N929UA

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.