# NTSB CEN20CA326: Hughes 369A, N911EP, St Louis, MO, August 6, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 4 · Data collection · Final report - Date: August 6, 2020, 15:15 local (20:15 UTC) - Place: St Louis, MO - Coordinates: 38.663612, -90.644721 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.6636&lon=-90.6447&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing: Hard landing](https://openairdocs.org/ntsb-events/092) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 4 - Basic report with no Prelim publish - NTSB office: Central Region - Parties: FAA FSDO - NTSB case key (mKey): 101751 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN20CA326 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/101751/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=101751 - Page: https://openairdocs.org/ntsb/CEN20CA326 ## Probable cause The flight instructor's failure to maintain helicopter control which resulted in a hard landing while preforming a practice autorotation. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Performance/control parameters: descent rate](https://openairdocs.org/ntsb-findings/01062037): Aircraft › Aircraft oper/perf/capability · Capability exceeded (probable cause); cases with it: [All aircraft, 242 cases](https://openairdocs.org/ntsb-findings/01062037/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Instructor/check pilot (probable cause); cases with it: [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Wind: tailwind](https://openairdocs.org/ntsb-findings/03034015): Environmental issues › Conditions/weather/phenomena · Effect on operation; cases with it: [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. - [Landing: Other weather encounter](https://openairdocs.org/ntsb-events/400); cases with it: [All aircraft, 1,127 cases](https://openairdocs.org/ntsb-events/400/sequence.md) - [Landing: Attempted remediation/recovery](https://openairdocs.org/ntsb-events/060); cases with it: [All aircraft, 1,422 cases](https://openairdocs.org/ntsb-events/060/sequence.md) - [Landing: Hard landing](https://openairdocs.org/ntsb-events/092) (defining event); cases with it: [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) ## Analysis The instructor reported that during the instructional flight, he was manipulating the controls and accepted the option to land on the taxiway; he decreased the throttle for a full touchdown auto rotation. About 50 ft above the ground (agl), he flared the helicopter and leveled off about 5 to 10 ft agl. The instructor reported that everything seemed "normal" at this point. He then raised the collective, but the descent was not arrested, so he raised the collective full up. The helicopter landed hard and shook violently. The instructor closed the throttle to which stopped the fuel supply. The tailboom was substantially damaged. The flight instructor reported that there were no mechanical anomalies with the helicopter that would have precluded normal operation. The instructor added that he felt a slight tailwind after exiting the helicopter and that the tail wind caused a "vortex ring state" which stalled the main rotor blades. ## Aircraft - Registration: N911EP (not matched to a registry record) - Reported make and model: Hughes 369A (No Series) - Category: Helicopter - Serial number: 591176 - Airframe hours: 1229.4 - Engines: Rolls Royce 250-c20C turbo shaft - Damage: Substantial damage - Flight: Public aircraft, Public use - Operator: St Louis County Police Department - Registered owner: St Louis County Police Department - Airworthiness certificate: None - Last inspection: 100 hour, August 4, 2020 - Departed: KSUS, St Louis, MO - Destination: KSUS, St Louis, MO - Airport: KSUS, Spirit of St Louis Airport - Equipment: ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 51; injuries: none; flight instructor, commercial; instrument ratings: helicopter; medical: class 2, with waivers/limitations; seat: left; restraint: 4-point; flight hours: 6,814 total, 6,814 in this make and model, 6,338 as pilot in command - Pilot; age 39; injuries: none; commercial; medical: class 2, without waivers/limitations; last flight review June 18, 2020; seat: right; restraint: 4-point; flight hours: 635 total, 91 in this make and model, 585 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: variable at 3 knots - Visibility: 10 statute miles - Temperature: 81 °F, dew point 55 °F - Altimeter: 30.09 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 20200806008229A](https://openairdocs.org/incident/20200806008229A), Aug 6, 2020: Hughes 369A, Chesterfield, MO, Substantial damage. The pilot and instructor were 1.5 hours into the training for the commercial rated pilot. This was the first landing upon return to their home airport after… ## Docket (2 files) The files NTSB released with the investigation on October 9, 2020, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=101751. 1.5 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=10174098&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Photos (item 2, PDF, 3 pages, 349 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=10173295&FileExtension=pdf&FileName=Photos-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.