Severe icing was the apparent cause of the airplane crash Monday that killed eight Utahns, according to flight data released Saturday by the National Transportation and Safety Board.
The NTSB did not release the official "probable cause" of the accident but said the airplane's ground speed had slowed to 47 mph - an almost impossible position from which to recover - before it dropped to the ground."They've told me it's 100 percent conclusive that ice was the cause. He picked up so much (ice) that he just stalled out and lost elevation. He lost all of his flight control," said Al Alder, owner of West Flight Aviation and a close acquaintance of the downed craft's pilot, Richard Shipman, and co-pilot, Scott Bogan.
Alder said the flight data he received from the NTSB also indicated the airplane, a Mitsubishi MU-2 twin engine turboprop, was traveling between 500 and 575 mph when it hit the ground.
The highest ground speed the plane ever traveled during its flight from Salt Lake City to Malad, Idaho, was about 275 mph, according to the data. The craft's cruising speed is 365 mph.
"It took 18 seconds for them to fall from 16,000 feet. If someone puts a lock on your elevators and rudder, there's nothing you can do, especially with that airplane. And that's what happened, it just froze up," Alder said.
Michael Stockhill, senior air safety investigator for the board, would not confirm that ice in fact was the probable cause of the crash. However, he said a King Air turboprop aircraft traveling at the same altitude and in the same direction as the Mitsubishi experienced "moderate" icing eight to 12 minutes after the crash.
"It got bad enough that the (King Air) pilot dropped down to 12,000 feet. He had no more problems at that elevation," Stockhill said.
Moderate icing is defined by the NTSB as a rate of accumulation of such that even short encounters become potentially hazardous. Severe icing means that all anti-icing measures fail and immediate diversion is necessary to maintain control.
Some aviation experts speculated in the first days after the accident that one or more of the plane's propeller blades broke off.
A crash of another Mitsubishi MU-2 in 1993 that killed South Dakota Gov. George Mickelson was blamed on a failed propeller hub that caused a blade to break off in flight.
But Stockhill said the propellers on aircraft that went down this week had been completely redesigned from the original. "That's not a factor anymore," he said.
The NTSB completed its on-site investigation of the crash on private land Thursday. Wreckage has been taken to a storage site in Oregon where board investigators will continue their work.
Stockhill and his team plan to complete a factual report and then turn over their findings to the board within six months.
The five-member panel will then release the "probable cause" of the crash.
Stockhill said he has also requested assistance from the board's Washington, D.C., staff to study meteorological conditions and the aircraft's performance during the flight.
"The engines were developing power (about the time it fell from the sky) but we don't know yet how much," he said.
Killed in the crash were four of Salt Lake-based Swire Coca-Cola USA's top executives: J. Craig Taylor, 39, president and chief executive officer; Bradley C. Moore, 36, vice president and chief financial officer; Gary Barber, 42, vice-president of marketing; and Merlin Mikkelsen, 36, marketing analyst. Also killed were Scopes-Garcia-Carlisle Advertising co-founder William J. Garcia, 44, and account executive Bruce Keyes, 31.
Shipman, 47, owner of Pro Air Services, and Bogan, 27, were also killed.
Services for seven of the victims were held Friday and Saturday. Moore's funeral is set for Monday.
*****
ADDITIONAL INFORMATION
Plane crash
Mitsubishi MU-2 Twin Turboprop
Elevation 15,700 ft.
Pilot declares emergency, plane stalls at 47 MPH, 6:18.00 A.M.
500-575 MPH, Near-vertical impact, 6:18.18 A.M.
Source: NTSB, National Weather Service