# NTSB CEN10CA371: Brantly B-2B, N9011R, East Troy, WI, July 4, 2010

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Data collection · Final report
- Date: July 4, 2010, 17:45 local (22:45 UTC)
- Place: East Troy, WI
- Coordinates: 42.797222, -88.372497 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=42.7972&lon=-88.3725&mi=10
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Defining event: [Landing: Roll over](https://openairdocs.org/ntsb-events/097)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report December 20, 2010
- Report: Approved by Office Director
- NTSB office: Central Region
- Parties: Federal Aviation Administration
- NTSB case key (mKey): 76534
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN10CA371
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/76534/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=76534
- Page: https://openairdocs.org/ntsb/CEN10CA371

## Probable cause

The pilot's failure to maintain control during landing.

## 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: [Brantly B-2B, 6 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=1440506), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md)
- [Wind: gusts](https://openairdocs.org/ntsb-findings/03034045): Environmental issues › Conditions/weather/phenomena · Not specified; cases with it: [Brantly B-2B, 4 cases](https://openairdocs.org/ntsb-findings/03034045/cases.md?model=1440506), [All aircraft, 1,199 cases](https://openairdocs.org/ntsb-findings/03034045/cases.md)
- [Wind: crosswind](https://openairdocs.org/ntsb-findings/03034040): Environmental issues › Conditions/weather/phenomena · Not specified; cases with it: [Brantly B-2B, 1 case](https://openairdocs.org/ntsb-findings/03034040/cases.md?model=1440506), [All aircraft, 1,008 cases](https://openairdocs.org/ntsb-findings/03034040/cases.md)

## Sequence of events

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

- [Landing: Roll over](https://openairdocs.org/ntsb-events/097) (defining event); cases with it: [Brantly B-2B, 3 cases](https://openairdocs.org/ntsb-events/097/sequence.md?model=1440506), [All aircraft, 261 cases](https://openairdocs.org/ntsb-events/097/sequence.md)

## Analysis

The helicopter pilot performed a straight-in autorotation to runway 18 for a rotor rpm check. The engine rpm began to rapidly increase and the pilot rolled the throttle completely off and lowered collective. He reported that the left skid was coming off the ground and he applied full left cyclic and full down collective. The aircraft teetered and continued to roll right. The pilot stated that the helicopter had an articulated landing gear system. He said that the struts travel approximately seven to eight inches and “if only one side retracts it causes a ‘rolling moment’.” About 22 minutes before the accident, the recorded winds about seven nautical miles and 155 degrees from the accident site were 200 degrees at 14 knots with gusts to 32 knots. An examination of the accident helicopter’s controls and landing gear revealed no preexisting anomalies.

## Factual narrative

Maintenance was performed on the aircraft’s fuel system and flight test was required. The pilot made a normal takeoff with a right hand traffic pattern. A normal approach was performed with a go-around. A second right pattern to runway 18 was performed. The pilot performed a straight-in auto-rotation for a rotor RPM check. He stated that he flared at 25 feet above the ground, leveled at 5 feet with the “(power off),” and then performed a hovering auto-rotation where both skids contacted the ground with zero forward airspeed and a heading was maintained. The pilot noticed the engine RPM began to rapidly increase and he rolled the throttle completely off and lowered collective. He reported that the left skid was coming off the ground and he applied full left cyclic and full down collective. The aircraft teetered with the left skid approximately four to six inches above ground and the aircraft continued to roll right. The pilot stated, “I believe the maneuver was performed successfully and either a strong wind gust or mechanical defect caused the roll over.” The pilot subsequently stated that the helicopter had an articulated landing gear system. He said that the struts travel approximately seven to eight inches and “if only one side retracts it causes a ‘rolling moment’.” About 22 minutes before the accident, the recorded winds about seven nautical miles and 155 degrees from the accident site were 200 degrees at 14 knots with gusts to 32 knots. An examination of the accident helicopter’s controls and landing gear revealed no anomalies.

## Aircraft

- Registration: [N9011R](https://openairdocs.org/aircraft/N9011R), registered now, S/N 2013 (OpenAirDocs)
- Reported make and model: BRANTLY B-2B
- Registry model: [Brantly B-2B](https://openairdocs.org/model/brantly-b-2b) (registry code 1440506) (OpenAirDocs)
- Category: Helicopter
- Serial number: 2013
- Airframe hours: 602
- Engines: Lycoming IVO-360 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Flight test, Part 91
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, July 4, 2010
- Departed: 57C, East Troy, WI
- Destination: 57C, East Troy, WI
- Airport: 57C, East Troy Municipal Airport, runway 18, grass/turf

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 28; injuries: none; flight instructor, commercial; instrument ratings: helicopter; medical: class 1, without waivers/limitations; last flight review June 10, 2010; seat: right; flight hours: 2,603 total, 70 in this make and model, 2,575 as pilot in command, 200 in the last 90 days, 85 in the last 30 days, 0 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 200° at 14 knots, gusting 32
- Visibility: 10 statute miles
- Lowest ceiling: 9,000 ft broken
- Temperature: 79 °F, dew point 70 °F
- Altimeter: 29.88 inHg
- Observed at: BUU, 7 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 20100704055359A](https://openairdocs.org/incident/20100704055359A), Jul 4, 2010: Brantly B-2B, East Troy, WI, Substantial damage. Pilot landed the helicopter from a hovering autorotation on the turf runway 18 at East Troy Municipal Airport (57C) at the conclusion of a maintenance check…

## Docket (2 files)

The files NTSB released with the investigation on August 12, 2010, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=76534. 1.2 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40333630&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF
- Additional Statement to Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 2, .PDF, 106 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40333632&FileExtension=.PDF&FileName=Additional%20Statement%20to%20Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-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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