# NTSB ATL01LA108: Bell 47G, N6327D, Berry, AL, September 7, 2001 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 7, 2001, 10:30 local (15:30 UTC) - Place: Berry, AL - Coordinates: 33.659595, -87.60025 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.6596&lon=-87.6003&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report August 28, 2002 - Report: Approved by Office Director - Parties: Federal Aviation Administration Birmingham FSDO-09 - NTSB case key (mKey): 53476 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ATL01LA108 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/53476/pdf - Page: https://openairdocs.org/ntsb/ATL01LA108 ## Probable cause The failure of the main rotor system stabilizer damper control horn assembly, resulting in an uncontrolled descent and subsequent collision with a tree and terrain. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, maneuvering - rotor system,stabilizer bar - failure (cause) - Forced landing, descent - uncontrolled - In flight collision with terrain/water, descent - uncontrolled - object - tree(s) ## Analysis While maneuvering, at a low altitude, the pilot heard "a pop or a bang outside the helicopter." As the pilot started a left turn, he noticed a "mushiness" in the cyclic control, followed by a loss of left and right cyclic control. The pilot attempted to reach a clearing, but the helicopter went into an uncommanded left turn. When the pilot attempted to slow the helicopter with the collective, the helicopter tilted back to the right, impacted a small tree, touched down on its right skid first, and flipped up on its nose. Examination of the wreckage revealed "ground metal shavings" near the rotor head stabilator damper horn assembly where the control horn attach to the splined shaft. ## Factual narrative On September 7, 2001, about 1030 central daylight time, a Bell 47G, N6327D, registered to Helicopter Services of Alabama, collided with terrain four miles northeast of Berry, Alabama, after experiencing a loss of lateral cyclic control. The public use law enforcement surveillance flight was conducted under the provisions of Title 14 CFR Part 91 with no flight plan on file. Visual meteorological conditions prevailed at the time of the accident. The helicopter sustained substantial damage, and the commercial pilot and passenger were not injured. The local flight departed Richard Arthur Field in Fayette, Alabama, about 0940. According to the pilot, the helicopter had completed several surveillance orbits to both the left and to the right at altitudes ranging from approximately 150 feet to 800 feet above ground level (AGL) and at speeds ranging from approximately 40 mph to 65 mph. The passenger, a Fayette County, Alabama, Sheriff's Office employee, directed the pilot where to fly. The pilot, at the passenger's request, had begun searching for a place to land. While at approxmately 800 feet AGL at approxmately 50 mph, the pilot "lowered the collective and did a 180-degree very steep approach leveling off back to the east approx 150 feet AGL." The pilot flew over the intended landing area approximately 100 feet AGL and 65 mph and reported hearing "a pop or a bang outside the helicopter, and at that same time I had started a shallow climb out to gain some altitude." The pilot started a left turn and noticed "mushiness" in lateral cyclic, then a loss of left and right cyclic contol. The pilot said the helicopter "started feeling like the rotor disc was tilting left and right on its own, back and forth." The pilot lowered the collective and started a descent, which the pilot reported "seemed to lessen the rotor system's left and right tilt." The pilot attempted to reach a clearing, but the helicopter went to the left on its own. As the helicopter neared the ground, the pilot attempted to slow it down with the collective, and it tilted back to the right. The helicopter impacted a small tree, touched down on its right skid first, and flipped up on its nose. After the helicopter came to rest, fuel poured in onto the backs of the pilot and passenger. They punched out the bubble of the helicopter, unfastened their seat belts, and exited the helicopter. Damage to the helicopter included: separated tail rotor, destroyed main rotor blades, broken engine mounts, separated cabin, broken bubble, separated left skid toe, fuel tanks bent on inside by mast, and bent stabilizer bar rod and counterweights. An examination of the wreckage by an airframe and powerplant mechanic revealed "ground metal shavings" in the damper frame assembly where the control horn contacts the splined shaft (see attached mechanic's statement). The mechanic reported that "a failure on this part would have caused control loss." A review of records from the Bell Helicopter Flight Safety Department revealed that N6327D had been previously involved in two accidents and was subsequently rebuilt and modified from a D-Model to a G-Model. ## Aircraft - Registration: [N6327D](https://openairdocs.org/aircraft/N6327D), registered now, S/N 828, built 1952 (OpenAirDocs) - Reported make and model: Bell 47G - Registry model: [Bell 47G](https://openairdocs.org/model/bell-47g) (registry code 1181002) (OpenAirDocs) - Registry engine: [Franklin 6V4 series](https://openairdocs.org/engine/franklin-6v4-series) (registry code 27033, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 828 - Airframe hours: 6743 - Engines: Lycoming V0435 280 horsepower reciprocating - Damage: Substantial damage - Flight: Public aircraft, Part 91 - Operator: Mt. Hebron Helicopters - Registered owner: Helicopter Services of Alabama - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, April 5, 2001, 53 hours before - Departed: M95, Fayette, AL - Airport: M95, Richard Arthur Field, runway 18, 4,838 × 80 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 37; injuries: none; commercial; medical: class 2, valid medical--w/ waivers/lim; last flight review November 11, 1999; seat: left; flight hours: 473 total, 125 in this make and model, 390 as pilot in command, 58 in the last 90 days, 30 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 130° at 6 knots - Visibility: 7 statute miles - Lowest ceiling: 1,200 ft broken - Temperature: 75 °F, dew point 72 °F - Altimeter: 30.06 inHg - Observed at: BHM, 40 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20010907026269A](https://openairdocs.org/incident/20010907026269A), Sep 7, 2001: Bell 47G, Berry, AL, No damage. (-23) The pilot was flying over hostile terrain conducting police surveillance on a suspected drug smuggling operation, accompanied by the local sheriff.… ## Other investigations on N6327D (2) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB LAX79DUQ26](https://openairdocs.org/ntsb/LAX79DUQ26), Apr 2, 1979: Bell 47G2M (N6327D), Guadalupe, CA, substantial damage - [NTSB LAX75FUQ09](https://openairdocs.org/ntsb/LAX75FUQ09), Sep 27, 1974: Bell 47G (N6327D), Lancaster, CA, substantial damage From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.