What happened
On October 4, 2014, a Zlín Z 226MS, registration OK-KMJ, was performing a training flight near Vrchlabí, Czech Republic. The flight involved a pilot in training for the TOW qualification and an instructor flying a towed glider. The flight plan intended for the glider to detach at approximately 1,000 meters for independent landings.
During the flight, at an altitude of approximately 500 meters, the engine began to lose power and subsequently failed completely. The instructor, observing the sudden descent of the towing aircraft, disconnected the glider and performed a safe landing at the Vrchlagí aerodrome. The pilot of the Zlín Z 226MS attempted to restart the engine by cycling the magnetos, but the engine failed to respond. Due to the low altitude and the presence of a headwind, the pilot was unable to reach the runway and instead performed an emergency landing into terrain west of the airfield. Just before touchdown, the aircraft struck a pasture fence, causing significant damage, including the complete separation of the right wing.
The investigation
The ÚZPLN investigation focused on the technical condition of the aircraft and the sequence of events leading to the engine failure. A technical inspection of the Zlín Z 226MS revealed no mechanical defects in the engine, fuel system, or ignition components. However, investigators found that the auxiliary fuel tank was empty, while the main tanks still contained usable fuel.
Analysis of the fuel system showed that when the fuel selector is set to the auxiliary tank position, the engine draws fuel from that tank, which is replenished only by a small bypass flow from the fuel pump. This bypass flow is insufficient to maintain the level, leading to a net depletion of the auxiliary tank. The investigation also noted that the pilot had not visually verified the fuel quantity before the flight and had not personally refueled the aircraft that day.
Findings
- The engine failure was caused by the complete depletion of fuel from the auxiliary tank.
- The pilot likely failed to perform the required pre-flight checks and inadvertently set the fuel selector to the auxiliary tank position instead of the main tank position.
- The pilot's attempts to restart the engine were unsuccessful because the fuel supply had been interrupted.
- The pilot could have successfully reached the airfield if the engine failure had been managed differently or if the descent rate had been controlled.
- The aircraft struck a fence during the forced landing, resulting in substantial structural damage.