On March 11, 2001, an Enstrom F-28C (registration N5687H) was involved in an aviation accident near Orlando, FL. Investigators recorded the probable cause as: The exhaust stack of the turbocharger had broken, allowing hot exhaust (1,500 degrees C) to ignite the aluminum engine shroud. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter was destroyed by fire after a forced landing following an engine malfunction. Smoke and rough running preceded the landing; all occupants evacuated. The fire originated from a broken turbocharger exhaust stack.
Incident Overview
A helicopter experienced an engine malfunction shortly after takeoff. The aircraft had climbed to an altitude of approximately 250 to 300 feet when the engine began to run rough and the pilot observed smoke emanating from the engine. A forced landing was executed with power remaining, touching down in a fairgrounds. Following the landing, the pilot and passengers evacuated the helicopter without incident.
Fire Development and Response
Shortly after evacuation, a fire ignited in the engine area. The source of the fire was the turbocharger exhaust. The aluminum engine shroud became engulfed in flames as a result of exposure to the hot exhaust gases. The pilot attempted to suppress the fire using onboard firefighting agent; however, the supply was exhausted before the fire was fully extinguished. The fire then rekindled and rapidly consumed the helicopter. By the time fire department personnel arrived, the aircraft was completely destroyed.
Post-Incident Examination
An examination of the turbocharger exhaust system revealed the cause of the fire. The exhaust stack had fractured, allowing high-temperature exhaust gases—measured at approximately 1,500 degrees Celsius—to directly impinge upon and ignite the aluminum engine shroud. The failure of the exhaust stack was the initiating event that led to the in-flight engine roughness and subsequent fire.
Probable cause
The exhaust stack of the turbocharger had broken, allowing hot exhaust (1,500 degrees C) to ignite the aluminum engine shroud.