# NTSB WPR12LA244: Hiller UH-12B, N93467, Pasco, WA, June 4, 2012

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: June 4, 2012, 06:45 local (13:45 UTC)
- Place: Pasco, WA
- Coordinates: 46.386112, -119.241386 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=46.3861&lon=-119.2414&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering-low-alt flying: Low altitude operation/event](https://openairdocs.org/ntsb-events/220)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report March 13, 2013
- Report: Approved by Office Director
- NTSB office: Western Pacific Region
- Parties: Spokane FSDO
- NTSB case key (mKey): 83846
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR12LA244
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/83846/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=83846
- Page: https://openairdocs.org/ntsb/WPR12LA244

## Probable cause

The pilot's failure to maintain the helicopter's rotor rpm while maneuvering at a low altitude over a fruit orchard.

## Findings

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

- [Performance/control parameters: prop/rotor parameters](https://openairdocs.org/ntsb-findings/01062052): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Hiller UH-12B, 1 case](https://openairdocs.org/ntsb-findings/01062052/cases.md?model=4360110), [All aircraft, 182 cases](https://openairdocs.org/ntsb-findings/01062052/cases.md)
- [Action: incorrect action performance](https://openairdocs.org/ntsb-findings/02041015): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Hiller UH-12B, 1 case](https://openairdocs.org/ntsb-findings/02041015/cases.md?model=4360110), [All aircraft, 1,386 cases](https://openairdocs.org/ntsb-findings/02041015/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: Low altitude operation/event](https://openairdocs.org/ntsb-events/220) (defining event); cases with it: [Hiller UH-12B, 1 case](https://openairdocs.org/ntsb-events/220/sequence.md?model=4360110), [All aircraft, 780 cases](https://openairdocs.org/ntsb-events/220/sequence.md)
- [Maneuvering-low-alt flying: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Hiller UH-12B, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=4360110), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)

## Analysis

The pilot of the helicopter was maneuvering at a low altitude over a fruit orchard to dry the trees. After completing one section of the orchard, he climbed higher in order to check for obstacles near the adjacent orchard that he planned to dry next. While descending into position to work the adjacent orchard, the pilot noticed that the main rotor rpm was beginning to decay. Although he added some power, the rpm decay continued. He therefore made the decision to lower the collective, but realized he was too low to do so. Because he still had some forward airspeed and was able to maintain a controlled descent, the pilot maneuvered to land in an opening between the trees; however, the helicopter impacted trees just before it touched down. A postaccident examination of the engine and airframe revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.

## Factual narrative

On June 4, 2012, about 0645 Pacific daylight time, a Hiller UH-12B helicopter, N93467, impacted fruit trees in an orchard near Pasco, Washington. The commercial pilot, who was the sole occupant, was not injured, but the helicopter, which was being operated by Larsen Helicopter Operations, sustained substantial damage. The 14 Code of Federal Regulations Part 91 fruit orchard drying operation was being performed in visual meteorological conditions. The pilot departed Tri-Cities Airport, Pasco, Washington, about 0615. No flight plan had been filed. According to the pilot, who had just completed drying one section of the orchard with the air blast from his main rotor blades, he ascended to about 100 to 150 feet above the trees in order to look for any obstacles around a separate section of the orchard that he was going to dry next. He then started to descend to the low level that he would be working at over the trees. During that descent, he realized that the helicopter's main rotor rpm, which had been in the lower part of the normal operating range at the beginning of the descent, had begun to decrease. He therefore began to roll on the throttle in order to compensate, but the rpm continued to decay. He then decided to lower the collective in an attempt to recover the rotor rpm, but by then he was about 20 feet above the trees. He therefore rolled the throttle to full power, and tried to pump the collective, but the rpm continued to decay. Because he still had some forward airspeed and enough rotor rpm to keep the helicopter in a controlled slow descent, the pilot maintained a level attitude and maneuvered the helicopter to a position between two rows of trees, where it settled to the terrain in the upright position. Just before the helicopter settled to the terrain, both its main rotor and the tail rotor came in contact with the fruit trees. After an initial examination at the accident site by a Federal Aviation Administration Inspector, the helicopter was taken to the facilities of AvTech Services, in Maple Valley, Washington. There, both the engine and the airframe were examined by an NTSB Aviation Safety Investigator. That examination confirmed spark at all spark plug leads, compression in all cylinders, gear continuity to the accessory section, and normal wear of the spark plug electrodes. In addition, after disassembly, the carburetor bowl was determined to contain a small amount of fuel consistent with aviation low lead, and except for a small sliver of metal in its inlet finger screen, the carburetor showed no evidence of preimpact anomalies or malfunction. The oil filter contained no metal or foreign debris, and the internal gearing appeared to be well lubricated, with no visible sign of thermal distress. The engine could not be test run due to impact damage to the crankcase, but at the time of the completion of the examination, no evidence of any preimpact malfunction associated with the airframe or engine had been found. And, althoughthe pilot reported that during the engine start process it appeared that there may not have been sufficient voltage coming from the battery, he did not report any unusual engine sounds or engine performance irregularities at any time during the flight.

## Aircraft

- Registration: [N93467](https://openairdocs.org/deregistered/N93467-2018-01-10), registration cancelled 2018-01-10, S/N 589, 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 6V4 series](https://openairdocs.org/engine/franklin-6v4-series) (registry code 27033, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 589
- Airframe hours: 3627
- Engines: FRANKLIN 6v-335-b 210 horsepower reciprocating
- Damage: Substantial damage
- Flight: Other work use, Part 91
- Operator: Larsen Helicopter Operations
- Registered owner: Environmental Site Restoration Inc
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, March 18, 2012
- Departed: KPSC, Pasco, WA
- Destination: KPSC, Pasco, WA

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 31; injuries: none; commercial, flight instructor; medical: class 2, without waivers/limitations; last flight review September 21, 2011; seat: center; flight hours: 569 total, 40 in this make and model, 510 as pilot in command, 50 in the last 90 days, 20 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 10 statute miles
- Lowest ceiling: 11,000 ft overcast
- Temperature: 48 °F

## 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 20120604011459A](https://openairdocs.org/incident/20120604011459A), Jun 4, 2012: Hiller UH-12B, Pasco, WA, Substantial damage. Pilot was maneuvering while drying cherries at low altitude, experienced a low RPM condition and put aircraft down into field impacting cherry trees.

## Docket (3 files)

The files NTSB released with the investigation on January 28, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=83846. 2.8 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 2.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40385554&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF
- Engine Examination Report (item 2, .PDF, 43 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40385925&FileExtension=.PDF&FileName=Engine%20Examination%20Report-Master.PDF
- Release of Aircraft Wreckage, NTSB Form 6120.15 (item 3, .PDF, 160 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40385555&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.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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