Synopsis
At 0938, the aircraft was climbing through 9,000 feet when the pilot received clearance to climb to flight level 210 (FL210). Approximately ten minutes later, the air traffic controller observed that the aircraft's Mode C transponder return was no longer displayed on radar. Attempts to establish radio communication with the pilot were unsuccessful. The aircraft subsequently broke up in flight, and the wreckage came to rest in a creek and on marshland. Both occupants were killed.
Accident Sequence and Radar Data
Radar data indicated that the aircraft was climbing at 115 knots and 1,100 feet per minute. As it passed approximately 16,000 feet mean sea level (MSL), the rate of climb decreased to about 750 feet per minute before increasing again to 1,200 feet per minute. The aircraft reached a peak altitude of around 18,200 feet MSL. At the time and location corresponding to this peak altitude, primary radar targets appeared and persisted for several minutes. Subsequently, the aircraft entered a steep descent and impacted the terrain.
Wreckage Distribution and Examination
The main wreckage was submerged in a creek and scattered across marshland. A large section of the right outboard wing panel was discovered approximately two miles east of the main wreckage. The right engine was located between 800 and 1,200 feet northeast of the main wreckage, resting in four feet of water. Examination of the right outboard wing revealed evidence of failure from upward and aft overload. No pre-accident mechanical failures or malfunctions were identified that would have caused the in-flight breakup. Organic material was found on the left engine inlet screen, but its source could not be determined. The accident site was situated along a bird migration route.
Investigation Findings
The official investigation determined that the occurrence involved an airframe/component/system failure or malfunction during the climb phase. The specific reason for the occurrence was undetermined. It was found that the aircraft's design stress limits were exceeded, resulting in wing overload and subsequent wing separation. A second occurrence involved an in-flight collision with terrain and water during an uncontrolled descent; the terrain condition was water.
Probable Cause
The probable cause, as stated by the investigation, includes an undetermined reason for the occurrence, exceedance of design stress limits, wing overload, and wing separation, leading to an in-flight breakup and subsequent collision with terrain and water.