# NTSB ERA23LA289: Hughes 269A, N90270, Anderson, SC, June 27, 2023 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 4 · Limited · Final report - Date: June 27, 2023, 17:30 local (21:30 UTC) - Place: Anderson, SC - Coordinates: 34.494583, -82.709389 - Nearby events: https://openairdocs.org/map.md?lat=34.4946&lon=-82.7094&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing: Ground resonance](https://openairdocs.org/ntsb-events/232) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 4 - Basic report with no Prelim publish - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO - NTSB case key (mKey): 192536 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA23LA289 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192536/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=192536 - Page: https://openairdocs.org/ntsb/ERA23LA289 ## Probable cause The mechanics’ improper torquing of the main rotor blade dampers, which resulted in a ground resonance event during landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Maintenance](https://openairdocs.org/ntsb-findings/02062000): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Hughes 269A, 1 case](https://openairdocs.org/ntsb-findings/02062000/cases.md?model=4470402), [All aircraft, 143 cases](https://openairdocs.org/ntsb-findings/02062000/cases.md) - [Main rotor system: main rotor blade system](https://openairdocs.org/ntsb-findings/01046210): Aircraft › Aircraft propeller/rotor · Incorrect service/maintenance (probable cause); cases with it: [Hughes 269A, 1 case](https://openairdocs.org/ntsb-findings/01046210/cases.md?model=4470402), [All aircraft, 60 cases](https://openairdocs.org/ntsb-findings/01046210/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040); cases with it: [Hughes 269A, 1 case](https://openairdocs.org/ntsb-events/040/sequence.md?model=4470402), [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md) - [Landing: Ground resonance](https://openairdocs.org/ntsb-events/232) (defining event); cases with it: [Hughes 269A, 3 cases](https://openairdocs.org/ntsb-events/232/sequence.md?model=4470402), [All aircraft, 21 cases](https://openairdocs.org/ntsb-events/232/sequence.md) ## Analysis Prior to the accident flight, the pilot reported experiencing vibrations in the helicopter. The pilot (who was also a mechanic) and another mechanic adjusted the main rotor dampers to address the issue. Following this adjustment, a 10-minute ground run was performed without any observed problems. The pilot then conducted a test flight during, which no issues were detected. Upon landing and while reducing the rotor rpm, the helicopter began to shake violently. The pilot attempted to perform the ground resonance recovery procedure and climbed the helicopter, but the vibration worsened, and he subsequently landed. After contacting the ground, the helicopter shook and spun uncontrollably before coming to a stop. The airframe and main rotor were substantially damaged during the accident sequence. Federal Aviation Administration inspectors examined the helicopter after the accident and found that the yellow main rotor blade’s damper had significantly higher torque than the red and blue blades, and that none of the dampers were torqued to the specification in the helicopter’s maintenance manual. The manual also described that incorrect torque adjustments of the dampers could result in “…conditions that may result in ground resonance and destruction of the helicopter. During a subsequent discussion with the assisting mechanic, he stated that he, “may have unintentionally over-torqued the blade [damper].” Based on this information, it is likely that the mechanics’ improper maintenance of the helicopter’s main rotor dampers resulted in the ground resonance event experienced at the conclusion of the post maintenance test flight test flight. ## Aircraft - Registration: [N90270](https://openairdocs.org/aircraft/N90270), registered now, S/N 66-18283, built 1966 (OpenAirDocs) - Reported make and model: HUGHES 269A - Registry model: [Hughes 269A](https://openairdocs.org/model/hughes-269a) (registry code 4470402) (OpenAirDocs) - Registry engine: [Lycoming HIO-360 series](https://openairdocs.org/engine/lycoming-hio-360-series) (registry code 41524, reciprocating) (OpenAirDocs) - Category: Helicopter - Serial number: 66-18283 - Year built: 1966 - Airframe hours: 6354 - Engines: Lycoming HIO-360-81A 180 horsepower reciprocating - Damage: Substantial damage - Flight: Flight test, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, September 28, 2022, 3 hours before - Destination: Same as departure - Airport: AND, Anderson Regional Airport - Equipment: Handheld GPS, Onboard weather ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; seat: right; restraint: 4-point; flight hours: 8,460 total, 1,120 in this make and model, 8,212 as pilot in command, 49 in the last 90 days, 18 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 250° at 11 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 86 °F, dew point 63 °F - Altimeter: 29.84 inHg - Observed at: AND - METAR: METAR KAND 272156Z AUTO 25011KT 10SM CLR 30/17 A2984 RMK AO2 SLP093 T03000167= ## 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 20230627019109A](https://openairdocs.org/incident/20230627019109A), Jun 27, 2023: Hughes 269A, Anderson, SC, Substantial damage. The helicopter experienced a vibration earlier in the day. The pilot/[privacy data omitted]/mechanic performed a blade tension check by hand after landing. The… ## Other investigations on N90270 (2) 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 CHI91LA048](https://openairdocs.org/ntsb/CHI91LA048), Dec 26, 1990: Hughes 269A (N90270), Sellersburg, IN, substantial damage. Probable cause: A PILOT INDUCED LOSS OF ENGINE POWER BY INADVERTENT DEACTIVATION OF THE FUEL MIXTURE CONTROL. - [NTSB MIA87LA089](https://openairdocs.org/ntsb/MIA87LA089), Feb 20, 1987: Hughes 269A (N90270), Jacksonville, FL, substantial damage ## Docket (4 files) The files NTSB released with the investigation on December 7, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=192536. 30.3 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 28.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16097302&FileExtension=pdf&FileName=6120%20LA289_Redacted-Rel.pdf - FAA inspectors' statement (item 2, PDF, 3 pages, 125 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16267636&FileExtension=pdf&FileName=Inspectors%20Statements%20N90270_Redacted-Rel.pdf - Pilot / mechanic examination statement (item 3, PDF, 2 pages, 68 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16261051&FileExtension=pdf&FileName=MFR%20pilot%20mechanic%20record%20LA289-Rel.pdf - Investigative photos (item 4, PDF, 6 pages, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16258700&FileExtension=pdf&FileName=Investigative%20photos%20LA289-Rel.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.