Amateur-built SONEX accident near Methuen, Massachusetts, February 28, 2017

The NTSB's narrative final · quoted from the NTSB record

The sport pilot, who was the owner and builder of the experimental, amateur-built airplane, had not flown the airplane in over 4 months due to a fuel leak. Two days before the accident, he reported that he had corrected the leak by repairing a fuel outlet connection near the fuel shutoff valve in the cockpit. The pilot departed and remained in the airport traffic pattern with the intent of performing touch-and-go takeoffs and landings. During final approach for the first landing, several witnesses observed the airplane on fire before it suddenly entered a nose-down descent and impacted a residence. Examination of the wreckage revealed evidence of an inflight fire in the engine compartment; the bottom oil line where it attached to the oil filter by a blue aluminum nut was not secure. In addition, the fuel regulator fuel intake line at the regulator attach point had little torque and spun freely on the threads. Both connections were inside the engine compartment and shared no commonality with the pilots previously reported fuel leak at the outlet connection in the cockpit. It is likely that, while performing engine maintenance, the pilot failed to properly torque the oil and fuel regulator fittings. Normal engine vibrations during the flight likely resulted in one of the fittings becoming loose and introducing flammable liquid into the engine compartment. Upon contact with hot engine components, the fluid ignited and resulted in an engine compartment fire. Because both the oil and fuel systems were compromised by loose connections, whether the fire was caused by fuel or oil could not be determined. Although an autopsy of the pilot identified severe coronary artery disease, which would have placed him at high risk for an acute cardiovascular event, it is unlikely that symptoms from his heart disease contributed to his inability to manage the inflight emergency. The rapidly developing emergency caused by fire and smoke, distracted the pilot who had little recent experience in the airplane. The pilot's diverted attention likely resulted in his failure to recognized that the airplane was going to exceed its critical angle of attack and enter an aerodynamic stall.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.