ERA21LA309

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.

On July 30, 2021, about 1625 eastern daylight time, an Enstrom 280FX helicopter, N36DK, was destroyed when it was involved in an accident near Colchester, Vermont. The commercial pilot sustained serious injuries. The helicopter was operated by Beta Air LLC as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that he departed for a proficiency flight from Plattsburgh International Airport (PGB), Plattsburgh, New York, to Burlington International Airport (BTV), Burlington, Vermont. While enroute to BTV, the pilot “noticed something burning” and then “observed smoke in the cockpit.” He also observed a rapidly rising exhaust gas temperature despite moving the mixture to full rich and initiated a precautionary landing during which the helicopter lost partial and then total engine power. The pilot subsequently completed an autorotation landing on the Lake Champlain Causeway, striking trees before coming to rest on the road and rocks that lined the causeway. The pilot stated that, once he exited the helicopter, he saw flames and smoke coming from the engine compartment. He did not observe any fuel leaking onto the ground. According to a witness who was walking along the causeway, she heard something that sounded like a car accident and saw that the helicopter had impacted the causeway. She observed smoke emanating from the rear of the helicopter and saw the pilot evacuate from the wreckage. She helped the pilot move farther away from the helicopter and, shortly thereafter, saw fire consuming the helicopter (see the figure below). Figure. Helicopter fire (Source: social media site). Postaccident examination of the engine revealed significant soot and thermal damage. 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. The turbocharger exhaust and inlet clamps were intact and remained tightly installed with safety wires present. The turbocharger was partially disassembled, and the interior displayed no evidence of thermal damage. The flexible fuel and oil lines displayed significant thermal damage, and some were destroyed by fire. It was not possible to evaluate the lines for possible leakage due to the extensive thermal damage. The metal fuel lines were found securely connected to their respective attach points. Several oil lines were located near fire damage in the forward left portion of the engine compartment, where the thermal damage was most severe. Maintenance records revealed that, on March 12, 2021, the helicopter’s engine was replaced, and all fuel and oil hoses were replaced with new hoses. The helicopter had flown about 200 hours since this maintenance. On May 13, 2021, an annual inspection was completed, and the engine was found to be in an airworthy condition.