# NTSB WPR11LA244: Hiller UH-12E, N68012, Stockton, CA, June 1, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 1, 2011, 16:20 local (23:20 UTC) - Place: Stockton, CA - Coordinates: 38.091388, -121.359169 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.0914&lon=-121.3592&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report August 30, 2011 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 79286 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR11LA244 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/79286/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=79286 - Page: https://openairdocs.org/ntsb/WPR11LA244 ## Probable cause The pilot's failure to maintain clearance from obstacles. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Attention/monitoring: attention](https://openairdocs.org/ntsb-findings/02021510): Personnel issues › Psychological · Pilot (probable cause); cases with it: [Hiller UH-12E, 1 case](https://openairdocs.org/ntsb-findings/02021510/cases.md?model=4360122), [All aircraft, 226 cases](https://openairdocs.org/ntsb-findings/02021510/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Hiller UH-12E, 7 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=4360122), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Object/animal/substance: tree(s)](https://openairdocs.org/ntsb-findings/03022020): Environmental issues › Physical environment · Response/compensation (probable cause); cases with it: [Hiller UH-12E, 1 case](https://openairdocs.org/ntsb-findings/03022020/cases.md?model=4360122), [All aircraft, 933 cases](https://openairdocs.org/ntsb-findings/03022020/cases.md) - [Attention/monitoring: monitoring environment](https://openairdocs.org/ntsb-findings/02021545): Personnel issues › Psychological · Pilot (probable cause); cases with it: [Hiller UH-12E, 4 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md?model=4360122), [All aircraft, 809 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering-low-alt flying: 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) - [Maneuvering-low-alt flying: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Hiller UH-12E, 7 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=4360122), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Maneuvering-low-alt flying: 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) - [Landing-flare/touchdown: 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 initially reported that he was conducting low level agricultural drying of cherry trees when the tail rotor contacted a tree during a turn. He felt a shake or vibration through the controls and looked for a place to land. He was maneuvering the helicopter towards a road when the helicopter experienced a full left yaw. The pilot applied full right pedal to counter the yawing motion and entered autorotation through the trees to the ground. Subsequently the pilot revised his statement saying that the skids of his helicopter were at least 10-15 feet above the tallest tree when he felt a shake or vibration through the controls. Postaccident examination of the airplane by a mechanic and a FAA inspector found continuity between the tail rotor and the linkages through the drive train which lead to the main transmission. Control system continuity was also established. The tail boom near the tail rotor transmission was twisted clockwise, shearing the aluminum, which is consistent with a tail rotor imbalance condition. Tail rotor blade #1 was sheared off about one quarter of the distance between the blade root and the blade tip, and rotor blade #2 had compression deformation of the trailing edge near the blade root. The sheared off portion of tail rotor blade #1 was located in the orchard. Visual inspection found a circular impact deformation in the leading edge at the blade tip, separation of the blade tip weight from the blade, deformation of the blades surface area, and compression bending of the blade's trailing edge. The damage to blade #1 was consistent with an impact to a tree limb. ## Factual narrative On June 1, 2011, about 1620 Pacific daylight time (PDT), a Hiller UH-12E, N68012, performed an emergency autorotation into a grove of cherry trees while performing low level agricultural operations near Stockton, California. Alpine Helicopter's was operating the helicopter under the provisions of 14 Code of Federal Regulations (CFR) Part 137. The commercial pilot was not injured and the aircraft sustained substantial damage. Visual meteorological conditions prevailed at the time for the local area agricultural flight. The pilot initially reported that he was conducting low level agricultural drying of cherry trees when the tail rotor struck a tree during a turn. Later in the week the pilot revised his statement saying that the skids of his helicopter were at least 10-15 feet above the tallest tree when he felt a shake or vibration through the control surfaces. He looked for a place to land and was maneuvering the helicopter towards a road when the helicopter experienced a full left yaw. The pilot applied full right pedal to counter the yawing motion and entered autorotation through the trees to the ground. The main rotor blade, tail rotor blade, tail boom, front fuselage, skids, and the undercarriage of the helicopter were substantially damaged. The pilot did not report any emergency alarms or cautionary lights accompanying the accident sequence and sustained no injuries on impact. Post accident examination of the aircraft by a mechanic and a FAA inspector found continuity between the tail rotor and the linkages through the drive train which lead to the main transmission. Control system continuity was also established. The tail boom near the tail rotor transmission was twisted clockwise, shearing the aluminum. Tail rotor blade #1 was sheared off about one quarter of the distance between the blade root and the blade tip, and rotor blade #2 had compression deformation of the trailing edge near the blade root. The sheared off portion of tail rotor blade #1 was located in the orchard. Visual inspection found a circular impact deformation in the leading edge at the blade tip, separation of the blade tip weight from the blade, deformation of the blades surface area, and compression bending of the blade's trailing edge. ## Aircraft - Registration: [N68012](https://openairdocs.org/deregistered/N68012-2013-07-29), registration cancelled 2013-07-29, S/N 1500 (OpenAirDocs) - Reported make and model: HILLER UH-12E - Registry model: [Hiller UH-12E](https://openairdocs.org/model/hiller-uh-12e) (registry code 4360122) (OpenAirDocs) - Category: Helicopter - Serial number: 1500 - Airframe hours: 7316 - Engines: Lycoming V0-540 305 horsepower reciprocating - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Alpine Helicopter Service, Inc. - Registered owner: Dozhier Joel C - Airworthiness certificate: Standard, Normal; Special, Restricted (Special); Standard, Utility - Last inspection: 100 hour, March 11, 2011, 66 hours before - Departed: l53, Lodi, CA - Destination: l53, Lodi, CA - Airport: L53, Lodi Airport ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 31; injuries: none; commercial; medical: class 2, without waivers/limitations; last flight review July 20, 2010; seat: center; flight hours: 2,382 total, 1,375 in this make and model, 2,294 as pilot in command, 70 in the last 90 days, 27 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 4 knots - Visibility: 10 statute miles - Lowest ceiling: 9,000 ft broken - Temperature: 64 °F, dew point 50 °F - Altimeter: 29.92 inHg ## 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 20110601010959A](https://openairdocs.org/incident/20110601010959A), Jun 1, 2011: Hiller UH-12E, Stockton, CA, Destroyed. Pilot was performing low level agricultural operations drying cherry trees. Heavy vibration occurred and pilot initiated a precautionary landing when the… ## Other investigations on N68012 (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 DEN87LA157](https://openairdocs.org/ntsb/DEN87LA157), Jun 20, 1987: Hiller UH-12E (N68012), Ray, ND, substantial damage ## Docket (10 files) The files NTSB released with the investigation on July 5, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=79286. 4.0 MB in all. - Pilot Operator Aircraft Accident Report, NTSB Form 6120.1/2 (item 1, .PDF, 270 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350048&FileExtension=.PDF&FileName=Pilot%20Operator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1%2F2-Redacted.PDF - Pilot's Original Statement (item 2, .PDF, 20 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350089&FileExtension=.PDF&FileName=Pilot%27s%20Original%20Statement-Master.PDF - Picture 1. Front damage. (item 3, .PDF, 370 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350576&FileExtension=.PDF&FileName=Picture%201.%20Front%20damage.-Master.PDF - Picture 2. Side view of damage. (item 4, .PDF, 535 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350577&FileExtension=.PDF&FileName=Picture%202.%20Side%20view%20of%20damage.-Master.PDF - Picture 3. Tail rotor assembly. (item 5, .PDF, 337 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350578&FileExtension=.PDF&FileName=Picture%203.%20Tail%20rotor%20assembly.-Master.PDF - Picture 4. Twisting of the tail rotor. (item 6, .PDF, 205 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350579&FileExtension=.PDF&FileName=Picture%204.%20Twisting%20of%20the%20tail%20rotor.-Master.PDF - Picture 5. Tail rotor blade #2 trailing edge damage. (item 7, .PDF, 254 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350580&FileExtension=.PDF&FileName=Picture%205.%20Tail%20rotor%20blade%20%232%20trailing%20edge%20damage.-Master.PDF - Picture 6. Missing part of tail rotor #1 matched up to the rest of the blade. (item 8, .PDF, 266 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350581&FileExtension=.PDF&FileName=Picture%206.%20Missing%20part%20of%20tail%20rotor%20%231%20matched%20up%20to%20the%20rest%20of%20the%20blade.-Master.PDF - Picture 7. Damage to missing piece of tail rotor #1. (item 9, .PDF, 964 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350582&FileExtension=.PDF&FileName=Picture%207.%20Damage%20to%20missing%20piece%20of%20tail%20rotor%20%231.-Master.PDF - Picture 8. Tail rotor #1 damage to the tip. (item 10, .PDF, 751 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350583&FileExtension=.PDF&FileName=Picture%208.%20Tail%20rotor%20%231%20damage%20to%20the%20tip.-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.