What happened
The captain was finalizing passenger loading checklists while the first officer secured the cabin door and moved to the forward section of the aircraft. The captain initiated the number two engine start and began single-engine taxi operations, attempting a right turn to maintain clearance from a parked Dornier 228 (N264MC). As N259MC began rolling forward, the captain noticed that the nosewheel steering was unresponsive. He applied normal braking, but received no feedback or deceleration, causing the aircraft to begin an unintended left turn.
In response, the captain switched the hydraulic pump selector from 'Normal' to 'Manual On'. However, before sufficient hydraulic pressure could be established via battery power, N259MC collided with the parked N264MC. The accident resulted in damage to both aircraft. No injuries were reported among the crew or passengers.
The investigation
A thorough inspection of the aircraft systems revealed that the number two generator was not connected to the generator bus. Extensive checks found no part malfunctions or failures within the aircraft's mechanical systems. The nosewheel steering and normal brakes are electro-hydraulically actuated. Without generator power, and with the hydraulic switch in the 'Normal' position, these systems would not function. An emergency parking brake was available on board but was not utilized during the incident.
Findings
The investigation highlighted significant gaps in operational guidance. The training program, operations manual, and Dornier 228-series Pilot Operating Handbook did not address single-engine ground operations or the effects of an interruption in generator power. This lack of specific procedural guidance contributed to the crew's inability to manage the loss of hydraulic pressure effectively.
Safety message
Operators and manufacturers should ensure that training programs and operating manuals explicitly cover single-engine ground operations and emergency procedures for electrical system failures, particularly regarding the impact on electro-hydraulic systems.