# NTSB CEN12LA650: Hiller UH-12B, N94735, Rio Vista, TX, September 19, 2012 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 19, 2012, 10:45 local (15:45 UTC) - Place: Rio Vista, TX - Coordinates: 32.230785, -97.370635 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=32.2308&lon=-97.3706&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report June 4, 2013 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA FSDO - NTSB case key (mKey): 85106 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN12LA650 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/85106/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=85106 - Page: https://openairdocs.org/ntsb/CEN12LA650 ## Probable cause The catastrophic failure and disintegration of the No. 6 engine piston, which resulted in a total loss of engine power. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Power plant](https://openairdocs.org/ntsb-findings/01057100): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Hiller UH-12B, 1 case](https://openairdocs.org/ntsb-findings/01057100/cases.md?model=4360110), [All aircraft, 198 cases](https://openairdocs.org/ntsb-findings/01057100/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: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340); cases with it: [Hiller UH-12B, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=4360110), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Maneuvering-low-alt flying: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Hiller UH-12B, 2 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=4360110), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Autorotation: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Hiller UH-12B, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=4360110), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) ## Analysis The pilot reported that he was on a survey flight when the helicopter engine suddenly stopped; he elected to autorotate to a field. The area he landed in had high vegetation, which “grabbed” the helicopter skids and the helicopter impacted the ground hard. Examination of the helicopter revealed that the main rotor impacted the tailboom during the accident and the tail rotor had separated from the helicopter. Examination of the engine revealed the No. 6 piston had disintegrated catastrophically, which caused additional internal damage to the engine. ## Factual narrative On September 19, 2012, about 1045 central standard time, a Hiller UH-12B helicopter, N94735, experienced a loss of engine power while maneuvering at low altitude near Rio Vista, Texas. The student rated pilot, sole occupant, was not injured during forced landing and the helicopter was substantially damaged. The helicopter was owned and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Day visual meteorological conditions prevailed for the flight, which operated without a flight plan. The pilot reported that he was on a survey flight, looking at cattle and fences from the helicopter. He stated that the helicopter engine suddenly stopped, so he elected to autorotate to the field. The helicopter made a hard landing and the skids were caught by the high vegetation. An examination, by the responding Federal Aviation Administration (FAA) inspectors revealed that the helicopter’s, tailrotor and aft section of the tailboom had separated from the helicopter. The main rotor blade had damage consistent with impacting the tailboom. The engine was examined by an Airframe and Powerplant (A&P) mechanic, under the supervision of the FAA inspectors. The mechanic found no compression on the number five and number six cylinders; neither valve moved on the number six cylinder and only the intake on the five cylinder moved. The number six cylinder was removed and revealed damage to the crankcase and camshaft boss. Additionally, the number six connecting rod, piston pin, and plugs were found intact; however, the number six piston was missing; several pieces of metal were located in the engine. ## Aircraft - Registration: [N94735](https://openairdocs.org/aircraft/N94735), registered now, S/N 523, built 1953 (OpenAirDocs) - Reported make and model: HILLER UH-12B - Registry model: [Hiller UH-12B](https://openairdocs.org/model/hiller-uh-12b) (registry code 4360110) (OpenAirDocs) - Registry engine: [Franklin 6A4200 series](https://openairdocs.org/engine/franklin-6a4200-series) (registry code 27027, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 523 - Engines: FRANKLIN 6A4200 SERIES 200 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Departed: Rio Vista, TX - Destination: Rio Vista, TX ## Flight crew As NTSB recorded them. NTSB leaves out names. - Student pilot; age 51; injuries: none; student; medical: class 3, with waivers/limitations ## Weather - Conditions: Visual (VMC), Day - Wind: 150° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 73 °F, dew point 57 °F - Altimeter: 30.18 inHg - Observed at: KCPT ## 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 20120919023599A](https://openairdocs.org/incident/20120919023599A), Sep 19, 2012: Hiller UH-12B, Blum, TX, Substantial damage. On September 19 , 2012, at approximately 0955 CST, a Hiller UH-12B helicopter, N94735, experienced a loss of engine power while maneuvering at a low altitude… ## Other investigations on N94735 (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 CHI77FEM43](https://openairdocs.org/ntsb/CHI77FEM43), Sep 26, 1977: Hiller UH-12B (N94735), Carrollton, MI, destroyed ## Docket (5 files) The files NTSB released with the investigation on May 13, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=85106. 5.2 MB in all. - Pilot statement (memo) (item 1, .PDF, 143 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391745&FileExtension=.PDF&FileName=Pilot%20statement%20(memo)-Master.PDF - FAA memo w/Inspectors (item 2, .PDF, 142 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391759&FileExtension=.PDF&FileName=FAA%20memo%20w%2FInspectors-Master.PDF - Mechanic memo (item 3, .PDF, 137 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391764&FileExtension=.PDF&FileName=Mechanic%20memo-Master.PDF - Weather Reports and Records (item 4, .PDF, 38 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391749&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records-Master.PDF - Photo: aft tailboom and tailrotor (item 5, .PDF, 4.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391750&FileExtension=.PDF&FileName=Photo%3A%20aft%20tailboom%20and%20tailrotor-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.