# NTSB CEN19LA065: Robinson R44, N484AB, Uvalde, TX, January 8, 2019 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: January 8, 2019, 10:00 local (16:00 UTC) - Place: Uvalde, TX - Coordinates: 29.210277, -99.743057 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=29.2103&lon=-99.7431&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Defining event: [Initial climb: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: Minor injuries - Injuries: 1 minor, 1 uninjured - Status: Completed, report April 13, 2020 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 98883 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN19LA065 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/98883/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=98883 - Page: https://openairdocs.org/ntsb/CEN19LA065 ## Probable cause The slipping of the sprag clutch due to galling of the sprags and corresponding sprag contact surfaces within the clutch assembly, which rendered the helicopter uncontrollable. ## 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 · Malfunction (probable cause); cases with it: [Robinson Helicopter R44 II, 1 case](https://openairdocs.org/ntsb-findings/01046500/cases.md?model=7640122), [All aircraft, 10 cases](https://openairdocs.org/ntsb-findings/01046500/cases.md) - [Performance/control parameters](https://openairdocs.org/ntsb-findings/01062000): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Robinson Helicopter R44 II, 25 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md?model=7640122), [All aircraft, 1,269 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Initial climb: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333); cases with it: [Robinson Helicopter R44 II, 2 cases](https://openairdocs.org/ntsb-events/333/sequence.md?model=7640122), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md) - [Initial climb: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Robinson Helicopter R44 II, 74 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=7640122), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Autorotation: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Robinson Helicopter R44 II, 26 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=7640122), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Autorotation: 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 student pilot and flight instructor were conducting a local, instructional flight. The instructor reported that, as the student was transitioning the helicopter through effective translational lift about 40 knots airspeed, he raised the collective to increase the available power to the takeoff power setting. Shortly thereafter, he heard a loud "pop/bang sound," which was followed by an uncommanded right yaw and severe vibrations. Due to the low altitude and airspeed, the instructor immediately took the flight controls and initiated an autorotation. Upon touchdown, the helicopter tilted forward, and the instructor applied aft cyclic to correct; however, the main rotor blades contacted the tailboom, which resulted in the tailboom partially separating from the helicopter. During postaccident examination of the helicopter, the clutch assembly lubricant was drained, and metallic debris was found in the strainer. Disassembly of the clutch assembly revealed galling of the sprags and the corresponding sprag contact surfaces on the clutch shaft and hub. It is likely that the excessive galling resulted in the sprag clutch slipping, which produced the uncommanded right yaw and led to the student's and instructor's inability to maintain helicopter control. ## Factual narrative On January 8, 2019, about 1000 central standard time, a Robinson R44 II helicopter, N484AB, experienced a hard landing during an autorotation shortly after takeoff from Garner Field Airport, Uvalde, Texas. The flight instructor sustained minor injuries, the student pilot was not injured, and the helicopter sustained substantial damage. The helicopter was registered to and operated by a private individual as a Title 14 Code of Federal Regulations Part 91 instructional flight. Visual meteorological conditions prevailed at the time of the accident, and a flight plan was not filed. The local flight was originating at the time of the accident. According to the flight instructor, all pre-takeoff checks were normal with no anomalies noted. Once the helicopter was through effective translational lift and about 40 knots airspeed, the collective was raised to increase the available power to takeoff power setting. Shortly thereafter, a loud pop/bang was heard followed by an uncommanded right yaw and severe vibrations. Due to the low altitude and airspeed, the flight instructor immediately initiated an autorotation. Upon touchdown, the helicopter tilted forward with the main rotor blades about 6 inches from contacting the ground. The flight instructor applied aft cyclic to correct, and the main rotor blades contacted the tailboom. Postaccident examination of the helicopter revealed the tailboom was partially separated, and the tail rotor driveshaft system was damaged. During the examination, the clutch assembly lubricant was drained and an unusual amount of metallic debris was noted in the strainer. The clutch assembly was removed and sent to Robinson Helicopter Company for further examination. Examination and disassembly of the clutch assembly revealed galling of the sprags and the corresponding sprag contact surfaces on the shaft and hub. According to the Robinson R44 maintenance manual, the clutch assemblies are to be inspected for metallic flakes every 500 hours. The most recent inspection on the clutch assembly was completed on April 18, 2018, about 245 hours prior to the accident. ## Aircraft - Registration: [N484AB](https://openairdocs.org/aircraft/N484AB), registered now, S/N 11390 (OpenAirDocs) - Reported make and model: Robinson R44 (II) - Registry model: [Robinson Helicopter R44 II](https://openairdocs.org/model/robinson-helicopter-r44-ii) (registry code 7640122) (OpenAirDocs) - Registry engine: [Lycoming IO-540-AE1A5](https://openairdocs.org/engine/lycoming-io-540-ae1a5) (registry code 41899, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 11390 - Year built: 2006 - Airframe hours: 1680.9 - Engines: Lycoming IO-540-AE1A5 205 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, November 7, 2018, 245 hours before - Departed: UVA, Uvalde, TX - Destination: UVA, Uvalde, TX - Airport: UVA, Garner Field - Equipment: None ## Flight crew As NTSB recorded them. NTSB leaves out names. - Flight instructor; age 30; injuries: minor; commercial, flight instructor; instrument ratings: helicopter; medical: class 1, with waivers/limitations; last flight review August 15, 2018; seat: left; restraint: 3-point; flight hours: 2,650 total, 1,200 in this make and model, 2,600 as pilot in command, 250 in the last 90 days, 150 in the last 30 days, 5 in the last 24 hours - Student pilot; age 39; injuries: none; private; airplane ratings: single-engine land; medical: class 2, without waivers/limitations; seat: right; restraint: 3-point; flight hours: 400 total, 20 in this make and model, 320 as pilot in command, 25 in the last 90 days, 10 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 77 °F, dew point 59 °F - Altimeter: 29.95 inHg ## 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 20190108000159A](https://openairdocs.org/incident/20190108000159A), Jan 8, 2019: Robinson Helicopter Company R44 II, Uvalde, TX, Substantial damage. On January 8, 2019 at 1000 CDT, a Robinson R44 bearing registration number N484AB, registered to coejo aviation LLC. Impacted terrain immediately following… ## Docket (7 files) The files NTSB released with the investigation on February 21, 2019, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=98883. 6.1 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 857 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40470515&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Maintenance Logbook Entry (item 2, .PDF, 184 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40470516&FileExtension=.PDF&FileName=Maintenance%20Logbook%20Entry-Master.PDF - RHC Clutch Assembly Examination Summary (item 3, .PDF, 3.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40470517&FileExtension=.PDF&FileName=RHC%20Clutch%20Assembly%20Examination%20Summary-Master.PDF - RHC Maintenance Manual - Inspection Schedule (item 4, .PDF, 324 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40470518&FileExtension=.PDF&FileName=RHC%20Maintenance%20Manual%20-%20Inspection%20Schedule-Master.PDF - RHC Maintenance Manual - Clutch Assembly (item 5, .PDF, 563 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40470519&FileExtension=.PDF&FileName=RHC%20Maintenance%20Manual%20-%20Clutch%20Assembly-Master.PDF - RHC Illustrated Parts Catalog - Clutch Assembly (item 6, .PDF, 580 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40470520&FileExtension=.PDF&FileName=RHC%20Illustrated%20Parts%20Catalog%20-%20Clutch%20Assembly-Master.PDF - RHC R44 Service Bulletin SB-79 (item 7, .PDF, 210 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40470521&FileExtension=.PDF&FileName=RHC%20R44%20Service%20Bulletin%20SB-79-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.