Jet pitched wildly, killing 1, amid cockpit warnings: NTSB

Dana Hyde, CEO of the Millennium Challenge Corporation, participates in the Ghana Compact signing ceremony during the US Africa Leaders Summit at the State Department in Washington on Aug. 5, 2014. (AP Photo/J. Scott Applewhite, File)

HARTFORD, Conn. -

A business jet flying over New England violently pitched upward then downward, fatally injuring a passenger, after pilots responding to automated cockpit warnings switched off a system that helps keep the aircraft stable, U.S. transportation investigators reported Friday.

The National Transportation Safety Board didn't reach any conclusions in its preliminary report on the main cause of the deadly March 3 accident, but it described a series of things that went wrong before and after the plane swooped out of control.

Confronted with several alerts in the cockpit of the Bombardier jet, pilots followed a checklist and turned off a switch that "trims" or adjusts the stabilizer on the plane's tail, the report said.

The plane's nose then swept upward, subjecting the people inside to forces about four times the force of gravity, then pointed lower before again turning upward before pilots could regain control, the report said.

Pilots told investigators they did not encounter turbulence, as the NTSB had said in an initial assessment the day after the incident.

The trim system of the Bombardier Challenger 300 twin-engine jet was the subject of a Federal Aviation Administration mandate last year that pilots conduct extra safety checks before flights.

Bombardier did not respond directly to the report's contents, saying in a statement that it was "carefully studying" it. In a previous statement, the Canadian manufacturer said 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 traveling from Keene, New Hampshire, to Leesburg, Virginia, before diverting to Bradley International Airport in Connecticut. One passenger, Dana Hyde, 55, of Cabin John, Maryland, was brought to a hospital where she died from blunt-force injuries.

Hyde served in government positions during the Clinton and Obama administrations and was counsel for the 9/11 Commission, formally known as the National Commission on Terrorist Attacks Upon the United States.

It was unclear if Hyde was belted in her seat or up and about, in the cabin of the jet owned by Conexon, based in Kansas City, Missouri. Her husband and their son, along with the pilot and co-pilot, were not injured in the incident, the report said.

A representative of Conexon, a company specializing in rural internet, declined to comment Friday.

The report indicated 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 on.

Another warning indicated autopilot stabilizer trim failure. The plane abruptly pitched upward as the pilots moved the stabilizer trim switch from primary to off while working through procedures on a checklist, the report said.

The plane violently oscillated up and down and the "stick pusher" activated, the report said, meaning the onboard computer thought the plane was in danger of an aerodynamic stall.

John Cox, a former airline pilot and now a safety consultant, said "there are definitely issues" with the pilots' pre-flight actions, but he said they reacted correctly when they followed the checklist for responding to trim failure.

The flight crew was comprised of two experienced pilots with 5,000 and 8,000 hours of flying time, and held ratings needed to fly for an airline. But both were relatively new to the model of aircraft, earning their ratings last October.

The FAA issued its directive about Bombardier Challenger 300 jets last year after multiple instances in which the horizontal stabilizer on the aircrafts caused the nose of the plane to turn down after the pilot tried to make the aircraft climb.

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Sharp reported from Portland, Maine. AP Airlines Writer David Koenig in Dallas contributed to this report.