# NTSB WPR10FA199: Boeing 737-3H4, N624SW, Los Angeles, CA, April 10, 2010 - Type: NTSB accident investigation - Classification: Accident · No injuries · Field investigation · Final report - Date: April 9, 2010, 19:30 local (Apr 10, 2010, 02:30 UTC) - Place: Los Angeles, CA - Coordinates: 33.946666, -118.400276 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.9467&lon=-118.4003&mi=10 - Phase of flight: [Pushback/towing](https://openairdocs.org/ntsb-phases/200) (OpenAirDocs' grouping) - Defining event: [Pushback/tow-engine oper: Ground handling event](https://openairdocs.org/ntsb-events/080) - Highest injury: No injuries - Injuries: 109 uninjured - Status: Completed, report May 23, 2013 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration, Southwest Airlines - NTSB case key (mKey): 75710 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR10FA199 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/75710/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=75710 - Page: https://openairdocs.org/ntsb/WPR10FA199 ## Probable cause The tug operator’s failure to comply with company procedures when parking an unoccupied baggage tug, and the failure of the tug’s seat switch to disengage the electric motor when weight was removed from the driver’s seat. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Action](https://openairdocs.org/ntsb-findings/02041000): Personnel issues › Action/decision · Ground crew (probable cause); cases with it: [Boeing 737-3H4, 1 case](https://openairdocs.org/ntsb-findings/02041000/cases.md?model=138447K), [All aircraft, 111 cases](https://openairdocs.org/ntsb-findings/02041000/cases.md) - [Use of equip/info: use of policy/procedure](https://openairdocs.org/ntsb-findings/02063032): Personnel issues › Task performance · Ground crew (probable cause); cases with it: [Boeing 737-3H4, 1 case](https://openairdocs.org/ntsb-findings/02063032/cases.md?model=138447K), [All aircraft, 191 cases](https://openairdocs.org/ntsb-findings/02063032/cases.md) - [Object/animal/substance: ground vehicle](https://openairdocs.org/ntsb-findings/03022025): Environmental issues › Physical environment · Contributed to outcome (probable cause); cases with it: [Boeing 737-3H4, 1 case](https://openairdocs.org/ntsb-findings/03022025/cases.md?model=138447K), [All aircraft, 132 cases](https://openairdocs.org/ntsb-findings/03022025/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Pushback/tow-engine oper: Ground handling event](https://openairdocs.org/ntsb-events/080) (defining event); cases with it: [Boeing 737-3H4, 3 cases](https://openairdocs.org/ntsb-events/080/sequence.md?model=138447K), [All aircraft, 108 cases](https://openairdocs.org/ntsb-events/080/sequence.md) ## Analysis While the airplane was being pushed back for its flight, it was struck by a runaway baggage tug. The tug operator reported that he stopped on the ramp to pick up two bags. He exited the tug without setting its parking brake, turning off its engine, or placing the gear selector in neutral or park, which was not in accordance with the tug company’s ground equipment general driving rules. The tug operator then placed the first bag on the passenger seat, which company procedures caution against doing. While the tug operator was handling the second bag, the unoccupied tug began to move because the first bag had fallen off the passenger seat onto the accelerator pedal. The tug moved forward, struck a hydrant fueling cart on the ramp, and then veered toward the left side of the airplane. The tug impacted both of the airplane’s engines and its fuselage. If the tug operator had followed company driving rules, the accident could have been prevented. In addition, postaccident examination of the tug revealed that the electrical motor disengaging seat switch, which is designed to disengage the tug's electrical motor when weight is removed from the driver's seat, was inoperative; therefore, it did not prevent the tug from moving forward as designed. ## Factual narrative HISTORY OF FLIGHT On April 9, 2010, about 1930 Pacific daylight time, a Boeing 737-3H4, N624SW, sustained substantial damage when it was struck by a runaway baggage tug at the Los Angeles International Airport, Los Angeles, California. At the time, the airplane had one engine operating and was being pushed back for its flight by a pushback tug. None of the 2 airline transport pilots, the 3 flight attendants, or the 104 passengers were injured. There were no reported ground injuries. The airplane was registered to and operated by Southwest Airlines as flight number 579, under the provisions of Title 14 Code of Federal Regulations Part 121. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed. The scheduled domestic passenger flight had a planned destination of the Tucson International Airport, Tucson, Arizona. In a written statement, an airline ground service employee reported he drove a baggage tug close to gate 3, terminal 1, whereupon he exited the tug with the gear selector in forward and without setting the parking brake or turning off its electric motor. The employee reported he then walked around the tug to pick up two bags that were placed on the ramp. He picked up one of the bags and placed it on the passenger's seat of the unoccupied tug. As the employee was handling the second bag, he observed that the tug had started to move and was traveling in the direction of a hydrant fueling cart that was parked between gates 3 and 5. The ground service employee ran after the tug to get aboard it and attempt to stop its movement. He attempted to apply the brakes but had to exit the tug before it impacted the airplane. He stated that prior to exiting the tug, he noticed that the first bag he had placed on the tug was on the floor and likely resting on the accelerator pedal. The company issued a Safety Advisory (SA 10-06) on the accident that stated that the bag fell off the seat and onto the tug’s accelerator. Ground service employees located on the ramp near gate 3 stated that, initially, the tug rolled forward about 30 feet until it struck a hydrant fueling cart. The runaway tug veered off the side of the cart and continued rolling about 130 feet until it impacted the airplane’s number 1 engine. Subsequently, the tug impacted the left, lower side of the airplane's fuselage and belly, and proceeded beneath the airplane and came to a stop upon impacting the number 2 engine. DAMAGE TO AIRCRAFT Examination of the airplane by maintenance personnel revealed that the fuselage exhibited various skin punctures, dents and an internal frame shear tie was bent. The number 1 engine sustained damage to its cowl. The number 2 engine sustained damage to the engine, engine components, engine cowl and the engine pylon (including wing fairings, pylon structure, and mid-spar fitting to under wing fitting fuse pins). PERSONNEL INFORMATION The 47 year-old tug operator was on his first day back to work following an extendedleave of about 2 months. He has been employed with the company for about 7 ½ years. He received his initial Powered Industrial Truck Training (PITT) on December 13, 2006, and his three year refresher PITT training was completed on October 16, 2009. TESTS AND RESEARCH Examination of the tug by a National Transportation Safety Board (NTSB) investigator revealed that the seat switch was inoperative. According to the tug operator’s guide, when weight is removed from the driver's seat, the seat switch is designed to open the electric circuit thereby disengaging the tug's electrical motor. The weight activated switch is located beneath the driver's seat. Post-accident testing revealed that the tug would not move while pushing down on the accelerator pedal if the parking brake was set or the brakes applied, or with the directional control level in the neutral position. The company ground equipment general driving rules require unoccupied vehicles on the ramp to be placed in park or neutral, with the parking brake set and the engine turned off. The company ground equipment general driving rules has a caution which states never to transport any items (e.g., baggage, freight) on top of or in the passenger seating area of a vehicle. ## Aircraft - Registration: [N624SW](https://openairdocs.org/deregistered/N624SW-2021-05-18), registration cancelled 2021-05-18, S/N 27934, built 1996 (OpenAirDocs) - Reported make and model: BOEING 737-3H4 - Registry model: [Boeing 737-3H4](https://openairdocs.org/model/boeing-737-3h4) (registry code 138447K) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Airplane - Serial number: 27934 - Airframe hours: 46873 - Engines: General Electric CFM 56-3 20000 lbs thrust turbo fan; General Electric CFM 56-3 20000 lbs thrust turbo fan - Damage: Substantial damage - Flight: Part 121 - Operator: Southwest Airlines Co - Registered owner: Southwest Airlines Co - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, April 7, 2010 - Departed: LAX, Los Angeles, CA - Destination: TUS, Tucson, AZ - Flight plan: IFR - Airport: LAX, Los Angeles International, runway 24L, 10,285 × 150 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 56; injuries: none; airline transport; airplane ratings: multi-engine land, single-engine sea; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review November 1, 2009; seat: left; flight hours: 24,760 total, 20,993 in this make and model, 20,014 as pilot in command, 85 in the last 90 days, 4 in the last 30 days, 4 in the last 24 hours - Co-pilot; age 37; injuries: none; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review July 15, 2009; seat: right; flight hours: 10,000 total, 2,000 in this make and model, 5,000 as pilot in command, 225 in the last 90 days, 75 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Dusk - Wind: 240° at 10 knots - Visibility: 8 statute miles - Lowest ceiling: none - Temperature: 57 °F, dew point 50 °F - Altimeter: 29.87 inHg - Observed at: LAX ## 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 20100409034329A](https://openairdocs.org/incident/20100409034329A), Apr 9, 2010: Boeing 737-3H4, Los Angeles, CA, Substantial damage. On April 09, 2010 at 1930 pacific daylight time (pdy) a Boeing 737-3H4 was struk by a runaway baggage tug at the Los Angeles international airport (klax). The… ## Other investigations on N624SW (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 LAX06LA009](https://openairdocs.org/ntsb/LAX06LA009), Oct 13, 2005: Boeing 737-3H4 (N624SW), Phoenix, AZ, substantial damage. Probable cause: The failure of the other flight crew to maintain an adequate clearance from obstructions while taxiing. ## Docket (12 files) The files NTSB released with the investigation on March 19, 2013, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=75710. 2.6 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40385493&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Statement of Pilot (item 2, .PDF, 381 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40384916&FileExtension=.PDF&FileName=Statement%20of%20Pilot-Redacted.PDF - Airport Diagram (item 3, .PDF, 237 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40385494&FileExtension=.PDF&FileName=Airport%20Diagram-Master.PDF - Report of Ramp Supervisor (item 4, .PDF, 228 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40384446&FileExtension=.PDF&FileName=Report%20of%20Ramp%20Supervisor-Redacted.PDF - Record of Interview of Ramp Supervisor (item 5, .PDF, 72 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40385890&FileExtension=.PDF&FileName=Record%20of%20Interview%20of%20Ramp%20Supervisor-Redacted.PDF - Report of Ramp Agent Number 1 (item 6, .PDF, 121 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40384447&FileExtension=.PDF&FileName=Report%20of%20Ramp%20Agent%20Number%201-Redacted.PDF - Report of Ramp Agent Number 2 (item 7, .PDF, 70 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40384448&FileExtension=.PDF&FileName=Report%20of%20Ramp%20Agent%20Number%202-Redacted.PDF - Statement of Ground Service Equipment Foreman (item 8, .PDF, 14 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40384907&FileExtension=.PDF&FileName=Statement%20of%20Ground%20Service%20Equipment%20Foreman-Redacted.PDF - Record of Email (item 9, .PDF, 64 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40385891&FileExtension=.PDF&FileName=Record%20of%20Email-Master.PDF - Safety Bulletin (item 10, .PDF, 59 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40384917&FileExtension=.PDF&FileName=Safety%20Bulletin-Master.PDF - Ground Equipment General Driving Rules (item 11, .PDF, 42 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40385489&FileExtension=.PDF&FileName=Ground%20Equipment%20General%20Driving%20Rules-Redacted.PDF - Statement of Party Representatives to NTSB Investigation (item 12, .PDF, 60 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40385486&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.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.