# NTSB WPR12LA119: Boeing 737-7H4, N915WN, Pawnee, NE, February 23, 2012

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: February 23, 2012, 14:30 local (20:30 UTC)
- Place: Pawnee, NE
- Coordinates: 40.168888, -96.151947 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.1689&lon=-96.1519&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Defining event: [Enroute-cruise: Turbulence encounter](https://openairdocs.org/ntsb-events/360)
- Highest injury: Serious injuries
- Injuries: 1 serious, 1 minor, 138 uninjured
- Status: Completed, report January 31, 2013
- Report: Approved by Office Director
- NTSB office: Western Pacific Region
- Parties: Southwest Airlines, Lincoln FSDO
- NTSB case key (mKey): 82993
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR12LA119
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/82993/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=82993
- Page: https://openairdocs.org/ntsb/WPR12LA119

## Probable cause

The airplane's encounter with moderate turbulence during cruise flight, which resulted in a serious injury to a flight attendant.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Impairment/incapacitation: illness/injury](https://openairdocs.org/ntsb-findings/02012010): Personnel issues › Physical · Cabin crew; cases with it: [Boeing 737-7H4, 2 cases](https://openairdocs.org/ntsb-findings/02012010/cases.md?model=1384404), [All aircraft, 34 cases](https://openairdocs.org/ntsb-findings/02012010/cases.md)
- [Turbulence: clear air turbulence](https://openairdocs.org/ntsb-findings/03032015): Environmental issues › Conditions/weather/phenomena · Effect on operation (probable cause); cases with it: [Boeing 737-7H4, 7 cases](https://openairdocs.org/ntsb-findings/03032015/cases.md?model=1384404), [All aircraft, 78 cases](https://openairdocs.org/ntsb-findings/03032015/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Enroute-cruise: 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

The airplane had been cruising in smooth air conditions for over 30 minutes when it suddenly encountered 2 to 3 seconds of moderate turbulence. The momentary altitude and roll deviation of the airplane, which was corrected by the autopilot, threw one of the flight attendants against the airplane structure, which resulted in a serious injury to her hand. The flight crew had not been given any turbulence advisories by air route traffic controllers, and the flight crew had not overheard any airplanes in the area reporting moderate turbulence. Immediately after the encounter, the airplane continued in smooth air conditions.

## Factual narrative

On February 23, 2012, about 1430 central standard time, a Southwest Airlines Boeing 737-7H4, N915WN, encountered 2 to 3 seconds of moderate turbulence while in cruise flight between Chicago, Illinois, and Los Angles, California. The Captain and the First Officer, both of whom were airline transport pilots, were not injured, nor were any of the 135 passengers. One of the three flight attendants received minor injuries, and a second flight attendant received a serious injury to her right hand. The airplane was not damaged. The 14 Code of Federal Regulations Part 121 scheduled domestic passenger flight, which departed Chicago Midway Airport about 55 minutes prior to the turbulence encounter, was en route to Los Angeles International Airport, Los Angeles, California. At the time of the event, the airplane was in visual meteorological conditions on an Instrument Flight Rules flight plan. According to the flight crew, they were in level cruise flight in smooth air at Flight Level 360, when the airplane experienced the turbulence encounter. Although the airplane had encountered periods of light chop earlier in the flight, it had been in completely smooth air for about 30 minutes prior to the event, and there had been no report of turbulence from the Air Route Traffic Control Center, nor had the flight crew overheard any other aircrew stating that there was anything but smooth air in the area of the encounter. Although the flight attendants were in the process of serving drinks, the passenger seatbelt sign was still on from the earlier period of choppy air. At the moment of the encounter, the airplane experienced both a momentary altitude deviation and a left roll of less than 10 degrees, both of which were corrected by the autopilot, with a slight overshoot past the wings level position. During the encounter sequence, one flight attendant was thrown back against the aft galley door, whereupon her hand hit the recyclable can door. She then immediately felt pain in the hand. At that point in time, the Captain came on the public address system and directed the flight attendants to take their seats immediately, which they did until the flight crew was convinced that they had returned to smooth air conditions. Although the injured flight attendant continued her in-flight duties until the plane landed in Los Angeles, she ultimately went to Urgent Care for treatment. X-rays taken of her hand determined that she had a closed fracture of the carpal bone in her right hand. According to both flight crew members, the airplane reacted in a manner consistent with it flying through the wake of another preceding or crossing airplane, and after the few seconds of the turbulence encounter, followed by the correction by the autopilot, the airplane returned to straight and level flight in smooth air.

## Aircraft

- Registration: [N915WN](https://openairdocs.org/aircraft/N915WN), registered now, S/N 36888, built 2008 (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 series](https://openairdocs.org/engine/cfm-international-cfm56-7b24-series) (registry code 13044, turbo-fan) (OpenAirDocs)
- Category: Airplane
- Serial number: 36888
- Airframe hours: 14201
- Engines: CFM INTL CFM56-7B24 24200 lbs thrust turbo fan; CFM INTL CFM56-7B24 24200 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, February 9, 2012
- Departed: KMDW, Chicago, IL
- Destination: KLAX, Las Angeles, CA
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 52; injuries: none; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review November 2, 2011; seat: left; flight hours: 23,500 total, 20,550 in this make and model, 16,000 as pilot in command, 200 in the last 90 days, 75 in the last 30 days, 7 in the last 24 hours
- Co-pilot; age 44; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review September 17, 2011; seat: right; flight hours: 9,887 total, 6,010 in this make and model, 1,977 as pilot in command, 208 in the last 90 days, 75 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 300° at 19 knots, gusting 25
- Visibility: 10 statute miles
- Lowest ceiling: 3,200 ft overcast
- Temperature: 46 °F
- Altimeter: 29.43 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 20120223005039A](https://openairdocs.org/incident/20120223005039A), Feb 23, 2012: Boeing 737-7H4, Pawnee City, NE, No damage. Review of FDR data,flight plan and pilot statement indicates that aircraft incountered wake turbulence from another aircraft.

## Docket (6 files)

The files NTSB released with the investigation on November 30, 2012, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=82993. 60.1 MB in all.

- Flight Data Recorder 10 - Specialist's Factual Report (item 1, .PDF, 484 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40382232&FileExtension=.PDF&FileName=Flight%20Data%20Recorder%2010%20-%20Specialist%27s%20Factual%20Report-Master.PDF
- Flight Data Recorder 10 - Attachment 1 - Tabular Data - Flight - (CSV Format) (item 2, .CSV, 56.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40368154&FileExtension=.csv&FileName=Flight%20Data%20Recorder%2010%20-%20Attachment%201%20-%20Tabular%20Data%20-%20Flight%20-%20(CSV%20Format)-Master.csv
- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 3, .PDF, 2.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40380272&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF
- Record of Conversation - Captain (item 4, .PDF, 69 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40380263&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Captain-Master.PDF
- Record of Conversation - First Officer (item 5, .PDF, 69 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40380264&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20First%20Officer-Master.PDF
- Record of Conversation - Flight Attendant (item 6, .PDF, 24 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40380265&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Flight%20Attendant-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.

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