What happened
On July 25, 2018, a DA 20 C aircraft was being prepared for flight training at EPMO airport. Following refueling, the aircraft was turned 180 degrees and prepared for towing to the parking apron using a tractor. After the instructor attached the aircraft to the towing vehicle, the student pilot took his seat. The instructor issued the command "parking brake off" before boarding the tractor.
After receiving clearance from the airport dispatcher, the towing process to apron number 12 commenced. Approximately 150 meters into the maneuver, the instructor noticed a distinct squealing sound from the braking system and observed smoke emanating from the aircraft's landing gear. The towing operation was immediately halted. Although the instructor retrieved a fire extinguisher, the situation was resolved without the need for active firefighting. The parking brake was subsequently released, and the aircraft was towed to a hangar.
The investigation
The investigation focused on the sequence of events leading to the brake overheating. The instructor recorded in the aircraft logbook that the towing had occurred with the parking brake engaged. Technical inspections were performed on the aircraft, which included replacing the brake pads, inspecting the wheel bearings, and lubricating the components. Following these maintenance actions and a successful ground test of the braking system, the aircraft was returned to service.
Findings
- The primary cause of the incident was a misunderstanding of the command issued to the student pilot prior to the start of the towing operation, which resulted in the aircraft being towed with the parking brake engaged.