# NTSB GAA16LA117: Helicopteres Guimbal Cabri, N503DS, Beaumont, TX, January 30, 2016 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: January 30, 2016, 10:00 local (16:00 UTC) - Place: Beaumont, TX - Coordinates: 30.071388, -94.214164 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=30.0714&lon=-94.2142&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering-hover: Loss of tail rotor effectiveness](https://openairdocs.org/ntsb-events/242) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report November 29, 2016 - Report: Approved by Office Director - NTSB office: General Aviation Accidents - Parties: FAA Houston FSDO, Bureau d’Enquêtes et d’Analyses - NTSB case key (mKey): 92675 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=GAA16LA117 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/92675/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=92675 - Page: https://openairdocs.org/ntsb/GAA16LA117 ## Probable cause The pilot's inadequate compensation for wind during a hover-taxi and his failure to maintain helicopter control due to a loss of tail rotor effectiveness. ## 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: [Helicopteres Guimbal CABRI G2, 11 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=9000001), [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 · Capability exceeded (probable cause); cases with it: [Helicopteres Guimbal CABRI G2, 2 cases](https://openairdocs.org/ntsb-findings/01062052/cases.md?model=9000001), [All aircraft, 182 cases](https://openairdocs.org/ntsb-findings/01062052/cases.md) - [Wind: gusts](https://openairdocs.org/ntsb-findings/03034045): Environmental issues › Conditions/weather/phenomena · Response/compensation (probable cause); cases with it: [Helicopteres Guimbal CABRI G2, 2 cases](https://openairdocs.org/ntsb-findings/03034045/cases.md?model=9000001), [All aircraft, 1,199 cases](https://openairdocs.org/ntsb-findings/03034045/cases.md) - [Wind: tailwind](https://openairdocs.org/ntsb-findings/03034015): Environmental issues › Conditions/weather/phenomena · Response/compensation (probable cause); cases with it: [Helicopteres Guimbal CABRI G2, 1 case](https://openairdocs.org/ntsb-findings/03034015/cases.md?model=9000001), [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-hover: Other weather encounter](https://openairdocs.org/ntsb-events/400); cases with it: [Helicopteres Guimbal CABRI G2, 1 case](https://openairdocs.org/ntsb-events/400/sequence.md?model=9000001), [All aircraft, 1,127 cases](https://openairdocs.org/ntsb-events/400/sequence.md) - [Maneuvering-hover: Attempted remediation/recovery](https://openairdocs.org/ntsb-events/060); cases with it: [Helicopteres Guimbal CABRI G2, 6 cases](https://openairdocs.org/ntsb-events/060/sequence.md?model=9000001), [All aircraft, 1,422 cases](https://openairdocs.org/ntsb-events/060/sequence.md) - [Maneuvering-hover: Loss of tail rotor effectiveness](https://openairdocs.org/ntsb-events/242) (defining event); cases with it: [Helicopteres Guimbal CABRI G2, 2 cases](https://openairdocs.org/ntsb-events/242/sequence.md?model=9000001), [All aircraft, 100 cases](https://openairdocs.org/ntsb-events/242/sequence.md) - [Maneuvering-hover: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [Helicopteres Guimbal CABRI G2, 7 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=9000001), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Maneuvering-hover: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Helicopteres Guimbal CABRI G2, 10 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=9000001), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis According to the private pilot, after completing a local area flight, he was hover-taxiing the helicopter to the ramp on about a 065-degree heading. Once the helicopter was clear of the taxiway, the helicopter encountered a small wind gust, which the pilot classified as a "tailwind." He corrected the helicopter's subsequent left rotation by applying about one-quarter of right tail rotor pedal and noted that the airspeed was about 20 knots and the altitude was about 10 ft. About 1 second later, the helicopter encountered another more significant wind gust. The pilot noted that he applied full right tail rotor pedal but that the helicopter continued to rotate left and that he then "nudged" the cyclic to the right to "follow the left spin out" and regain control. The pilot was able to stop the forward momentum of the helicopter; however, the left skid contacted the ground, and the helicopter rolled left and impacted terrain. The pilot reported that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation and that he considered this a loss of tail rotor effectiveness event. The pilot reported that the wind at the airport at the time of the accident was from 220 degrees at 14 knots gusting to 24 knots. It is likely that the pilot did not maintain a nose-into-the-wind position and that, when the helicopter began to settle with power, it lost tail rotor effectiveness. ## Factual narrative On January 30, 2016, about 1000 central standard time, a Helicopteres Guimbal Cabri G2 helicopter, N503DS, collided with terrain during a hover taxi at the Beaumont Municipal Airport (BMT), Beaumont, Texas. The private pilot and sole passenger sustained no injury and the helicopter sustained substantial damage. The helicopter was registered to 503 Delta Sierra, LLC, and operated by Neches Helicopter Training, LLC as a day, visual flight rules (VFR) flight under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and no flight plan was filed. The flight originated from the Beaumont Municipal Airport (BMT), about 0830. According to the pilot, after the completion of a local area flight he was hover taxiing to the ramp on about a 065 degree heading to terminate the flight. Once the helicopter was clear of the taxiway, the helicopter encountered a small gust of wind which the pilot classified as a tail wind. He reported that he corrected the left rotation of the helicopter with about one quarter of right tail rotor pedal and noted that his airspeed was about 20 knots and his altitude was about 10 feet. The pilot reported that about one second later, he encountered a second gust of wind much greater than the first gust of wind. The pilot applied full right tail rotor pedal, the helicopter continued to rotate to the left, and he "nudged" the cyclic to the right to "follow the left spin out" and regain control. The pilot was able to stop the forward momentum of the helicopter however the left skid made contact with the ground and the helicopter rolled to the left and impacted terrain. The pilot reported that during this sequence, the helicopter rotated to the left twice terminating at about his original hover taxi heading. He further reported that he considers this a loss of tail rotor effectiveness (LTE) event. The helicopter sustained substantial damage to the fuselage, the main rotor system, the tailboom, and the tail rotor system. The pilot reported that the wind condition at the airport at the time of the accident was 14 knots gusting to 24 knots from 220 degrees. The pilot verified that there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation. ADDITIONAL INFORMATION Helicopteres Guimbal Cabri G2 Flight Testing The manufacturer reported that the helicopter was tested to wind conditions higher than the required 17 knots and found to be without LTE. The Cabri G2 Flight Manual states that a wind speed of 35 knots at all headings was demonstrated at sea level and that a wind speed of 25 knots at all headings was demonstrated at the maximum reduced weight for in ground effect hover performance. Helicopteres Guimbal Cabri G2 Service Letter SL 12-001 Yaw Control in Approach The manufacturer has published a service letter addressing yaw control. This service letter states in part: Extensive flight testing of theCabri G2 and of other helicopters equipped with a Fenestron have shown that such tail rotor, combining a large shroud and a relatively high disk loading, is immune to stall and to vortex-ring state commonly referred to as LTE (Loss of Tail Rotor Efficiency). The service letter also provides guidance with yaw control and states in part: Never wait to correct a sideslip – and particularly to the left – when approaching for a standard landing (30-60 knot approach). Use adequate pedal input without any hesitation. If there is a known cross wind, and particularly from the right hand, pay even more attention to keep the helicopter centerline aligned with the path and be prepared to do large pedals input. Never hesitate to apply full right pedal to correct a yawing to the left before it gets faster. Keep the pedal to its stop, until the rotation stops completely. When practicing spot-turns at low height above the ground, always do it "on the power pedal" – to the right in the Cabri G2 case. Then raising the collective in case of problem will stop the spin. Helicopteres Guimbal Cabri G2 Prolonged Yawing Fuel Sloshing On October 26, 2011 in Gloucestershire, United Kingdom, a Helicopteres Guimbal Cabri G2 sustained substantial damage when the pilot lost yaw control while landing, the engine lost power, and the helicopter landed hard. The Air Accidents Investigation Branch report (EW/G2011/10/16) states in part: The pilot stated that he believed that "slow application of right yaw pedal" was the cause of the accident. The manufacturer also believes that prolonged yawing can cause the engine to stop through fuel sloshing. It is understood that no preimpact mechanical anomalies were found after inspection. Loss of Tail Rotor Effectiveness The Federal Aviation Administration has published the Helicopter Flying Handbook FAA-H-8083-21A (2012).This handbook discusses loss of tail rotor effectiveness and states in part: Loss of tail rotor effectiveness (LTE) or an unanticipated yaw is defined as an uncommanded, rapid yaw towards the advancing blade which does not subside of its own accord. It can result in the loss of the aircraft if left unchecked. It is very important for pilots to understand that LTE is caused by an aerodynamic interaction between the main rotor and tail rotor and not caused from a mechanical failure. Some helicopter types are more likely to encounter LTE due to the normal certification thrust produced by having a tail rotor that, although meeting certification standards, is not always able to produce the additional thrust demanded by the pilot. LTE is an aerodynamic condition and is the result of a control margin deficiency in the tail rotor. It can affect all single rotor helicopters that utilize a tail rotor of some design. The design of main and tail rotor blades and the tail boom assembly can affect the characteristics and susceptibility of LTE but will not nullify the phenomenon entirely. ## Aircraft - Registration: [N503DS](https://openairdocs.org/aircraft/N503DS), registered now, S/N 1099, built 2015 (OpenAirDocs) - Reported make and model: HELICOPTERES GUIMBAL CABRI (G2) - Registry model: [Helicopteres Guimbal CABRI G2](https://openairdocs.org/model/helicopteres-guimbal-cabri-g2) (registry code 9000001) (OpenAirDocs) - Registry engine: [Lycoming O-360-J2A](https://openairdocs.org/engine/lycoming-o-360-j2a) (registry code 42314, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 1099 - Year built: 2015 - Airframe hours: 69.7 - Engines: Lycoming O-360-J2A 145 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, October 6, 2015 - Departed: BMT, Beaumont, TX - Destination: BMT, Beaumont, TX - Airport: BMT, Beaumont Muni, runway 13, 4,001 × 75 ft, asphalt - Equipment: Electronic multifunction display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 35; injuries: none; private; medical: class 3, with waivers/limitations; last flight review September 12, 2015; seat: right; restraint: 4-point; flight hours: 62 total, 22 in this make and model, 24 as pilot in command, 3 in the last 90 days, 1 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 190° at 10 knots, gusting 16 - Visibility: 10 statute miles - Temperature: 68 °F, dew point 57 °F - Altimeter: 30.02 inHg - Observed at: KBMT ## 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 20160130000609A](https://openairdocs.org/incident/20160130000609A), Jan 30, 2016: Helicopteres CABRI-G2, Beaumont, TX, Substantial damage. Pilot made approach to runway 13 at bmt airport. Pilot stated he was headed over to the FBO when his passenger suggested they taxi over and look at the… ## Docket (6 files) The files NTSB released with the investigation on August 8, 2016, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=92675. 4.3 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=40442890&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Accident Photographs (item 2, .PDF, 6 photos, 802 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442891&FileExtension=.PDF&FileName=Accident%20Photographs-Master.PDF - Pilot's Statement (item 3, .PDF, 171 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442892&FileExtension=.PDF&FileName=Pilot%27s%20Statement-Master.PDF - Manufacturer Statement (item 4, .PDF, 173 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442893&FileExtension=.PDF&FileName=Manufacturer%20Statement-Master.PDF - Helicopteres Guimbal Cabri G2 Service Letter 12-001 (item 5, .PDF, 336 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442894&FileExtension=.PDF&FileName=Helicopteres%20Guimbal%20Cabri%20G2%20Service%20Letter%2012-001-Master.PDF - AAIB Report EW/G2011/10/16 (item 6, .PDF, 248 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442895&FileExtension=.PDF&FileName=AAIB%20Report%20EW%2FG2011%2F10%2F16-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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.