Air Accidents Investigation Branch
Summary:
During a flight from the Royal London Hospital to RAF Northolt, G-LNDN suffered a series of seemingly unconnected electrical system faults.
The first faults related to the stability augmentation system and the commanders flight instrument displays but did not materially affect the conduct of the flight. Later, when approximately 4 nm from their destination, the pilots were alerted to electronic engine control system fault indications for both engines. A critical fault on the right engine required the pilots to manually control its throttle but the fault on the left engine was non-critical and the engine operated as expected in the NORMAL (automatic) control mode. The pilots were able to complete an uneventful approach and landing at RAF Northolt.
The investigation found that the electrical failures were the result of water ingress from the right engine bay onto electronic components located in the rear fuselage area.