# NTSB WPR10LA127: Hiller UH-12E, N36MV, Los Banos, CA, February 2, 2010 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: February 2, 2010, 13:20 local (21:20 UTC) - Place: Los Banos, CA - Coordinates: 37.051109, -120.923889 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.0511&lon=-120.9239&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-VFR pattern final: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report October 21, 2010 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration FSDO - NTSB case key (mKey): 75334 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR10LA127 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/75334/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=75334 - Page: https://openairdocs.org/ntsb/WPR10LA127 ## Probable cause A partial loss of engine power due to a failure of the throttle interconnect hardware, which resulted in a hard landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine controls: power lever](https://openairdocs.org/ntsb-findings/01057603): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Hiller UH-12E, 1 case](https://openairdocs.org/ntsb-findings/01057603/cases.md?model=4360122), [All aircraft, 95 cases](https://openairdocs.org/ntsb-findings/01057603/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach-VFR pattern final: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Hiller UH-12E, 3 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=4360122), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Emergency descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Hiller UH-12E, 14 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=4360122), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot of the helicopter had just completed an aerial application flight and was returning to land. As he approached the landing area, he began to apply power, but the engine did not respond. He continued to twist the throttle, but it felt loose with no resistance and the engine speed did not change. He aborted the landing approach and performed a run-on landing in a field; during the approach the engine speed began to decrease and the helicopter landed hard, causing substantial damage to the tail boom and lower fuselage. Postaccident examination revealed that the throttle control attach fitting located in the aft section of the collective control had become separated. The nuts and bolts attaching the fitting were not located. The lack of witness marks on the throttle fitting indicates that either the attachment bolt failed or rapidly unscrewed from its associated nut. The disconnection resulted in a loss of engine control and subsequent partial loss of engine power. The last annual inspection occurred 11 months and 250 flight hours prior to the accident. ## Factual narrative HISTORY OF FLIGHT On February 2, 2010, about 1320 Pacific standard time, a Hiller UH-12E helicopter, N36MV, landed hard near Los Banos, California. S and S Helicopters was operating the helicopter under the provisions of Title 14 Code of Federal Regulations Part 137 as an aerial application flight. The certificated commercial pilot was not injured. The helicopter sustained substantial damage. The local flight departed from a field near Los Banos. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot reported that he had just completed an aerial application over a wheat field, and was returning to land. As he approached the landing area at an altitude of about 30 feet above ground level, he began to apply power, but the engine did not respond. He continued to twist the throttle, but it felt loose with no resistance, and the engine speed did not change. He aborted the landing approach, and turned the helicopter towards a larger open field. He circled the field about three times while attempting to diagnose the problem. He then elected to perform a run-on landing; during the landing approach, the engine speed began to decrease, and the helicopter landed hard. During the landing sequence, the tailboom separated from the aft bulkhead, and the lower fuselage sustained crush damage. Post accident examination revealed that the throttle control fitting, located at the aft end of the collective stick assembly, had become separated from the cam lever rod bearing. According to the Hiller service manual applicable to this helicopter, the throttle control fitting is connected to the cam lever rod with an AN23-16A bolt, NAS43DD3-4 spacer, AN960PD10L washer, and a NAS679A3 nut. None of these fittings were located on the engine deck, and examination of the control arm mating surfaces revealed no gouges or fretting signatures. According to maintenance logbook entries, the helicopter underwent an annual inspection on February 25, 2009, at an airframe total time of 6,815 flight hours. According to the FAA inspector who responded to the accident, the helicopter’s total flight time at the time of the accident was 7,064 hours. ## Aircraft - Registration: [N36MV](https://openairdocs.org/deregistered/N36MV-2018-03-01), registration cancelled 2018-03-01, S/N 5060, built 1978 (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: 5060 - Airframe hours: 7064 - Engines: LYCOMING VO-540 SERIES 310 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Jeff Streeter Motor Sports Inc, doing business as S and S Helicopters - Registered owner: Jeff Streeter Motor Sports Inc - Airworthiness certificate: Special, Restricted (Special) - Last inspection: Annual, February 25, 2009, 249 hours before - Departed: Los Banos, CA - Destination: Los Banos, CA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; injuries: none; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review November 24, 2009; seat: center; flight hours: 18,500 total, 7,000 in this make and model, 18,500 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 3 statute miles - Lowest ceiling: none - Temperature: 52 °F, dew point 48 °F - Altimeter: 29.82 inHg - Observed at: MCE, 28 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 20100202026659A](https://openairdocs.org/incident/20100202026659A), Feb 2, 2010: Hiller UH-12E, Los Banos, CA, Substantial damage. When returning to the load truck after completion of an aerial application the pilot noticed that his throttle did not respond. The pilot was at an altitude of… ## Other investigations on N36MV (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 WPR14LA062](https://openairdocs.org/ntsb/WPR14LA062), Dec 9, 2013: Hiller UH 12E (N36MV), Chowchilla, CA, substantial damage. Probable cause: The failure of the torsional drive coupling, which resulted in a loss of drive to the main rotor system during low-altitude flight. ## Docket (6 files) The files NTSB released with the investigation on July 22, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=75334. 4.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 337 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40332680&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Photo 1 - Engine Throttle Control Fitting (item 2, .PDF, 480 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40332682&FileExtension=.PDF&FileName=Photo%201%20-%20Engine%20Throttle%20Control%20Fitting-Master.PDF - Photo 2 - Engine Throttle Control Fitting and Rod Bearing (item 3, .PDF, 676 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40332683&FileExtension=.PDF&FileName=Photo%202%20-%20Engine%20Throttle%20Control%20Fitting%20and%20Rod%20Bearing-Master.PDF - Photo 3 - Helicopter Damage (item 4, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40332684&FileExtension=.PDF&FileName=Photo%203%20-%20Helicopter%20Damage-Master.PDF - Airframe Logbook Excerpt (item 5, .PDF, 205 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40332685&FileExtension=.PDF&FileName=Airframe%20Logbook%20Excerpt-Redacted.PDF - Hiller Parts Manual Excerpts (item 6, .PDF, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40332681&FileExtension=.PDF&FileName=Hiller%20Parts%20Manual%20Excerpts-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.