# NTSB DCA23LA086: Boeing 737, N946WN, Denver, CO, November 30, 2022 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 4 · Limited · Final report - Date: November 29, 2022, 23:00 local (Nov 30, 2022, 06:00 UTC) - Place: Denver, CO · Estimated by Etcher and Fernando Avila, based on ADSB data and pilot's stmts - Coordinates: 40.309, -105.361 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.3090&lon=-105.3610&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-descent: Turbulence encounter](https://openairdocs.org/ntsb-events/360) - Highest injury: Serious injuries - Injuries: 1 serious, 1 minor, 6 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 4 - Basic report with no Prelim publish - NTSB office: Major Investigations Division - Parties: FAA - NTSB case key (mKey): 106401 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DCA23LA086 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/106401/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=106401 - Page: https://openairdocs.org/ntsb/DCA23LA086 ## Probable cause The flight’s encounter with mechanical turbulence. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Turbulence: terrain induced turbulence](https://openairdocs.org/ntsb-findings/03032010): Environmental issues › Conditions/weather/phenomena · Effect on personnel (probable cause); cases with it: [Boeing 737-7H4, 1 case](https://openairdocs.org/ntsb-findings/03032010/cases.md?model=1384404), [All aircraft, 70 cases](https://openairdocs.org/ntsb-findings/03032010/cases.md) - [Action: forgotten action/omission](https://openairdocs.org/ntsb-findings/02041035): Personnel issues › Action/decision · Cabin crew; cases with it: [Boeing 737-7H4, 2 cases](https://openairdocs.org/ntsb-findings/02041035/cases.md?model=1384404), [All aircraft, 440 cases](https://openairdocs.org/ntsb-findings/02041035/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-descent: Turbulence encounter](https://openairdocs.org/ntsb-events/360) (defining event); cases with it: [Boeing 737-7H4, 16 cases](https://openairdocs.org/ntsb-events/360/sequence.md?model=1384404), [All aircraft, 423 cases](https://openairdocs.org/ntsb-events/360/sequence.md) ## Analysis Southwest Airlines flight 136 encountered turbulence while descending through 15,600 ft into Denver International Airport (DEN), Denver, Colorado, and a flight attendant fractured her ribs. During the brief for the flight preceding the accident flight, the captain notified FA “A” that he would be requesting that the FAs take their seats about 25 minutes before their arrival at DEN. The captain stated that this was a routine part of his briefings for flights into DEN due to the unpredictable weather. FA “A” stated that she had been busy with her duties and about 4 hours had passed since the briefing. Subsequently, she had forgot to share this information with the other FAs. About 35 minutes before landing, the captain asked the cabin crew to clean up the cabin and take their seats. All three FAs located vacant passenger seats in the cabin and were seated. When the captain “double chimed” the cabin at about 16,000 ft (indicating the cabin should be secured early), all three FAs stood up to return to their jump seats. Shortly thereafter, the airplane experienced moderate turbulence. FA “B” reported that as she was walking through the aisle, the turbulence occurred, and the airplane “dropped”. She went into the air before falling onto a row of seats. As she attempted to sit in one of the seats, the airplane dropped again, and she fell to the floor. Following the turbulence, the first officer stated that he gave a pilot report (PIREP) to air traffic control at DEN and the flight proceeded to its destination and landed without further incident. After landing, the flight crew was informed that FA “B” required medical attention. Emergency medical services arrived and transported FA “B” to the emergency room where she was diagnosed with multiple rib fractures. A post-accident review of meteorological conditions showed no significant meteorological information (SIGMETs). Upper air model data at the time of the accident revealed limited wind shear around the accident altitude. Weather radar data from the National Weather Service station located in Watkins, Colorado (located 6 nautical miles southeast of DEN) showed no reflectivity that suggested convective activity or other precipitation. There was one applicable PIREP from about 85 minutes earlier that reported moderate turbulence between 10,000 ft and 13,500 ft (MSL) about 35 miles east-southeast of the accident location near DEN. Analysis of the aggregate weather information suggested the turbulence was likely mechanical in nature and caused by significant surface winds in the vicinity of mountainous terrain. ## Aircraft - Registration: [N946WN](https://openairdocs.org/aircraft/N946WN), registered now, S/N 36918, built 2010 (OpenAirDocs) - Reported make and model: BOEING 737 (7H4) - Registry model: [Boeing 737-7H4](https://openairdocs.org/model/boeing-737-7h4) (registry code 1384404) (OpenAirDocs) - Registry engine: [CFM International CFM56-7B24/3 series](https://openairdocs.org/engine/cfm-international-cfm56-7b24-3-series) (registry code 13074, turbo-fan) (OpenAirDocs) - Category: Airplane - Serial number: 36918 - Year built: 2010 - Airframe hours: 40908 - Engines: CFM INTL CFM56-7B24/3 22800 lbs thrust turbo fan; CFM INTL CFM56-7B24/3 22800 lbs thrust turbo fan - Damage: No damage - Flight: Part 121 - Operator: Southwest Airlines Co - Registered owner: Southwest Airlines Co - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, November 24, 2022 - Departed: SLC, Salt Lake City, UT - Destination: DEN, Denver, CO - Flight plan: IFR - Equipment: Angle of attack indicator, Auto-pilot, Data recorder, ADS-B, Electronic flight bag or handheld device, Electronic multifunction display, Electronic primary flight display, Heads up display, Onboard weather, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 50; injuries: none; commercial, airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review November 6, 2022; seat: left; flight hours: 14,954 total, 12,568 in this make and model, 141 in the last 90 days, 69 in the last 30 days, 0 in the last 24 hours - Co-pilot; age 37; injuries: none; airline transport, private, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review November 14, 2022; seat: right; flight hours: 2,280 total, 25 in this make and model, 880 as pilot in command, 25 in the last 90 days, 25 in the last 30 days, 0 in the last 24 hours - Cabin crew; injuries: none; seat: none; restraint: lap only - Cabin crew; injuries: serious; seat: none; restraint: none - Cabin crew; injuries: minor; seat: none; restraint: none ## Weather - Conditions: Visual (VMC), Night - Wind: 150° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 52 °F, dew point 57 °F - Altimeter: 30.00 inHg - Turbulence: Moderate - Observed at: KDEN ## Docket (3 files) The files NTSB released with the investigation on October 16, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=106401. 4.2 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 2.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16216349&FileExtension=pdf&FileName=SWA%20136%206120_print_Redacted3-Rel.pdf - Crew statements (item 2, PDF, 5 pages, 221 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15730202&FileExtension=pdf&FileName=SWA%20136%20Crew%20Statements_Redacted-Rel.pdf - Meteorology - weather, swa 136 (item 3, PDF, 2 pages, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=15932184&FileExtension=pdf&FileName=DCA23LA086_Weather_SWA136_Redacted-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.