Piper PA-28-161 N8878E accident near Elkmont, Alabama

Probable cause

A stuck exhaust valve, which resulted in a total loss of engine power at low altitude. Contributing to the accident were the pilot’s decision to fly at a low altitude, which reduced his forced landing options when the loss of engine power occurred; and poor long-term engine maintenance, which resulted in the buildup of combustion by-products on exhaust valve parts. Contributing to the pilot’s poor aeronautical decision-making was his underlying attention deficit hyperactivity disorder.

NTSB analysis

The 18-year-old pilot had obtained his private pilot certificate about 16 months before the accident, bought the airplane 25 days before the accident, and had an estimated 5 hours of flight experience in the airplane at the time of the accident. The pilot was moving the airplane to the airport where it would be permanently based. GPS data indicated that the airplane was maneuvering and descending to about 300 ft above ground level near a small community when it began a climbing turn. A witness reported that, about that time, he heard a "pop" sound and that the engine then lost power. The airplane subsequently descended into a telephone pole, hit the ground, and then slid into and bounced off of a vacant house. Large open fields began about 1,200 ft east and northeast of the airplane's final documented in-flight position before the descent.

Postaccident examination of all four engine cylinders revealed extensive deposits of combustion by-products on the exhaust valves, guides, and valve seats, indicating that a stuck exhaust valve likely resulted in the loss of engine power.

Review of available maintenance logbooks, which began with entries from almost 15 years before the accident, revealed that the engine's total time in service at that time was 4,377 hours and that the time since major overhaul (TSMO) was 1,995 hours. For a 6-year period ending about 3 years before the accident, no maintenance items were recorded, and there were only 5 hours of operation noted between those dates. The latest annual inspection was completed about 6 months before the accident at an engine TSMO of 2,198 hours. No engine compression results were noted; however, the same technician who completed the inspection did record results about 1 year earlier, and all of the recorded compressions were 70 pounds per square inch or higher at that time. The engine TSMO was 2,203 hours at the time of the accident. An engine manufacturer service instruction recommended that the time between overhauls should be 2,000 hours and noted that "engines that do not accumulate the hourly period of [TSMO]…are recommended to be overhauled in the twelfth year." The evidence indicates that the airplane had a history of poor engine maintenance.

The pilot had been diagnosed with and was receiving medication for attention deficit hyperactivity disorder (ADHD), which can cause attention deficits, susceptibility to distraction, and impulsivity and impairments in motor inhibition, reaction time, visual-motor coordination, executive functioning, decision-making, and rule-governed behavior. The pilot did not report either the ADHD or the medication he was using to treat it on his only application for a Federal Aviation Administration medical certificate; if he had reported this information, his medical certification would have been deferred at least until he had undergone extensive neuropsychological evaluation and review.

The pilot was maneuvering the airplane, which had a poor engine maintenance history, at a very low altitude. When the engine lost power, the resultant forced landing was made to relatively confined terrain. If the pilot had been flying at a higher altitude, he would have had the option of landing in larger fields. His decision to maneuver as low as he did likely resulted from his ADHD in combination with his age and relatively low flight experience (about 180 total flight hours), which would have made him more susceptible to bad decision-making.

Text from the NTSB. Open the NTSB docket for ERA14LA057 for the full record.