Primary finding
Probable cause
failure of the #3 cylinder exhaust valve. A factor was the pilot's need to perform an evasive maneuver to avoid colliding with an automobile.
Investigator assessment
Analysis narrative
The pilot reported that during cruise the engine suddenly made a loud pop sound then began vibrating violently. The pilot set up to make a forced landing on a road but had to overshoot the intended landing spot due to a car. After touchdown, the pilot had insufficient distance to stop prior to colliding with a curb. During the engine examination the #3 cylinder exhaust valve head was found separated from the valve stem, and a large hole was noted in the piston. The valve head was destroyed. Review of the maintenance records revealed that the engine had 2,131 hours since major overhaul. Lycoming recommends a 2,000-hour time between overhauls.
Source record
Factual narrative
On October 29, 1995, at 1315 hours mountain standard time, a Piper PA-28-140, N8074C, collided with ground obstructions during a forced landing on a road near Congress, Arizona. The forced landing was precipitated by a loss of power in cruise flight. The aircraft was owned and operated by the pilot and was on a personal cross-country flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft incurred substantial damage. The certificated private pilot and his one passenger were not injured. The flight originated from Bullhead City, Arizona, on the day of the accident at 1200 as a flight to Phoenix. The pilot reported that during level cruise the engine suddenly made a loud pop sound then began vibrating violently. The pilot set up to make a forced landing on a road, but had to overshoot the intended landing spot due to a car. After touchdown, the pilot had insufficient distance to stop prior to colliding with a curb. The engine was examined by FAA airworthiness inspectors. The number 3 cylinder exhaust valve head was found separated from the valve stem and a large hole was noted in the piston. The valve head was destroyed. Review of the maintenance records revealed that the engine had 2,131 hours since major overhaul. Lycoming recommends a 2,000-hour time between overhauls. -