NTSB Factual Report

On May 8, 2004, approximately 1822 central daylight time, an Aeronca 7AC single-engine airplane, N3708E, registered to and operated by a private individual, sustained substantial damage during a forced landing to a road following a loss of engine power near Fort Stockton, Texas. The commercial pilot and the passenger were not injured. A visual flight rules (VFR) flight plan was filed for the cross-country flight that departed Culberson County Airport (VHN) near Van Horn, Texas, about 1710, destined for Fort Stockton-Pecos County Airport (FST), Pecos, Texas. Visual meteorological conditions prevailed for the personal flight conducted under 14 Code of Federal Regulations Part 91.

In a written statement, the 821-hour pilot reported that while in cruise flight at 2,500 feet mean sea level approximately 25 miles west of Fort Stockton, he noticed the oil temperature gauge indicated 240 degrees (red line was 145 degrees). He reduced engine rpm from 2,400 to 2,200, and increased the airplane's mixture setting. The oil temperature began to decrease. Shortly after, about 17 miles west of Fort Stockton, the engine suddenly began to lose power. The pilot increased the mixture setting to "full rich", and applied carburetor heat, but the engine continued to lose power. He was unable to maintain altitude and executed a forced landing to a service road on Interstate 10. Upon landing, the pilot was unable to keep the airplane straight due to the strong, gusting crosswinds and collided with a metal fence post and mesquite trees. The pilot reported that the right wing and fuselage sustained structural damage.

A Federal Aviation Administration inspector performed an examination of the engine. According to the inspector, the engine was manually rotated, and compression and valve train continuity were established for each cylinder. The top and bottom spark plugs were removed; the #2 and #4 plugs appeared to be oily, and the #1 and #3 plugs appeared white in color. The oil, which was changed approximately 8 hours before the accident, was dark in color.

When asked how this accident could have been prevented, the pilot reported, "I probably leaned engine too much too long causing the oil temp[erature] to reach 240 degrees. Run aircraft more rich to provide better cooling to internal combustion chambers."

Weather at Fort Stockton at 1753 was reported as wind from 130 degrees at 17 knots gusting to 24 knots, visibility 10 miles, and clear skies.

NTSB Probable Cause

The pilot's improper leaning of the fuel/air mixture in-flight, which resulted in a loss of engine power. Factor were the wind gusts and the crosswind.