The instrument-rated pilot was on a 234-nm instrument flight rules (IFR) cross-country flight over mountainous terrain in the Beech B36TC.
During the flight, he notified a controller at the Air Route Traffic Control Center (ARTCC) that the plane was picking up too much ice and requested to divert to an airport located about 96 miles ahead of his position and to descend to 11,000 feet mean sea level (msl).
The controller informed the pilot that he could descend to 12,000 feet msl for terrain clearance.
Over the following few minutes, the ARTCC controller notified the pilot several times that he had to maintain an altitude of 12,000 feet or above due to terrain clearance, all of which the pilot acknowledged. Following a low-altitude alert issued by the controller, the pilot stated his altitude was 11,500 feet.
Subsequently, he advised the controller that he was having engine problems and needed to go to an airport immediately.
When the controller asked the pilot to verify his altitude, the pilot responded that he was at 10,000 feet. The controller then asked the pilot if he was able to climb, and the pilot responded “negative.”
The controller advised the pilot of an airport that was 24 miles behind his position and asked if he wanted to divert. He said yes and asked for guidance to the airport.
About a minute later, he advised the controller that the plane had “just lost its engine.”
The controller advised the pilot that the airport was at the pilot’s six o’clock position and suggested a heading of 253°, adding that another airport was right below their position. There were no further communications with the accident airplane.
Wreckage and impact signatures were found consistent with a wings-level, slightly nose-low descent into trees and terrain near Yellow Pine, Idaho. All five on board the plane died.
Airmen’s Meteorological Information (AIRMETs) for IFR and mountain obscuration conditions, low-level wind shear and turbulence, and moderate icing were issued for the flight track area and timeframe.
In addition to the AIRMETs, multiple pilot reports included reports of light rime-type icing between 8,000 feet and 13,000 feet throughout the region. National Weather Service data was consistent with the pilot reports and AIRMET that were current at the time.
Investigators were unable to determine whether the pilot obtained weather information regarding his planned flight.
It is likely that the loss of engine power was due to a combination of structural and induction icing during the continued flight in icing conditions in an airplane that was not certified for flight in icing conditions.
The National Transportation Safety Board determined the probable cause of the accident as the pilot’s continued flight into known light-to-moderate icing conditions over mountainous terrain. Contributing to the accident was the loss of engine power due to induction icing.
NTSB Identification: WPR14FA094
This December 2013 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.