DEN08LA074

According to the pilot, while in cruise flight at 7,000 feet in instrument meteorological conditions, he encountered embedded thunderstorms and up and down drafts. Multiple unusual attitudes were encountered and engine power was lost. Shortly thereafter, the airplane entered a flat spin, from which the pilot was unable to recover. The airplane impacted a field in a flat attitude, resulting in substantial damage. An examination of the airplane's systems and an engine run revealed no anomalies. Satellite and radar data depicted embedded towering cumulus clouds and rain shower activity in the accident area.

On April 11, 2008, at 1017 central daylight time, a Grumman American Aviation AA-5A, N9764U, piloted by a private pilot, was substantially damaged when it impacted terrain 25 nautical miles northwest of Beaumont, Texas. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 Code of Federal Regulations Part 91 on an instrument flight rules flight plan. The private pilot sustained serious injuries. The cross-country flight departed David Wayne Hooks Memorial Airport (DWH) Houston, Texas, approximately 0945, and was en route to Hattiesburg, Mississippi.

According to the Pilot/Operator Aircraft Accident Report Form submitted by the pilot, he departed DWH in visual flight rules (VFR) conditions and encountered instrument flight rules conditions (IFR) at 7,000 feet mean sea level (msl), while en route. He "suspected possible convection ahead" and asked air traffic control (ATC) about any "weather advisories." Prior to receiving information from ATC he "encountered… embedded thunderstorms." The autopilot disengaged and "numerous unusual attitudes were experienced." The airplane entered a dive and the pilot reduced power and recovered to level flight at which time he "encountered an updraft." The engine "quit" and he recovered to a level flight attitude. Shortly thereafter, the airplane entered a flat spin and the pilot was unable to recover.

According to the ATC controller, the pilot of the accident airplane questioned him about "any weather on his route." The controller advised the pilot "no weather was observed." The pilot requested a turn and the controller approved the turn. He reported observing the altitude change to 7,300 feet, then 6,800 feet and "continue to descend." The controller contacted the pilot and the pilot responded that he needed help. Due to a systems issue, audio recordings of ATC communications were not available.

Radar data, provided in National Track Analysis Program (NTAP) format, depicted the accident flight from the time of departure until the time of the accident. The airplane initially climbed to 7,100 feet. At 1015 the airplane climbed to 7,200 feet and 33 seconds later descended to an altitude of 6,800 feet. Radar data depicted the airplane climb up to 7,300 feet 14 seconds later and then initiate a descent to the point of impact. The last radar data was recorded at 1017:20 at an encoded altitude of 700 feet.

The airplane impacted an open field in a flat attitude. Both wings were bent up and wrinkled along the leading edge. The fuselage was wrinkled aft of the cabin on the left side and the vertical stabilizer separated partially from the empennage and was bent aft. An examination of the airframe and flight controls, conducted by the Federal Aviation Administration (FAA) inspector who traveled to the scene, revealed no anomalies.

The airplane was recovered to Beaumont for further examination. On May 28, 2008, the engine was examined and test run by an investigator from Lycoming Engines, under the auspices of the FAA. The examination revealed no anomalies. The engine started without hesitation and rpms were increased. The engine ran for three minutes without issue.

The closest official weather observation station was Southeast Texas Regional Airport (BPT), Beaumont, Texas, located 28 nautical miles (nm) southeast of the accident site. The elevation of the weather observation station was 16 feet msl. The routine aviation weather report (METAR) for BPT, issued at 0953, reported, winds 190 degrees at 5 knots, visibility 9 miles; sky condition few clouds at 7,000 feet; temperature 25 degrees Celsius (C); dewpoint minus 21 degrees C; altimeter, 29.86 inches.

GOES 12 visible satellite images depicted a band of stratocumulus clouds with some embedded towering cumulus clouds in the accident area. Level II Doppler weather radar in Houston, Texas, (approximately 65 miles southwest of the accident location) scanned the accident area between 1011 and 1041. Data indicated reflectivity values of 0 to 30 dBz.

Airman's Meteorological Information (AIRMET) for instrument flight rules (IFR) and mountain obscuration (SIERRA), turbulence (TANGO), and icing (ZULU) were all issued for areas in Texas, including the accident airplane's route of flight. Significant IFR and icing conditions were not expected outside of convective activity. AIRMET TANGO forecasted moderate turbulence below 14,000 feet.