# NTSB DCA17CA042: Boeing 737 824, N24202, Denver, CO, December 14, 2016 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Data collection · Final report - Date: December 13, 2016, 18:47 local (Dec 14, 2016, 01:47 UTC) - Place: Denver, CO - Coordinates: 39.86, -104.669998 - Nearby events: https://openairdocs.org/map.md?lat=39.8600&lon=-104.6700&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, 173 uninjured - Status: Completed, report February 23, 2017 - Report: Approved by Office Director - NTSB office: Major Investigations Division - NTSB case key (mKey): 94507 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DCA17CA042 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/94507/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=94507 - Page: https://openairdocs.org/ntsb/DCA17CA042 ## Probable cause An inadvertent encounter with mountain wave 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 737-824, 1 case](https://openairdocs.org/ntsb-findings/03032010/cases.md?model=13844BZ), [All aircraft, 70 cases](https://openairdocs.org/ntsb-findings/03032010/cases.md) - [Turbulence: terrain induced turbulence](https://openairdocs.org/ntsb-findings/03032010): Environmental issues › Conditions/weather/phenomena · Awareness of condition (probable cause); cases with it: [Boeing 737-824, 1 case](https://openairdocs.org/ntsb-findings/03032010/cases.md?model=13844BZ), [All aircraft, 70 cases](https://openairdocs.org/ntsb-findings/03032010/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 737-824, 5 cases](https://openairdocs.org/ntsb-events/360/sequence.md?model=13844BZ), [All aircraft, 423 cases](https://openairdocs.org/ntsb-events/360/sequence.md) ## Analysis On December 13, 2016, at 1847 mountain standard time, United Airlines flight 1545, a Boeing 737-800, N24202, experienced turbulence during descent that resulted in one flight attendant sustaining a serious injury. There were no injuries to the other passengers and crew onboard and the airplane was not damaged. The flight was operating under the provisions of 14 Code of Federal Regulations Part 121 as a regularly scheduled passenger flight from San Francisco International Airport (SFO), California to Denver International Airport (DEN), Colorado. The flight landed at DEN with no further incident. According to the operator, weather forecasts indicated that mountain wave turbulence was expected over the Sierra Nevada mountains and moderate turbulence was forecast for the descent in to DEN below 17,000 feet. As the airplane descended through approximately FL270 the captain advised the flight attendants "it's going to get bumpy" and to be seated. The flight crew reported that passing through approximately FL220 the airplane experienced increasing turbulence and then at about FL200 experienced a "big jolt." The flight attendant in position 2L was securing the galley at the time of the turbulence and was thrown to the ceiling and then struck her face on the galley counter while falling to the floor. She suffered multiple injuries including a large gash to her cheek and a fractured facial bone. ## Factual narrative On December 13, 2016, at 1847 mountain standard time, United Airlines flight 1545, a Boeing 737-800, N24202, experienced turbulence during descent that resulted in one flight attendant sustaining a serious injury. There were no injuries to the other passengers and crew onboard and the airplane was not damaged. The flight was operating under the provisions of 14 Code of Federal Regulations Part 121 as a regularly scheduled passenger flight from San Francisco International Airport (SFO), California to Denver International Airport (DEN), Colorado. The flight landed at DEN with no further incident. According to the operator, weather forecasts indicated that mountain wave turbulence was expected over the Sierra Nevada mountains and moderate turbulence was forecast for the descent in to DEN below 17,000 feet. As the airplane descended through approximately FL270 the captain advised the flight attendants "it's going to get bumpy" and to be seated. The flight crew reported that passing through approximately FL220 the airplane experienced increasing turbulence and then at about FL200 experienced a "big jolt." The flight attendant in position 2L was securing the galley at the time of the turbulence and was thrown to the ceiling and then struck her face on the galley counter while falling to the floor. She suffered multiple injuries including a large gash to her cheek and a fractured facial bone. ## Aircraft - Registration: [N24202](https://openairdocs.org/aircraft/N24202), registered now, S/N 30429, built 2000 (OpenAirDocs) - Reported make and model: BOEING 737 824 (824) - Registry model: [Boeing 737-824](https://openairdocs.org/model/boeing-737-824) (registry code 13844BZ) (OpenAirDocs) - Registry engine: [CFM International CFM56 series](https://openairdocs.org/engine/cfm-international-cfm56-series) (registry code 13802, turbo-fan) (OpenAirDocs) - Category: Airplane - Serial number: 30429 - Year built: 2000 - Engines: CFM INTL. CFM56 SERIES turbo fan; CFM INTL. CFM56 SERIES turbo fan - Damage: No damage - Flight: Part 121 - Operator: United Airlines - Registered owner: Wells Fargo Bank Northwest NA Trustee - Airworthiness certificate: Standard, Transport - Departed: SFO, San Francisco, CA - Destination: DEN, Denver, CO - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 47; injuries: none; commercial, private, airline transport; airplane ratings: single-engine land, multi-engine land, single-engine sea; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review November 24, 2015; seat: left; restraint: 5-point; flight hours: 16,730 total, 4,698 in this make and model, 9,430 as pilot in command, 184 in the last 90 days, 64 in the last 30 days, 5 in the last 24 hours - Co-pilot; age 53; injuries: none; military, commercial, airline transport, private, flight engineer; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, waiver time limited special; last flight review October 25, 2016; seat: right; restraint: lap only; flight hours: 5,960 total, 3,150 in this make and model, 0 as pilot in command, 241 in the last 90 days, 80 in the last 30 days, 7 in the last 24 hours ## Weather - Conditions: Instrument (IMC), Night - Turbulence: Moderate ## Other investigations on N24202 (1) 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 DEN07IA037](https://openairdocs.org/ntsb/DEN07IA037), Dec 16, 2006: Boeing 737-824 (N24202), Colorado Spring, CO, incident, minor damage. Probable cause: A short circuit in the primary (non-rechargeable) battery, most likely due to it being recharged. This internal short led to thermal runaway, battery failure, and an explosion. ## Docket (8 files) The files NTSB released with the investigation on February 23, 2017, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=94507. 4.4 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 596 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40458904&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Flight Crew Statements (item 2, .PDF, 199 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40449532&FileExtension=.PDF&FileName=Flight%20Crew%20Statements-Master.PDF - Cabin Crew Statements (item 3, .PDF, 65 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40449533&FileExtension=.PDF&FileName=Cabin%20Crew%20Statements-Master.PDF - Flight Data Plots and Charts (item 4, .PDF, 520 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40449534&FileExtension=.PDF&FileName=Flight%20Data%20Plots%20and%20Charts-Master.PDF - Flight Release (item 5, .PDF, 371 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40449535&FileExtension=.PDF&FileName=Flight%20Release-Master.PDF - UAL Turbulence Guidance (item 6, .PDF, 444 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40449536&FileExtension=.PDF&FileName=UAL%20Turbulence%20Guidance-Master.PDF - UAL Weather Analysis (item 7, .PDF, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40449537&FileExtension=.PDF&FileName=UAL%20Weather%20Analysis-Master.PDF - Party Form (item 8, .PDF, 72 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40449538&FileExtension=.PDF&FileName=Party%20Form-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.