Incident Overview
On 23 November 1998, a BAe 146-300 operated by an airline on a scheduled flight from Hannover to Milan experienced a series of electrical malfunctions shortly after takeoff. The aircraft was occupied by four crew members (two pilots and two cabin crew) and four passengers (three adults and one infant). No injuries were reported, and the aircraft sustained no damage.
Sequence of Events
During the initial climb, shortly after rotation, both the primary flight display (PFD) and navigation display (ND) on the right side of the cockpit went blank. Simultaneously, both yaw dampers, which had been active, disengaged. The first officer attempted to reactivate the yaw dampers without success.
As the landing gear was retracted, multiple amber warning lights illuminated on the overhead panel. The pilot in command (PIC), who was flying the aircraft, identified failures including the loss of AC bus 2 and DC bus 2. The PIC decided to return to Hannover and initiated a visual circuit pattern.
During the downwind leg, the landing gear was extended. Shortly after, a complete electrical failure occurred. This resulted in the loss of the EFIS displays on the PIC's side, the loss of radio communication, and the failure of instrument lighting. The flight data recorder (FDR) stopped recording at this point, and the transponder also ceased functioning.
Final Approach and Landing
In conditions of poor visibility and low cloud ceiling, the PIC managed to complete the circuit and land the aircraft. Upon touchdown, all four main landing gear tires burst. During the landing roll, the PIC noted that the spoilers did not deploy and the braking system was inoperative. The engines could not be brought to idle and had to be shut down manually. Nosewheel steering also failed, making directional control difficult. The aircraft came to a stop approximately 400 meters before the end of the runway.
Investigation Findings
The technical investigation revealed that earlier on the ground, the crew observed an unstable voltage reading on battery #2 (BAT #2). Battery #1 (BAT #1) showed a constant 28 V. The PIC decided to have a mechanic disconnect BAT #2. However, due to the arrangement of the batteries—BAT #1 was installed on the right (in the direction of flight) and BAT #2 immediately to its left—the mechanic mistakenly disconnected BAT #1 instead. The battery compartment was poorly visible, contributing to the error.
Further examination found that BAT #2 had severely corroded contacts, explaining the fluctuating voltage. Additionally, the hydraulic-driven standby generator was found to be faulty.
The electrical system was configured such that with BAT #1 disconnected, the aircraft was operating without a proper electrical backup. The total power loss after gear extension was attributed to the shutdown of the auxiliary power unit (APU) and the failure of the standby generator.
The cockpit voice recorder (CVR) was found to contain recordings from an earlier flight and was not operational for this incident.
Analysis and Conclusions
The investigation determined that the incident resulted from the aircraft being operated in an impermissible system configuration, a condition that was only partially detectable to the flight crew. The battery mix-up and subsequent failures led to a cascading electrical failure.