# NTSB WPR15LA219: Garlick UH1H, N121PT, Walla Walla, WA, July 21, 2015

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: July 20, 2015, 17:40 local (Jul 21, 2015, 00:40 UTC)
- Place: Walla Walla, WA
- Coordinates: 46.051666, -118.089996
- Nearby events: https://openairdocs.org/map.md?lat=46.0517&lon=-118.0900&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering-hover: Loss of lift](https://openairdocs.org/ntsb-events/500)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report June 5, 2018
- Report: Approved by Office Director
- NTSB office: Western Pacific Region
- Parties: FAA
- NTSB case key (mKey): 91596
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR15LA219
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/91596/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=91596
- Page: https://openairdocs.org/ntsb/WPR15LA219

## Probable cause

The helicopter’s reduction in aerodynamic lift while operating in variable wind conditions for reasons that could not be determined because postaccident examination did not reveal any evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Bell UH-1H, 4 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=1181407), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md)
- [Wind: variable wind](https://openairdocs.org/ntsb-findings/03034025): Environmental issues › Conditions/weather/phenomena · Effect on operation (probable cause); cases with it: [Bell UH-1H, 1 case](https://openairdocs.org/ntsb-findings/03034025/cases.md?model=1181407), [All aircraft, 113 cases](https://openairdocs.org/ntsb-findings/03034025/cases.md)
- [Object/animal/substance: tree(s)](https://openairdocs.org/ntsb-findings/03022020): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Bell UH-1H, 1 case](https://openairdocs.org/ntsb-findings/03022020/cases.md?model=1181407), [All aircraft, 933 cases](https://openairdocs.org/ntsb-findings/03022020/cases.md)
- [Terrain: mountainous/hilly terrain](https://openairdocs.org/ntsb-findings/03021010): Environmental issues › Physical environment · Effect on operation; cases with it: [Bell UH-1H, 2 cases](https://openairdocs.org/ntsb-findings/03021010/cases.md?model=1181407), [All aircraft, 329 cases](https://openairdocs.org/ntsb-findings/03021010/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Maneuvering-hover: Loss of lift](https://openairdocs.org/ntsb-events/500) (defining event); cases with it: [Bell UH-1H, 1 case](https://openairdocs.org/ntsb-events/500/sequence.md?model=1181407), [All aircraft, 252 cases](https://openairdocs.org/ntsb-events/500/sequence.md)
- [Maneuvering-hover: Attempted remediation/recovery](https://openairdocs.org/ntsb-events/060); cases with it: [Bell UH-1H, 1 case](https://openairdocs.org/ntsb-events/060/sequence.md?model=1181407), [All aircraft, 1,422 cases](https://openairdocs.org/ntsb-events/060/sequence.md)
- [Autorotation: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Bell UH-1H, 3 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=1181407), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md)
- [Landing: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Bell UH-1H, 8 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1181407), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)
- [Landing: Roll over](https://openairdocs.org/ntsb-events/097); cases with it: [Bell UH-1H, 3 cases](https://openairdocs.org/ntsb-events/097/sequence.md?model=1181407), [All aircraft, 261 cases](https://openairdocs.org/ntsb-events/097/sequence.md)
- [Post-impact: Fire/smoke (post-impact)](https://openairdocs.org/ntsb-events/170); cases with it: [Bell UH-1H, 1 case](https://openairdocs.org/ntsb-events/170/sequence.md?model=1181407), [All aircraft, 354 cases](https://openairdocs.org/ntsb-events/170/sequence.md)

## Analysis

The commercial pilot reported that the helicopter was in a 165-ft hover in a narrow creek valley, over a shallow creek and that he was filling a fire bucket, which was attached to the helicopter via a long line. The terrain rose between 200 and 400 ft on either side of the creek. About 1 minute into the hover, the pilot felt the helicopter start to settle. He applied collective to arrest the settling, but the helicopter continued to settle. The pilot said that there was no yaw or unusual vibration or noise during the event, only a smooth settling of the helicopter and that the engine did not respond when he manipulated the collective. He immediately lowered the collective and performed a hovering autorotation toward an embankment. When the pilot raised the collective for the landing, the engine did not respond. The rotors struck several trees, then the helicopter spun 180°, landed hard, and rolled over onto its right side. After the accident, the engine continued to run until the pilot shut off the fuel and secured the battery. The helicopter was destroyed by postcrash fire. Postaccident examination of the helicopter did not reveal any evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. Examination of the engine revealed compressor blade damage, rotational scoring witness marks, and metal splatter, consistent with the engine operating at the time of the accident. An automated surface observation system (ASOS) located 10 miles west of the accident reported that, about 1 hour before the accident, the wind was from 250°, gusting to 22 knots. An unofficial weather station located 6 miles southwest of the accident site recorded that, about 3 minutes before the accident, the wind was from 239o at 20 knots, gusting to 30 knots. The ASOS reported that, about 13 minutes after the accident, the wind was from 239o at 14 knots. Given these conditions, orographic wind turbulence could not be ruled out as a factor.

## Factual narrative

Orographic wind affects are discussed in AC-00-57, Hazardous Mountainous Winds and Their Visual Indicators. The following was extracted from Section 3.3 Low-Level Mountain Flying, " Aircraft engaged in low-level flight operations over mountainous terrain in the presence of strong winds (20 kt or greater at ridge level) can expect to encounter moderate or greater turbulence, strong up-and-down drafts, and very strong rotor and shear zones. This is particularly true for general aviation aircraft." On July 20, 2015, about 1740 Pacific daylight time, a Garlick Helicopters, UH-1H, N121PT, landed hard after the pilot sensed that the helicopter was settling while in a high hover, 10 miles east of Walla Walla, Washington. The commercial pilot received minor injuries and the helicopter was destroyed by a postaccident fire. The helicopter was registered to LRH Equipment LLC, and operated under the provisions of 14 Code of Federal Regulations Part 133, under contract to the Oregon State Department of Forestry for firefighting services. Visual meteorological conditions prevailed for the flight, which operated on a company visual flight rules flight plan. The pilot stated to the NTSB investigator-in-charge (IIC) that he was in a 165-foot hover over a shallow creek, filling a fire bucket which was attached to the helicopter via a long line. Filling the fire bucket from the creek takes about 2 minutes. The creek bed was situated in a narrow valley with terrain rising between 200 feet and 400 feet either side of the creek. About 1 minute into the hover, the pilot sensed the helicopter start to settle. He applied collective to arrest the settling but the helicopter continued to settle. The pilot said that there was no yaw, or unusual vibration or noise during the event, only a smooth settling of the helicopter, and the engine system didn't respond when he manipulated the collective. He immediately lowered the collective, and performed a hovering autorotation toward the stream embankment. When he applied up collective for the landing, the engine did not respond. The helicopter's rotors struck a number of trees, the helicopter then turned 180o, landed hard, and rolled over onto its right side. The engine continued to run until the pilot shut off the fuel and secured the battery after the accident. The pilot egressed the helicopter and hiked out of the area. Weather conditions at Walla Walla Regional Airport, Walla Walla, WA, which was 10 miles west of the accident site were reported by the airport operated ASOS (automated surface observation system) at 1753 PDT as wind from 250o at 14 knots, 10 statute miles visibility, clear sky, temperature was 36o C, dew point was -02o C, and atmospheric pressure was 29.83 inHg. About one hour prior to the accident the Walla Walla ASOS recorded wind from 250o degrees, at 13 knots gusting to 22 knots. An unofficial weather station located 6 miles to the southwest of the accident site recorded wind from 239o at 20 knots withgusts of 30 knots at 1743. The pilot stated that the winds in the canyon area were light and variable, and above the canyon the wind was driving the smoke from the fire to the north. The helicopter wreckage was recovered and transported to a storage facility in Auburn, Washington. On October 1, 2015, the wreckage was examined by the NTSB IIC, the pilot, a FAA Inspector, and a technical representative from the engine manufacturer (Honeywell). The helicopter had been exposed to an extreme postcrash fire which destroyed the entire fuselage, engine case, and main transmission case. All major components of the helicopter were laid out, engine, transmission, main rotor hub & blades, tail boom, and tail rotor hub & blades. The remaining wreckage was contained in large agricultural grain bags. The grain bags were emptied one at a time and sorted through by hand. The exam verified that the majority of the helicopter was accounted for, however, the fuel control, droop compensator and half of the KaFlex shaft were not accounted for and presumed to either have been destroyed by the fire or remnants remained at the accident site. Complete accounting of all elements and/or components of the helicopter was not possible. There was no evidence of mechanical malfunctions or failures of the flight control system, main transmission, or rotor systems that would have precluded normal helicopter operation. The engine components were sent to Honeywell, Phoenix, AZ, for further examination. On December 9, 2015, a tear down and inspection of the engine components was conducted at the Honeywell facility in Phoenix, AZ, under the oversight of the NTSB IIC. Honeywell determined that the gas producer section of the engine blade failures were the result of short term overheating beyond the capacity of the blade material accompanied with high rotational speeds resulting in stress rupture of the blades. Metallic splatter was adhered to the combustion chamber deflector. Examination of the compressor section revealed that all of the blades of the axial compressor rotor section were either separated at the platform or were missing from the assembly. The axial compressor vane assemblies were fractured and bent. There was brown earthen debris adhered to the flow path surfaces and vanes of the centrifugal compressor impeller. Several vanes of the centrifugal compressor were bent at the impeller inlet opposite the direction of rotation. There was leading edge damage of all of the vanes at the inlet to the centrifugal compressor impeller. The shroud line edge of all of the centrifugal compressor impeller vanes displayed rotational scoring at the exducer end with corresponding rotational scoring to the impeller shroud. There was earthen debris adhered to the centrifugal compressor shroud. Honeywell concluded that the type and degree of damage was indicative of an engine that was rotating and operating at the time of impact. No pre-existing condition was found that would have preventednormal operation.

## Aircraft

- Registration: [N121PT](https://openairdocs.org/aircraft/N121PT), registered now, S/N 64-13711, built 1964 (OpenAirDocs)
- Reported make and model: GARLICK UH1H
- Registry model: [Bell UH-1H](https://openairdocs.org/model/bell-uh-1h) (registry code 1181407) (OpenAirDocs)
- Registry engine: [Lycoming T-53 series](https://openairdocs.org/engine/lycoming-t-53-series) (registry code 41552, turbo-shaft) (OpenAirDocs)
- Category: Helicopter
- Serial number: 64-13711
- Year built: 1964
- Airframe hours: 12168.9
- Engines: LYCOMING T-53-L-703 1800 horsepower turbo shaft
- Damage: Destroyed
- Fire: On-Ground
- Flight: Firefighting, Part 133
- Operator: Lrh Equipment LLC
- Registered owner: Lrh Equipment LLC
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, June 3, 2015, 4 hours before
- Departed: Walla Walla, WA
- Destination: Walla Walla, WA
- Flight plan: Company VFR
- Equipment: None

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 60; injuries: minor; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review March 15, 2014; seat: left; restraint: 4-point; flight hours: 25,200 total, 2,280 in this make and model, 25,200 as pilot in command, 203 in the last 90 days, 67 in the last 30 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 250° at 14 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 97 °F, dew point 28 °F
- Altimeter: 29.82 inHg
- Observed at: KALW, 10 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 20150720011009A](https://openairdocs.org/incident/20150720011009A), Jul 20, 2015: Bell UH-1H, Walla Walla, WA, Destroyed. Pilot reported rotor RPM decay while hovering to pick up water from a stream for firefighting. No master caution or other warnings were given. Engine RPM was…

## Docket (9 files)

The files NTSB released with the investigation on March 21, 2018, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=91596. 8.5 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40461183&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF
- Maps or Charts of Accident Area (item 2, .PDF, 521 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40461184&FileExtension=.PDF&FileName=Maps%20or%20Charts%20of%20Accident%20Area-Master.PDF
- Weather Reports and Records (item 3, .PDF, 115 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40461185&FileExtension=.PDF&FileName=Weather%20Reports%20and%20Records-Master.PDF
- Airframe and Engine Examination (item 4, .PDF, 18 photos, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40461186&FileExtension=.PDF&FileName=Airframe%20and%20Engine%20Examination-Master.PDF
- Memorandum for Record - Telephone Interview, Pilot (item 5, .PDF, 158 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40461187&FileExtension=.PDF&FileName=Memorandum%20for%20Record%20-%20Telephone%20Interview,%20Pilot-Master.PDF
- Statement of Party Representatives to NTSB Investigation (item 6, .PDF, 2.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40461188&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.PDF
- Release of Aircraft Wreckage, NTSB Form 6120.15 (item 7, .PDF, 558 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40461189&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Master.PDF
- Evidence Control Form (item 8, .PDF, 85 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40461190&FileExtension=.PDF&FileName=Evidence%20Control%20Form-Master.PDF
- On-Scene Photos (Courtesy of AvTech) (item 9, .PDF, 8 photos, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40461191&FileExtension=.PDF&FileName=On-Scene%20Photos%20(Courtesy%20of%20AvTech)-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.

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