What happened
On October 19, 2014, a SIAI Marchetti S.205-18/R, registration N108MW, was performing a private VFR flight from the Speck-Fehraltorf airfield (LSZK) in Switzerland. The aircraft was carrying the pilot and three passengers. During the initial takeoff roll on the 600-meter grass runway, the pilot noticed the airspeed indicator was not functioning because the pitot tube cover had been left on. After aborting the first attempt and removing the cover, a second takeoff was initiated.
The aircraft rotated approximately two-thirds of the way down the runway at an indicated speed of about 65 knots. Shortly after liftoff, at an altitude of roughly 4 meters, the aircraft failed to gain sufficient altitude. The pilot attempted to adjust the pitch and direction to avoid terrain, but the aircraft began to sink. Realizing the climb was unsustainable, the pilot retracted the throttle, leading to a forced landing in a field approximately 57 meters past the end of the runway. The aircraft struck the ground with its right main gear first, eventually coming to rest on its belly after traversing a road and a cornfield. There were no injuries to the four occupants, though the aircraft sustained heavy damage.
The investigation
SUST examined the technical condition of the aircraft and the operational circumstances of the flight. The investigation revealed that the N108MW was in poor technical condition, with several mechanical deficiencies noted. While the engine and propeller were found to be capable of producing normal power on a test stand, the investigation highlighted that the aircraft was operating at a high takeoff mass of approximately 1220 kg.
Investigators also reviewed the pilot's actions and the lack of available performance data. The investigation found that the pilot lacked a calculated basis for takeoff performance, making it impossible to accurately estimate available climb reserves. Furthermore, the investigation looked into the aircraft's maintenance and found that the stall warning system was inoperative and that the aircraft had previously been fueled with unleaded automotive gasoline without an approved supplemental type certificate (STC).
Findings
- The primary cause of the accident was an inadequate takeoff technique relative to the high takeoff mass, which prevented the aircraft from maintaining altitude after leaving ground effect.
- The stall warning system was inoperative, meaning the pilot was not alerted to the approaching critical flight condition.
- There was no calculated performance basis available to the pilot to determine takeoff capabilities for the specific weight and conditions.
- The aircraft was heavily loaded, leaving very little margin for error during the initial climb.