# NTSB DFW05IA200: Airbus A320-232, N496UA, Denver, CO, August 3, 2005 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: August 3, 2005, 08:40 local (14:40 UTC) - Place: Denver, CO - Coordinates: 39.861667, -104.673057 - Nearby events: https://openairdocs.org/map.md?lat=39.8617&lon=-104.6731&mi=10 - Phase of flight: [Taxi](https://openairdocs.org/ntsb-phases/250) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 324 uninjured - Status: Completed, report May 30, 2006 - Report: Approved by Office Director - Parties: FAA, United Airlines - NTSB case key (mKey): 62257 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DFW05IA200 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/62257/pdf - Page: https://openairdocs.org/ntsb/DFW05IA200 ## Probable cause (aircraft 2) The captain's failure to maintain sufficient clearance while taxiing to an assigned gate, which resulted in a collision with an airplane that had been pushed back (and holding) from another gate. Also causal was the tug operator's failure to follow published company procedures resulting in the holding airplane being pushed back too far, which reduced wingtip clearance of the taxiing airplane. ## Probable cause (aircraft 1) The captain's failure to maintain sufficient clearance while taxiing to an assigned gate, which resulted in a collision with an airplane that had been pushed back (and holding) from another gate. Also causal was the tug operator's failure to follow published company procedures resulting in the holding airplane being pushed back too far, which reduced wingtip clearance of the taxiing airplane. ## Analysis (aircraft 2) While taxiing east on Taxiway AA toward Gate A-48, an Airbus A320 collided with another Airbus A320 from the same company that had been pushed back from Gate A-40 and was holding on the ramp for the inbound traffic to clear. According to company policy, airplanes departing Concourse A were pushed back until the main landing gear wheels sat on the centerline of Taxiway AS, the northern taxiway. This policy assured airplanes taxiing on Taxiway AA (the southern taxiway) adequate wingtip clearance (about 30 feet), assuming their nose wheel stayed on the centerline. A witness said the holding airplane was pushed back too far from Taxiway AS and the taxiing airplane's nose wheel was on the centerline of Taxiway AA. As the inbound airplane taxied behind the holding airplane, its left winglet cut through the bottom section of holding airplane's tail cone. The flight crew on the inbound airplane recognized that the holding airplane was pushed back further than normal from the gate and elected to increase their wing tip clearance by moving to the right of the Taxiway AA centerline approximately 5 to 6 feet. As they approached the holding airplane, the captain reduced forward speed to a crawl, determined there was sufficient clearance between the two airplanes, and continued to taxi to their assigned gate. The flight crew onboard the holding airplane felt the airplane move slightly as the inbound airplane taxied behind them. Shortly after, both flight crews were notified of the collision. ## Analysis (aircraft 1) While taxiing east on Taxiway AA toward Gate A-48, an Airbus A320 collided with another Airbus A320 from the same company that had been pushed back from Gate A-40 and was holding on the ramp for the inbound traffic to clear. According to company policy, airplanes departing Concourse A were pushed back until the main landing gear wheels sat on the centerline of Taxiway AS, the northern taxiway. This policy assured airplanes taxiing on Taxiway AA (the southern taxiway) adequate wingtip clearance (about 30 feet), assuming their nose wheel stayed on the centerline. A witness said the holding airplane was pushed back too far from Taxiway AS and the taxiing airplane's nose wheel was on the centerline of Taxiway AA. As the inbound airplane taxied behind the holding airplane, its left winglet cut through the bottom section of holding airplane's tail cone. The flight crew on the inbound airplane recognized that the holding airplane was pushed back further than normal from the gate and elected to increase their wing tip clearance by moving to the right of the Taxiway AA centerline approximately 5 to 6 feet. As they approached the holding airplane, the captain reduced forward speed to a crawl, determined there was sufficient clearance between the two airplanes, and continued to taxi to their assigned gate. The flight crew onboard the holding airplane felt the airplane move slightly as the inbound airplane taxied behind them. Shortly after, both flight crews were notified of the collision. ## Factual narrative (aircraft 2) On August 3, 2005, at 0840 mountain daylight time, an Airbus A320-232 airplane, N496UA, operated by United Airlines d/b/a Ted Airlines, sustained minor damage to its left winglet when it struck the tail cone of another Airbus A320-232, N472UA, d/b/a Ted Airlines, while taxiing to Gate A-48 on the south side of Concourse A at the Denver International Airport (DEN), near Denver, Colorado. Both airplanes were operated by and registered to United Airlines, of Chicago, Illinois. There were no injuries to the crew or passengers on either airplane. Visual meteorological conditions prevailed for the scheduled, domestic flight conducted under 14 Code of Federal Regulations Part 121. N472UA had been pushed back from Gate A-40 and was destined for Las Vegas, Nevada. N496UA had just arrived from Phoenix, Arizona. According to a Ted Airlines ramp supervisor, since gate A-40 was angled and adjacent to the center terminal building, the pushback was "doglegged" and company policy required two wing walkers to assist the tug operator. The pushback procedure required the tug operator to push the airplane straight back 5 or 6 feet, and then turn the airplane so its main landing gear wheels were perpendicular to and on the centerline of Taxiway AA. He said the purpose of placing the main landing gear wheels on the Taxiway AA centerline was to assure adequate clearance for airplane's taxiing on Taxiway AS. In addition, he said the wing walkers only responsibility was to ensure clearance between the airplane and vehicles on the ramp. They were not responsible for the airplane's position during pushback. In an interview, the tug operator stated that he pushed N472UA back so its main landing gear was placed just aft of the Taxiway AA centerline. After the airplane had been pushed back, and before the tug was released, ground crews placed about five more pieces of luggage into the cargo hold. After the luggage was loaded, the tug operator and wing walkers disconnected the tug and went inside the terminal. The tug operated did not see the collision and was later notified of the event. A witness, an airport engineer, observed N472UA as it was pushed back from Gate A-40, which was an angled gate (NE/SW) located immediately east of the center terminal. He watched the tug operator push the airplane back and also observed two wing walkers escorting the airplane. Though the witness could not confirm how far back the main landing gear wheels were positioned from the Taxiway AA centerline, he did say that it was "pushed back too far." He said the tug operator and two wing walkers then unhooked the tug and walked back to the terminal. During that time, N496UA was taxing from west to east on Taxiway AS toward Gate A-48, and had just passed under the crossover bridge. The witness stated that N496UA's nose wheel was "definitely" on the Taxiway AS centerline as it taxied. As N496UA taxied behind N472UA, its left winglet cut through the bottom section of N472UA's tail cone, about one-foot aft of the APU maintenance doors. In a written statement, the flight crew from N496UA stated that they received clearance to transition from Taxiway AS and proceed eastbound on Taxiway AA to Gate A-48, which is beyond Gate A-40. As they taxied toward the crossover bridge, they noticed that N472UA was pushed back from the gate and "appeared to be out of position" reducing the normal clearance between the two aircraft. The flight crew elected to increase their wing tip clearance by moving to the right of the centerline approximately 5-6 feet just after they passed under the crossover bridge. As they approached N472UA, the Captain slowed the taxi speed to a crawl and determined there was sufficient clearance between the two aircraft. After crossing behind N472UA, N496UA taxied to Gate 48. The flight crew aboard N472UA stated they felt a "slight movement" as N496UA taxied behind them. Immediately, the crew looked out the right cockpit window and observed no visible damage to N496UA's left wing. Shortly after, N472UA began to taxi when they were told to stop due to damage on the tail cone. Examination of both airplanes revealed that N496UA sustained minor damage (scratches only) to the top of its left winglet, and N472UA sustained minor damage to the tail cone. The damage consisted of a tear in the skin about three feet forward of the aft-tip of the tail cone. The auxiliary power unit was not damaged. A review of engineering drawings and measurements taken on the ramp revealed that if the main landing gear of an Airbus A320 was parked on the Taxiway AA centerline, and the nose wheel of an Airbus A320 was on the centerline of Taxiway AS, there would have been approximately 30 feet of clearance between the parked airplane's tail cone and a taxiing airplane's wingtip. As a result of the incident, United Airlines agreed to install stop-blocks and gate identifiers at each gate on Concourse A. They also plan to work with DEN airport operations personnel to review and modify existing airport engineering drawings to properly reflect the addition of the stop-blocks. United Airlines will also revise pushback procedures to reflect the painted stop-blocks as the new stopping point. ## Factual narrative (aircraft 1) On August 3, 2005, at 0840 mountain daylight time, an Airbus A320-232 airplane, N496UA, operated by United Airlines d/b/a Ted Airlines, sustained minor damage to its left winglet when it struck the tail cone of another Airbus A320-232, N472UA, d/b/a Ted Airlines, while taxiing to Gate A-48 on the south side of Concourse A at the Denver International Airport (DEN), near Denver, Colorado. Both airplanes were operated by and registered to United Airlines, of Chicago, Illinois. There were no injuries to the crew or passengers on either airplane. Visual meteorological conditions prevailed for the scheduled, domestic flight conducted under 14 Code of Federal Regulations Part 121. N472UA had been pushed back from Gate A-40 and was destined for Las Vegas, Nevada. N496UA had just arrived from Phoenix, Arizona. According to a Ted Airlines ramp supervisor, since gate A-40 was angled and adjacent to the center terminal building, the pushback was "doglegged" and company policy required two wing walkers to assist the tug operator. The pushback procedure required the tug operator to push the airplane straight back 5 or 6 feet, and then turn the airplane so its main landing gear wheels were perpendicular to and on the centerline of Taxiway AA. He said the purpose of placing the main landing gear wheels on the Taxiway AA centerline was to assure adequate clearance for airplane's taxiing on Taxiway AS. In addition, he said the wing walkers only responsibility was to ensure clearance between the airplane and vehicles on the ramp. They were not responsible for the airplane's position during pushback. In an interview, the tug operator stated that he pushed N472UA back so its main landing gear was placed just aft of the Taxiway AA centerline. After the airplane had been pushed back, and before the tug was released, ground crews placed about five more pieces of luggage into the cargo hold. After the luggage was loaded, the tug operator and wing walkers disconnected the tug and went inside the terminal. The tug operated did not see the collision and was later notified of the event. A witness, an airport engineer, observed N472UA as it was pushed back from Gate A-40, which was an angled gate (NE/SW) located immediately east of the center terminal. He watched the tug operator push the airplane back and also observed two wing walkers escorting the airplane. Though the witness could not confirm how far back the main landing gear wheels were positioned from the Taxiway AA centerline, he did say that it was "pushed back too far." He said the tug operator and two wing walkers then unhooked the tug and walked back to the terminal. During that time, N496UA was taxing from west to east on Taxiway AS toward Gate A-48, and had just passed under the crossover bridge. The witness stated that N496UA's nose wheel was "definitely" on the Taxiway AS centerline as it taxied. As N496UA taxied behind N472UA, its left winglet cut through the bottom section of N472UA's tail cone, about one-foot aft of the APU maintenance doors. In a written statement, the flight crew from N496UA stated that they received clearance to transition from Taxiway AS and proceed eastbound on Taxiway AA to Gate A-48, which is beyond Gate A-40. As they taxied toward the crossover bridge, they noticed that N472UA was pushed back from the gate and "appeared to be out of position" reducing the normal clearance between the two aircraft. The flight crew elected to increase their wing tip clearance by moving to the right of the centerline approximately 5-6 feet just after they passed under the crossover bridge. As they approached N472UA, the Captain slowed the taxi speed to a crawl and determined there was sufficient clearance between the two aircraft. After crossing behind N472UA, N496UA taxied to Gate 48. The flight crew aboard N472UA stated they felt a "slight movement" as N496UA taxied behind them. Immediately, the crew looked out the right cockpit window and observed no visible damage to N496UA's left wing. Shortly after, N472UA began to taxi when they were told to stop due to damage on the tail cone. Examination of both airplanes revealed that N496UA sustained minor damage (scratches only) to the top of its left winglet, and N472UA sustained minor damage to the tail cone. The damage consisted of a tear in the skin about three feet forward of the aft-tip of the tail cone. The auxiliary power unit was not damaged. A review of engineering drawings and measurements taken on the ramp revealed that if the main landing gear of an Airbus A320 was parked on the Taxiway AA centerline, and the nose wheel of an Airbus A320 was on the centerline of Taxiway AS, there would have been approximately 30 feet of clearance between the parked airplane's tail cone and a taxiing airplane's wingtip. As a result of the incident, United Airlines agreed to install stop-blocks and gate identifiers at each gate on Concourse A. They also plan to work with DEN airport operations personnel to review and modify existing airport engineering drawings to properly reflect the addition of the stop-blocks. United Airlines will also revise pushback procedures to reflect the painted stop-blocks as the new stopping point. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Collision between aircraft (other than midair), taxi - clearance - not maintained, pilot in command (cause) - object - aircraft parked/standing - procedures/directives - not followed, ground personnel (cause) - Collision between aircraft (other than midair), standing - clearance - not maintained, flightcrew of other aircraft (cause) - procedures/directives - not followed, ground personnel (cause) ## Aircraft 1 - Registration: [N496UA](https://openairdocs.org/aircraft/N496UA), registered now, S/N 1845, built 2002 (OpenAirDocs) - Reported make and model: Airbus A320-232 - Registry model: [Airbus A320-232](https://openairdocs.org/model/airbus-a320-232) (registry code 3940004) (OpenAirDocs) - Registry engine: [IAE V2500SERIES](https://openairdocs.org/engine/iae-v2500series) (registry code 34601, turbo-jet) (OpenAirDocs) - Category: Airplane - Serial number: 1845 - Airframe hours: 9616 - Engines: International Aero Engines V2527-A5 27000 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Registered owner: United Air Lines - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, July 1, 2005, 182 hours before - Departed: PHX, Phoenix, AZ - Destination: DEN, Denver, CO - Flight plan: IFR - Airport: DEN, Denver International Airport ## Aircraft 2 - Registration: [N472UA](https://openairdocs.org/aircraft/N472UA), registered now, S/N 1435, built 2001 (OpenAirDocs) - Reported make and model: Airbus Industrie A320-232 - Registry model: [Airbus Industrie A320-232](https://openairdocs.org/model/airbus-industrie-a320-232) (registry code 3930326) (OpenAirDocs) - Registry engine: [IAE V2500SERIES](https://openairdocs.org/engine/iae-v2500series) (registry code 34601, turbo-jet) (OpenAirDocs) - Category: Airplane - Serial number: 1435 - Airframe hours: 14729 - Engines: International Aero Engines V2527-A5 27000 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Registered owner: United Air Lines - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, May 1, 2005, 843 hours before - Departed: DEN, Denver, CO - Destination: LAS, Las Vegas, NV - Flight plan: IFR - Airport: DEN, Denver International Airport ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot, aircraft N496UA; age 41; injuries: none; commercial, flight instructor, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review February 1, 2005; seat: left; flight hours: 8,079 total, 2,182 in this make and model, 5,154 as pilot in command - Pilot, aircraft N496UA; age 42; injuries: none; flight instructor, commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review February 1, 2005; seat: right; flight hours: 5,549 total, 4,023 in this make and model - Pilot, aircraft N472UA; age 44; injuries: none; commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; seat: left; flight hours: 8,045 total, 568 in this make and model, 8,045 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: 240° at 8 knots - Visibility: 10 statute miles - Lowest ceiling: 8,500 ft broken - Temperature: 73 °F, dew point 48 °F - Altimeter: 30.14 inHg - Observed at: DEN ## FAA reports on this event (2) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Incident 20050803016822I](https://openairdocs.org/incident/20050803016822I), Aug 3, 2005: Airbus A320232, Denver, CO, Minor damage. (-23) N472UA, was pushed back from gate A40, (main gear on as taxi route stop spot) stopped and preparing for departure. N496UA taxied behind N472UA and it's… - [Incident 20050803016821I](https://openairdocs.org/incident/20050803016821I), Aug 3, 2005: Airbus A320232, Denver, CO, Minor damage. (-23) N472UA, was pushed back from gate A40, (main gear on as taxi route stop spot) stopped and preparing for departure. N496UA taxied behind N472UA and it's… From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date; 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.