Quad City CHALLENGER II N732LS accident near Redlands, California

Probable cause

Structural failure of the right wing during the landing approach due to the separation of the wing's fabric covering.

NTSB analysis

The pilot of the experimental light-sport airplane had just completed a 40-minute-flight, and was turning from the downwind to base leg when at 450 feet above ground level, the airplane rapidly descended and collided with terrain below. The damage to the forward section of the fuselage, the position of the main wreckage, and the minimal damage to surrounding trees indicated a near vertical impact attitude. The location of the right wing, along with the aft downward bending damage observed to its main spars and tensile failure of the forward spar attach point, indicated that the wing separated from the airplane in a down and aft motion during flight. The airplane's flight profile was not conducive to a negative overload failure of the right wing. The outboard right wing ribs failed in tensile overload, and the wing fabric material was observed attached only at the aft spar, and in-trail of the wing. These signatures indicated that the material had become separated from the wing structure in flight. The separation most likely created a high drag, ‘parachute’ effect with resultant failure of the wing. The airplane was built about 18 years prior to the accident, and appeared to have been flown as an unregistered airplane prior to purchase by the two pilots. New wing covering had been installed by the pilots the year prior to the accident, and cursory tensile testing of fabric samples revealed that the material had a breaking strength comparable to similar light aircraft fabric. The pilot-rated passenger was an insulin-dependent diabetic, however, it was not possible to determine whether his condition had any relation to the circumstances of the accident.

Text from the NTSB. Open the NTSB docket for WPR09LA453 for the full record.