Amateur-built Challenger LSS N95478 accident near Moses Lake, Washington

Probable cause

The pilot's inability to maintain control due to an in-flight separation of the vertical fin as a result of the failure of the airplane's builder to properly secure the vertical fin to the fuselage.

NTSB analysis

The pilot was completing a local flight and entered the downwind leg of the traffic pattern at the destination airport. As the airplane was on the downwind leg and almost abeam the runway identifier numbers, the engine power reduced and the nose pitched up about 15 degrees. The airplane made a tight turn onto the base leg and then overshot final approach. The airplane was high and appeared to be configured in a slip (right wing low) while approaching the runway. When reaching about 30 feet above ground level (agl), the airplane pitched nose high, as if the pilot was attempting to flare. The engine power slowly increased and the airplane turned about 45 degrees, barely clearing a hangar and power lines. The airplane made numerous erratic maneuvers while varying altitudes between 45 and 300 feet agl. It then pitched up about 65 degrees nose high and made a left bank. It subsequently stalled and continued in a spin about 360 degrees before impacting a field located adjacent to the runway. A postaccident examination revealed that the vertical fin had separated from the fuselage attach points and remained attached to the airplane only by the horizontal tail plane struts, the elevator control push rods, and the rudder cables. Examination revealed that the vertical fin attach tubes (forward and aft) had not been secured to the fuselage attach tubing. The bolts designed to secure the vertical fin to the fuselage were not attached; rather, the bolts were secured to the fuselage tubing and the undrilled vertical fin attach tubing was resting on top of the bolts. The build manual for the airplane states that during assembly, the builder must remove the bolts secured to the fuselage attach tubing and insert the vertical fin attach tubing. Following insertion the builder is instructed to drill the vertical fin tubing and secure the bolt through both pieces of tubing.

Text from the NTSB. Open the NTSB docket for LAX08LA160 for the full record.