What happened
On March 10, 2001, a Sukhoi Su-26, registration RA44543, was performing aerobatic maneuvers near the Casarrubios del Monte Aerodrome in Toledo, Spain. The aircraft, which was in Spain to finalize a sale from a British owner to a Spanish citizen, was being used for a test flight to assess its condition.
While executing a climbing snap roll at approximately 2,000 feet, the pilot experienced a sudden loss of rudder control. Although a brief moment of control was regained, the aircraft quickly became unmanageable. At an altitude of 800 feet, the pilot was forced to bail out via parachute. The pilot landed at approximately 600 feet, suffering minor injuries, including a broken tooth and a split lip caused by the parachute harness during the jump. The aircraft crashed into the ground and was destroyed.
The investigation
Investigators examined the wreckage and discovered that the rudder control cable had become loose at the cockpit end. The inspection of the tensioner revealed that the cable had separated from one of its terminals.
Technical analysis of the tensioner components showed a manufacturing defect: a 9mm step in the terminal orifice, caused by improper machining, prevented the cable from seating correctly. Furthermore, the cable had not been sufficiently tightened, and the cross-section of the cable had been reduced by approximately 20% due to the way it was fastened, making it prone to breakage. Additionally, the investigation found that the tensioner terminal was not an original part manufactured by Sukhoi. The investigation also noted that the aircraft's tail dimensions were larger than the manufacturer's specifications.
Findings
- The primary cause of the accident was the breakage of a rudder control system tensioner, which subsequently jammed the elevator control mechanism.
- The failure of the tensioner was due to a manufacturing defect in the terminal and incorrect assembly of the cable.
- The aircraft had undergone various modifications in Lithuania, including engine and tail changes, but there were no maintenance records available for these works.
- The maintenance center responsible for the modifications was not authorized to perform work on this aircraft type under the regulations of the Russian Federation or Lithuania.
- The aircraft was operating in Spain without the specific authorization required for foreign-registered aircraft performing aerobatic maneuvers.