What happened
On November 30, 2004, a Zenair CH 601 UL Zodiac ultralight, identified as 971-BI, was performing local circuit training at Saint-François aerodrome. During the initial climb, the pilot noticed that the engine power could not be reduced using the left-hand throttle lever, as the engine remained at full power. To maintain control, the pilot continued the circuit by operating the control stick with the left hand and using the right-hand throttle lever to manage power.
During the final approach, the pilot deployed the landing flaps and made the decision to shut down the engine at an altitude of approximately 500 feet. Shortly after the engine was stopped, the propeller ceased rotation, causing the aircraft's airspeed to drop and its glide path to fall below the required approach slope. The aircraft landed approximately 50 meters short of the runway threshold and came to rest in a ditch near the runway entrance. The impact caused damage to the propeller, the nose gear, and the engine cowling, but no injuries were reported.
The investigation
The investigation focused on the mechanical failure of the power control mechanism. Investigators examined the throttle control rod, which is made of stainless steel and passes through the firewall via a cable guide. The examination revealed that the rod had been severed near its attachment point.
Metallurgical analysis showed an