On March 18, 2016, about 0807 central daylight time, a Grumman American AA-5 single-engine airplane, N9582L, was substantially damaged after it impacted trees and terrain near East Side Airport (3TS0), Longview, Texas. The pilot was seriously injured. The airplane was registered to and operated by the pilot under Title 14 Code of Federal Regulations Part 91 as a personal flight. Low instrument meteorological conditions (IMC) prevailed, and no flight plan had been filed. The airplane departed 3TS0 at 0805 for a local flight. A witness saw the southeast bound airplane enter low overcast clouds immediately after takeoff. He heard the airplane begin a left turn and then saw the airplane emerge from the base of the overcast in a nose-down, steep left bank. The pilot recovered, and then the airplane reentered the clouds. The witness heard the impact a few minutes later. Evidence at the scene showed the airplane was northwest bound when it struck 40-foot tall trees and terrain, coming to rest inverted about 75 feet from the initial impact point. The impact resulted in the complete separation of the right wing and substantial damage to the fuselage, empennage, and left wing. An examination of the airplane and its systems revealed no anomalies. Weather observed at 0753 at East Texas Regional Airport (GGG), located 7 miles south of 3TS0, was as follows: Wind, 110° at 5 knots; visibility, 5 miles, mist; ceiling, 600 feet overcast,; temperature, 13° C.; dew point, 12°C.; altimeter setting, 29.86 inches of mercury.