AAIB investigation to British Aerospace (BAe) ATP, SE-MHF
Loss of electrical power during cruise, 8 nm west of Milton Keynes, 3 May 2018.
Summary:
The aircraft experienced a loss of DC electrical power during the cruise whilst operating a cargo flight from East Midlands Airport to Stansted Airport, resulting in the loss of a significant number of flight deck instruments and systems. The crew decided to return to East Midlands Airport where they made a normal landing, following which DC electrical power was restored without crew action. The loss of electrical power was consistent with a failure of the No 1 Transformer Rectifier Unit (TRU) or its contactor, followed by a subsequent failure of the DC essential busbar COUPLE function. Subsequent testing of the aircraft’s electrical system did not identify the cause of either failure.
The investigation identified that the aircraft’s FDR was recording intermittently due to corrosion caused by moisture ingress. Two safety recommendations are made, relating to the prevention of moisture entering the FDR on BAe ATP aircraft with the Large Freight Door (LFD) modification and for the replacement of flight recorders using magnetic tape.
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