# NTSB CEN15IA337: Boeing 737, N779SW, Denver, CO, August 5, 2015 - Type: NTSB incident investigation - Classification: Incident · Minor injuries · Incident investigation · Final report - Date: August 4, 2015, 18:00 local (Aug 5, 2015, 00:00 UTC) - Place: Denver, CO - Coordinates: 39.861667, -104.673057 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.8617&lon=-104.6731&mi=10 - Phase of flight: [Pushback/towing](https://openairdocs.org/ntsb-phases/200) (OpenAirDocs' grouping) - Defining event: [Pushback/tow-engine oper: Ground collision](https://openairdocs.org/ntsb-events/200) - Highest injury: Minor injuries - Injuries: 1 minor, 148 uninjured; on the ground: 1 minor - Status: Completed, report September 12, 2016 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Southwest Airlines, FAA FSDO - NTSB case key (mKey): 91711 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN15IA337 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/91711/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=91711 - Page: https://openairdocs.org/ntsb/CEN15IA337 ## Probable cause The gate lead/pushback driver's failure to recognize that the provisioning truck was within the safety zone of the gate during his walkaround due to distractions, which resulted in the subsequent collision between the airplane and the truck. Contributing to the collision was the provisioning truck driver's failure to recognize he was parked in the safety zone of an active gate adjacent to his assigned gate, and the guide agent's improper assumption that the safety zone was properly cleared by the gate lead/pushback driver. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Attention/monitoring: monitoring environment](https://openairdocs.org/ntsb-findings/02021545): Personnel issues › Psychological · Ground crew (probable cause); cases with it: [Boeing 737-7H4, 1 case](https://openairdocs.org/ntsb-findings/02021545/cases.md?model=1384404), [All aircraft, 809 cases](https://openairdocs.org/ntsb-findings/02021545/cases.md) - [Attention/monitoring: task monitoring/vigilance](https://openairdocs.org/ntsb-findings/02021520): Personnel issues › Psychological · Ground crew (probable cause); cases with it: [Boeing 737-7H4, 2 cases](https://openairdocs.org/ntsb-findings/02021520/cases.md?model=1384404), [All aircraft, 330 cases](https://openairdocs.org/ntsb-findings/02021520/cases.md) - [Communication (personnel): lack of communication](https://openairdocs.org/ntsb-findings/02063510): Personnel issues › Task performance · Ground crew; cases with it: [Boeing 737-7H4, 2 cases](https://openairdocs.org/ntsb-findings/02063510/cases.md?model=1384404), [All aircraft, 84 cases](https://openairdocs.org/ntsb-findings/02063510/cases.md) - [Attention/monitoring: attention](https://openairdocs.org/ntsb-findings/02021510): Personnel issues › Psychological · Ground crew (probable cause); cases with it: [Boeing 737-7H4, 2 cases](https://openairdocs.org/ntsb-findings/02021510/cases.md?model=1384404), [All aircraft, 226 cases](https://openairdocs.org/ntsb-findings/02021510/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 collision](https://openairdocs.org/ntsb-events/200) (defining event); cases with it: [Boeing 737-7H4, 8 cases](https://openairdocs.org/ntsb-events/200/sequence.md?model=1384404), [All aircraft, 618 cases](https://openairdocs.org/ntsb-events/200/sequence.md) ## Analysis During the pushback of a scheduled domestic passenger flight, the airplane's left wing collided with a provisioning truck, rolling the truck onto its side and resulting in minor damage to the airplane. The truck driver stated that he was waiting to service an inbound airplane at the adjacent gate and was likely parked within the safety zone of the incident airplane's gate. The gate lead/pushback driver for the incident airplane stated that he walked past the truck during the pre-pushback walk around but did not recall seeing the truck within the safety zone. The gate lead reported problems with his headset and personal life stress. It is likely that the gate lead was distracted by both during his walk around. Additionally, a guide agent positioned at the airplane's right wing stated that he saw the provisioning truck but assumed that it was not an issue since the gate lead had conducted a walkaround before pushback. ## Factual narrative On August 4, 2015, about 1800 mountain daylight time, a Boeing 737-700 airplane, N779SW, sustained minor damage when it collided with a provisioning truck at Denver International Airport (DEN), Denver, Colorado. The flight crew and passengers on board the airplane were not injured. The driver in the service truck sustained minor injuries. The aircraft was registered to and operated by Southwest Airlines under the provisions of 14 Code of Federal Regulations Part 121 as a scheduled domestic passenger flight. Visual meteorological conditions prevailed prior to and during the ground operations. The flight was originating at the time of the collision.The airplane was parked at Gate C28. A video of the event was provided to the investigator-in-charge by Southwest Airlines. The video started at a time stamp of 05:56:43 PM (MDT) on August 4, 2015. When the video started the provisioning truck was already parked on the far side of the airplane. The following is a timeline of the significant events captured by the video: 05:57:44 – Luggage belt pulls away from the right front side of the airplane 05:58:15 – The jet bridge starts to pull away from the airplane 05:58:36 – The gate lead appears to start his walk around 05:59:02 – The gate lead moves a safety cone from under the left wing and starts to walk towards the rear of the airplane (after this he is no longer visible to the camera) 05:59:29 – The gate lead is visible again under the empennage of the airplane 06:00:28 – The gate lead boards the airplane tug and the wing walker walks towards the right wing tip 06:00:53 – The Southwest Airlines (SWA) airplane scheduled for gate 26 arrives and starts to turn towards the gate 06:01:02 – The tug driver started to push the SWA airplane at gate 28 back as the SA airplane at gate 26 continued to pull in 06:01:17 – The collision between the airplane's left wing and the provisioning truck started 06:01:24 – The airplane stopped moving backwards and the truck stopped its roll The outboard trailing edge of the left wing collided with the fiberglass box on the passenger's side of the provisioning truck. The provisioning truck rolled and came to rest on the driver's side of the truck. The pushback driver immediately stopped the operations and the driver of the provisioning truck egressed from the truck without further incident. The trailing edge of the wing sustained minor impact damage to the skin, 2 inches in width and 18 inches in length. According to an interview with the lead agent/tug driver for gate 28, this was his first airplane of the day. He conducted a walk around the airplane but did not recall seeing the provisioning truck parked inside of the safety area. After understanding that he was cleared to push back by both the wing walker and the pilot, he started to push back. He stopped the push when he felt the tug or jerk of the airplane as it hit the provisioning truck. He commented that his headset was having issues. He also commented that he wasstressed and potentially distracted by personal issues. In an interview with the guide agent, he stated that he did see the provisioning truck but it was not clear to him that it was in the safety area for gate 28. He assumed that it was clear and no issue as the lead agent/tug driver had walked passed it during his walk around and had subsequently announced that the walk around was complete. He was on the opposite side of the airplane during the pushback and commented that a second wing walker would have prevented this from happening. According to an interview with the provisions agent, he had parked outside of the safety area for gate 26 but acknowledged later that he was likely within the safety area for gate 28. He was awaiting an inbound airplane to service at gate 26. He also commented that he had never been told to remain clear of safety areas for adjacent gates, only to move his truck if he were asked. He did not receive such a request from the ground crew for gate 28. The Ground Operations Manual – 5.19.2 Pushback Procedures and Radio Communications and the Prepush Checklist (WN-1095 – REV. 11/12) for the pushback driver included an observation for the driver to ensure that the safety zone was clear of FOD, personnel, and equipment. The Provisioning Manual – Safety Section – 10.5 Driving and Ramp Safety 2.6.7 (Parking of Provisioning Vehicles Between Safety Zones – stated "Employees holding short at the gate for incoming aircraft should always make sure they are outside the safety zone. In addition, they should be aware of incoming flights that are to arrive at the adjacent gate and of flights that are pushing from an adjacent gate." ## Aircraft - Registration: [N779SW](https://openairdocs.org/deregistered/N779SW-2024-10-28), registration cancelled 2024-10-28, S/N 27884, built 2000 (OpenAirDocs) - Reported make and model: BOEING 737 (700) - Registry model: [Boeing 737-7H4](https://openairdocs.org/model/boeing-737-7h4) (registry code 1384404) (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: 27884 - Year built: 2000 - Airframe hours: 54165 - Engines: CFM INTL. CFM56 SERIES turbo fan; CFM INTL. CFM56 SERIES turbo fan - Damage: Minor damage - Flight: Part 121 - Operator: Southwest Airlines - Registered owner: Southwest Airlines - Airworthiness certificate: Standard, Normal - Last inspection: July 29, 2015 - Departed: SAN, San Diego, CA - Destination: SJC, San Jose, CA - Flight plan: IFR - Airport: KDEN, Denver International Airport - Equipment: Electronic flight bag or handheld device, Data recorder, Angle of attack indicator, Stall warning system, Onboard weather, Heads up display, Electronic primary flight display, Electronic multifunction display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 61; injuries: none; airline transport, commercial, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review March 23, 2015; seat: left; restraint: 3-point; flight hours: 22,952 total, 16,152 in this make and model, 19,950 as pilot in command, 203 in the last 90 days, 56 in the last 30 days, 0 in the last 24 hours - Co-pilot; age 39; injuries: none; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review May 9, 2015; seat: right; restraint: 3-point; flight hours: 12,801 total, 2,726 in this make and model, 3,086 as pilot in command, 260 in the last 90 days, 76 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 40° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 41 °F - Altimeter: 30.06 inHg - Observed at: KDEN ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Incident 20150804013609I](https://openairdocs.org/incident/20150804013609I), Aug 4, 2015: Boeing 737-7H4, Denver, CO, Minor damage. On 08/04/2015 at 18:00 hrs MDT, N779SW a Boeing 737-7H4 sustained minor damage during push back from gate C28 at Denver International Airport, CO. There were… ## Docket (11 files) The files NTSB released with the investigation on July 19, 2016, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=91711. 4.1 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442406&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Ramp Employee Statements (item 2, .PDF, 56 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442407&FileExtension=.PDF&FileName=Ramp%20Employee%20Statements-Master.PDF - Provisioning Truck Agent Statement (item 3, .PDF, 28 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442408&FileExtension=.PDF&FileName=Provisioning%20Truck%20Agent%20Statement-Master.PDF - Interview Summary Notes - Pushback Driver - Jefferies (item 4, .PDF, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442409&FileExtension=.PDF&FileName=Interview%20Summary%20Notes%20-%20Pushback%20Driver%20-%20Jefferies-Master.PDF - Interview Summary Notes - Guide Agent - McCormack (item 5, .PDF, 48 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442410&FileExtension=.PDF&FileName=Interview%20Summary%20Notes%20-%20Guide%20Agent%20-%20McCormack-Master.PDF - Interview Summary Notes - Provisioning Agent - Shielly (item 6, .PDF, 48 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442411&FileExtension=.PDF&FileName=Interview%20Summary%20Notes%20-%20Provisioning%20Agent%20-%20Shielly-Master.PDF - Video Summary (item 7, .PDF, 5 photos, 267 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442412&FileExtension=.PDF&FileName=Video%20Summary-Master.PDF - DEN Gate 24, 26, & 28 (item 8, .PDF, 132 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442413&FileExtension=.PDF&FileName=DEN%20Gate%2024,%2026,%20%26%2028-Master.PDF - Southwest Airlines Ground Ops Excerpts (item 9, .PDF, 656 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442414&FileExtension=.PDF&FileName=Southwest%20Airlines%20Ground%20Ops%20Excerpts-Master.PDF - SWA Safety Alert - Ground Ops and Provisioning (item 10, .PDF, 151 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442415&FileExtension=.PDF&FileName=SWA%20Safety%20Alert%20-%20Ground%20Ops%20and%20Provisioning-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 11, .PDF, 644 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40442416&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-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.