Amateur-built LIGHTNING N59JL accident near Franklin, Virginia

Probable cause

A partial loss of engine power due to pre-ignition damage to the No. 2 cylinder piston and the pilot's exceedance of the airplane's critical angle of attack while maneuvering in the airport traffic pattern, which resulted in an aerodynamic stall.

NTSB analysis

The commercial pilot was conducting a local personal flight with a pilot-rated passenger in the experimental, amateur-built airplane. During the initial climb, when the airplane was at 100 ft above ground level (agl), the pilot felt a vibration that soon stopped. She continued the takeoff and noted that all exhaust gas temperature (EGT) readings were higher than normal, with the No. 2 cylinder EGT over the maximum red line limit; the engine then lost partial power. She kept full throttle applied, informed her passenger of the discrepancy, and remained in the traffic pattern to return to the airport. While flying about 200 ft agl and turning onto the base leg of the airport traffic pattern, she reduced the throttle to slow the airplane from 80 to 75 mph; at that moment, the left wing dropped immediately, which she later indicated was consistent with an aerodynamic stall although she did not feel any airframe buffet. The airplane impacted and remained suspended in trees a few feet off the ground.

Postaccident examination of the engine revealed damage to the No. 2 cylinder piston consistent with pre-ignition. This damage was likely the source of the partial loss of engine power. While the pilot was using an oil additive, the investigation could not determine whether the additive contributed to pre-ignition.

The airplane was not equipped with stall warning protection. Although the pilot/builder had accrued about 290 flight hours in the accident airplane and should have been familiar with its aerodynamic stall characteristics, stall warning protection could have alerted the pilot to an impending stall so that she could take action to avoid the stall.

Text from the NTSB. Open the NTSB docket for ERA17LA067 for the full record.