# NTSB WPR09TA277: Hughes OH-6A, N6641D, Benson, AZ, June 4, 2009 - Type: NTSB accident investigation - Classification: Accident · No injuries · Final report - Date: June 4, 2009, 08:50 local (15:50 UTC) - Place: Benson, AZ - Coordinates: 31.999444, -110.35778 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=31.9994&lon=-110.3578&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: Hard landing](https://openairdocs.org/ntsb-events/092) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report November 9, 2009 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Avitation Administration - NTSB case key (mKey): 73967 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR09TA277 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/73967/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=73967 - Page: https://openairdocs.org/ntsb/WPR09TA277 ## Probable cause The pilot under instruction's inadequate autorotation technique and the instructor pilot’s delayed remedial action to arrest the rate of descent of the helicopter while in an autorotation flare. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Action: delayed action](https://openairdocs.org/ntsb-findings/02041025): Personnel issues › Action/decision · Instructor/check pilot (probable cause); cases with it: [Hughes OH-6A, 1 case](https://openairdocs.org/ntsb-findings/02041025/cases.md?model=4470905), [All aircraft, 894 cases](https://openairdocs.org/ntsb-findings/02041025/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Hughes OH-6A, 3 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=4470905), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-flare/touchdown: Hard landing](https://openairdocs.org/ntsb-events/092) (defining event); cases with it: [Hughes OH-6A, 2 cases](https://openairdocs.org/ntsb-events/092/sequence.md?model=4470905), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) ## Analysis The instructor pilot reported that they were practicing autorotations to the runway. During a straight-in autorotation at approximately 200 feet above ground level, the instructor called for an increase in throttle to bring rotor rpm into the normal operating range in preparation for landing. Between 200 feet and 100 feet agl, the instructor assisted the flying pilot with the throttle increase when he realized that the pilot had delayed throttle application. The flying pilot then initiated the flare at approximately 50 feet agl. The flying pilot leveled the helicopter and applied collective to slow the descent rate. Upon realizing that the descent rate had not been checked prior to beginning the flare, the instructor joined the flying pilot on the controls. The helicopter landed hard on the runway and bounced, rotated to the left of runway heading as it touched down a second time, resulting in the collapse of the right landing skid. The pilot reported that were no mechanical anomalies with the flight control systems. ## Factual narrative On June 4, 2009, at 0850 mountain standard time (MST), a Hughes OH-6A, N6641D, experienced a hard landing at Benson Municipal Airport, Benson, Arizona. The public-use flight was operated by U.S. Customs and Border Protection as a pilot training flight under the provisions of Title 14 of the Code of Federal Regulations, Part 91. Neither commercial pilot was injured, and the helicopter was substantially damaged. Visual conditions prevailed, and no flight plan had been filed. The flight originated at Tucson International Airport, Tucson, Arizona, at 0715. The instructor pilot reported that they were practicing autorotations to the runway. During a straight in autorotation at approximately 200 feet agl, the instructor called for an increase in throttle to bring rotor rpm into the normal operating range in preparation for landing. Between 200 feet and 100 feet agl the instructor assisted the flying pilot with the throttle increase when he realized that the pilot had delayed throttle application. The flying pilot initiated the flare at approximately 50 feet agl. The flying pilot leveled the helicopter and applied collective to slow the descent rate. Upon realizing that the descent rate had not been checked prior to beginning the flare, the instructor joined the flying pilot on the controls. The helicopter landed hard on the runway and bounced, rotated to the left of runway heading as it touched down a second time, resulting in the collapse of the right landing skid. The helicopter came to rest on the runway heading 150 degrees to the left of runway heading. Examination of the helicopter by a Federal Aviation Administration (FAA) inspector revealed structural damage to the right landing skid and the fuselage of the helicopter. The pilot indicated that there were no mechanical anomalies with the flight control systems prior to the flight. Weather conditions reported at Fort Huachuca, Arizona, at 0755 MST, 24 miles to south of the accident location, indicated that the wind was variable at 1 knot, and visibility was 50 miles with a ceiling of 20,000 feet. ## Aircraft - Registration: [N6641D](https://openairdocs.org/deregistered/N6641D-2018-05-31), registration cancelled 2018-05-31, S/N 66-07855 (OpenAirDocs) - Reported make and model: HUGHES OH-6A - Registry model: [Hughes OH-6A](https://openairdocs.org/model/hughes-oh-6a) (registry code 4470905) (OpenAirDocs) - Category: Helicopter - Serial number: 66-07855 - Airframe hours: 6141 - Engines: Allison (R/R) 250-C20B 420 horsepower turbo shaft - Damage: Substantial damage - Flight: Public aircraft - federal, Part 91 - Operator: Dept of Homeland Security - Registered owner: Department Of Homeland Security - Last inspection: 100 hour, May 6, 2009, 45 hours before - Departed: KTUS, Tucson, AZ - Destination: E95, Benson, AZ - Airport: E95, Benson Municipal Airport, runway 10, 4,000 × 75 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; injuries: none; commercial, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: helicopter, airplane; medical: class 1, without waivers/limitations; last flight review May 15, 2009; seat: left; flight hours: 5,500 total, 990 in this make and model, 3,500 as pilot in command, 141 in the last 90 days, 38 in the last 30 days, 0 in the last 24 hours - Co-pilot; age 38; injuries: none; commercial, flight instructor; airplane ratings: single-engine land; instrument ratings: airplane, helicopter; medical: class 2, without waivers/limitations; last flight review April 3, 2009; seat: right; flight hours: 1,540 total, 208 in this make and model, 1,260 as pilot in command, 144 in the last 90 days, 69 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 1 knots - Visibility: 50 statute miles - Lowest ceiling: 200 ft broken - Temperature: 84 °F, dew point 16 °F - Altimeter: 30.12 inHg - Observed at: KFHU, 24 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 20090604018059A](https://openairdocs.org/incident/20090604018059A), Jun 4, 2009: Hughes OH6A, Benson, AZ, Substantial damage. (-23) While practicing autorotation procedures, touched, down, aircraft jumped off runway, not enough RPM to maintain flight. Contracted ground second time and… ## Docket (3 files) The files NTSB released with the investigation on August 31, 2009, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=73967. 2.0 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 671 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40316846&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Photo 1 - Left side of the helicopter (item 2, .PDF, 629 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40316847&FileExtension=.PDF&FileName=Photo%201%20-%20Left%20side%20of%20the%20helicopter-Master.PDF - Photo 2 - Right side of the helicopter (item 3, .PDF, 654 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40316848&FileExtension=.PDF&FileName=Photo%202%20-%20Right%20side%20of%20the%20helicopter-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.