NTSB Identification: SEA94FA096.
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Nonscheduled 14 CFR
Accident occurred Sunday, April 03, 1994 in LAMOILLE, NV
Probable Cause Approval Date: 06/05/1995
Aircraft: BELL 206B3, registration: N27736
Injuries: 4 Fatal,1 Serious.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

THE HELICOPTER (HEL) WAS LANDED AT A REMOTE SITE DUE TO POOR WEATHER. AFTER LANDING, SNOW FELL & ACCUMULATED ON THE AIRFRAME. NO EXTERNAL ENGINE SNOW COVERS WERE AVAILABLE. THE AIR INDUCTION SYSTEM HAD SNOW BAFFLES & PARTICLE SEPARATORS, BUT THE ENGINE WAS NOT EQUIPPED WITH AN (OPTIONAL) AUTO RE-LIGHT IGNITION SYSTEM. THE PLENUM AT THE ENGINE INTAKE WAS INACCESSIBLE TO THE PILOT FOR REMOVAL OF ANY SNOW THAT MAY HAVE ACCUMULATED. ABOUT 1 HR AFTER LANDING, HE RESTARTED THE ENGINE & RAN IT ABOUT 15 TO 20 MIN. AFTER ABOUT ANOTHER HOUR, HE RESTARTED THE ENGINE AGAIN & RAN IT ABOUT 5 MIN. AFTER DISCUSSING SITUATION WITH DIR OF OPS BY RADIO, HE THEN TOOK OFF WITH A GROSS WEIGHT & DENSITY ALTITUDE OF ABOUT 2940 LBS & 7000', RESPECTIVELY. SHORTLY AFTER LIFT-OFF, THE ENGINE LOST POWER. DURING AN AUTOROTATION, THE HEL IMPACTED ON A 30 DEG SLOPE & ROLLED OVER. THE FLIGHT MANUAL (F/M) SHOWED THAT AT 2940 LBS, THE MAXIMUM DENSITY ALTITUDE FOR A SAFE AUTOROTATIVE LANDING WAS 2500'. THE F/M LIMITED HOVER FLIGHT IN FALLING AND/OR BLOWING SNOW TO A DURATION OF 20 MIN, AFTER WHICH THE HEL MUST BE LANDED & CHECKED FOR SNOW AND/OR ICE ACCUMULATION. HOWEVER, GROUND OPERATION IN THESE CONDITIONS WAS NOT ADDRESSED. TESTS OF SNOW/ICE INGESTION IN AN EARLIER MODEL OF THE SAME ENGINE (ALLISON 250-C18) RESULTED IN FLAMEOUTS WITH SLUGS OF SNOW THAT WERE AS LITTLE AS 30 GRAMS.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THE INGESTION OF FOREIGN MATERIAL (SNOW) IN THE ENGINE, WHICH RESULTED IN A FLAMEOUT (LOSS OF ENGINE POWER). FACTORS RELATED TO THE ACCIDENT WERE: THE ADVERSE WEATHER CONDITIONS (SNOW FALLING & HIGH DENSITY ALTITUDE), THE LACK OF SNOW COVERS TO PROTECT THE ENGINE INTAKES WHILE PARKED AND AWAITING FOR THE WEATHER CONDITIONS TO IMPROVE, IMPROPER PLANNING/DECISION BY THE PILOT AND THE COMPANY/OPERATOR MANAGEMENT, INADEQUATE INFORMATION IN THE FLIGHT MANUAL, AND THE LACK OF SUITABLE TERRAIN FOR AN EMERGENCY LANDING.

Full narrative available

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