ASDE-X Failed To Alert in LaGuardia Runway Collision

LaGuardia Airport’s surface detection system failed to generate an alert as air traffic control cleared an aircraft rescue and firefighting (ARFF) vehicle to cross Runway 4 in front of an Air Canada Express CRJ900 that was descending through 100 feet on final approach, according to information presented by NTSB Chair Jennifer Homendy and investigator in charge Doug Brazy. Operating as Jazz Aviation Flight 8646, the CRJ900 collided with the ARFF vehicle on Runway 4 at night on March 22, killing the two pilots and injuring 41, including passengers, cabin crew, and ARFF vehicle occupants. The investigation is ongoing.

Last week, the NTSB took possession of the cockpit voice recorder (CVR) and flight data recorder (FDR) and transported them to NTSB headquarters in Washington for analysis. The CVR contained more than 25 hours of audio across four channels, while the FDR contained approximately 80 hours of data. An NTSB CVR group is transcribing the accident flight recording.

Brazy presented a summary of events captured on the CVR during the final three minutes of the recording, with all times referenced to the end of the recording. At the 3:07 mark, the approach controller instructed the crew to contact LaGuardia Tower. At 2:45, the crew lowered the landing gear and, at 2:22, checked in with the tower, which cleared Flight 8646 to land on Runway 4 at 2:17, advising the crew that they were number two for landing.

The crew set flaps to 30 degrees at 1:52 and to 45 degrees at 1:33. At 1:26, a TAWS callout indicated 1,000 feet agl. The crew confirmed the landing checklist was complete at 1:12. At 0:54, the crew acknowledged that the aircraft was 500 feet ago and on a stable approach.

At 1:03, an airport vehicle made a radio transmission to the tower; that transmission was stepped on by another radio transmission whose source had not yet been identified.

The critical sequence began at 0:40 , when the tower asked which vehicle needed to cross a runway. At 0:28, truck one—the ARFF vehicle—transmitted to the tower; the tower acknowledged at 0:26. At 0:25, truck one requested to cross Runway 4 at Taxiway Delta. At 0:20, the tower cleared the ARFF vehicle to cross Runway 4 at Taxiway Delta. One second later, TAWS indicated the aircraft was 100 feet agl. At 0:17, truck one read back the runway crossing clearance.

At 0:14, the 50-foot TAWS callout occurred, followed by the 30-foot callout at 0:12, at which point the tower simultaneously instructed a Frontier Airlines flight to hold position. The 20- and 10-foot callouts followed at 0:11 and 0:10, respectively. At 0:09, the tower instructed truck one to stop. At 0:08, a sound consistent with the aircraft’s landing gear contacting the runway was captured on the recording. At 0:06, controls were transferred from the first officer, who had been flying, to the captain. At 0:04, the tower again instructed truck one to stop. The recording ended at 0:00.

The ARFF vehicles had been dispatched to respond to United Airlines Flight 2384, which was at the gate following two aborted takeoffs and a reported smell of fumes or smoke in the cabin. Other ARFF vehicles were positioned behind truck one but did not begin to cross the runway.

LaGuardia (KLGA) is equipped with ASDE-X, a safety system that allows controllers to track the surface movement of aircraft and vehicles. An analysis by the FAA’s technical center found that the system did not generate an alert before the collision.

Homendy quoted the analysis at the briefing: “ASDE-X did not generate an alert due to the close proximity of vehicles merging and unmerging near the runway, resulting in the inability to create a track of high confidence.” The ASDE-X replay showed two radar returns on Taxiway Delta.

Truck one carried no transponder and was therefore tracked by radar rather than by transponder signal, but neither return was shown crossing onto the runway. Homendy said there was no indication any of the ARFF vehicles at KLGA were equipped with transponders. The runway status lights appeared to be functioning in the ASDE-X replay, pending verification by FAA technical operations personnel.

Two controllers were in the tower cab at the time of the collision: a local controller and a controller in charge. The local controller, who manages active runways and the surrounding airspace, had signed on at 22:45 with a shift scheduled to end at 06:45. The controller in charge, responsible for overall safety of operations, had signed on at 22:30 and was simultaneously performing the duties of the clearance delivery position.

It is unclear who was performing the duties of the ground controller, responsible for managing aircraft and vehicle movements on taxiways, as of the March 24 briefing, with conflicting information still being reconciled. Homendy said the two-controller “midnight shift” configuration is standard operating procedure at KLGA and common practice across the national airspace, but noted that the NTSB has previously raised concerns about fatigue during the midnight shift. She said there is no indication that fatigue was a factor in this accident.

Homendy cautioned against attributing the accident to controller distraction, calling it a high-workload environment and noting that several questions about staffing and concurrent operations remained unanswered. “We rarely, if ever, investigate a major accident where it was one failure,” she said. “When something goes wrong, that means many, many things went wrong.” Interviews with the local controller were scheduled to begin the afternoon of March 24.

A preliminary report is expected within 30 days of the accident. A final report with a probable cause determination is expected in 12 to 24 months.