# NTSB DEN04IA124: Boeing 737-500, N929UA, Denver, CO, August 7, 2004 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: August 7, 2004, 17:12 local (23:12 UTC) - Place: Denver, CO - Coordinates: 39.851112, -104.667221 - Nearby events: https://openairdocs.org/map.md?lat=39.8511&lon=-104.6672&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 113 uninjured - Status: Completed, report January 24, 2005 - Report: Approved by Office Director - Parties: FAA Flight Standards District Office - NTSB case key (mKey): 59904 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN04IA124 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/59904/pdf - Page: https://openairdocs.org/ntsb/DEN04IA124 ## Probable cause the inaccurate radar information due to the failure of the Airport Movement Area Surveillance radar resulting in the tower calling for the airplane to abort the takeoff, subsequently causing tire and brake damage to the airplane. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Miscellaneous/other, takeoff - aborted - radar - failure,total (cause) - radar traffic information service - inaccurate (contributing factor) - Airframe/component/system failure/malfunction, takeoff - aborted - landing gear,tire - deflated - landing gear,normal brake system - overtemperature ## Analysis According to the FAA, takeoff clearance for the flight was cancelled due to a target detected at the departure end of the runway by the airport movement area safety system (AMASS) radar system. According to a written statement from the flight crew, they successfully aborted the takeoff and were able to taxi to a deicing pad. In the captain's conversation with the tower supervisor, the supervisor stated that the tower initiated the abort call because of a target indicated on their radar. The airplane sustained damage to the tires and brakes. After the abort, hundreds of targets were displayed on the tower's radar and the supervisor believed there was a computer malfunction. Postincident investigation revealed that a dual air conditioning unit failure had occurred within the Airport Surface Detection Equipment (ASDE) equipment room. Equipment room temperatures had elevated and caused the equipment failure. ## Factual narrative On August 7, 2004, at 1712 mountain daylight time, a Boeing 737-500, N929UA, operated by United Airlines as flight 1223, sustained minor damage during an aborted takeoff at Denver International Airport, Denver, Colorado. Visual meteorological conditions prevailed at the time of the incident. The scheduled domestic passenger flight was being operated on an instrument flight rules flight plan under the provisions of Title 14 CFR Part 121. The airline transport captain, the airline transport first officer, 3 cabin crew and 108 passengers reported no injuries. The cross-country flight was originating at the time of the incident and was en route to Los Angeles, California. According to FAA, the crew of Flight 1223 was told to abort the takeoff because the Airport Movement Area Surveillance System (AMASS) radar system had detected a target at the departure end of runway 25. The crew successfully aborted the takeoff and were able to taxi to a deicing pad. The airplane waited for 90 minutes for a "brake cooling period," allowing a tire to be changed so that the airplane could taxi to the gate. In the captain's conversation with the tower supervisor, the supervisor stated that the tower initiated the abort call because of a target indicated on their radar. After the abort, hundreds of targets were displayed on the tower's radar and the supervisor believed there was a computer malfunction. According to the FAA's Denver International Airport Airway Facilities Office, postincident investigation revealed that a dual air conditioning unit failure had occurred within the Airport Surface Detection Equipment (ASDE) equipment room. Equipment room temperatures had elevated and caused the equipment failure. The temperature had not risen high enough to initiate an automatic switch to the back-up unit. The airplane sustained deflation of four main landing gear tires and damage to four main landing gear brake assemblies. ## Aircraft - Registration: [N929UA](https://openairdocs.org/deregistered/N929UA-2019-09-06), registration cancelled 2019-09-06, S/N 26652, built 1992 (OpenAirDocs) - Reported make and model: Boeing 737-500 - Registry model: [Boeing 737-522](https://openairdocs.org/model/boeing-737-522) (registry code 138449F) (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: 26652 - Airframe hours: 34436 - Engines: General Electric CFM56 20000 lbs thrust turbo fan; General Electric CFM56 20000 lbs thrust turbo fan - Damage: Minor damage - Flight: Part 121 - Registered owner: United Air Lines Inc - Airworthiness certificate: Standard, Transport - Last inspection: Continuous airworthiness, June 28, 2003, 2,639 hours before - Departed: DEN, Denver, CO - Destination: LAX, Los Angeles, CA - Flight plan: IFR - Airport: DEN, Denver International Airport, runway 25, 12,000 × 150 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 46; injuries: none; commercial, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; last flight review May 1, 2003; seat: left; flight hours: 8,282 total, 7,746 in this make and model, 6 in the last 24 hours - Co-pilot; age 42; injuries: none; commercial, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; last flight review February 1, 2003; seat: right; flight hours: 4,205 total, 3,425 in this make and model, 6 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 210° at 13 knots - Visibility: 10 statute miles - Lowest ceiling: 15,000 ft broken - Temperature: 82 °F, dew point 45 °F - Altimeter: 30.07 inHg - Observed at: DEN, 2 nm away 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.