NTSB releases preliminary report on deadly Snohomish County plane crash

A federal safety agency said Saturday that four people who died when a small plane crashed north of Seattle last month were conducting test flights to gather baseline information before the Cessna 208B was modified with a new aerodynamic drag reduction system.

The National Transportation Safety Board released its preliminary report Saturday about the Nov. 18 crash in Snohomish, Washington.

The crew of the Cessna 208B had already done three days of test flights, but the day before the crash they ended early because one of the crew members felt ill. The crew went back up the following day and was testing the Cessna’s aft center-of-gravity stall characteristics when the plane crashed, the agency said.

Witnesses said the airplane broke up in flight and descended in a near-vertical corkscrew to the ground and several witnesses reported seeing a white plume of smoke as the airplane broke into pieces, the NTSB report said. The agency has previously said a wing broke away from the plane during the crash.

NTSB: Wing broke off in-flight before deadly plane crash in Snohomish County

NTSB officials say the Cessna 208B airplane's right wing separated in flight and landed about 200 yards from the main crash site, in an agricultural field near Harvey Airfield. The cause of the wing separation has not yet been determined.

The Snohomish County Medical Examiner previously identified the victims as three men from Washington state: Nathan Precup, 33, of Seattle; Nate Lachendro, 49, of Gig Harbor; and Scott Brenneman, 52, of Roy; as well as David Newton, 67, of Wichita, Kansas.

Raisbeck Engineering of Seattle was having the Cessna 208B test flown before modifying the aircraft, according to a statement from Raisbeck President Hal Chrisman.

He said the aircraft had not yet been modified. The flight crew included two "highly-experienced" test pilots, a flight test director and an instrumentation engineer who were collecting "baseline aircraft performance data," Chrisman said.

Read the findings below: