# NTSB CEN18LA247: Safari 400, N326RW, Aguilares, TX, July 2, 2018 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: July 2, 2018, 11:30 local (16:30 UTC) - Place: Aguilares, TX - Coordinates: 27.149999, -99.11 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=27.1500&lon=-99.1100&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed, report April 13, 2020 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 97655 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN18LA247 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/97655/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=97655 - Page: https://openairdocs.org/ntsb/CEN18LA247 ## Probable cause The loss of tail rotor control due to the in-flight failure of the tail rotor pinion. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Tail rotor drive system](https://openairdocs.org/ntsb-findings/01046500): Aircraft › Aircraft propeller/rotor · Failure (probable cause); cases with it: [Ronnie Koonce SAFARI 400, 1 case](https://openairdocs.org/ntsb-findings/01046500/cases.md?model=05637OM), [All aircraft, 10 cases](https://openairdocs.org/ntsb-findings/01046500/cases.md) - [Performance/control parameters: yaw control](https://openairdocs.org/ntsb-findings/01062024): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Ronnie Koonce SAFARI 400, 1 case](https://openairdocs.org/ntsb-findings/01062024/cases.md?model=05637OM), [All aircraft, 149 cases](https://openairdocs.org/ntsb-findings/01062024/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Ronnie Koonce SAFARI 400, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=05637OM), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Uncontrolled descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Ronnie Koonce SAFARI 400, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=05637OM), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The private pilot departed in an amateur-built helicopter on a local flight for phase I flight test requirements. The helicopter was between 20 and 30 ft above ground level when it started to shudder. The pilot looked for a place to land and then heard a "pop"; the helicopter then lost tail rotor authority. The helicopter started to rotate counterclockwise, and the pilot attempted to stop the rotation without success. The helicopter impacted the ground and rolled onto its left side, which resulted in substantial damage. Postaccident examination of the transmission revealed that the tail rotor pinion had failed. There was no damage to the tail rotor blades or the tail rotor driveshaft. Laboratory examination of the tail rotor pinion revealed that both halves of the pinion shaft fracture surface exhibited mechanical damage by recontact resulting in rubbing of the fracture surfaces. No evidence of a preexisting crack was observed. Microhardness measurement values were consistent with the specifications for the pinion shaft. There were no other mechanical anomalies with the helicopter or its systems that would have precluded normal operations. The lack of damage to the tail rotor blades and tail rotor driveshaft is consistent with the failure of the tail rotor pinion in flight and not as a result of ground impact. Due to the recontact rubbing of the fracture surface, the investigation was not able to determine the exact reason for the pinion failure. ## Factual narrative On July 2, 2018, about 1130 central daylight time, an amateur-built Safari Helicopters 400 helicopter, N326RW, impacted the ground following a loss of control near Aguilares, Texas. The private pilot sustained serious injuries, and the helicopter sustained substantial damage. The helicopter was owned by Panda Ventures, LLC, and was operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no Federal Aviation Administration (FAA) flight plan had been filed for the flight. The personal flight departed Slator Ranch, near Aguilares, Texas, about 1000.According to a statement given to the responding FAA inspector, the pilot was working on the Phase I flight test requirements following the experimental certification of his helicopter. The helicopter had about 25 hours total time since it was built from a commercial kit. The helicopter was in straight and level flight, between 20 and 30 ft above ground level when it started to shudder. The pilot started to look for a place to land; he then heard a "pop" and the helicopter immediately lost tail rotor authority. The helicopter started to rotate counterclockwise, and the pilot attempted to stop the rotation without success. The helicopter impacted the ground and rolled onto its left side. The fuselage was crushed and buckled, and both main rotor blades were substantially damaged. A teardown and examination of the transmission revealed that the tail rotor pinion had failed. The tail rotor pinion was located inside of the transmission. The exterior of the transmission exhibited impact damage at the mast but was otherwise unremarkable. There was no damage to the tail rotor blades or the tail rotor driveshaft. There were no other mechanical anomalies noted with the helicopter or its systems that would have precluded normal operations. The tail rotor pinion was shipped to the National Transportation Safety Board's Materials Laboratory for further examination. Examination revealed that the tail rotor pinion shaft fractured between the portion carrying a beveled gear and that containing a helical gear. Both halves of the pinion shaft fracture surface exhibited mechanical damage by recontact resulting in rubbing of the fracture surfaces. No evidence of a preexisting crack was observed. The overall fracture macro-morphology was consistent with bending overstress. Microhardness measurement values were consistent with the specifications for the pinion shaft. Details of this examination are contained in a specialist report in the public docket for this accident. According to a representative with Safari Helicopters, prior to the accident, Safari Helicopters found that a batch of pinions and gears were not hardened properly. The pinion in the accident helicopter was not part of the batch with the hardening issue. ## Aircraft - Registration: [N326RW](https://openairdocs.org/deregistered/N326RW-2024-01-24), registration cancelled 2024-01-24, S/N 6686, built 2018 (OpenAirDocs) - Reported make and model: SAFARI 400 - Registry model: [Ronnie Koonce SAFARI 400](https://openairdocs.org/model/ronnie-koonce-safari-400) (registry code 05637OM) (OpenAirDocs) - Registry engine: [Aerosport O-360](https://openairdocs.org/engine/aerosport-o-360) (registry code 01300, reciprocating) (OpenAirDocs) - Category: Helicopter, amateur-built - Serial number: 6686 - Year built: 2018 - Airframe hours: 24.33 - Engines: Aero Sport Power Ltd. O-360-C2A 185 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, May 15, 2018 - Departed: Slator Ranch, TX - Destination: Slator Ranch, TX - Equipment: Electronic primary flight display, Electronic multifunction display, ADS-B, Satellite tracking device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 57; injuries: serious; private; airplane ratings: multi-engine land, single-engine land, single-engine sea; medical: class 3, with waivers/limitations; last flight review December 5, 2017; seat: left; restraint: 3-point; flight hours: 13,425 total, 27 in this make and model, 35 in the last 90 days, 10 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 140° at 11 knots, gusting 16 - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 93 °F, dew point 72 °F - Altimeter: 29.96 inHg - Observed at: KLRD, 23 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 20180702009009A](https://openairdocs.org/incident/20180702009009A), Jul 2, 2018: Ronnie Koonce SAFARI 400, Aguilares, TX, Substantial damage. Pilot was attempting to further phase I requirements following certification. During flight the aircraft started to vibrate. The pilot turned and started to… ## Docket (6 files) The files NTSB released with the investigation on November 13, 2019, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=97655. 2.9 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40477986&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Pilot Statement to FAA (item 2, .PDF, 56 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40477987&FileExtension=.PDF&FileName=Pilot%20Statement%20to%20FAA-Master.PDF - Record of Conversation - FAA Inspector (item 3, .PDF, 57 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40477988&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20FAA%20Inspector-Master.PDF - Record of Conversation - Safari Helicopter (item 4, .PDF, 56 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40477989&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Safari%20Helicopter-Master.PDF - NTSB Materials Laboratory Report (item 5, .PDF, 467 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40477990&FileExtension=.PDF&FileName=NTSB%20Materials%20Laboratory%20Report-Master.PDF - Accident Report Photographs (item 6, .PDF, 6 photos, 801 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40477991&FileExtension=.PDF&FileName=Accident%20Report%20Photographs-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.