What happened
On April 25, 2024, a Cessna 208 Caravan, registered F-GUTS, was performing a ferry flight from Verona, Italy, to Gap-Tallard aerodrome in France. Upon arrival at Gap-Tallard, the pilot opted to join the circuit for runway 02 to avoid interfering with an aircraft performing parachute drops.
While on the downwind leg, the pilot reduced power and experienced sudden, intense vibrations. The aircraft's propeller pitch began to move toward a feathered position, significantly impacting performance. During the base leg, the aircraft's ground speed was approximately 100 kt. As the pilot flew over the runway threshold at an altitude of roughly 185 ft, it became clear that a landing on the paved runway was not possible. The pilot attempted to maneuver the aircraft but ultimately executed a forced landing in a clearing north of the runway. The aircraft struck a bank at the edge of the field, causing substantial damage to the airframe. The pilot evacuated the aircraft without assistance.
The investigation
The investigation focused on the mechanical failure of the powerplant, which featured a Pratt & Whitney Canada PT6A-114A engine and a McCauley three-blade variable-pitch propeller. Investigators examined the propeller governor and the recent maintenance history of the aircraft.
Records showed that a maintenance operation involving the removal and reinstallation of the propeller had been performed by a Part 1-approved organization approximately 33 flight hours prior to the accident. Physical examination of the wreckage revealed that the propeller reversing lever had been incorrectly installed. Specifically, the lever was positioned on top of a metal guide rather than underneath it. This error allowed the carbon block to slip out of its groove, which subsequently allowed the reversing lever to move and actuate the Beta valve, driving the propeller into the feathered position.
Findings
- The primary cause of the propeller feathering was the incorrect installation of the propeller reversing lever during a previous maintenance session.
- The maintenance organization did not classify the propeller reinstallation as a critical task, which likely resulted in the absence of a secondary inspection or double-check of the lever's position.
- The design of the existing metal guide allowed for this incorrect installation to occur.
- The pilot's arrival in the circuit at an altitude approximately 750 ft higher than recommended, combined with inadequate flight path management following the engine malfunction, contributed to the aircraft flying over the runway threshold at a dangerously low height.