What happened
On 5 July 2017, a PS-28 Cruiser, registration HB-WXA, departed Lausanne-La Blécherette airport in Switzerland for a training flight to Neuchâtel. The crew, consisting of a student pilot and an instructor, had previously completed several circuits at Neuchâtel before departing for the return leg.
During the initial climb from runway 05, the aircraft experienced a sudden and significant loss of engine power. Flight data recorded the engine RPM dropping from 5,100 to 3,150 in less than ten seconds. As the airspeed decreased from 61 kt to 54 kt, the aircraft entered a left turn. The bank angle increased steadily while the pitch and vertical speed decreased, eventually causing the aircraft to enter a nose-down spin. The aircraft crashed into a wooded area near the edge of Lake Neuchâtel. The accident resulted in two fatalities and the destruction of the aircraft.
The investigation
The investigation focused on the mechanical state of the engine and the maintenance history of the aircraft. Investigators examined the wreckage and retrieved flight data from the Electronic Flight Instrument System (EFIS). Technical analysis of the powerplant revealed that the needle of the right carburetor had separated from its circlip and become wedged in the main jet. This separation was attributed to the fixation screw not being properly secured during a previous maintenance interval.
Furthermore, investigators found that one connector for an electronic module in the ignition system was not properly locked, which may have led to a disconnection during flight due to engine vibrations. The investigation also reviewed the maintenance programme, noting that the interval for complete carburetor inspections had been extended from the manufacturer's recommended 200 hours to 400 hours.