NTSB Identification: LAX03FA051.
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Accident occurred Monday, December 16, 2002 in Anaheim Hills, CA
Probable Cause Approval Date: 04/28/2005
Aircraft: Piper PA-24-250, registration: N6268P
Injuries: 2 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The airplane sustained an in-flight breakup following an encounter with weather. The flight was in instrument conditions on an IFR clearance and being radar vectored to the ILS final approach course at 3,000 feet when the breakup occurred. The left wing tip and the outboard 1/2 of the left and right horizontal stabilators were the first pieces of wreckage in the 1/4-mile long debris path. The horizontal stabilators exhibited permanent down deformation at the separation points. The wings exhibited both up and down permanent deformation of the spars and other structural elements. The fracture surfaces at the separation points for the wings and stabilators were consistent with structural overload. There is no record that the pilot requested or received a preflight weather briefing. The National Weather Service (NWS) issued SIGMETs and AIRMETs for occasional severe turbulence, strong gusty winds, low level wind shear, and for occasional severe rime to mixed icing in clouds. The SIGMETs and AIRMETS were valid prior to the pilot's departure and covered the timeline of the flight. The NWS weather radar depicted moderate intensity echoes extending over the accident site. While en route at 1219, the pilot requested the current destination weather from the center controller, who provided the METAR report of 10 miles visibility and broken layers at 4,000 and 20,000 feet. Shortly after the pilot was given this observation, the destination conditions rapidly deteriorated to include lowering ceilings, strong and gusty winds, and moderate to heavy rain showers. The destination weather 30 minutes prior to the accident included winds gusting to 21 knots with scattered clouds at 3,800 feet, and a broken layer at 10,000 feet. A special observation issued about 5 minutes prior to the accident indicated that winds were gusting 14 to 19 knots, visibility was 2 miles in moderate rain and mist, a broken ceiling was at 2,800 feet, and the sky was overcast at 5,000 feet. It noted that rain began about 15 minutes earlier than the observation time. Five minutes after the accident, another observation reported that the winds were gusting to 21 knots, visibility was 1 1/2 miles with moderate rain, and broken and overcast ceilings at 2,100 feet and 4,700 feet respectively. The crew of a Boeing 757 making the approach 10 minutes after the accident reported a 45-knot crosswind shear at 100 feet, and light to moderate turbulence throughout the approach. An analysis of the weather conditions at the time of the accident, including radar and satellite sensor imagery, disclosed that strong weather echoes existed near the accident site with embedded areas of intense to extreme echoes. The tops were in excess of 33,000 feet. The analysis indicated that several low level wind shear layers were present with moderate to severe turbulence.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: the pilot's encounter with forecast severe turbulence during an inadvertent penetration of an intense weather cell, which resulted in the pilot exceeding the design structural limits of the airplane. A factor in the accident was the pilot's inadequate preflight planning and preparation, and his failure to obtain a complete weather briefing. Full narrative available
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