What happened
On Wednesday, September 22, 1999, at 15:30, a Socata MS 893 A Rallye Commodore, registration F-BSVZ, was performing a functional engine test flight following ground testing at the Challes-les-Eaux aerodrome. The flight was a local mission conducted under CAVOK weather conditions.
During the climb, the pilot maintained a vertical ascent over the airfield. As the pilot initiated a descent, an audible noise, described as similar to a snapping cable, was heard. Following this sound, the pilot observed that while the elevator remained effective for nose-down inputs, it no longer provided nose-up authority. To manage the situation, the pilot utilized the trim system and engine power to maintain control, eventually performing a cautious landing.
The investigation
The investigation focused on the mechanical integrity of the elevator control linkage. Upon inspection of the aircraft on the ground, investigators discovered that the clevis pin connecting the bellcrank to the elevator cables had fractured.
Records indicated that the aircraft had been maintained by an approved maintenance organization and had undergone all required periodic inspections. The aircraft had flown 61 hours since the last inspection of the control linkage and 170 hours since its airworthiness certificate was renewed. No specific maintenance interventions on the elevator control system were recorded in the aircraft logbook during these intervals.
Findings
- The failure was caused by the fracture of the clevis pin connecting the bellcrank to the elevator cables.
- The breakage resulted from wear caused by friction.
- This wear may have been caused by insufficient lubrication, potentially exacerbated by high tension in the dual elevator cables.