Thursday, February 16, 2017

Bell 206B, N866H: Accident occurred July 30, 2014 at David Wayne Hooks Memorial Airport (KDWH), Spring, Harris County, Texas

Aviation Accident Final Report -  National Transportation Safety Board: https://app.ntsb.gov/pdf

Docket And Docket Items - National Transportation Safety Board: https://dms.ntsb.gov/pubdms

Aviation Accident Data Summary -  National Transportation Safety Board:   https://app.ntsb.gov/pdf

http://registry.faa.gov/N866H

Flight Standards District Office:  FAA Houston FSDO-09

NTSB Identification: CEN14LA465
14 CFR Public Aircraft
Accident occurred Wednesday, July 30, 2014 in Spring, TX
Probable Cause Approval Date: 01/14/2015
Aircraft: BELL 206B, registration: N866H
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot reported that he completed the preflight inspection of the helicopter while it was still in the hangar and that it was then moved onto the ramp. When the pilot arrived to start the helicopter, he was distracted by a cell phone call and did not perform an exterior check of the helicopter. The main rotor tie-down was still attached to the main rotor when the pilot engaged the engine. He was monitoring the cockpit gauges during the engine start when he noticed an individual approaching the helicopter waving his hands. He then heard a "thump," and he initiated an emergency shutdown. He reported no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation. The examination of the helicopter revealed that the tie-down strap had broken during the engine start and had gotten caught on the tail rotor output shaft, which resulted in substantial damage to the tail boom, tail rotor blades, and vertical fin. 

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilot's distraction by a cell phone call, which led to his failure to perform an exterior check of the helicopter and resulted in a tie-down strap remaining attached to the main rotor during the engine start. 

On July 30, 2014, about 1030 central daylight time, a Bell 206B, N866H, sustained substantial damage during engine start-up at the David Wayne Hooks Airport (DWH), Spring, Texas. The pilot was not injured. The helicopter was owned by Helicopter Services Inc. and operated by the Harris County Sheriff's Office as a local public aircraft flight. Visual meteorological conditions prevailed at the time of the accident. No flight plan was filed. The helicopter was departing on a local flight. 

The pilot reported that he completed the preflight of the helicopter while it was still in the hangar, after which time the helicopter was moved onto the ramp. When the pilot arrived to start the helicopter, he was distracted by a phone call on his cellular phone and did not do an exterior check of the helicopter. The main rotor tie-down was still attached when the pilot engaged the engine. He was monitoring the cockpit gauges during the engine start when he noticed another officer approaching the helicopter waving his hands. He heard a "thump" and he initiated an emergency shutdown. The pilot stated that the engine start was aborted at 15 percent N1 (compressor speed), 25 percent N2 (power turbine speed), rotor rpm was less than 20 percent NR (main rotor rpm), and the TOT (turbine outlet temperature) did not exceed startup limits. He reported that there was no malfunction or system failure of the helicopter before the accident.

The examination of the helicopter revealed that the tie-down strap had broken during the engine start and became caught on the tail rotor output shaft. The strap hit the tail boom and dented and gouged about the last two feet of the tail boom which required the skin to be replaced. The main rotor blade tip cap pulled loose. The main rotor blades were still serviceable, but they were replaced because they were 120 hours from the required replacement interval. The tail rotor blades were dented beyond limits and were replaced. The vertical fin was gouged; and although the honeycomb panel was repairable, the vertical fin was replaced instead of waiting for it to be overhauled. The tail rotor gearbox, the tail rotor hub, and the freewheeling unit needed to be inspected for sudden stoppage, which resulted in the units being overhauled. It was determined that the aggregate damage would affect the structural strength or performance of the helicopter and required major repair or replacement; therefore it was considered substantial damage.

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