What happened
On 17 June 1998, a Cessna 310R, registration G-BWYE, was conducting a cargo flight from Brussels to Glasgow at Flight Level 100. While in the cruise phase, the pilot heard a loud bang, followed by the appearance of acrid smoke emanating from the instrument panel behind the radio stack.
At the time of the incident, the aircraft was under the direction of London Air Traffic Control. The controller informed the pilot that Luton Airport was approximately 10 to 15 nautical miles away and that the cloudbase was 3,000 feet. Due to concerns regarding a potential loss of radio communications, the pilot requested an immediate approach. London ATC provided a descent and transferred the flight to Luton. To mitigate the risk of navigational radio failure, the pilot was vectored for a Surveillance Radar Approach (SRA). Once the aircraft descended below the clouds, the pilot was able to complete the landing visually and without further incident.
Following the landing, the pilot attempted to reset the circuit breaker for the radio stack lighting. Upon doing so, smoke reappeared and the circuit breaker tripped again. The Airport Fire Service attended the scene.
The investigation
An examination of the aircraft was conducted by an engineer from the operating company. The inspection revealed heat damage located behind the instrument panel, specifically in the area of the throttle quadrant. This damage was linked to a small, encapsulated static inverter, nearby wiring, and several associated connections.
Upon further inspection by the AAIB, the inverter was sectioned to determine the exact nature of the failure. While the external appearance suggested an internal failure, the internal examination of the component showed no evidence of internal overheating or burning.