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19971012030609A

Accident · Destroyed
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FAA accident report · Bell 206B · Sago, WV · October 12, 1997

FAA Aviation Safety Information Portal

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Date
October 12, 1997 · 11:13 local
Place
Sago, WV
Phase of flight
Fcd/Prec Ldg From Cruise
Operating rules
Air taxi and commuter (Part 135)
Operator
BATA
Damage
Destroyed
Aircraft
N911RH
NTSB investigation
NTSBIAD98FA005
Reported as
Bell 206B
Reported engine
Allison 250C20B
People aboard
4
Fatal injuries
4
Pilot’s flight hours
14,000 total9,200 in this make and model
N911RHRegistration cancelled May 23, 2017 · Bell 206BS/N 1583 · Built 1975Airframe modelBell 206BEngine modelAllison 250 SER 400HPTurbo-shaft

From the FAA’s Accident/Incident Data System (AIDS), through its Aviation Safety Information Portal, as reported. The NTSB investigates accidents separately, and its record of an accident is the fuller one. The aircraft is matched to the registry by N-number and event date, checked against the reported make and model; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

What happened

The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.

Bell 206B crashed in wooded area all 4 POB suffered fatal inj, acft was destroyed, Sago, WV (.4) a helicopter was transporting passengers to a remote site when it dropped in a flat attitude and impacted into trees. A witness said he watched as the helicopter approached and circled the local area. As the helicopter flew overhead for the second time, he waved his arms to attract the pilot's attention. As the helicopter continued past him again, he thought that they were taking aerial photographs of the site. He said that the helicopter appeared to be lower and slower on its second pass overhead. Examination of the engine revealed uncommanded engine shut downs. During bench testing, the power turbine governor failed to limit fuel flow, and during disassembly it was revealed that a machine self locking hex nut had backed off the muscles valve stem. Examination of the muscles valve components revealed that the threaded valve stem was below the minimum requirements for a unj thread, and the flank angle was too large. The turbine governor, with zero time since overhaul, was installed on the engine in January 1997. The governor was last overhauled at the manufacturer's facility du ring may-june 1996.

As the FAA filed it

BELL 206B CRASHED IN WOODED AREA ALL 4 POB SUFFERED FATAL INJ, ACFT WAS DESTROYED, SAGO, WV (.4) A HELICOPTER WAS TRANSPORTING PASSENGERS TO A REMOTE SITE WHEN IT DROPPED IN A FLAT ATTITUDE AND IMPACTED INTO TREES. A WITNESS SAID HE WATCHED AS THE HELICOPTER APPROACHED AND CIRCLED THE LOCAL AREA. AS THE HELICOPTER FLEW OVERHEAD FOR THE SECOND TIME, HE WAVED HIS ARMS TO ATTRACT THE PILOT'S ATTENTION. AS THE HELICOPTER CONTINUED PAST HIM AGAIN, HE THOUGHT THAT THEY WERE TAKING AERIAL PHOTOGRAPHS OF THE SITE. HE SAID THAT THE HELICOPTER APPEARED TO BE LOWER AND SLOWER ON ITS SECOND PASS OVERHEAD. EXAMINATION OF THE ENGINE REVEALED UNCOMMANDED ENGINE SHUT DOWNS. DURING BENCH TESTING, THE POWER TURBINE GOVERNOR FAILED TO LIMIT FUEL FLOW, AND DURING DISASSEMBLY IT WAS REVEALED THAT A MACHINE SELF LOCKING HEX NUT HAD BACKED OFF THE MUSCLES VALVE STEM. EXAMINATION OF THE MUSCLES VALVE COMPONENTS REVEALED THAT THE THREADED VALVE STEM WAS BELOW THE MINIMUM REQUIREMENTS FOR A UNJ THREAD, AND THE FLANK ANGLE WAS TOO LARGE. THE TURBINE GOVERNOR, WITH ZERO TIME SINCE OVERHAUL, WAS INSTALLED ON THE ENGINE IN JANUARY 1997. THE GOVERNOR WAS LAST OVERHAULED AT THE MANUFACTURER'S FACILITY DU RING MAY-JUNE 1996.

NTSB investigation

The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.

NTSB IAD98FA005Accident · 4 fatalField investigationFinal reportSago, WVThe improper overhaul of the turbine governor by the manufacturer, which resulted in the loss of power.Oct 12, 1997 · Destroyed