# NTSB DEN05IA076: Boeing 737-322, N305UA, Denver, CO, May 17, 2005 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: May 17, 2005, 08:56 local (14:56 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: 187 uninjured - Status: Completed, report October 27, 2005 - Report: Approved by Office Director - Parties: Denver, Colorado - NTSB case key (mKey): 61512 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN05IA076 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/61512/pdf - Page: https://openairdocs.org/ntsb/DEN05IA076 ## Probable cause (aircraft 2) the improper use of procedure used by the ground personnel resulting in the right wing of the aircraft colliding with the left wing of another aircraft. A factor in this incident was the failure to maintain clearance by the flight crew of the other aircraft. ## Probable cause (aircraft 1) the pilot's failure to maintain clearance resulting in the left wing of the aircraft striking the right wing of an adjacent aircraft. A factor in this incident was the improper procedure performed by the ground crew (of the second aircraft involved). ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - On ground/water collision with object, taxi - to takeoff - improper use of procedure, ground personnel (contributing factor) - clearance - not maintained, pilot in command (cause) - object - aircraft parked/standing - On ground/water collision with object, taxi - pushback/tow - improper use of procedure, ground personnel (contributing factor) - clearance - not maintained, flightcrew of other aircraft (cause) - object - aircraft moving on ground ## Analysis (aircraft 2) The two Boeing 737 company aircraft were involved in a ground collision while on the ramp. The first airplane, N305UA, was pushed straight back from its gate via a tug and wing walker. The airplane was disconnected from the tug and its engines were running. The pilots received hand signals from the tug operator releasing them from his guidance. The second airplane, N373UA, was being pushed back an adjacent gate via a tug and wing walker. The wing walker, who was positioned at the front of the right wing, stopped the pushback. The wing walker and tug operator had a brief discussion which resulted in the tug operator pulling the aircraft back toward the gate. The pilots of the first airplane visually cleared the area and began to taxi by turning to the west. During the turn, the left wing tip of the first airplane struck the right wing tip of the second company airplane. ## Analysis (aircraft 1) The two Boeing 737 company aircraft were involved in a ground collision while on the ramp. The first airplane, N305UA, was pushed straight back from its gate via a tug and wing walker. The airplane was disconnected from the tug and its engines were running. The pilots received hand signals from the tug operator releasing them from his guidance. The second airplane, N373UA, was being pushed back an adjacent gate via a tug and wing walker. The wing walker, who was positioned at the front of the right wing, stopped the pushback. The wing walker and tug operator had a brief discussion which resulted in the tug operator pulling the aircraft back toward the gate. The pilots of the first airplane visually cleared the area and began to taxi by turning to the west. During the turn, the left wing tip of the first airplane struck the right wing tip of the second company airplane. ## Factual narrative (aircraft 2) See narrative for DEN05IA076A. ## Factual narrative (aircraft 1) On May 17, 2005, at 0856 mountain daylight time, a Boeing 737-322, N305UA, operated by United Air Lines, flight 229, sustained minor damage when it collided with N373UA, another Boeing 737-322 operated by United Air Lines, flight 424, while taxiing at Denver International Airport (DEN), Denver, Colorado. Visual meteorological conditions prevailed at the time of the incident. Both flights were being conducted with instrument flight rules flight plans under the provisions of 14 CFR Part 121. The 2 pilots, 3 flight attendants, and 120 passengers aboard flight 229 and the 2 pilots, 3 flight attendants and 57 passengers aboard flight 424 were not injured. The flights were originating at the time of the accident, and were en route to San Jose, California and Minneapolis Minnesota respectively. N305UA had completed a straight pushback from gate B19 via a tug and wing walker. The airplane was disconnected from the tug and its engines were running. The pilots received hand signals from the tug operator releasing them from his guidance. N373UA was being pushed back from gate B21 via a tug and wing walker. The wing walker, who was positioned at the front of the right wing, stopped the pushback. The wing walker and tug operator had a brief discussion which resulted in the tug operator pulling the aircraft back toward the gate. The pilots of N305UA visually cleared the area and began to taxi by turning to the west. During the turn, the left wing tip of N305UA struck the right wing tip of N373UA. N373UA was positioned a reported "5 to 10 feet too far west" at the time of the accident. Post-accident inspection by airline maintenance personnel revealed that the left wingtip of N305UA and the right wingtip of N373UA had scratches, dents, and broken navigation lights and lenses. There was no structural damage found to either aircraft. ## Aircraft 1 - Registration: [N305UA](https://openairdocs.org/deregistered/N305UA-2013-03-18), registration cancelled 2013-03-18, S/N 23666, built 1987 (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: 23666 - Airframe hours: 53316 - Engines: General Electric CFM56-3-C1 20000 lbs thrust turbo fan; General Electric CFM56-3-C1 20000 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Registered owner: United Air Lines - Airworthiness certificate: Standard, Transport - Departed: DEN, Denver, CO - Destination: SJC, San Jose, CA - Flight plan: IFR - Airport: DEN, Denver International Airport ## Aircraft 2 - Registration: [N373UA](https://openairdocs.org/deregistered/N373UA-2009-07-14), registration cancelled 2009-07-14, S/N 24638, 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: 24638 - Airframe hours: 45202 - Engines: General Electric CFM56-3-C1 20000 lbs thrust turbo fan; General Electric CFM56-3-C1 20000 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Registered owner: Wilmington Trust Co. - Airworthiness certificate: Standard, Transport - Departed: DEN, Denver, CO - Destination: MSP, Minneapolis, MN - Flight plan: IFR - Airport: DEN, Denver International Airport ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot, aircraft N305UA; age 45; injuries: none; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review October 1, 2004; seat: left; flight hours: 6,192 in this make and model - Co-pilot, aircraft N305UA; age 50; injuries: none; airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; seat: right; flight hours: 5,766 in this make and model - Pilot, aircraft N373UA; age 45; injuries: none; flight engineer, flight instructor, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review September 1, 2004; seat: left; flight hours: 7,361 in this make and model - Co-pilot, aircraft N373UA; age 39; injuries: none; flight engineer, airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review July 1, 2004; seat: right; flight hours: 5,323 in this make and model ## Weather - Conditions: Visual (VMC), Day - Wind: 220° at 12 knots - Visibility: 10 statute miles - Lowest ceiling: 13,000 ft broken - Temperature: 66 °F, dew point 34 °F - Altimeter: 29.51 inHg - Observed at: DEN ## Other investigations on N305UA (2) 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 LAX90IA293](https://openairdocs.org/ntsb/LAX90IA293), Aug 21, 1990: Boeing 737-322 (N305UA), Los Angeles, CA, incident, minor damage. Probable cause: IMPROPER MAINTENANCE SERVICE BY A COMPANY EMPLOYEE WHO ALLOWED A FOREIGN OBJECT (FLASHLIGHT) TO REMAIN IN THE LANDING GEAR EXTEND/RETRACT LINKAGE DURING A NIGHT SERVICING BEFORE THE FLIGHT. - [NTSB CHI88IA015](https://openairdocs.org/ntsb/CHI88IA015), Oct 29, 1987: Boeing 737-322 (N305UA), Chicago, IL, incident, no damage 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.