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Special Report: USAir Flight 1493

By: Chris Kilroy

The wreckage of USAir Flight 1493. (File Photo)
It was just after 6:00pm on the evening of February 2, 1991 and USAir flight 1493 was preparing to land at Los Angeles International Airport in California. Six crew members and 83 passengers were aboard the 737 during its three hour flight from Columbus, Ohio. On the ground, Skywest's flight 5569 was preparing for takeoff. The Metroliner carrying 10 passengers and two crew was bound for Palmdale, California, flying one of the many rush hour commuter flights out of the Los Angeles area. USAir 1493 was cleared for the ILS 24L approach as Skywest 5569 was taxing away from the gate towards runway 24L. Due to traffic, Skywest 5569 was cleared to taxi to 24L and enter at the intersection of taxiway 45, some 2,200ft from the runway threshold.

As the Skywest Metro awaited its takeoff clearance, USAir 1493 touched down near the threshold of runway 24L and shortly thereafter slammed into 5569. Both aircraft skidded down the runway, the Metro crushed beneath the 737's fuselage. The wreckage came to rest on the far side of the taxiway against an empty building. All 12 in the Skywest aircraft were killed as were 21 people in the USAir 737, including the Captain.

Clearly both aircraft believed they had sole use of the runway at the time of the crash. In order to determine the the origin of the confusion, a careful analysis of radio transcripts and ATC procedures at Los Angeles International was begun. After receiving clearance from Clearance Delivery, the flight strips go directly to the local controller(LC), bypassing the ground controller(GC). While this lessened the GC's workload by not having to mark the flight strips, it actually increased the LC's workload by denying them information regarding the aircraft's position on the field. Aircraft were allowed to request intersection departures directly from the GCs. Because Skywest 5569 was taxing from the south side of the airport, it had been in contact with both GC1 and GC2 on its way to runway 24L and had been cleared to hold short at taxiway 45 before contacting LC2.

In its initial call to LC2, it reported "at [taxiway] 45 we'd like to go from here if we can." After the accident, LC2 reported that she had not heard the "at [taxiway] 45" part of the transmission. Because the flight strips bypassed the GCs, there was no indication for LC2 as to the aircraft's position. LC2 then cleared 5569 to taxi up to and hold short of runway 24L which was acknowledged. During this time, another flight, Wings West 5006, had just landed and was attempting to clear the runway. The crew had inadvertently changed frequencies and was out of contact with LC2. Skywest 5569 was cleared into position and hold on runway 24L.

Communications with Wings West 5006 was re-established just after this instruction and several seconds were spent with uneccesary transmissions regarding the loss of communication. Southwest 725 was also preparing for takeoff at the time and LC2 also cleared it to taxi up to and hold short of runway 24L. Just after this, USAir 1493 called for landing clearance "on the left side, two four left." LC2 confirmed that Southwest 725 was holding short and then cleared 1493 to land. Shortly thereafter, Wings West 5072 called ready for departure. There was no flight strip in front of LC2 for 5072, so she and several others began a search for it.

It was found still at the Clearance Delivery station, believed to still be waiting for initial contact. Just after the strip was found, LC2 saw 1493 touchdown and cleared 725 to taxi into position and hold. Just seconds after this transmission, 1493 collided with 5569 still sitting in position and holding at the intersection of taxiway 45 and runway 24L.

The First Officer of 1493 reported that the touchdown was normal. As the nose was being lowered, he reported that the landing lights began to reflect on 5569's propellers and its rear position light became visible. Maximum braking was applied, but there was insufficient space and time to avoid the collision. He did not report hearing that another aircraft had been placed into position on runway 24L even though 1493 had come on to LC2's frequency prior to the instructions.

LC2 was clearly distracted by several events in the few short minutes prior to the accident. Allowing 5569 to make an intersection departure was acceptable and she cleared the flight into position prior to giving 1493 landing clearance. The initial confusion with 5006 caused her to lose awareness of 5569's position. The futher confusion regarding the flight strip of 5072 caused her again to avert her attention from the situation on the active runways. She later said she had believed 5072 taxied in front of the tower to runway 24L was actually 5569 and formed a mental picture that all was correct.

The NTSB cited many factors as contributing to the cause of the accident. Primary was Air Traffic Control procedures at Los Angeles International Airport. The FAA later required LAX to revise its flight strip handling to relieve the local controllers (LCs) from carrying the full responsibility of flight strip marking and handling and allowing better awareness during high workloads. LC2 was also cited for becoming distracted and allowing a breakdown in awareness during the incident period. The NTSB also cited lighting placement on the Metro, showing that its light blended with and were not conspicuous against the runway environment background during low light periods. Although both flight crews were operating within their ATC clearances, they were both still responsible for "see and avoid" operations since conditions were VFR.

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