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N1285S accident description

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Tail numberN1285S
Accident dateOctober 05, 1999
Aircraft typeBell 206B
LocationCentreville, AL
Additional details: None

NTSB description

HISTORY OF FLIGHT

On October 5, 1999, at an unknown time, a Bell BHT 206B III, N1285S, registered to Third Coast Aviation, Inc., dba Cane Air Aviation Services, Inc., operating as a Title 14 CFR Part 137 aerial application flight, crashed near the vicinity of Centreville, Alabama. Visual meteorological conditions prevailed and no flight plan was filed. The helicopter was destroyed and the commercially-rated pilot and a passenger received fatal injuries. The flight departed a clearing adjacent to U.S. Highway 82 about 5.5 miles northwest of Centerville about 1150.

According to the ground handling crew, the flight lifted off about 1150 with the spray tract owner in the left front seat for the purpose of outlining the boundaries for arsenal herbicide spraying of a tree tract. No one saw the crash, but when the helicopter did not return within about 30 minutes, the ground crew organized a search of the spray tract, finding nothing. A friend of the passenger, waiting for completion of the spray mission, also became alarmed and alerted sheriff's department personnel, who in turn, alerted their helicopter unit. At about 1504, the wreckage was found by aerial search by a Tuscaloosa Police Department helicopter.

The ground crew stated they had fuelled the helicopter with 10 gallons of kerosene at the completion of an earlier spray mission at a location 8 to 10 miles from the accident departure clearing and drove the "batch truck" to join the helicopter and pilot at the clearing. They arrived about 1130 to find the helicopter parked and the pilot waiting. After a briefing between pilot, tract owner, and ground crew about where the ground crew would set up the landing site for loading and fuelling, the crew was into their preparations when they noticed the helicopter lift off. The lift off appeared and sounded normal.

PERSONNEL INFORMATION

FAA inspectors reported that examination of the pilot's logbook revealed that flight times had not been kept current and only total civilian times were indicated. The family stated that the pilot had flown over 1,500 hours while an Army aviator between 1986 and 1993, flying OH-58's, Apaches, and Cobras. Information on the pilot is contained in this report on page 3, under First Pilot Information.

AIRCRAFT INFORMATION

The helicopter was equipped with externally mounted spray gear, and when used in commercial agricultural operations, operated in the restricted category under FAA operating certificate No. T34G163J. A copy of the restrictions are included in this report under, "Other Pertinent Forms and Reports." According to a placard at the fuel fill station on the right side of the aircraft, maximum fuel capacity was 96.7 gallons vs the standard 76 gallons due to the installation of a "range extender" fuel filler modification. The helicopter was equipped with the WAG flagger, a cockpit displayed, GPS based aerial application swath indicator.

METEOROLOGICAL INFORMATION

Visual meteorological conditions prevailed at the time of the accident. Meteorological information is contained in this report on page 3, under, " Weather Information".

WRECKAGE AND IMPACT INFORMATION

The accident site is located on the edge of a field that had been cut clear of trees about 5 1/2 miles northwest of the city limits of Centreville, Alabama, at coordinates, N 33.01.52.5 by W 87.15.00 and at about 400 feet elevation. The site corresponds to the closest clear area, along a direct route, (360 degrees, magnetic) between where a ground crewman saw the rotorcraft after lift off and the tract to be sprayed. The wreckage path began with tree canopy breakage near the edge of the clearing and continued for 120 feet on a heading of 350 degrees. After collision with the first tree, a large pine at about 50 feet above ground level, and the second tree, a 9-inch diameter oak about 30 feet further along the wreckage path, about 45 feet above ground level, in a relatively level attitude, the helicopter's rate of descent increased and a left bank developed until ground impact about 60 feet into the cleared area. The wreckage path was littered with spray nozzles that had been stripped from the spray boom by tree impact. Ground impact occurred at the base of an 8-inch diameter dead tree stump, contributing to airframe damage by sudden stoppage. Main and tail rotor leading edges revealed little impact damage. The main wreckage came to rest on a heading of 290 degrees, 65 degrees, left side down, to the horizon. The aft half of the tail boom with tail rotor and vertical stabilizer still attached was lying at 5 o'clock, 15 feet from the main wreckage. The forward tail boom half had been ripped and slung by main rotor strike, 30 feet away at about 2 o'clock. The pilot's collective and cyclic control sticks were broken at the floor board. The cockpit throttle control was 1/8 turn less than full, and the linkage at the fuel control showed full throttle. A Hurst tool, (hydraulic metal cutter) had been used on the canopy bows to extricate the left seat occupant. The fuel cell had been breached but the site lacked the smell of jet fuel, and police reported they encountered no smell of jet fuel upon their first arrival. There was evidence of a very small amount of fuel spill in the dirt once the wreckage was moved.

The engine revealed no evidence of ingestion of foreign object or tree foliage, no compressor blade deformation, or any rotational scarring of the compressor liner. The fuel pump filter/bowl contained about 50 cc's of dark stained fuel and the filter element had a normal appearance. The high pressure fuel filter, (governor) had no fuel present and the fuel line from the fire shield to the fuel spray nozzle contained one drop of fuel. The oil tank was undamaged and contained an adequate quantity of oil. Both chip detectors were clear of any metal filings. The engine-to-transmission drive shaft outer coupling/inner coupling assembly was found disconnected at the engine side of the outer coupling and its four bolt/locknut fasteners or any remnants of them, could not be found. The machined mating holes that accepted the four mating bolts were found elongated, and the hole walls revealed thread scarring. The transmission isolation mount revealed gouging damage that appeared to match smearing of flanges on the forward side, ( transmission side) of one or both of the outer coupling halves. Grease spattering in a circumferential pattern emanating from the inner gear was evident in the plenum area. The drive shaft outer coupling/inner coupling, the inner gear, and its lock ring were removed and sent to the NTSB Materials Laboratory for analysis of the damaged mating holes. The wing-nut/drain valve on the bottom of the airframe fuel filter was found in the full in and locked position which would have allowed a thin stream of fuel to continually escape. The engine/transmission plenum area in the vicinity of the airframe fuel filter had not sustained impact deformation that might have impinged upon and forced the wing-nut to the open and locked position. About 1 1/2 tablespoons of dirt was removed from the airframe fuel filter and its filter element, postcrash. The airframe fuel filter-to-fuel pump fuel line revealed insulation shredding that appeared to have been caused by contact with a section of the tail rotor drive shaft while rotating.

MEDICAL AND PATHOLOGICAL INFORMATION

Postmortem examinations of the pilot and passenger were conducted by Dr. J. R. Glenn, M. D., State Medical Examiner, Alabama Department of Forensic Sciences, Tuscaloosa, Alabama. The cause of death in both cases was attributed to multiple blunt force trauma secondary to the helicopter crash. No findings that could be considered causal were noted. Toxicological tests were conducted on both occupants at the Federal Aviation Administration Research Laboratory, Oklahoma City, Oklahoma. The tests were negative for ethanol, carbon monoxide, basic, acidic, and neutral drugs.

TESTS AND RESEARCH

The fuelling source, aboard the batch truck, was analyzed for water using water sensitive paste, with negative findings. Additionally, visual examination of fuel samples revealed no contaminants.

The Rolls-Royce Allison 250-C20B engine, serial no. 830809, was removed and shipped to the Rolls-Royce Allison factory test facility, Indianapolis, Indiana. Except for a 1/2 inch-deep by 4 inch-long by 3 inch-wide dent in the outer combustion case, small dents in the exhaust stacks, and replacing a crash damaged no. 8 bearing oil scavenge line, the engine appeared undamaged, and once mounted in the test cell, performed to within 7.8 per cent of new engine specifications at take-off power. The Rolls-Royce Allison report is included in this report under, "Reports from Parties to the Investigation."

The engine-to-transmission drive shaft outer coupling/inner coupling assembly, inner gear, and lock ring were examined by the NTSB Material Laboratory for damage analysis. Bench binocular microscope examination of the machined holes of the outer coupling flanges and smears on the flanges, themselves, revealed evidence of drive train torsion stress consistent with sudden stoppage of the main rotor. There appeared to be no evidence that suggested that the coupling assembly became disconnected precrash. The laboratory report is included in this report under, "Factual Report of Materials Laboratory".

ADDITIONAL INFORMATION

The wreckage, minus the engine, the drive shaft outer coupling/inner coupling assembly, inner gear, and lock ring, the pilot's flight log, and the rotorcraft logs, was released to the owner/operator on October 7, 1999. The engine, model 250-C20B, serial no. 830809, was returned to a representative of the owner/operator on November 19, 1999. The drive shaft coupling assembly was returned to a representative of the owner/operator on February 1, 2000. The log books were returned to a representative of the owner/operator by the FAA on March 21, 2000.

(c) 2009-2011 Lee C. Baker. For informational purposes only.