According to US transportation investigators, a business jet flying over New England violently pitched upward then downward, killing a passenger, after pilots responding to automated cockpit warnings turned off a system that helps keep the aircraft stable.
In its preliminary report on the main cause of the deadly March 3 accident, the National Transportation Safety Board did not reach any conclusions, but it did describe a series of things that went wrong before and after the plane swooped out of control.
When confronted with several alerts in the Bombardier jet’s cockpit, pilots followed a checklist and turned off a switch that “trims” or adjusts the stabiliser on the plane’s tail, according to the report.
The plane’s nose then swept upward, subjecting passengers to forces four times that of gravity, then pointed lower before turning upward again before pilots could regain control, according to the report.
The pilots told investigators they did not experience turbulence, contrary to what the NTSB said in an initial assessment the day after the incident.
Last year, the Federal Aviation Administration mandated that pilots conduct additional safety checks before flights on the trim system of the Bombardier Challenger 300 twin-engine jet.
Bombardier did not directly respond to the report’s contents, instead stating that it was “carefully studying” it. The Canadian manufacturer previously stated that it stood behind its Challenger 300 jets and their airworthiness.
“We will continue to fully support and provide assistance to all authorities as needed,” the company said Friday.
The two pilots and three passengers were on their way from Keene, New Hampshire, to Leesburg, Virginia, when they were forced to divert to Bradley International Airport in Connecticut. Dana Hyde, 55, of Cabin John, Maryland, was one of the passengers who died as a result of blunt-force injuries.
Hyde worked in the Clinton and Obama administrations, and he was a member of the 9/11 Commission, formally known as the National Commission on Terrorist Attacks Upon the United States.
It was unclear whether Hyde was belted in her seat or moving around in the cabin of the Conexon jet, based in Kansas City, Missouri.
According to the report, her husband and son, as well as the pilot and co-pilot, were not injured in the incident.
Conexon, a company that specialises in rural internet, declined to comment on Friday.
The pilots aborted their initial takeoff because no one removed a plastic cover from one of the exterior tubes that determine airspeed, and they took off with a rudder limiter fault alert activated, according to the report.
Another warning indicated that the autopilot stabiliser trim had failed.
According to the report, the plane abruptly pitched upward as the pilots switched the stabiliser trim switch from primary to off while going through checklist procedures.
According to the report, the plane violently oscillated up and down, and the “stick pusher” activated, indicating that the onboard computer thought the plane was in danger of an aerodynamic stall.
Former airline pilot and safety consultant John Cox said the pilots’ pre-flight actions had “definitely issues,” but he said they reacted correctly when they followed the checklist for responding to trim failure.
The flight crew included two experienced pilots with 5,000 and 8,000 hours of flight time, as well as the ratings required to fly for an airline.
However, both were new to the model of aircraft, having received their ratings in October of last year.
The FAA issued its directive about Bombardier Challenger 300 jets last year after multiple incidents in which the aircraft’s horizontal stabiliser caused the nose of the plane to turn down after the pilot attempted to climb.
