On June 12, 1991, a Boeing DHC-6-300 (registration N242CA) operated by Corporate Air, Inc. was involved in an aviation accident near Denver, CO. Investigators recorded the probable cause as: The hydraulic system circuit breaker was not engaged during engine start, resulting in a loss of hydraulic pressure to the brakes. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 4 related events involving the same aircraft type or operator are linked below.
During a maintenance test flight, an aircraft moved forward after engine start due to a disengaged hydraulic circuit breaker, leading to a collision with a parked aircraft.
Preflight and Engine Start
At dawn, a pilot and a mechanic conducted a preflight inspection of the aircraft before a local maintenance test flight. The aircraft's engines were started with the hydraulic system circuit breaker not engaged.
Loss of Brake Pressure
As the right engine's RPM increased, the aircraft began to move forward. The pilot attempted to apply the brakes but discovered that there was no hydraulic pressure in the brake lines.
Collision
Before corrective action could be taken, the aircraft struck a parked aircraft.
Cause
The hydraulic system circuit breaker was not engaged when the engines were started, rendering the brakes inoperative.
Probable cause
The hydraulic system circuit breaker was not engaged during engine start, resulting in a loss of hydraulic pressure to the brakes.