# NTSB GAA17CA237: Brantly B 2B, N2198U, Earl Park, IN, April 18, 2017

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Data collection · Final report
- Date: April 18, 2017, 10:30 local (15:30 UTC)
- Place: Earl Park, IN
- Coordinates: 40.420833, -87.252502 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.4208&lon=-87.2525&mi=10
- Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping)
- Defining event: [Takeoff: Loss of tail rotor effectiveness](https://openairdocs.org/ntsb-events/242)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report October 31, 2017
- Report: Approved by Office Director
- NTSB office: General Aviation Accidents
- Parties: FAA
- NTSB case key (mKey): 95025
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=GAA17CA237
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/95025/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=95025
- Page: https://openairdocs.org/ntsb/GAA17CA237

## Probable cause

The pilot’s failure to recognize that he was operating in the weathercock stability flight regime of loss of tail rotor effectiveness, which resulted in a loss of directional control during the execution of a right pedal turn.

## Findings

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

- [Info processing/decision: identification/recognition](https://openairdocs.org/ntsb-findings/02041510): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Brantly B-2B, 2 cases](https://openairdocs.org/ntsb-findings/02041510/cases.md?model=1440506), [All aircraft, 559 cases](https://openairdocs.org/ntsb-findings/02041510/cases.md)
- [Planning/preparation: flight planning/navigation](https://openairdocs.org/ntsb-findings/02061025): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Brantly B-2B, 1 case](https://openairdocs.org/ntsb-findings/02061025/cases.md?model=1440506), [All aircraft, 179 cases](https://openairdocs.org/ntsb-findings/02061025/cases.md)
- [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)
- [Performance/control parameters: directional control](https://openairdocs.org/ntsb-findings/01062020): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [Brantly B-2B, 3 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md?model=1440506), [All aircraft, 3,958 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md)
- [Wind: gusts](https://openairdocs.org/ntsb-findings/03034045): Environmental issues › Conditions/weather/phenomena · Effect on operation; 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)

## Sequence of events

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

- [Takeoff: Loss of tail rotor effectiveness](https://openairdocs.org/ntsb-events/242) (defining event); cases with it: [Brantly B-2B, 2 cases](https://openairdocs.org/ntsb-events/242/sequence.md?model=1440506), [All aircraft, 100 cases](https://openairdocs.org/ntsb-events/242/sequence.md)
- [Takeoff: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Brantly B-2B, 8 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=1440506), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md)
- [Takeoff: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Brantly B-2B, 6 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=1440506), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)

## Analysis

The pilot in the helicopter reported that, after 30 minutes of "hover pattern work," he decided to depart the practice area. He reported that the wind at the time of the accident was from 150° between 5 and 15 knots with 30-knot wind gusts. The pilot exited the practice area. He made a right pedal turn at 25 to 30 ft above ground level to return to the practice area. About 120° after beginning the right pedal turn, he felt a high wind gust, and the helicopter began to rotate to the right, "which I could not terminate through the controls." The helicopter descended, struck the ground, and rolled onto its left side. The helicopter sustained substantial damage to the main rotor drive system and the tail rotor drive system. According to the Federal Aviation Administration Helicopter Flying Handbook (FAA-8083-21A), The Helicopter Instructors Flying Handbook (FAA-8083-4), and Advisory Circular (AC) 90-95 Unanticipated Rapid Right Yaw, Loss of Tail Rotor Effectiveness (LTE) is a critical; low-speed aerodynamic flight characteristic which can result in an uncommanded rapid yaw rate which does not subside of its own accord and, if not corrected, can result in the loss of aircraft control. According to FAA-8083-21A, Chapter 11-20, paragraph 2: Weathercock Stability (120–240°) In this region, the helicopter attempts to weathervane, or weathercock, its nose into the relative wind. Unless a resisting pedal input is made, the helicopter starts a slow, uncommanded turn either to the right or left, depending upon the wind direction. If the pilot allows a right yaw rate to develop and the tail of the helicopter moves into this region, the yaw rate can accelerate rapidly. In order to avoid the onset of LTE in this downwind condition, it is imperative to maintain positive control of the yaw rate and devote full attention to flying the helicopter. Weathercock stability is defined as a region of loss of tail rotor effectiveness (120 degree - 240 degree tailwind) that will weathervane the helicopter, and if not prevented will result in a loss of helicopter control about the horizontal axis. The handbook further states: Pilots who put themselves in situations where the combinations above occur should know that they are likely to encounter LTE. The key is to not put the helicopter in a compromising condition but if it does happen being educated enough to recognize the onset of LTE and be prepared to quickly react to it before the helicopter cannot be controlled. According to AC 90-95, Section 10. a. 1-2 (page 8), Recommended Recovery Techniques: a. If a sudden unanticipated right yaw occurs, the pilot should perform the following: (1) Apply full left pedal. Simultaneously, move cyclic forward to increase speed. If altitude permits, reduce power. (2) As recovery is affected, adjust controls for normal forward flight. b. Collective pitch reduction will aid in arresting the yaw rate but may cause an increase in the rate of descent. Any large, rapid increase in collectiveto prevent ground or obstacle contact may further increase the yaw rate and decrease rotor rpm. Per the National Transportation Safety Board Pilot Aircraft Accident Report, the pilot reported that he should have exited the practice area to the west with an immediate left turn to the south, allowed the helicopter to establish translational lift, and increased airspeed and altitude before making a turn to return to the practice area. "My initial plan was flawed from the outset, in retrospect." The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.

## Factual narrative

The pilot in the helicopter reported that after 30 minutes of "hover pattern work" he decided to depart the practice area. He reported that the wind at the time of the accident was from 150° with 30 kt. wind gusts. The pilot tookoff to the northwest. He made a right pedal turn to return to the practice area. About 120° after beginning the right pedal turn, he felt a high wind gust and the helicopter began to rotate to the right "which I could not terminate through the controls." The helicopter descended and struck the ground and rolled onto its left side. The helicopter sustained substantial damage to the main rotor drive system and the tail rotor drive system. According to the Federal Aviation Administration Helicopter Flying Handbook (FAA-8083-21A) and The Helicopter Instructors Flying Handbook (FAA-8083-4) and Advisory Circular (AC) 90-95 Unanticipated rapid right yaw; Loss of Tail Rotor Effectiveness (LTE) is a critical; low-speed aerodynamic flight characteristic which can result in an uncommanded rapid yaw rate which does not subside of its own accord and, if not corrected, can result in the loss of aircraft control. According to the Federal Aviation Administration Helicopter Flying Handbook (FAA-8083-21A), Chapter 11-20, paragraph 2: Weathercock Stability (120–240°) In this region, the helicopter attempts to weathervane, or weathercock, its nose into the relative wind. Unless a resisting pedal input is made, the helicopter starts a slow, uncommanded turn either to the right or left, depending upon the wind direction. If the pilot allows a right yaw rate to develop and the tail of the helicopter moves into this region, the yaw rate can accelerate rapidly. In order to avoid the onset of LTE in this downwind condition, it is imperative to maintain positive control of the yaw rate and devote full attention to flying the helicopter. Weathercock stability is defined as a region of loss of tail rotor effectiveness (120 degree - 240 degree tailwind) that will weathervane the helicopter, and if not prevented will result in a loss of helicopter control about the horizontal axis. According to the Helicopter Flying Handbook (FAA 8083-21A): Pilots who put themselves in situations where the combinations above occur should know that they are likely to encounter LTE. The key is to not put the helicopter in a compromising condition but if it does happen being educated enough to recognize the onset of LTE and be prepared to quickly react to it before the helicopter cannot be controlled. According to Federal Aviation Administration Advisory Circular 90-95, Section 10. a. 1-2 (page 8), Recommended Recovery Techniques: a. If a sudden unanticipated right yaw occurs, the pilot should perform the following: (1) Apply full left pedal. Simultaneously, move cyclic forward to increase speed. If altitude permits, reduce power. (2) As recovery is effected, adjust controls for normal forward flight. b. Collective pitch reduction will aid in arresting the yaw rate butmay cause an increase in the rate of descent. Any large, rapid increase in collective to prevent ground or obstacle contact may further increase the yaw rate and decrease rotor rpm. Per the National Transportation Safety Board Pilot Aircraft Accident Report, the pilot reported that he should have allowed the helicopter to fly establish translational lift, increase airspeed and altitude before making a turn. "My initial plan was flawed from the outset, in retrospect." The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.

## Aircraft

- Registration: [N2198U](https://openairdocs.org/deregistered/N2198U-2018-12-15), registration cancelled 2018-12-15, S/N 409, built 1964 (OpenAirDocs)
- Reported make and model: BRANTLY B 2B
- Registry model: [Brantly B-2B](https://openairdocs.org/model/brantly-b-2b) (registry code 1440506) (OpenAirDocs)
- Registry engine: [Lycoming O&VO-360 series](https://openairdocs.org/engine/lycoming-o-vo-360-series) (registry code 41514, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 409
- Year built: 1964
- Airframe hours: 1269.2
- Engines: Lycoming IVO760 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, May 2, 2015
- Departed: II08, Earl Park, IN
- Destination: II08, Earl Park, IN
- Flight plan: VFR
- Airport: II08, Rheude

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 68; injuries: none; private; medical: class 3, without waivers/limitations; last flight review October 18, 1995; seat: right; restraint: lap only; flight hours: 119.1 total, 10.1 in this make and model, 84.1 as pilot in command

## Weather

- Conditions: Visual (VMC), Day
- Wind: 130° at 14 knots, gusting 17
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 66 °F, dew point 39 °F
- Altimeter: 30.18 inHg
- Observed at: KRZL, 20 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 20170418003339A](https://openairdocs.org/incident/20170418003339A), Apr 18, 2017: Brantly B-2B, Earl Park, IN, Destroyed. On April 18, 2017 at about 1020 eastern daylight time, a Brantly B2-B helicopter, N2198U sustained substantial damage when it impacted a field and rolled on…

## Other investigations on N2198U (1)

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 CHI95LA130](https://openairdocs.org/ntsb/CHI95LA130), Apr 19, 1995: Brantly Helicopter B-2B (N2198U), Winfield, KS, substantial damage. Probable cause: The total failure of the rotor drive system clutch assembly due to excessive wear of the clutch assembly. A factor in this accident was the soft ground in the emergency landing area.

## Docket (2 files)

The files NTSB released with the investigation on September 25, 2017, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=95025. 1.1 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 841 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40456611&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF
- Photos (Courtesy of FAA) (item 2, .PDF, 2 photos, 274 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40456612&FileExtension=.PDF&FileName=Photos%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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