What happened
On July 19, 2017, a flight instructor and a student pilot were conducting a training flight from Speck-Fehraltorf, Switzerland, in a Jodel D11-2. During the flight, the crew encountered sudden, intense turbulence while turning after a departure from runway 30. Due to the severity of the turbulence, the student pilot handed control of the aircraft to the instructor. Observing a change in wind direction, the instructor decided to perform a shortened approach to runway 12 to land as quickly as possible.
During the final approach to runway 12, the aircraft experienced significant airspeed fluctuations, ranging from 85 km/h to 150 km/h due to heavy gusts. As the aircraft reached the middle of the runway, the instructor realized the remaining distance was insufficient for a safe landing and initiated a go-around at a very low altitude. While turning into the departure path at approximately 60 ft AGL, the aircraft encountered a powerful tailwind component.
Despite applying full power, the aircraft failed to maintain altitude. The instructor attempted to maintain a speed of 80–90 km/h to avoid a stall, but the combination of the tailwind, the rising terrain ahead, and the low altitude caused the aircraft to lose control. The aircraft rolled sharply to the left, struck vegetation in a rapeseed field, and eventually impacted an asphalt road in an inverted position. The impact resulted in 2 serious injuries.
The investigation
The BFU investigation focused on the meteorological conditions, the aircraft's performance, and the crew's decision-making. Investigators analyzed GPS flight tracks, airspeed data, and local weather radar. The investigation also reviewed the flight school's organizational structure and the pilot's credentials. Technical examination of the Jodel D11-2 revealed no mechanical failures or engine malfunctions prior to the accident. However, the investigation noted that the high density altitude, caused by an ambient temperature of 31°C, significantly reduced engine and aerodynamic performance.
Findings
- The primary cause of the accident was a loss of control resulting from a stall during the go-around.
- The decision to execute the go-around was made too late and at too low an altitude.
- The aircraft was operating in a highly turbulent environment characterized by strong wind shear and a sudden tailwind component.
- The aircraft was flying at a high mass, near its maximum allowable limit.
- High density altitude significantly degraded the aircraft's climb performance.
- The rising terrain in the direction of flight left no margin for error during the altitude loss.