Piper PA-28-151 N33563 accident near Hope Mills, North Carolina

Probable cause

A loss of engine performance due to carbon fouling of three spark plugs that, when combined with the airplane’s high gross weight condition, resulted in a collision with trees and terrain.

NTSB analysis

The private pilot and two passengers boarded the fully fueled airplane for a cross-country flight. Weight and balance calculations showed that the airplane was about 150 to 200 lbs below the maximum gross weight and the weather conditions were warm and humid at the time. A witness, who observed the loading of the airplane and noted the heat and humidity, expressed some concern to the pilot who assured him that he was within limits. There were no reported anomalies during the taxi, engine run-up, or the subsequent takeoff roll, but shortly after beginning the initial climb, while climbing through 450 ft mean sea level (msl), 290 ft above ground level (agl), the pilot noticed a drop in airspeed and was unable to maintain altitude. The passenger stated the engine sounded good, but the airplane wasn’t climbing. Unable to maintain level flight, the pilot lowered the airplane’s nose to maintain airspeed and avoid a stall. The airplane impacted trees and terrain about 3/4 of a mile from the departure end of the runway. The resulting impact caused a postcrash fire.

Postaccident examination of the engine and components revealed the propeller was likely under power at the time of impact. In addition, three of the eight spark plugs were carbon-fouled, two of which were on the No. 1 cylinder. This fouling is typically caused by a rich fuel-air mixture, especially during ground operations or low power settings. The deposits can hinder the spark plug's ability to fire effectively, leading to reduced engine performance. The reduced spark plug efficiency led to reduced engine performance and, when combined with the airplane’s high gross weight and the ambient temperature and humidity, led to the airplane’s inability to climb and maintain altitude and resulted in impact with trees and terrain.

Text from the NTSB. Open the NTSB docket for ERA24LA230 for the full record.