What happened
During a maintenance ferry flight, the aircraft experienced significant performance issues during the takeoff roll. A mechanic was operating the controls from the right seat as captain. As the aircraft accelerated down the runway, it failed to reach expected speeds and would not rotate, even when the pilot applied full aft pressure on the control yoke. Recognizing the inability to achieve flight conditions, the captain aborted the takeoff. The aircraft eventually came to a stop at the end of the runway, with the right landing gear extending into the overrun area beyond the paved surface. Following the stop, crew members extinguished two small fires that had developed in the main gear brakes.
The investigation
Investigators examined the aircraft to determine why it failed to accelerate properly during the critical takeoff phase. While the specific mechanical failure preventing acceleration was not definitively identified, the condition of the braking system provided clear clues. Both main brake assemblies showed signs of having been subjected to extreme heat followed by rapid cooling. Additionally, an inspection of the brake components revealed that all brake puck linings were worn thin.
Findings
The physical damage observed on the brake assemblies was consistent with a scenario where the aircraft attempted to take off with the parking brake engaged or due to the inadvertent application of the toe brakes during the takeoff roll. This condition would explain both the failure to accelerate above normal rotation speeds and the subsequent overheating and fire in the main gear brakes.
Safety message
This incident highlights the critical importance of verifying brake release prior to takeoff, particularly during maintenance ferry flights where standard operational procedures may be altered.