# NTSB WPR13IA226: Boeing 737-7H4, N913WN, Phoenix, AZ, May 10, 2013 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: May 10, 2013, 09:07 local (16:07 UTC) - Place: Phoenix, AZ - Coordinates: 33.433887, -112.006942 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=33.4339&lon=-112.0069&mi=10 - Phase of flight: [Pushback/towing](https://openairdocs.org/ntsb-phases/200) (OpenAirDocs' grouping) - Defining event: [Pushback/tow-engine start-up: Ground collision](https://openairdocs.org/ntsb-events/200) - Highest injury: No injuries - Injuries: 59 uninjured - Status: Completed, report July 30, 2014 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration, Southwest Airlines - NTSB case key (mKey): 86861 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR13IA226 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/86861/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=86861 - Page: https://openairdocs.org/ntsb/WPR13IA226 ## Probable cause The failure of the tug operator and wing walker to adequately monitor the environment during pushback of the airplane from the gate in preparation for flight, which led to the collision of the airplane with an adjacently parked airplane. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Use of equip/info: use of equip/system](https://openairdocs.org/ntsb-findings/02063015): Personnel issues › Task performance · Ground crew (probable cause); cases with it: [Boeing 737-7H4, 2 cases](https://openairdocs.org/ntsb-findings/02063015/cases.md?model=1384404), [All aircraft, 1,391 cases](https://openairdocs.org/ntsb-findings/02063015/cases.md) - [Attention/monitoring: monitoring other aircraft](https://openairdocs.org/ntsb-findings/02021540): Personnel issues › Psychological · Ground crew (probable cause); cases with it: [Boeing 737-7H4, 2 cases](https://openairdocs.org/ntsb-findings/02021540/cases.md?model=1384404), [All aircraft, 231 cases](https://openairdocs.org/ntsb-findings/02021540/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 start-up: 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 While being pushed back from the gate by a tug in preparation for flight, the airplane collided with an airplane parked to its right. The pushback into an adjacent alleyway required the tug operator to accomplish a turn reversal to properly align the airplane. Further, the tug operator and wing walker slowed down the tug's speed during the turn to ensure that they avoided baggage carts located near the right engine. The turn was performed too tightly, and, when the tug operator's and wing walker's attention was focused on clearing the nearby carts, the airplane's right winglet struck the parked, unoccupied airplane's left horizontal stabilizer and elevator. ## Factual narrative On May 10, 2013, about 0907 mountain standard time, a Boeing 737-7H4, N913WN, collided with a parked, unoccupied Boeing 737-7H4, N776WN, at the Sky Harbor International Airport, Phoenix, Arizona. The airplane had one engine operating and was being pushed back for its flight by a pushback tug. The 2 airline transport pilots, 3 flight attendants and 54 passengers were not injured. There were no reported ground injuries. The airplane was registered to and operated by Southwest Airlines 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 Reno International Airport, Reno, Nevada, and was originating at the time. According to company ground personnel, the airplane was parked at gate C-1, which is positioned next to the terminal building. An unoccupied, adjacently parked airplane was on its right side, at gate C-3. The parking gate required the airplane to be pushed back into an adjacent alleyway. A turn reversal unto the alleyway, commonly referred to as a "S" type turn maneuver, would be accomplished. Performing this type of turn initially required the tug operator to turn towards the airplane parked on its right side, until adequate spacing was achieved with the terminal building, and then turn in the opposite direction for nearly 180 degrees, to correctly position the airplane in the alleyway. During the turn towards the parked airplane, the wing walker reported that the pushback tug operator turned tight. Also during the turn, the wing walker further reported that they had to slow down the tug's speed in order to ensure they avoided the baggage carts located near the right engine. With their attention focused on clearing the airplane's engine from the nearby carts, the wing walker looked back, and noticed the right wing tip moving towards the left horizontal stabilizer of the adjacently parked airplane, but was unable to get the tug operators attention in time to stop. Subsequently, the airplane's right winglet struck the parked, unoccupied airplane's left horizontal stabilizer and elevator. The pushback tug operator was hired in the previous year, and was qualified on the tug. During an interview with the National Transportation Safety Board (NTSB) investigator in charge (IIC), he stated that he has performed numerous pushbacks at similar gates near the terminal building. The wing walker had 18 years' experience with the company and was qualified. The operator's pushback procedures were followed, with the exception of a pre-brief for the pushback not being accomplished. Examination of both airplanes by NTSB investigators revealed that the pushback airplane, N913WN, sustained minor damage to the right winglet while the parked airplane sustained damage to its horizontal stabilizer and elevator. The pushback tug was examined by the operator and NTSB investigatorsand was fully functional with no anomalies noted. ## Aircraft - Registration: [N913WN](https://openairdocs.org/aircraft/N913WN), registered now, S/N 29840, 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: 29840 - Year built: 2008 - Airframe hours: 17245 - Engines: CFM INTL CFM56-7B24 24200 lbs thrust turbo fan; CFM INTL CFM56-7B24 24200 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Operator: Southwest Airlines Co, doing business as Southwest Airlines Co - Registered owner: Southwest Airlines Co - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, May 4, 2013 - Departed: PHX, Phoenix, AZ - Destination: RNO, Reno/Tahoe Intl, NV - Flight plan: IFR - Airport: PHX, Phoenix Sky Harbor Int'l - Equipment: Stall warning system, Auto-pilot, Data recorder, Electronic multifunction display, Satellite tracking device ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 55; injuries: none; airline transport, private, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review March 26, 2013; seat: left; restraint: 3-point; flight hours: 11,500 total, 9,500 in this make and model, 11,300 as pilot in command - Co-pilot; age 39; injuries: none; airline transport, commercial, military, private; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review August 12, 2012; seat: right; restraint: 3-point; flight hours: 7,500 total, 4,500 in this make and model, 2,000 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 77 °F, dew point 37 °F - Altimeter: 29.97 inHg - Observed at: PHX ## 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 20130510007111A](https://openairdocs.org/incident/20130510007111A), May 10, 2013: Boeing 737-7H4, Phoenix, AZ, Substantial damage. Swaa N913NW was pushed back from the passenger loading gate when the right wing tip winglet contacted the left hand horizontal leading edge of another parked… ## Other investigations on N913WN (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 DCA11CA014](https://openairdocs.org/ntsb/DCA11CA014), Dec 18, 2010: Boeing 737-7H4 (N913WN), Philadelphia, PA, substantial damage. Probable cause: the failure of the ground operations personnel to maintain awareness of the relative position of the two airplanes. ## Docket (8 files) The files NTSB released with the investigation on June 2, 2014, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=86861. 5.1 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 3.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40412962&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Southwest Phoenix Base Interview Summaries (item 2, .PDF, 321 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40412963&FileExtension=.PDF&FileName=Southwest%20Phoenix%20Base%20Interview%20Summaries-Master.PDF - Flight Crew and Cabin Crew Statements (item 3, .PDF, 47 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40412964&FileExtension=.PDF&FileName=Flight%20Crew%20and%20Cabin%20Crew%20Statements-Redacted.PDF - Ground Personnel Statements (item 4, .PDF, 84 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40412965&FileExtension=.PDF&FileName=Ground%20Personnel%20Statements-Redacted.PDF - Record of Conversation - D Post, Southwest Airlines (item 5, .PDF, 32 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40412966&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20D%20Post,%20Southwest%20Airlines-Master.PDF - WN-1095 Pre-Push Checklist (item 6, .PDF, 287 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40412967&FileExtension=.PDF&FileName=WN-1095%20Pre-Push%20Checklist-Master.PDF - Operator Pushback Procedures (item 7, .PDF, 173 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40412968&FileExtension=.PDF&FileName=Operator%20Pushback%20Procedures-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 8, .PDF, 359 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40412969&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.