# NTSB ATL96LA104: Hiller UH-12E, N102HT, Cottondale, FL, July 11, 1996 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 11, 1996, 17:30 local (22:30 UTC) - Place: Cottondale, FL - Coordinates: 30.789545, -85.370452 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=30.7895&lon=-85.3705&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report April 29, 1997 - Report: Approved by Office Director - NTSB case key (mKey): 3739 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ATL96LA104 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/3739/pdf - Page: https://openairdocs.org/ntsb/ATL96LA104 ## Probable cause failure of the main rotor drive torsional coupling and inner gimbal ring, which resulted in jamming of the flight controls during an attempted autorotation. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - rotor drive system,engine to transmission drive - failure,total (cause) - Forced landing, emergency descent/landing - autorotation - initiated, pilot in command - Loss of control - in flight, emergency descent/landing - rotorcraft flight control - jammed - In flight collision with terrain/water, descent - uncontrolled ## Analysis Approximately two minutes into the climbout, the pilots felt a vibration in the airframe followed by a loud bang. The pilots entered an autorotation and selected a field for a forced landing. The pilots reported that, subsequently, as they were attempting to control the helicopter, the flight controls would not respond to inputs. Control of the helicopter was lost, and it impacted the ground inverted. Examination of the helicopter disclosed that the main drive clutch and engine gimble ring with the torsional coupling had failed. Debris from the failed components was not recovered for examination. A review of the maintenance logs showed that the drive coupling assembly had 511 hours of total service since new. Wreckage examination also disclosed that the entire transmission assembly had rotated from its normally installed position, and that the flight control rods were displaced from their normal position. ## Factual narrative On July 11, 1996, at 1730 central daylight time, a Hiller UH-12E, N102HT collided with the ground and was substantially damaged during a forced landing near Cottondale, Florida. Neither of the two commercial pilots were injured. The helicopter was being operated under the provisions of Title 14 CFR Part 91 by the pilot. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed for the local flight. The flight departed Jackson Heliport at 1715 Central Daylight Time. Approximately two minutes into the climbout, the pilots felt a vibration in the airframe followed by a loud bang. The pilots initially stated that the helicopter had lost tail rotor control, at which time they selected a field for a forced landing. As the pilots attempted to control the helicopter, they reported that the flight controls would not respond to the inputs. Total control of the helicopter was lost; the helicopter impacted the ground inverted. Examination of the helicopter disclosed that the main drive clutch and engine gimble ring with the torsional coupling had failed. Debris from the failed components was not recovered for examination. A review of the maintenance logs showed that the drive coupling assembly had 511 hours of total time in service since new. The wreckage examination also disclosed that the entire transmission assembly had rotated from its normally installed position, and that the flight control rods were displaced from their normal positions. ## Aircraft - Registration: [N102HT](https://openairdocs.org/deregistered/N102HT-2013-08-14), registration cancelled 2013-08-14, S/N 5218, built 1983 (OpenAirDocs) - Reported make and model: Hiller UH-12E - Registry model: [Hiller UH-12E](https://openairdocs.org/model/hiller-uh-12e) (registry code 4360122) (OpenAirDocs) - Registry engine: [Lycoming VO-540 series](https://openairdocs.org/engine/lycoming-vo-540-series) (registry code 41582, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 5218 - Airframe hours: 515 - Engines: Lycoming VO-540-C2A 305 horsepower reciprocating - Damage: Substantial damage - Flight: Part 91 - Operator: James E Willoughby - Registered owner: Helicopter Technology, Inc. - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, July 5, 1996, 3 hours before - Departed: JACKSON HELPRT, FL ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 45; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: center; flight hours: 5,567 total, 77 in this make and model, 5,493 as pilot in command, 166 in the last 90 days, 2 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 60° at 10 knots - Visibility: 6 statute miles - Lowest ceiling: none - Temperature: 90 °F, dew point 72 °F - Altimeter: 29.00 inHg - Observed at: DHN, 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 19960711044029A](https://openairdocs.org/incident/19960711044029A), Jul 11, 1996: Hiller UH12E, Cottondale, FL, Substantial damage. Loud bang vibration on climbout. Lost tail rotor control. Impacted inverted main drive clutch and gimble failed. 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.