AAIB investigation to Boeing 737-4Q8, G-JMCR 4 June 2019
Partial electrical failure followed by missed approach, Brussels National Airport, Belgium, 4 June 2019.
Introduction:
Annex 13 to the Convention on International Civil Aviation places a responsibility on the State of Occurrence, in this case Belgium as represented by the Air Accident Investigation Unit (AAIU), to commence an investigation. However, the State of Occurrence may, by mutual agreement, delegate the investigation to another State. On 5 June 2019, the AAIU delegated responsibility for this investigation to the State of Registration, as represented by the AAIB.
Synopsis:
While descending to land at Brussels National Airport, a partial electrical failure occurred resulting in the loss of a number of systems including the electronic and analogue flight instruments on the left side of the cockpit. The pilot declared a MAYDAY and aware that a thunderstorm was approaching the airfield, assessed that the weather reported by Air Traffic Control (ATC) would allow him to continue and land at Brussels. However, visual references were lost at a late stage of the approach when the aircraft entered a heavy rain shower. A go-around was initiated during which the pilots estimated the amount of thrust required; the aircraft initially appeared to be slow to accelerate and establish a positive rate of climb. The aircraft entered an orbit and subsequently landed successfully from a second approach. The electrical failure was caused by a fault in the transfer relay which resulted in the loss of power to a number of electrical buses. The aircraft documentation was unclear as to which aircraft in the fleet were configured to enable the cockpit instruments to be powered from a standby electrical source; this may have affected the pilots understanding of the failure. Safety action has been taken by the operator to provide clarity in the aircraft documentation.
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