RICHFIELD, UT, USA
N206AH
BELL 206L-1
THE PILOT REPORTED THAT THE HELICOPTER HAD BEEN STRANDED ON TOP OF A HILL FOR SEVERAL DAYS DUE TO ADVERSE WEATHER CONDITIONS AND SNOW FALL. BEFORE LEAVING THE HELICOPTER ON THE HILL, THE PILOT STATED THAT HE USED JACKETS AND CUSHIONS TO ATTEMPT TO COVER THE ENGINE INLETS, AS PROTECTIVE COVERINGS WERE NOT AVAILABLE. WHEN THE HELICOPTER WAS RETRIEVED, SNOW HAD ACCUMULATED IN THE INLETS. AFTER THE AIRFRAME AND ENGINE INLETS HAD BEEN CLEANED OF THE SNOW AND ICE BUILD UP, THE ENGINE WAS STARTED AND WARMED BEFORE TAKEOFF. SHORTLY AFTER TAKEOFF, THE ENGINE LOST POWER AND THE PILOT INITIATED AN AUTOROTATION TO SLIGHTLY SLOPING TERRAIN. THE HELICOPTER LANDED HARD. DURING ENGINE INSPECTION, IT WAS FOUND THAT AT LEAST SIX COMPRESSOR BLADES WERE BENT. NO INSPECTION WINDOWS WERE INSTALLED IN THE COWLING, WHICH WOULD HAVE ALLOWED THE PILOT TO VIEW THE PLENUM CHAMBER FOR ICE OR SNOW. POST ACCIDENT INSPECTION OF THE ENGINE DID NOT REVEAL EVIDENCE OF A MECHANICAL FAILURE OR MALFUNCTION.
On April 23, 1995, at 1600 mountain daylight time, a Bell 206L-1, N206AH, experienced a loss of engine power shortly after takeoff from a mountain top near Richfield, Utah. During the autorotation, the helicopter landed hard. Visual meteorological conditions prevailed at the time and no flight plan was filed. The helicopter was substantially damaged and the commercial pilot and his passenger were not injured. The flight was en route to Richfield, Utah. During a telephone interview and subsequent written statement, the pilot stated that the helicopter had been stranded on top of the hill for five days due to adverse weather and heavy snow fall. No inlet covers were available so the pilot used coats and other soft items to cover the inlets to keep snow from accumulating against the front of the particle separator. When the weather cleared and the helicopter was to be retrieved, the pilot stated that snow had to be cleared from the structure and the engine inlets. After the snow was removed, the pilot started and warmed the engine for approximately 15 minutes before take off. After the helicopter lifted off, the pilot maintained a hover for a moment to check that all instruments were in the green before proceeding down the hill. Approximately one minute after take off, the engine lost power. The pilot was unable to restart the engine and initiated a 180 degree turning autorotation. The helicopter landed hard on slightly sloping terrain. Company personnel who had been on site, stated that visible snow and ice were removed from the engine inlet (particle separator) and transmission compartments. Heat was applied to the engine, fuel control, transmission and swirl tube inlets of the particle separator. The helicopter was then started and the pilot of the second helicopter stated that he first noticed snow and then water being ejected from the turbine exhaust during the start. The engine was warmed for approximately 10 minutes with the engine de-ice on. The particle separator purge ports were checked for positive airflow. Both helicopters then took off down the hill and the pilot in the trailing helicopter stated that he noticed a "white plume of smoke from the exhaust...." A mayday call was heard and the accident helicopter entered an autorotation into the wind. During the engine inspection and review of the maintenance logbooks, it was found that an Allison 250-C30P engine had been installed under the authority of a Supplemental Type Certificate dated April 16, 1984. This model engine requires the installation of a particle separator when the aircraft is being used in adverse weather conditions. The particle separator was installed on June 28, 1988 in accordance with a service instruction, however, it did not bear a data plate to identify the part or serial number. It was also noted that there were no inspection windows in the cowling for viewing the plenum chamber behind the particle separator for debris. Without inspection windows, the pilot was unable to determine if the chamber was contaminated with snow or ice. Snow baffles were not installed for the flight. The participant from Bell Helicopters reported that the 206L-1 airframe is not certified for the installation of the inspection windows. The engine that is normally installed, the Allison 250- C28B, contains an internal particle separator and does not require an inspection window. During the engine inspection, at least six compressor blades were bent with no marks on the blades. No foreign object debris was found in the engine particle separator. The remainder of the inspection did not reveal any mechanical failures or malfunctions.
ICE INGESTION. FACTORS TO THE ACCIDENT WERE: AIRCRAFT PROTECTIVE COVERINGS WERE UNAVAILABLE, INADEQUATE PREFLIGHT INSPECTION, AND UNEVEN TERRAIN.
Source: NTSB Aviation Accident Database
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