Enstrom 280 accident near Colchester, Vermont, July 30, 2021

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

The commercial pilot reported that while enroute he smelled and then observed smoke in the cockpit. He also observed a rapidly rising exhaust gas temperature despite moving the mixture to full rich. The pilot initiated a precautionary landing during which the helicopter experienced a partial and then total loss of engine power. During the final segment of the autorotation, the helicopter impacted trees and landed hard on a causeway. Postaccident examination of the engine found significant soot and thermal damage, which precluded a determination of the specific source of the in-flight engine fire. However, one cause of the fire could be eliminated. Specifically, the heaviest area of thermal damage was located around the No. 3 cylinder near the turbocharger. The outer portion of the turbocharger displayed significant thermal damage, but the turbocharger exhaust and inlet clamps were intact and remained tightly installed with safety wires present. Therefore, leakage of exhaust gases from the turbocharger was not the cause of the in-flight fire. The external damage to the turbocharger indicated that its high temperature surfaces were possible ignition sources for an ignitable liquid, such as lubricating oil or fuel. The flexible fuel and oil lines all displayed significant thermal damage, and some were destroyed by fire. Several oil lines were located near the thermal damage in the forward left portion of the engine compartment. Therefore, lubricating oil from these lines was a possible fuel source for the fire. In addition, because the flexible fuel lines were either damaged or destroyed, fuel from these lines could not be eliminated as a source of fuel for the in-flight fire.

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.