National Transportation Safety Board
Aviation Incident Final Report

 

 

Location:

Denver, CO

Incident Number:

CEN15IA337

Date & Time:

08/04/2015, 1800 MDT

Registration:

N779SW

Aircraft:

BOEING 737

Aircraft Damage:

Minor

Defining Event:

Ground collision

Injuries:

1 Minor, 148 None

Flight Conducted Under:

Part 121: Air Carrier - Scheduled

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.

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this incident to be:
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

Personnel issues

Monitoring environment - Ground crew (Cause)

Task monitoring/vigilance - Ground crew (Cause)

Lack of communication - Ground crew

Attention - Ground crew (Factor)

Factual Information

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 was stressed 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."

 

History of Flight

Pushback/tow-engine oper

Ground collision (Defining event)

 

 

Pilot Information

Certificate:

Airline Transport; Flight Instructor; Commercial

Age:

61

Airplane Rating(s):

Multi-engine Land; Single-engine Land

Seat Occupied:

Left

Other Aircraft Rating(s):

None

Restraint Used:

 

Instrument Rating(s):

Airplane

Second Pilot Present:

Yes

Instructor Rating(s):

Airplane Multi-engine; Airplane Single-engine

Toxicology Performed:

 

Medical Certification:

Class 1 With Waivers/Limitations

Last FAA Medical Exam:

03/11/2015

Occupational Pilot:

Yes

Last Flight Review or Equivalent:

03/23/2015

Flight Time:

22952 hours (Total, all aircraft), 16152 hours (Total, this make and model), 19950 hours (Pilot In Command, all aircraft), 203 hours (Last 90 days, all aircraft), 56 hours (Last 30 days, all aircraft), 0 hours (Last 24 hours, all aircraft)

 

 

Co-Pilot Information

Certificate:

Airline Transport

Age:

39

Airplane Rating(s):

Multi-engine Land; Single-engine Land

Seat Occupied:

Right

Other Aircraft Rating(s):

 

Restraint Used:

 

Instrument Rating(s):

Airplane

Second Pilot Present:

Yes

Instructor Rating(s):

None

Toxicology Performed:

 

Medical Certification:

Class 1 With Waivers/Limitations

Last FAA Medical Exam:

05/19/2015

Occupational Pilot:

Yes

Last Flight Review or Equivalent:

05/09/2015

Flight Time:

12801 hours (Total, all aircraft), 2726 hours (Total, this make and model), 3086 hours (Pilot In Command, all aircraft), 260 hours (Last 90 days, all aircraft), 76 hours (Last 30 days, all aircraft), 0 hours (Last 24 hours, all aircraft)

 

 

Aircraft and Owner/Operator Information

Aircraft Make:

BOEING

Registration:

N779SW

Model/Series:

737 700

Aircraft Category:

Airplane

Year of Manufacture:

 

Amateur Built:

No

Airworthiness Certificate:

Normal

Serial Number:

27884

Landing Gear Type:

Retractable - Tricycle

Seats:

143

Date/Type of Last Inspection:

07/29/2015,

Certified Max Gross Wt.:

154500 lbs

Time Since Last Inspection:

 

Engines:

2 Turbo Fan

Airframe Total Time:

54165 Hours at time of accident

Engine Manufacturer:

CFM INTL.

ELT:

C91A installed, not activated

Engine Model/Series:

CFM56 SERIES

Registered Owner:

Southwest Airlines

Rated Power:

hp

Operator:

Southwest Airlines

Operating Certificate(s) Held:

Flag carrier (121)

 

Meteorological Information and Flight Plan

Conditions at Accident Site:

Visual Conditions

Condition of Light:

Day

Observation Facility, Elevation:

KDEN, 5433 ft msl

Distance from Accident Site:

 

Observation Time:

1753 MDT

Direction from Accident Site:

 

Lowest Cloud Condition:

Few / 11000 ft agl

Visibility

10 Miles

Lowest Ceiling:

None

Visibility (RVR):

 

Wind Speed/Gusts:

6 knots /

Turbulence Type Forecast/Actual:

/ None

Wind Direction:

40°

Turbulence Severity Forecast/Actual:

/ N/A

Altimeter Setting:

30.07 inches Hg

Temperature/Dew Point:

31°C / 5°C

Precipitation and Obscuration:

No Obscuration; No Precipitation

Departure Point:

San Diego, CA (SAN)

Type of Flight Plan Filed:

IFR

Destination:

San Jose, CA (SJC)

Type of Clearance:

None

Departure Time:

1426 PDT

Type of Airspace:

 

 

Airport Information

Airport:

Denver International Airport (KDEN)

Runway Surface Type:

N/A

Airport Elevation:

5433 ft

Runway Surface Condition:

 

Runway Used:

N/A

IFR Approach:

None

Runway Length/Width:

 

VFR Approach/Landing:

None

 

Wreckage and Impact Information

Crew Injuries:

5 None

Aircraft Damage:

Minor

Passenger Injuries:

143 None

Aircraft Fire:

None

Ground Injuries:

1 Minor

Aircraft Explosion:

None

Total Injuries:

1 Minor, 148 None

Latitude, Longitude:

39.861667, -104.673056 (est)

 


 


Administrative Information

Investigator In Charge (IIC):

Jennifer Rodi

Report Date:

09/12/2016

Additional Participating Persons:

LeRoy Sutton; FAA FSDO; Denver, CO

Erin Carroll; Southwest Airlines; Dallas, TX

Publish Date:

09/12/2016

Note:

The NTSB did not travel to the scene of this incident.

Investigation Docket:

http://dms.ntsb.gov/pubdms/search/dockList.cfm?mKey=91711