# NTSB DFW08LA100: Hiller UH-12E, N34SD, Quinton, OK, April 7, 2008 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: April 7, 2008, 12:30 local (17:30 UTC) - Place: Quinton, OK - Coordinates: 35.121944, -95.368614 - Nearby events: https://openairdocs.org/map.md?lat=35.1219&lon=-95.3686&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 24, 2008 - Report: Approved by Office Director - Parties: FAA FSDO, Hiller Aircraft - NTSB case key (mKey): 67832 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DFW08LA100 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/67832/pdf - Page: https://openairdocs.org/ntsb/DFW08LA100 ## Probable cause An undetermined mechanical malfuction associated with the tail rotor drive system which led to a loss of control. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Tail rotor drive system: tail rotor gearbox](https://openairdocs.org/ntsb-findings/01046520): Aircraft › Aircraft propeller/rotor · Failure (probable cause); cases with it: [Hiller UH-12E, 2 cases](https://openairdocs.org/ntsb-findings/01046520/cases.md?model=4360122), [All aircraft, 12 cases](https://openairdocs.org/ntsb-findings/01046520/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Hiller UH-12E, 5 cases](https://openairdocs.org/ntsb-events/330/sequence.md?model=4360122), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Enroute-cruise: Loss of tail rotor effectiveness](https://openairdocs.org/ntsb-events/242); cases with it: [Hiller UH-12E, 1 case](https://openairdocs.org/ntsb-events/242/sequence.md?model=4360122), [All aircraft, 100 cases](https://openairdocs.org/ntsb-events/242/sequence.md) - [Autorotation: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Hiller UH-12E, 4 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=4360122), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The pilot reported hearing a loud noise and experiencing vibrations while piloting his helicopter in cruise about 1,000 feet above the ground. The pilot performed an autorotation to an open field, and was able to maintain control of the helicopter throughout the autorotaion. The pilot reported that a tail rotor strike did not occur. Failed parts from the transmission, tail rotor blades, and associated tail rotor drive hardware were submitted to the NTSB for metallurgical examination. All parts appeared to have failed in overload; however, the origin of the overload failures, or whether they were pre- or post-impact, could not be determined ## Factual narrative On April 7, 2008, at approximately 1230 central daylight time, a Hiller UH-12E helicopter, N34SD, was returning to a landing zone after an agricultural application when a loud noise was heard with associated vibrations. The pilot elected to perform an autorotation into a nearby field. The commercial pilot, the sole occupant of the helicopter, was not injured. The helicopter was owned and operated by Texas Air Cargo Inc. The local flight originated from private property located approximately 5 miles north of Quinton, Oklahoma. Visual meteorological conditions prevailed and no flight plan was filed for the 14 Code of Federal Regulations Part 137 agricultural application flight. According to the pilot, the helicopter was cruising at approximately 1,000 feet above ground level when a loud noise was heard by the pilot. The pilot reported that he quickly reduced engine power and began an autorotation. Furthermore, the pilot stated there was no difficulty controlling the helicopter through the emergency landing and he was able to perform a normal flare touching down with no associated side angle. The pilot stated that the gearbox had failed resulting in the damage to the helicopter. On-scene photos were provided by the pilot. The photos provided revealed a fracture of the tail rotor gearbox yoke, twisting of the drive shaft, and damage to the tail rotor blades. The pilot and his employees reported no evidence of a ground strike existed at the accident scene. Furthermore, another individual reported recovering a tail rotor blade "some distance" from the site of the autorotation. On a NTSB Form 6120, the pilot reported having 33,000 total hours with 30 hours in make and model. Parts from the helicopter were recovered for examination. A metallurgic examination was conducted by the NTSB laboratory and revealed all components failed as a result of overload. Additionally, no fatigue failures were detected. An automated weather reporting station located at McAlister Regional Airport (MLC), approximately 28 nautical miles to the south-east of the accident site, reported winds from 110 degrees at 11 knots gusting to 14 knots, visibility 10 statute miles, ceiling broken at 6,000 feet, temperature 75 degrees Fahrenheit, dew point 50 degrees Fahrenheit, and a barometric pressure of 29.93 inches of Mercury. ## Aircraft - Registration: [N34SD](https://openairdocs.org/aircraft/N34SD), registered now, S/N 1618, built 1965 (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 41534, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 1618 - Airframe hours: 4068 - Engines: Lycoming VO-540-C2A 305 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Registered owner: Texas Air Cargo Inc. - Airworthiness certificate: Special, Restricted (Special); Standard, Normal - Last inspection: Annual, December 1, 2007 - Departed: Quinton, OK - Airport: runway NA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 65; injuries: none; flight instructor, flight engineer, airline transport; airplane ratings: single-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review November 1, 2007; seat: center; flight hours: 33,000 total, 30 in this make and model ## Weather - Conditions: Visual (VMC) - Wind: 110° at 11 knots, gusting 14 - Visibility: 10 statute miles - Lowest ceiling: 6,000 ft broken - Temperature: 75 °F, dew point 50 °F - Altimeter: 29.93 inHg - Observed at: MLC ## 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 20080407833479A](https://openairdocs.org/incident/20080407833479A), Apr 7, 2008: Hiller UH12E, Quinton, OK, Substantial damage. (-23) On April 7, 2008, the pilot of N34SD was returning to a loading area in his helicopter, a Hiller 12E, N34SD after an aerial application in a field near… ## Other investigations on N34SD (1) 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 CEN09CA359](https://openairdocs.org/ntsb/CEN09CA359), Jun 11, 2009: Hiller UH-12E (N34SD), Stringtown, OK, substantial damage. Probable cause: The pilot's failure to maintain clearance from power lines. Contributing to the accident was the pilot's preoccupation with personal affairs. 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.