# NTSB LAX96LA222: Boeing 737-322, N371UA, San Francisco, CA, June 7, 1996 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 6, 1996, 22:05 local (Jun 7, 1996, 05:05 UTC) - Place: San Francisco, CA - Coordinates: 37.609786, -122.380699 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.6098&lon=-122.3807&mi=10 - Phase of flight: [Pushback/towing](https://openairdocs.org/ntsb-phases/200) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 220 uninjured - Status: Completed, report May 23, 1997 - Report: Approved by Office Director - NTSB case key (mKey): 29464 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX96LA222 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29464/pdf - Page: https://openairdocs.org/ntsb/LAX96LA222 ## Probable cause (aircraft 2) inadequate visual lookout by the United Airlines tug driver during the pushback operation. Contributing factors were: the driver's reduced ability to observe the American B-767 due to the nighttime condition, and United Airlines management's failure to ensure that safety procedures were followed. ## Probable cause (aircraft 1) inadequate visual lookout by the United Airlines tug driver during the pushback operation. Contributing factors were: the driver's reduced ability to observe the American B-767 due to the nighttime condition, and United Airlines management's failure to ensure that safety procedures were followed. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Collision between aircraft (other than midair), taxi - pushback/tow - light condition - bright night (contributing factor) - visual lookout - inadequate, driver of vehicle (cause) - visual/aural detection, driver of vehicle (contributing factor) - inadequate surveillance,inadequate procedure, company/operator mgmt (contributing factor) - Collision between aircraft (other than midair), taxi - to takeoff - light condition - bright night (contributing factor) - visual lookout - inadequate, driver of vehicle (cause) - visual/aural detection, driver of vehicle (contributing factor) - inadequate surveillance,inadequate procedure, company/operator mgmt (contributing factor) ## Analysis (aircraft 2) At night, a tail-to-tail ground collision occurred in an alleyway between an outbound United Boeing 737, N371UA, and an outbound American Boeing 767, N335AA. At the time, the B-737 was under tug control while being pushed back without the aid of wing walkers from gate number 77. The United B-737 was beginning to taxi from the same alleyway following its earlier uneventful pushback with the aid of wing walkers from gate number 63. According to the B-737's tug driver, during pushback she had observed a nearby food service truck and had initially slowed her speed to ensure its passage. Thereafter, she continued pushing the B-737 toward the designed alleyway location. Suddenly, an impact occurred and the tug driver for the first time observed an American B-767 was already located in the alleyway. United management reported that during pushback operations it was the tug driver's responsibility to ensure that adequate clearance existed. Nine months earlier United management was aware that aircraft utilizing its gate number 77 did not have the minimum 25-foot aircraft wing tip clearance as required by the City of San Francisco. City personnel agreed to allow United gate usage provided United 'guarantee the use of wing walkers.' ## Analysis (aircraft 1) At night, a tail-to-tail ground collision occurred in an alleyway between an outbound United Boeing 737, N371UA, and an outbound American Boeing 767, N335AA. At the time, the B-737 was under tug control while being pushed back without the aid of wing walkers from gate number 77. The United B-767 was beginning to taxi from the same alleyway following its earlier uneventful pushback with the aid of wing walkers from gate number 63. According to the B-737's tug driver, during pushback she had observed a nearby food service truck and had initially slowed her speed to ensure its passage. Thereafter, she continued pushing the B-737 toward the designed alleyway location. Suddenly, an impact occurred and the tug driver for the first time observed an American B-767 was already located in the alleyway. United management reported that during pushback operations it was the tug driver's responsibility to ensure that adequate clearance existed. Nine months earlier United management was aware that aircraft utilizing its gate number 77 did not have the minimum 25-foot aircraft wing tip clearance as required by the City of San Francisco. City personnel agreed to allow United gate usage provided United 'guarantee the use of wing walkers.' ## Factual narrative (aircraft 2) On June 6, 1996, at 2205 hours Pacific daylight time, a United Airlines Boeing 737-322, N371UA, operating as scheduled passenger flight number 2546 to Seattle, Washington, collided on the ground with an American Airlines Boeing 767-223, N335AA, operating as scheduled passenger flight number 18 to New York City, New York. The collision occurred between the "E" and "F" concourses in an alleyway at the San Francisco International Airport, San Francisco, California. At the time, the United aircraft was under tug control while being pushed back from gate number 77, and the American aircraft was commencing to taxi for takeoff from the same alleyway following its uneventful pushback from gate number 63. During the aircraft tail-to-tail collision, the United aircraft was substantially damaged, and neither its 5 crew members nor 50 passengers were injured. The American aircraft received minor damage, and neither its 11 crew members nor 154 passengers were injured. The captains in both aircraft had received clearances for their respective pushbacks, and the American aircraft was pushed back first. According to American, wing walkers had been used during the pushback operation, and its aircraft was positioned at its customary location in the alleyway. Thereafter, the captain started both engines. The push tractor disconnected from the aircraft, and along with the wing walkers proceeded back to the gate. Upon arrival at the gate one of the wing walkers observed that the aircraft had just been impacted by a United aircraft. According to a representative from United Airlines, no wing walkers were used during its pushback operation. Also, it was United's policy that prior to pushing the accident aircraft into the alleyway, it was the tug driver's responsibility to ensure that adequate clearance existed from other aircraft. The United tug driver reported, in pertinent part, that after initiating the pushback she slowed her speed to allow for the passage of a food service truck. Then she continued with the pushback operation and looked for the lead-in line where the aircraft was to be positioned in the alleyway. The tug driver further reported that approaching the lead-in line the aircraft "lunged toward me abruptly." The tug driver asked the pilot what was wrong and whether he applied brakes. The pilot, who described the aircraft as having experienced a "shudder," responded that he had not applied the brakes. The tug driver indicated that she initially believed something might be wrong with the tug; however, she proceeded with another pushback effort. After restarting the pushback she observed for the first time the landing gear of a Boeing 767 which was already located in the alleyway. The Boeing 767 was located directly behind the Boeing 737. It was then that she realized a collision had occurred. In September of 1995, United Airlines management was aware that aircraft utilizing its gate number 77 did not have the minimum 25-foot aircraft wing tip clearance in the alleyway as required by the City of San Francisco. City personnel agreed to allow United to paint temporary aircraft lead-in lines at the gate and to allow Boeing 737 aircraft gate usage provided United "guarantee the use of wing walkers." ## Factual narrative (aircraft 1) On June 6, 1996, at 2205 hours Pacific daylight time, a United Airlines Boeing 737-322, N371UA, operating as scheduled passenger flight number 2546 to Seattle, Washington, collided on the ground with an American Airlines Boeing 767-223, N335AA, operating as scheduled passenger flight number 18 to New York City, New York. The collision occurred between the "E" and "F" concourses in an alleyway at the San Francisco International Airport, San Francisco, California. At the time, the United aircraft was under tug control while being pushed back from gate number 77, and the American aircraft was commencing to taxi for takeoff from the same alleyway following its uneventful pushback from gate number 63. During the aircraft tail-to-tail collision, the United aircraft was substantially damaged, and neither its 5 crew members nor 50 passengers were injured. The American aircraft received minor damage, and neither its 11 crew members nor 154 passengers were injured. The captains in both aircraft had received clearances for their respective pushbacks, and the American aircraft was pushed back first. According to American, wing walkers had been used during the pushback operation, and its aircraft was positioned at its customary location in the alleyway. Thereafter, the captain started both engines. The push tractor disconnected from the aircraft, and along with the wing walkers proceeded back to the gate. Upon arrival at the gate one of the wing walkers observed that the aircraft had just been impacted by a United aircraft. According to a representative from United Airlines, no wing walkers were used during its pushback operation. Also, it was United's policy that prior to pushing the accident aircraft into the alleyway, it was the tug driver's responsibility to ensure that adequate clearance existed from other aircraft. The United tug driver reported, in pertinent part, that after initiating the pushback she slowed her speed to allow for the passage of a food service truck. Then she continued with the pushback operation and looked for the lead-in line where the aircraft was to be positioned in the alleyway. The tug driver further reported that approaching the lead-in line the aircraft "lunged toward me abruptly." The tug driver asked the pilot what was wrong and whether he applied brakes. The pilot, who described the aircraft as having experienced a "shudder," responded that he had not applied the brakes. The tug driver indicated that she initially believed something might be wrong with the tug; however, she proceeded with another pushback effort. After restarting the pushback she observed for the first time the landing gear of a Boeing 767 which was already located in the alleyway. The Boeing 767 was located directly behind the Boeing 737. It was then that she realized a collision had occurred. In September of 1995, United Airlines management was aware that aircraft utilizing its gate number 77 did not have the minimum 25-foot aircraft wing tip clearance in the alleyway as required by the City of San Francisco. City personnel agreed to allow United to paint temporary aircraft lead-in lines at the gate and to allow Boeing 737 aircraft gate usage provided United "guarantee the use of wing walkers." ## Aircraft 1 - Registration: [N371UA](https://openairdocs.org/deregistered/N371UA-2011-09-16), registration cancelled 2011-09-16, S/N 24540, built 1989 (OpenAirDocs) - Reported make and model: Boeing 737-322 - Registry model: [Boeing 737-322](https://openairdocs.org/model/boeing-737-322) (registry code 138447Y) (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: 24540 - Airframe hours: 18843 - Engines: GE CFM56-3-C1 20000 lbs thrust turbo fan - Damage: Substantial damage - Flight: Part 121 - Operator: United Airlines, Inc. - Registered owner: Wilmington Trust Co. Trustee - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, October 17, 1995 - Departed: SFO - Destination: SEA, SEATTLE, WA - Flight plan: IFR - Airport: SFO, San Francisco Intl ## Aircraft 2 - Registration: [N335AA](https://openairdocs.org/deregistered/N335AA-2015-12-09), registration cancelled 2015-12-09, S/N 22333, built 1987 (OpenAirDocs) - Reported make and model: Boeing 767-223 - Registry model: [Boeing 767-223](https://openairdocs.org/model/boeing-767-223) (registry code 1385123) (OpenAirDocs) - Registry engine: [GE CF6-80 series](https://openairdocs.org/engine/ge-cf6-80-series) (registry code 30025, turbo-fan) (OpenAirDocs) - Category: Airplane - Serial number: 22333 - Engines: GE CF6-80A turbo fan - Damage: Minor damage - Flight: Part 121 - Operator: American Airlines, Inc. - Registered owner: Wilmington Trust Co. Trustee - Airworthiness certificate: Standard, Transport - Departed: SFO - Destination: JFK, NEW YORK CITY, NY - Flight plan: IFR - Airport: SFO, San Francisco Intl ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot, aircraft N371UA; age 47; flight instructor, airline transport, flight engineer; airplane ratings: single-engine sea, multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 14,469 total, 2,660 in this make and model - Pilot, aircraft N335AA; age 54; flight instructor, airline transport, flight engineer; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 25,000 total, 2,942 in this make and model ## Weather - Conditions: Visual (VMC), Night/bright - Wind: 280° at 12 knots - Visibility: 15 statute miles - Lowest ceiling: none - Temperature: 57 °F, dew point 46 °F - Altimeter: 29.00 inHg ## FAA reports on this event (2) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19960606045451A](https://openairdocs.org/incident/19960606045451A), Jun 6, 1996: Boeing 737322, San Francisco, CA, Substantial damage. On pushback via tug tail collided with a 767 N335AA that was already on taxiway. No wing walkers per city agreement - [Accident 19960606045452A](https://openairdocs.org/incident/19960606045452A), Jun 6, 1996: Boeing 767223, San Francisco, CA, Minor damage. (.4)At night, a tail-to-tail ground collision occurred in an alleyway between an outbound united Boeing 737, N371UA, and an outbound American Boeing 767,… ## Other investigations on N371UA (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 LAX99LA291](https://openairdocs.org/ntsb/LAX99LA291), Sep 2, 1999: Boeing 737-322 (N371UA), Santa Barbara, CA, minor damage. Probable cause: The flight's encounter with wake vortices from a preceding heavy aircraft. 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.