# NTSB CEN11LA200: Hughes 369D, N112AS, Henryetta, OK, February 23, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: February 23, 2011, 16:20 local (22:20 UTC) - Place: Henryetta, OK - Coordinates: 35.37611, -96.046943 - Nearby events: https://openairdocs.org/map.md?lat=35.3761&lon=-96.0469&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report August 22, 2011 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA Flight Standards District Office, Rolls-Royce North America, Boeing Helicopters, Aerial Solutions, FAA Flight Standards District Offuice - NTSB case key (mKey): 78407 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN11LA200 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/78407/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=78407 - Page: https://openairdocs.org/ntsb/CEN11LA200 ## Probable cause Failure of the cyclic control system for reasons undetermined. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 8 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=4470706), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) - [Rotorcraft flight control: main rotor control](https://openairdocs.org/ntsb-findings/01046710): Aircraft › Aircraft propeller/rotor · Failure (probable cause); cases with it: [Hughes Helicopters HUGHES 369D, 1 case](https://openairdocs.org/ntsb-findings/01046710/cases.md?model=4470706), [All aircraft, 28 cases](https://openairdocs.org/ntsb-findings/01046710/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Hughes Helicopters HUGHES 369D, 4 cases](https://openairdocs.org/ntsb-events/333/sequence.md?model=4470706), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) - [Landing: Roll over](https://openairdocs.org/ntsb-events/097); cases with it: [Hughes Helicopters HUGHES 369D, 3 cases](https://openairdocs.org/ntsb-events/097/sequence.md?model=4470706), [All aircraft, 261 cases](https://openairdocs.org/ntsb-events/097/sequence.md) ## Analysis The helicopter was facing into the wind and hovering, with an external load, over an open field adjacent to the work area. The pilot made a 180-degree right pedal turn to enter the work area, approximately 120 feet above the ground. While trimming for the left quartering tailwind, he heard a loud "pop" and felt a "thump" in his seat. He was unable move the cyclic control to the left, and the helicopter started a right banking turn. The helicopter rolled sharply to the right and impacted the ground. A postaccident examination of the helicopter revealed no discrepancies. Flight control continuity was established from the cockpit to the flight controls. When the flight controls were manipulated, no obstructions or binding were noted. ## Factual narrative On February 23, 2011, approximately 1620 central standard time, a Hughes 369D, N112AS, registered to and operated by Aerial Solutions, Inc., was substantially damaged when it struck the ground and rolled over 12 miles southwest of Henryetta, Oklahoma. Visual meteorological conditions prevailed at the time of the accident. The external load flight was being conducted under the provisions of 14 Code of Federal Regulations (CFR) Part 133 without a flight plan. The pilot, the sole occupant on board, was not injured. The local flight had originated at 1400 from the landing zone where the accident occurred. The external load suspended under the helicopter was a patented Aerial Saw, used to cut vegetation along power line right-of-ways. The Aerial Saw consisted of a row of ten 24-inch diameter circular blades mounted on a saw bar channel, driven by belts in the channel, and connected to a gas powered engine. The engine was mounted above the saw bar in a framed cage and was suspended below the helicopter by sections of aluminum tubing. The saw and motor section were hinged to allow the saw to swing fore and aft, but not sideways. The tubular sections were also hinged so that the helicopter could land with the saw stretched out in front of it. The pilot could manage the saw by turning the saw bar left or right, change the saw speed or turn the saw motor on or off. The saw blades are normally pointed in the same direction of the helicopter's travel. The Aerial saw suspended on an 80-foot beam and weighed 822 pounds. At the time of the accident, the saw was idling. According to the accident report submitted by the operator, the helicopter was facing into the wind and hovering with the external load over an open field adjacent to the work area approximately 120 feet above the ground. The pilot made a 180-degree right pedal turn to enter the work area. While trimming for a left quartering tailwind, reported to be 200 degrees at 11 knots, he heard a loud "pop" and felt a "thump" in his seat. He was unable to move the cyclic control to the left, and helicopter started a right banking turn. The collective control was lowered and aft cyclic control was applied. This lowered the external load to the ground and caused the helicopter to stabilize by the pilot pulling aft on the external load. All efforts to move the cyclic control to the left were unsuccessful. At 5 feet above the ground, as the pilot leveled the helicopter, it rolled sharply to the right and impacted the ground, coming to rest on its left side. The wreckage was examined and documented by Federal Aviation Administration (FAA) inspectors at the accident site, then transported to Air Salvage of Dallas (Texas) where, on April 12, 2011, it was examined in greater detail by FAA inspectors and representatives of Boeing Helicopters and Rolls Royce. Flight control continuity was established from the cockpit to the control deck. All controls were moved, and no obstructions or binding were noted. The trimactuators were tested. The lateral trim actuator would not operate due to wires being severed during the accidence sequence, but full left lateral trim input was noted. With the wires connected, the lateral trim motor functioned normally. A support on the lower non-rotating portion of the swashplate was fractured in overload during the accident sequence. There was damage on the mating surfaces between the non-rotating and rotating surfaces of the swashplate. The cowling around the swashplate showed evidence of fiberglass debonding and was missing a fastener. The damage to the inlet fairing was a result of the accident sequence from helicopter roll over and the fairing contacting rotating and broken/flailing upper flight control parts. The Boeing Helicopter representatives did not find any anomalies that would cause binding of the controls. Damage to the rotor system was consistent with power being developed. No powerplant discrepancies were noted. No post-accident examination of the Aerial Saw was performed. ## Aircraft - Registration: [N112AS](https://openairdocs.org/aircraft/N112AS), registered now, S/N 900808D, built 1980 (OpenAirDocs) - Reported make and model: HUGHES 369D - Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs) - Registry engine: [Allison 250 SER 250HP](https://openairdocs.org/engine/allison-250-ser-250hp) (registry code 03002, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 900808D - Airframe hours: 27823 - Engines: Rolls-Royce Allison 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: External load, Part 133 - Operator: Aerial Solutions, Inc. - Registered owner: Aerial Solutions, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, February 16, 2011, 29 hours before - Departed: Henryetta, OK - Destination: NONE, Henryetta, OK ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 32; injuries: none; commercial; airplane ratings: single-engine land; medical: class 2, with waivers/limitations; last flight review July 20, 2010; seat: left; flight hours: 715 total, 522 in this make and model, 623 as pilot in command, 128 in the last 90 days, 90 in the last 30 days, 7 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 200° at 8 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 75 °F, dew point 59 °F - Altimeter: 29.87 inHg - Observed at: OKM, 20 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 20110223006119A](https://openairdocs.org/incident/20110223006119A), Feb 23, 2011: Hughes 369D, Henryetta, OK, Substantial damage. While approaching to land the pilot heard a load pop and lost lateral control with the cyclic. He lowered collective and proceeded to lower the external load… ## Docket (6 files) The files NTSB released with the investigation on June 21, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=78407. 1.6 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 573 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40347896&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - FAA Inspector's Statement (item 2, .PDF, 9 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40347900&FileExtension=.PDF&FileName=FAA%20Inspector%27s%20Statement-Master.PDF - Weather Reports and Records (item 3, .PDF, 3 photos, 45 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40347902&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records-Master.PDF - Photo 1 Front view of N112AS laying on its left side (item 4, .PDF, 362 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40347897&FileExtension=.PDF&FileName=Photo%201%20Front%20view%20of%20N112AS%20laying%20on%20its%20left%20side-Master.PDF - Photo 2 Top view of N112AS (item 5, .PDF, 356 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40347898&FileExtension=.PDF&FileName=Photo%202%20Top%20view%20of%20N112AS-Master.PDF - Photo 3 Bottom view of N112AS (item 6, .PDF, 283 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40347899&FileExtension=.PDF&FileName=Photo%203%20Bottom%20view%20of%20N112AS-Master.PDF 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.