Introduction
On September 17, 2017, at approximately 15:00 local time (12:00 UTC), a serious incident occurred involving an MXP140 ultra-light aircraft with registration marks YU-A019. The aircraft was operated by a pilot-owner and was performing entertaining flights from Slivnitsa airfield. The incident was investigated by the Air Accident Investigation Unit (AAIU) at the Ministry of Transport, Information Technology and Communications.
History of the Flight
The pilot, acting as aircraft commander, planned an entertainment flight with his son. Pre-flight preparations included refueling 12 liters of A-95 gasoline into the right half-wing tank and conducting a pre-flight inspection, which indicated the aircraft was in order. The pilot performed all procedures according to the Airplane Operation Manual. Takeoff from runway 08 occurred at 14:50 local time. After flying in the area of Slivnitsa airfield, the pilot initiated a landing approach at a speed of about 55 knots, landing at approximately 15:00. Touchdown on runway 08 occurred at 45 knots, and the aircraft continued its landing run at 35 to 40 knots until about 100 meters before the end of runway 08.
Incident Details
According to the pilot's account, the intention was to demonstrate stopping by using the brakes. However, upon attempting to apply the brakes, the pilot found they did not operate synchronously. A second brake application caused the aircraft to roll 45 degrees to the left, exit the runway, and stop at the peripheral fence of the airfield. The final position of the aircraft was 75 meters northeast from the threshold of runway 26, at coordinates 42°50'41.637"N 023°01'03.775"E. The aircraft had turned 180 degrees. Examination of the runway surface revealed braking tracks 39 meters long ending 49 meters from the end of runway 08. At the end of these tracks, a 5-meter trace of working fluid (possibly brake fluid) was found. Another 5-meter fluid trace was located 5 meters before the end of runway 08.
Damage and Injuries
The aircraft sustained minor damage, as documented in photographs taken during the investigation. The pilot and the passenger (the pilot's son) were not injured, as indicated in the injuries table showing no fatalities or serious injuries.
Investigation Findings
The investigating commission determined the cause of the serious incident. The investigation concluded that the incident resulted from an error made by the pilot in piloting procedure during the landing stage. This error was associated with an inadequate decision to demonstrate intensive braking and a sudden failure of the braking system.
Probable Cause
The probable cause, as stated by the commission, is: "An error was made by the pilot in piloting procedure during the landing stage associated with an inadequate decision for intensive braking demonstration and a sudden failure of the braking system."