# NTSB NYC07LA105: Boeing 737-300, N648SW, La Plata, MD, April 25, 2007 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: April 25, 2007, 19:35 local (23:35 UTC) - Place: La Plata, MD - Coordinates: 38.454723, -77.04972 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=38.4547&lon=-77.0497&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 1 serious, 102 uninjured - Status: Completed, report May 6, 2009 - Report: Approved by Office Director - Parties: FAA/FSDO, Southwest Airlines, SWA/Cabin Attendant's Union (TWU-556) - NTSB case key (mKey): 65648 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=NYC07LA105 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/65648/pdf - Page: https://openairdocs.org/ntsb/NYC07LA105 ## Probable cause An in-flight encounter with turbulence and the flight crew's failure to advise the cabin crew about potential forecast turbulence, as reported by the flight attendant. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - In flight encounter with weather, approach - weather forecast - not coordinated/diseminated, flightcrew (cause) - weather condition - turbulence in clouds ## Analysis The flight was descending through a layer of broken clouds during approach for landing when it encountered turbulence. A flight attendant who was standing in the aft galley sustained a fractured ankle. The weather packet issued to the flight crew contained airmen's meteorological information which warned of moderate turbulence for altitudes below 12,000 feet in the accident location. The operator's procedures required the flight crew to brief the cabin crew prior to each flight regarding the forecast turbulence for the trip, but the injured flight attendant stated that the briefing did not contain any significant turbulence potential information, and that there were not any en route turbulence updates. ## Factual narrative HISTORY OF FLIGHT On April 25, 2007, about 1935 eastern daylight time, a Boeing 737-300, N648SW, encountered turbulence while descending in clouds near La Plata, Maryland. One flight attendant sustained serious injuries. The two airline transport pilots, two other flight attendants, and 98 passengers were not injured. The flight was operated by Southwest Airlines, under the provisions of 14 Code of Federal Regulations (CFR) Part 121, as scheduled passenger flight number 111. Instrument meteorological conditions prevailed and an instrument flight rules flight plan had been filed for the flight that departed Birmingham International Airport (BHM), Birmingham, Alabama, and was destined for Baltimore Washington International Airport (BWI), Baltimore, Maryland. The airplane had been slowed to 250 knots, and was descending through a layer of broken clouds during approach for landing when it encountered turbulence. The altitude at the time of the turbulence encounter was approximately 13,000 feet above mean sea level (MSL). The captain stated that the airplane "encountered light turbulence and one moderate jolt," which created a "momentary (less than 1 second) weightless experience." The first officer, who was the pilot flying, stated that "there were no reports of turbulence on the arrival or descent, and the radar did not show any significant weather." The airplane "entered the clouds and began to pick up some light turbulence." The crew "changed the radar to a closer range but saw nothing." The airplane then "experienced a moderate vertical jolt, and dropped suddenly." The first officer estimated that the airplane was in the turbulence "for no more than about a minute." The injured flight attendant said that she was standing alone in the aft galley, working, when "all of a sudden the [airplane] dropped" and she "went up in the air." When she came down, her "left foot turned outwards," she felt a "pop" in her ankle, and her left foot collapsed. She ended up seated on the galley floor, and "couldn't move." According to a second flight attendant, she and a third flight attendant were in the forward galley when they "hit some turbulence." These two flight attendants then took their seats and "buckled up." Both the injured flight attendant and one of the other flight attendants said that the seatbelt sign was illuminated. The flight crew had not advised the cabin crew to be seated before the event occurred. PERSONNEL INFORMATION The captain held an airline transport pilot certificate with multiple ratings, including a type rating for the Boeing 737. Her most recent Federal Aviation Administration (FAA) first-class medical certificate was issued November 16, 2006. The captain reported 12,700 total hours of flight experience in the Boeing 737. The first officer held an airline transport pilot certificate with multiple ratings, including airplane multi-engine land. His most recent FAA first-class medical certificate was issued on May 4, 2006. The first officer reported 4,400 hours of flight experience in the Boeing 737. At the time of the event, the injured flight attendant had been employed in that capacity by the operator for 36 years. In an interview with a Safety Board investigator, the injured flight attendant stated that she had been on this particular trip sequence for approximately six weeks, and was familiar with the passenger loads and the cabin service workload, which she characterized as "pretty busy." On the accident flight, she was wearing leather shoes that she referred to as "flats," which have an enclosed heel, and a heel height of approximately 1/2 inch. AIRCRAFT INFORMATION The airplane was equipped with a weather radar system, and the flight crew reported that they were using the radar during the approach. The airborne weather radar system depicted atmospheric moisture, but did not directly depict atmospheric turbulence. METEOROLOGICAL INFORMATION Terminal Area Forecast The BWI terminal area forecast (TAF) for the period from 1700 to 2000 forecast winds from 090 degrees at 8 knots, 5 miles visibility, light rain showers and mist, and an overcast ceiling at 2,000 feet. Surface Conditions in Vicinity of Turbulence Encounter The 1856 surface observation at Quantico Marine Corps Airfield (NYG), Quantico, Virginia, approximately 11 miles west of the turbulence encounter, reported wind from 060 degrees at 5 knots, visibility 10 miles, broken ceiling at 7,500 feet, overcast ceiling at 9,500 feet, temperature 23 degrees Celsius (C), dew point 14 degrees C, and an altimeter setting of 29.83 inches of mercury. The 1956 NYG surface observation reported wind from 030 degrees at 9 knots, visibility 10 miles, broken ceilings at 7,500 and 10,000 feet, temperature 21 degrees C, dew point 12 degrees C, and an altimeter setting of 29.86 inches of mercury. This report also noted that rain began at 18 minutes past the hour, and ended at 49 minutes past the hour. The weather echoes provided by ground-based Doppler radar located in Sterling Virginia (KLWX), approximately 30 miles northwest of the turbulence encounter location, indicated that the intensity of the radar returns was gradually diminishing over the period bracketing the accident time, consistent with the advent of sunset. In addition, the cells were drifting southeast under the influence of northwesterly upper level winds. The KLWX 1932:04 (2332:04 UTC) 3.52-degree elevation sweep, which had a beam center at about 15,400 feet above mean sea level, showed a very light (5 dBZ) echo just upwind of the turbulence encounter location. The next 3.52-degree scan at 1937:51 (2337:51 UTC) indicated that the same cell was then slightly downwind of the turbulence encounter location. Lower angle beam sweeps before and after the event indicated very light radar returns in the turbulence encounter location. The KLWX weather radar showed no signatures of rapidly developing convective clouds, which are normally associated with strong up- and down-drafts. The flight weather packet issued to the flight crew contained a turbulence AIRMET ("Tango") which was issued at 1645, and was valid until 2300. The AIRMET warned of "moderate turbulence" for altitudes below 12,000 feet for an area which included the location where the turbulence encounter occurred, as well as BWI. The AIRMET also contained the statement "NO SGFNT TURB EXP OUTSIDE CONVTV ACT" which indicated that no significant turbulence could be expected when the airplane was not in clouds that exhibited vertical development. The weather packet did not contain any NOTAMs or PIREPs relevant to this event. FLIGHT RECORDERS Flight recorder data provided by the operator indicated that the airplane experienced a vertical acceleration minimum value of approximately 0.4 of the force of gravity ("g"), followed 1 second later by a positive peak of approximately 2.0g. The corresponding lateral acceleration peak values were approximately 0.09g and -0.06g, respectively. Longitudinal acceleration remained approximately zero until the vertical acceleration peak, when it peaked at approximately 0.06g. The acceleration sensors were installed near the airplane's center of gravity (CG), and since an airborne airplane has freedom of motion in six degrees, the accelerations measured at the CG may not be representative of those experienced elsewhere in the airplane. Accelerations in the cockpit or the aft cabin can be significantly less than or greater than those at the CG, and can differ significantly from each other as well. At the time the airplane experienced the cited acceleration values, the computed airspeed was 230 knots, and the pressure altitude was approximately 13,000 feet. ADDITIONAL INFORMATION The operator's cockpit and cabin procedures required that the flight crew brief the cabin crew prior to each flight regarding the forecast turbulence for the trip. The injured flight attenda ## Aircraft - Registration: [N648SW](https://openairdocs.org/deregistered/N648SW-2024-11-07), registration cancelled 2024-11-07, S/N 27718, built 1997 (OpenAirDocs) - Reported make and model: BOEING 737-300 - Registry model: [Boeing 737-3H4](https://openairdocs.org/model/boeing-737-3h4) (registry code 138447K) (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: 27718 - Airframe hours: 33850 - Engines: CFM International CFM-56-3B1 turbo fan; CFM International CFM-56-3B1 turbo fan - Damage: No damage - Flight: Part 121 - Registered owner: Southwest Airlines Co - Airworthiness certificate: Standard, Normal - Last inspection: Continuous airworthiness, March 1, 2007 - Departed: BHM, Birmingham, AL - Destination: BWI, Baltimore, MD - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; injuries: none; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane, helicopter; medical: class 1, without waivers/limitations; last flight review December 1, 2006; seat: left; flight hours: 12,722 in this make and model - Co-pilot; age 53; injuries: none; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review May 1, 2006; seat: right; flight hours: 4,434 in this make and model ## Weather - Conditions: Instrument (IMC), Night - Wind: 60° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: 7,500 ft broken - Temperature: 73 °F, dew point 57 °F - Altimeter: 29.82 inHg - Observed at: NYG, 12 nm away ## 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 20070425008189A](https://openairdocs.org/incident/20070425008189A), Apr 25, 2007: Boeing 7373H4, Baltimore, MD, No damage. (-23) Short description: flight attendant b was securing aft galley when aircraft dropped. She came down on her left ankle and felt a pop. Passengers assisted… ## Other investigations on N648SW (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 LAX08IA065](https://openairdocs.org/ntsb/LAX08IA065), Feb 24, 2008: Boeing 737-300 (N648SW), Las Vegas, NV, incident, no damage. Probable cause: An inadvertent encounter with severe turbulence during descent and the failure of two passenger seat belt attach fittings. Contributing to the incident was the failure of the operator to comply with… 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.