible alert and the pilot again observed low voltage cautions for both main electrical busbars. The pilot decided to return to Leeds-Bradford Airport but did not declare an emergency because “the checklist suggests 30 minutes time available”. The abnormal checklist for low volts refers to two more checklists; 4B.3.7-voltage and 4B.4.6 - l/r altn fail.
The pilot reported that the checks required by 4B.3.7 were completed, but not those in 4B.4.6 because an alternator failure was not displayed. The first action in checklist 4B.3.7 is to ensure that the alternators are switched on.
Following the checklist, the pilot reduced electrical loads but the busbar voltages decreased to 21 volts as the aircraft was on the downwind leg. After completing the pre-landing checks the pilot used a GPS tracking device to send a message to the operator informing them of the problem and selected the ILS approach plate on an electronic tablet. The electrical load was further reduced by switching off the lights apart from the strobes. As the aircraft started the turn onto the base leg the busbar voltages decreased rapidly and the pilot informed ATC that communications might be lost. They provided vectors to intercept the ILS, clearance to land and requested confirmation of the number of people on board.
The pilot responded and having acquired the localiser the landing gear was lowered and the aircraft captured the glideslope for the landing. Shortly after, all electrical power was lost, which resulted in the loss of the electronic flight displays.
The pilot switched on the emergency power for the standby artificial horizon, levelled off, and started a turn to the right. The cloud base was approximately 700 to 800 ft agl so, when a suitable gap was found, the pilot descended whilst maintaining sight of the ground. With the aid of a mobile phone based flight planning application, the pilot was able to return to the airport where an uneventful landing was carried out".
=AAIB Conclusion= The most likely scenario is that the alternators were not switched on prior to takeoff and the pilot did not identify the incorrect switch position. When the aircraft battery depleted the electronic displays failed, but the engines continued to operate because, despite being off, the alternators continue to power the ECUs and fuel pumps. The pilot successfully returned to the airport with the aid of a mobile phone and the standby artificial horizon".
=Damage Sustained to Airframe= Per the above AAIB report, No damage was sustained. However, the operator issued an Operational Crew Instruction to: 1. Require pilots to complete the before engine start checklist as a read-anddo checklist instead of from memory. 2. Highlight the fact that the G1000 does not show if an alternator is switched on or off. 3. Highlight the requirements of the low voltage abnormal checklist and require pilots to study it prior to their next flight in a DA 42. 4. Remind pilots that the AFM does not permit flight with a discharged battery under IFR or night VFR conditions
G HAKA Directflight Diamond DA42NG Twin Star tight turn Cambridge UK 5 May 2020:
DA42 lost electrical power shortly after take-off because the alternators had not been switched ON after engine start issues. The G1000 display does not show if an alternator status and when they are OFF shows battery voltage instead.https://t.co/7sWJx3bLo0pic.twitter.com/2nj0N0Hxqp