Firefighter heard 'stop, stop' before LaGuardia jet crash, but didn't know who it was for, NTSB says

NEW YORK — A firefighter whose truck collided with an Air Canada Express jet last month on a runway at LaGuardia Airport in New York, killing both pilots, heard an air traffic controller warn "stop, stop, stop" but didn't know who it was for, federal investigators said Thursday. Just seconds earlier, the controller had cleared the fire truck to cross the runway, but the truck started to move while warning lights that act as a stop sign for crossing traffic were still lit, the National Transportation Safety Board said in a preliminary report on the March 22 crash. Because the truck lacked a transponder, a crash prevention system in the control tower was unable to reliably determine its position, "did not predict a potential conflict with the landing airplane" and did not generate an audio or visual alert, the report said, pointing to a series of lapses and failures that contributed to the crash. After the air traffic controller's initial stop warning, the fire truck's turret operator heard the controller say, "Truck 1, stop, stop, stop," and realized he was telling the truck to halt, the report said. By that time, the truck was already on the runway as Air Canada Express Flight 8646 was landing and speeding toward it. The turret operator, one of two crew members in the fire truck, recalled to investigators that as the vehicle turned left, he saw the airplane's lights on the runway, the report said. The plane registered a speed of 104 mph (167 kph) just before the collision. The truck was going about 30 mph (48 kph). The frantic warning came after an air traffic controller had cleared the truck to cross the runway just 12 seconds before the plane touched down, investigators said. Pilots killed, 39 people hurt, including fire crew members The plane, a CRJ900 regional jet from Montreal, was carrying 76 people. The crash killed pilots Antoine Forest, 30, and Mackenzie Gunther, 24. The two fire truck crew members were among 39 people taken to hospitals with injuries. Six people were described as seriously injured. A flight attendant still strapped in her seat survived after being thrown onto the tarmac. Another flight attendant reported taking his seat in the rear of the plane for landing and described the flight as normal until he felt an impact, the report said. He didn't know what had happened and attempted to call the pilots but received no response, the report said. It was the first deadly crash at LaGuardia in 34 years. The tower at LaGuardia was busier than usual the night of the crash because flight delays pushed the number of arrivals and departures after 10 p.m. to more than double what was scheduled, according to data from aviation analytics firm Cirium. Two air traffic controllers were on duty, consistent with normal scheduling, the report said. Planes were landing every few minutes, with a dozen flights arriving between 11 p.m. and when the crash happened less than 40 minutes later. At the same time, the tower was coordinating the emergency response to an unusual odor making flight attendants feel ill in the cabin of an outbound United Airlines jet. The fire truck was leading a convoy of vehicles, including four fire trucks, a police car and a stair truck, in response to that emergency. Airport had technology meant to prevent crashes The warning lights — known as runway entrance lights — were lit until the fire truck reached the edge of the runway, about three seconds before the collision, the report said. By design, they turn off two or three seconds before a plane reaches a runway intersection, the report said. The runway warning lights in place at 20 of the nation's busiest airports are one of the backup systems designed to help prevent a crash. Aviation experts say the fire truck driver should have known not to cross the runway while the warning lights were shining red, even after the controller gave clearance for the trucks to move. LaGuardia is one of 35 major U.S. airports with an advanced surface surveillance system that combines radar data with information from transponders inside planes and ground vehicles to help prevent runway incursions. Controllers have a display in the tower that's supposed to show the location of every plane and vehicle. The system, known as ASDE-X, didn't sound an alarm partly because the radar had trouble distinguishing the closely spaced trucks and the radar targets intermittently merged on the display. Only two targets were displayed just before the crash, even though there were seven vehicles. None were equipped with transponders that would have allowed the system to precisely track their movements. According to air traffic control transmissions, Flight 8646 was cleared to land on Runway 4 at 11:35 p.m. About two minutes later — and 25 seconds before the crash — the fire crew asked to cross the same runway, which was between the airport's fire station and where the United Airlines jet had parked. Five seconds later, with Flight 8646 approaching the runway a little more than 100 feet (30 meters) above the ground, an air traffic controller cleared the fire truck to cross the runway. Then, just nine seconds before the crash, the controller frantically told the fire crew: "Stop, stop, stop, stop. Truck 1. Stop, stop, stop, stop." A second later, the plane's landing gear touched down. Funk reported from Omaha, Nebraska. This story has been corrected to show that pilot Antoine Forest was 30, not 24; and pilot Mackenzie Gunther was 24, not 30.