On May 20, 1993, a Hiller UH-12C (registration N46937) operated by Jocher, Arthur H. was involved in an aviation accident near Sarasota, FL. Investigators recorded the probable cause as: THE PILOT-IN-COMMAND'S IMPROPER APPLICATION OF THE FLIGHT CONTROLS DURING AN AUTOROTATIVE LANDING, RESULTING IN AN IN-FLIGHT COLLISION WITH WIRES AND TERRAIN. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A commercial pilot initiated a forced landing after an engine RPM fluctuation; the helicopter hit power lines during deceleration. Investigation found carburetor contamination and unperformed service bulletins.
Accident Narrative
A commercial pilot was conducting a cruise flight at approximately 400 feet above ground level when he observed a sudden drop in engine revolutions per minute (RPM). Shortly after, the RPM increased. The pilot then initiated a forced landing by entering autorotation. During the subsequent deceleration, the helicopter collided with power lines and crashed.
Investigation Findings
Review of the helicopter's maintenance logbooks revealed that the carburetor float assembly had not been replaced. Additionally, numerous service bulletin procedures pertaining to the MA 4-5 carburetor had not been performed. A disassembly inspection of the carburetor found contamination: sand was present in the carburetor bowl, the fuel inlet assembly was dirty, and the pump plunger assembly was rusty.