# NTSB GAA18CA247: Robinson Helicopter R44, N4487D, Sonora, TX, April 18, 2018

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Data collection · Final report
- Date: April 18, 2018, 11:00 local (16:00 UTC)
- Place: Sonora, TX
- Coordinates: 30.211666, -100.4775 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=30.2117&lon=-100.4775&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: 2 uninjured
- Status: Completed, report October 24, 2018
- Report: Approved by Office Director
- NTSB office: General Aviation Accidents
- Parties: FAA
- NTSB case key (mKey): 97156
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=GAA18CA247
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/97156/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=97156
- Page: https://openairdocs.org/ntsb/GAA18CA247

## Probable cause

The pilot’s failure to maintain clearance from trees while maneuvering at a low altitude.

## Findings

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

- [Performance/control parameters: altitude](https://openairdocs.org/ntsb-findings/01062012): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Robinson Helicopter R44, 22 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md?model=7640120), [All aircraft, 1,310 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md)
- [Attention/monitoring: monitoring environment](https://openairdocs.org/ntsb-findings/02021545): Personnel issues › Psychological · Pilot (probable cause); cases with it: [Robinson Helicopter R44, 21 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md?model=7640120), [All aircraft, 809 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md)
- [Object/animal/substance: tree(s)](https://openairdocs.org/ntsb-findings/03022020): Environmental issues › Physical environment · Effect on operation (probable cause); cases with it: [Robinson Helicopter R44, 4 cases](https://openairdocs.org/ntsb-findings/03022020/cases.md?model=7640120), [All aircraft, 933 cases](https://openairdocs.org/ntsb-findings/03022020/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: [Robinson Helicopter R44, 26 cases](https://openairdocs.org/ntsb-events/220/sequence.md?model=7640120), [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: [Robinson Helicopter R44, 56 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=7640120), [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); cases with it: [Robinson Helicopter R44, 43 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=7640120), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md)
- [Landing: Roll over](https://openairdocs.org/ntsb-events/097); cases with it: [Robinson Helicopter R44, 17 cases](https://openairdocs.org/ntsb-events/097/sequence.md?model=7640120), [All aircraft, 261 cases](https://openairdocs.org/ntsb-events/097/sequence.md)

## Analysis

The pilot reported that, while he was spotting deer, the helicopter hit a treetop, damaging the tail rotor. The helicopter began to spin, and the pilot closed the throttle. He landed the helicopter, and it then rolled onto its left side. The helicopter sustained substantial damage to the tailboom and fuselage. The pilot reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation. The pilot's recommendation was to fly at a higher and safer altitude.

## Factual narrative

The pilot reported that, while spotting deer, the helicopter hit the top of a tree damaging the tail rotor. The helicopter began to spin, and the pilot closed the throttle. The helicopter landed and rolled onto its left side. The helicopter sustained substantial damage to the tail boom and fuselage. The pilot reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation. The pilot's recommendation was to fly at a higher and safer altitude.

## Aircraft

- Registration: [N4487D](https://openairdocs.org/deregistered/N4487D-2021-10-30), registration cancelled 2021-10-30, S/N 1654, built 2006 (OpenAirDocs)
- Reported make and model: ROBINSON HELICOPTER R44 (UNDESIGNAT)
- Registry model: [Robinson Helicopter R44](https://openairdocs.org/model/robinson-helicopter-r44) (registry code 7640120) (OpenAirDocs)
- Registry engine: [Lycoming O-540-F1B5](https://openairdocs.org/engine/lycoming-o-540-f1b5) (registry code 42353, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1654
- Year built: 2006
- Airframe hours: 3719.6
- Engines: LYCOMING O-540-F1B5 260 horsepower reciprocating
- Damage: Substantial damage
- Flight: Aerial observation, Part 91
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, April 6, 2018
- Flight plan: Unknown
- Equipment: None

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; injuries: none; commercial; airplane ratings: single-engine land; medical: class 2, without waivers/limitations; last flight review August 19, 2016; seat: right; restraint: 3-point; flight hours: 12,882 total, 9,558 in this make and model, 12,371 as pilot in command, 374 in the last 90 days, 47 in the last 30 days, 7 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 10° at 12 knots, gusting 21
- Visibility: 10 statute miles
- Lowest ceiling: 2,300 ft broken
- Temperature: 70 °F, dew point 59 °F
- Altimeter: 30.11 inHg
- Observed at: KECU, 22 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 20180418003799A](https://openairdocs.org/incident/20180418003799A), Apr 18, 2018: Robinson Helicopter R44, Sonora, TX, Substantial damage. Sonora, TX. N4487D, R-44, while spotting deer for a ground crew, the helicopter hit the top of a tree and took out the tail rotor. Pilot chopped the throttle…

## Docket (2 files)

The files NTSB released with the investigation on July 31, 2018, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=97156. 1.3 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 839 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40465526&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF
- Accident Pictures (item 2, .PDF, 4 photos, 426 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40465527&FileExtension=.PDF&FileName=Accident%20Pictures-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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