Factual Background
The aircraft, a Reims Aviation F172P registered as HB-CHX, was owned and operated by Motorfluggruppe Zürich. It operated under visual flight rules (VFR) for private flights.
On September 2, 2021, a 100-hour inspection was performed with no damage noted. A subsequent 50-hour inspection on October 12, 2021, also found no issues.
On January 2, 2022, the aircraft experienced a flat tire on the nose wheel while taxiing at Zurich airport. The tire and tube were replaced the next day, with no structural damage observed. On January 15, 2022, a carburetor fire occurred during engine start, which the crew reported to maintenance. Because the aircraft was nearing a 200-hour inspection, the operator decided to combine that inspection with repairs for the fire damage.
Discovery of Damage
On January 18, 2022, maintenance began. Mechanics discovered deformations in the outer fuselage structure near the nose gear and the right wing strut. Further examination revealed additional damage: fire wall deformation, cabin floor distortion, center console structure bending, lower fuselage frame damage, landing gear attachment deformation, engine mount distortion, and numerous popped rivets. Some damage was only visible after removing panels and carpets. The pattern indicated high vertical impact energy.
The Swiss Transportation Safety Investigation Board (STSB) found no reports of any event in its database, ECCAIRS 2, or from the operator that could explain the damage.
Analysis
Based on the extent and pattern of damage, the STSB concluded that a hard landing—potentially involving porpoising (a repeated bouncing on landing)—was the cause. Due to the damage being present at the January 18 inspection but absent at the October 12 check, the event must have occurred between those dates. The impact energy would likely have been perceptible to the occupants. The crew did not report the event.
Conclusion
The accident, which severely damaged the aircraft's fuselage structure, resulted from an uncontrolled ground contact. The crew did not report the incident.