# NTSB GAA15CA232: Robinson Helicopter R44 II, N804DF, Prairie Lea, TX, July 16, 2015

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Data collection · Final report
- Date: July 16, 2015, 08:30 local (13:30 UTC)
- Place: Prairie Lea, TX
- Coordinates: 29.713054, -97.77639 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=29.7131&lon=-97.7764&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: Minor injuries
- Injuries: 3 minor
- Status: Completed, report December 17, 2015
- Report: Approved by Office Director
- NTSB office: General Aviation Accidents
- Parties: FAA
- NTSB case key (mKey): 91827
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=GAA15CA232
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/91827/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=91827
- Page: https://openairdocs.org/ntsb/GAA15CA232

## Probable cause

The pilot's failure to maintain rotor rpm, resulting in an uncontrolled descent and collision with trees.

## Findings

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

- [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Robinson Helicopter R44 II, 99 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=7640122), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md)
- [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: [Robinson Helicopter R44 II, 17 cases](https://openairdocs.org/ntsb-findings/01062052/cases.md?model=7640122), [All aircraft, 182 cases](https://openairdocs.org/ntsb-findings/01062052/cases.md)
- [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 II, 39 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md?model=7640122), [All aircraft, 1,310 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md)
- [Wind: tailwind](https://openairdocs.org/ntsb-findings/03034015): Environmental issues › Conditions/weather/phenomena · Effect on equipment; cases with it: [Robinson Helicopter R44 II, 13 cases](https://openairdocs.org/ntsb-findings/03034015/cases.md?model=7640122), [All aircraft, 594 cases](https://openairdocs.org/ntsb-findings/03034015/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 II, 45 cases](https://openairdocs.org/ntsb-events/220/sequence.md?model=7640122), [All aircraft, 780 cases](https://openairdocs.org/ntsb-events/220/sequence.md)
- [Uncontrolled descent: Attempted remediation/recovery](https://openairdocs.org/ntsb-events/060); cases with it: [Robinson Helicopter R44 II, 24 cases](https://openairdocs.org/ntsb-events/060/sequence.md?model=7640122), [All aircraft, 1,422 cases](https://openairdocs.org/ntsb-events/060/sequence.md)
- [Uncontrolled descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Robinson Helicopter R44 II, 95 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=7640122), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)

## Analysis

The helicopter pilot reported that while flying at a low altitude and low airspeed, over tree-covered terrain, he made a steep left turn downwind, and the low rotor rpm horn sounded. He stated that he lowered the collective slightly and rolled on throttle, but the helicopter descended and impacted trees and terrain. The pilot reported that he completed a damage assessment and flew the helicopter to his home airport without further incident. Substantial damage was sustained to the helicopter left aft fuselage frame assembly.

## Factual narrative

The helicopter pilot reported that while flying at a low altitude and low airspeed, over tree-covered terrain, he made a steep left turn downwind, and the low rotor rpm horn sounded. He stated that he lowered the collective slightly and rolled on throttle, but the helicopter descended and impacted trees and terrain. The pilot reported that he completed a damage assessment and flew the helicopter to his home airport without further incident. Substantial damage was sustained to the helicopter left aft fuselage frame assembly. The pilot reported that there were no mechanical malfunctions or anomalies prior to or during the flight that would have prevented normal helicopter operation. ADDITIONAL INFORMATION Vortex Ring State (Commonly known as "settling with power") FAA-H-8023-21A identifies, "A vortex ring state may be entered during any maneuver that places the main rotor in a condition of descending in a column of disturbed air and low forward airspeed. Airspeeds that are below translational lift airspeeds are within this region of susceptibility to settling with power aerodynamics (pg. 11-10)." "Some of the situations that are conducive to a settling with power condition are: any hover above ground effect altitude, specifically attempting to hover OGE at altitudes above the hovering ceiling of the helicopter, attempting to hover OGE without maintaining precise altitude control, pinnacle or rooftop helipads when the wind is not aligned with the landing direction, and downwind and steep power approaches in which airspeed is permitted to drop below 10 knots depending on the type of helicopter (pg. 11-10)."

## Aircraft

- Registration: [N804DF](https://openairdocs.org/deregistered/N804DF-2019-11-04), registration cancelled 2019-11-04, S/N 11265, built 2006 (OpenAirDocs)
- Reported make and model: ROBINSON HELICOPTER COMPANY R44 II (II)
- Registry model: [Robinson Helicopter R44 II](https://openairdocs.org/model/robinson-helicopter-r44-ii) (registry code 7640122) (OpenAirDocs)
- Registry engine: [Continental IO-540 series](https://openairdocs.org/engine/continental-io-540-series) (registry code 17051, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 11265
- Year built: 2006
- Airframe hours: 1785.7
- Engines: Lycoming IO-540-AE1A5 260 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, May 1, 2015, 53 hours before
- Departed: X590, Fentress, TX
- Destination: X590, Fentress, TX
- Equipment: Stall warning system

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 61; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review September 1, 2014; seat: right; restraint: 3-point; flight hours: 6,750 total, 1,745 in this make and model, 6,750 as pilot in command, 61 in the last 90 days, 15 in the last 30 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 200° at 11 knots
- Visibility: 10 statute miles
- Lowest ceiling: 2,300 ft broken
- Temperature: 79 °F, dew point 72 °F
- Altimeter: 30.02 inHg
- Observed at: KHYI, 12 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 20150716014379A](https://openairdocs.org/incident/20150716014379A), Jul 16, 2015: Robinson Helicopter Company R44 II, Fentress, TX, Substantial damage. After conducting a downwind manuvering turn the low rotor RPM alert came on. Due to low altitude the pilot was unable to recover and made a hard landing from…

## Other investigations on N804DF (2)

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 GAA17CA165](https://openairdocs.org/ntsb/GAA17CA165), Feb 19, 2017: Robinson Helicopter R44 (N804DF), Spofford, TX, substantial damage. Probable cause: The pilot's decision to hover-taxi out of the hangar and his subsequent failure to maintain clearance from the hangar.
- [NTSB DFW08CA177](https://openairdocs.org/ntsb/DFW08CA177), Jul 5, 2008: Robinson R44 II (N804DF), Canyon Lake, TX, substantial damage. Probable cause: A total loss of tail rotor effectiveness. Contributing to the accident was the pilot's improper decision to operate inside the height velocity curve.

## Docket (2 files)

The files NTSB released with the investigation on December 9, 2015, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=91827. 4.2 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 3.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40434793&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF
- Photo (Courtesy of FAA) (item 2, .PDF, 1 photo, 265 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40434794&FileExtension=.PDF&FileName=Photo%20(Courtesy%20of%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.

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