# NTSB WPR09LA371: Sikorsky S-55, N1255T, Chelan, WA, July 24, 2009 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 24, 2009, 14:45 local (21:45 UTC) - Place: Chelan, WA - Coordinates: 47.866111, -119.942779 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.8661&lon=-119.9428&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-low-alt flying: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 20, 2010 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: FAA FSDO - NTSB case key (mKey): 74378 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR09LA371 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74378/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74378 - Page: https://openairdocs.org/ntsb/WPR09LA371 ## Probable cause Failure of a seal in the hydraulic system resulting in a loss of hydraulic pressure while maneuvering at low altitude. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Hydraulic power system: hydraulic, main system](https://openairdocs.org/ntsb-findings/01022910): Aircraft › Aircraft systems · Malfunction (probable cause); cases with it: [Sikorsky S55B, 1 case](https://openairdocs.org/ntsb-findings/01022910/cases.md?model=8141603), [All aircraft, 27 cases](https://openairdocs.org/ntsb-findings/01022910/cases.md) - [Terrain: rough terrain](https://openairdocs.org/ntsb-findings/03021015): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Sikorsky S55B, 1 case](https://openairdocs.org/ntsb-findings/03021015/cases.md?model=8141603), [All aircraft, 442 cases](https://openairdocs.org/ntsb-findings/03021015/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: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Sikorsky S55B, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=8141603), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing-landing roll: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Sikorsky S55B, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=8141603), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Sikorsky S55B, 2 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=8141603), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot was using rotor wash to dry cherries at low altitude when the helicopter lost hydraulic pressure. After clearing a stand of trees, the pilot made an emergency run-on landing into a vacant field. During the landing, one of the landing skids hit a large hole, and the main rotor severed the tail boom. Post accident examination revealed that an internal seal had leaked resulting in the loss of pressure in the hydraulic system. ## Factual narrative On July 24, 2009, about 1445 Pacific daylight time, a Sikorsky S-55, N1255T, encountered rough terrain during an off airport emergency landing near Chelan, Washington. The pilot/owner was operating the helicopter under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The certificated commercial pilot was not injured; the helicopter sustained substantial damage to the fuselage from impact forces. The local other work flight departed Chelan about 1245. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot was drying cherries at low altitude when the helicopter lost hydraulic pressure. He flew the helicopter up to clear the trees, and made a run-on landing into a vacant field. The helicopter encountered a large hole that he had not seen, and the main rotor severed the tail boom. The operator reported that post accident examination revealed that an internal seal had leaked resulting in the loss of pressure in the hydraulic system. To date, the National Transportation Safety Board Pilot/Operator Accident Report Form 6120.1/2 has not been submitted. ## Aircraft - Registration: [N1255T](https://openairdocs.org/aircraft/N1255T), registered now, S/N 55607, built 1954 (OpenAirDocs) - Reported make and model: SIKORSKY S-55 - Registry model: [Sikorsky S55B](https://openairdocs.org/model/sikorsky-s55b) (registry code 8141603) (OpenAirDocs) - Registry engine: [AiResearch TSE331 series](https://openairdocs.org/engine/airesearch-tse331-series) (registry code 01505, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 55607 - Airframe hours: 7530 - Engines: Aireasearch TSE331 turbo shaft - Damage: Substantial damage - Flight: Other work use, Part 91 - Operator: David C. Smith - Registered owner: David C. Smith - Airworthiness certificate: Standard, Normal - Departed: Chelan, WA - Destination: Chelan, WA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 67; injuries: none; flight instructor, commercial; airplane ratings: single-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; seat: right; flight hours: 35,000 total, 200 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 300° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: 9,000 ft broken - Temperature: 79 °F, dew point 50 °F - Altimeter: 29.98 inHg - Observed at: KEAT ## 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 20090724012789A](https://openairdocs.org/incident/20090724012789A), Jul 24, 2009: Skrsky S55B, Chelan, WA, Substantial damage. (-23) During cherry-drying hover over orchard, lost hydraulic power, pulled and cleared orchard, selected near-by vacant field and executed precautionary… ## Docket (2 files) The files NTSB released with the investigation on September 15, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74378. 73 KB in all. - Witness Statement - Record of Conversation Pilot (item 1, .PDF, 36 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40332320&FileExtension=.PDF&FileName=Witness%20Statement%20-%20Record%20of%20Conversation%20Pilot-Master.PDF - Record of Conversation FAA (item 2, .PDF, 37 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40332319&FileExtension=.PDF&FileName=Record%20of%20Conversation%20FAA-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.