Icing a factor in Oct. plane crashes | PostIndependent.com

Icing a factor in Oct. plane crashes

Carburetor icing played a role in two local small plane crashes in late October of last year.The National Transportation Safety Board has determined the probable causes of a crash in a residential neighborhood in Glenwood Springs Oct. 23, and a second one in the Flat Tops on Oct. 31. Icing contributed to both accidents.The NTSB blamed the Glenwood crash on Snowmass Village pilot Norm Cohen’s failure to apply heat to the carburetor to prevent icing.”Related factors were conditions conducive for carburetor icing and the lack of suitable terrain for a forced landing,” the NTSB concluded.Cohen crashed when his plane was coming in too high during a landing at the Glenwood Springs Municipal Airport, and he unsuccessfully tried to pull out of the landing in hopes of circling around and trying again.Cohen was flying towards Glenwood Springs at the time of the landing, and the plane hit the roof of a townhome near the airport. It then slid down and hit the side of an adjacent townhome, seriously injuring Cohen and substantially damaging the plane. No one on the ground was injured.The NTSB reported that Cohen had been flying for about an hour, and went into a descent while failing to provide carburetor heat.Carburetor icing can occur when humidity is sucked into the carburetor at cold enough temperatures, allowing ice to form and limiting air intake, said Grant Frost, a line technician for Corporate Aircraft Service at the Garfield County Regional Airport in Rifle. Pilots can divert heat from the engine exhaust to fend off icing.The air temperature was just above freezing when Cohen’s accident occurred.”According to the carburetor icing chart, conditions were conducive for ‘serious icing at cruise power,'” the NTSB found.Cohen applied heat to the carburetor in preparing for landing, but the engine failed to respond to the throttle when he tried to pull out of his landing, the agency reported. Inspectors found no problems with the engine after the accident, according to the NTSB.The second crash occurred about 12 miles up Coffee Pot Road, north of Glenwood Springs in the Flat Tops. Both the pilot, Ryan Dahlin, of Santa Maria, Calif., and his father, Esten Clarence Dahlin, of Florissant, were seriously injured when the plane suffered engine failure and the younger Dahlin was forced to crash-land his homebuilt plane. Hunters witnessed the crash and rescued the pair.The NTSB found that both dew point at the time and an air temperature that was around freezing were strongly conducive to carburetor icing. It blamed the crash on the icing and improper in-flight planning and decision-making by the pilot.The plane was flying from Morgan, Utah, and was headed to Colorado Springs. It stopped for fuel in Vernal, Utah, and the younger Dahlin said engine failure occurred about 45 minutes after he resumed flying. A commercial pilot, he told investigators that he didn’t encounter icing conditions.Dahlin searched for holes in the clouds and began to descend, but visibility was poor. He continually tried to restart the engine but the propeller seized when he attempted a forced landing on a road. The plane hit several aspen trees, then struck the ground and “nosed over,” the NTSB reported. The plane was destroyed when it caught fire after impact.An investigation of the engine found nothing that would have prevented its normal operation.Frost said he applies heat to the carburetor as part of his landing checkoff procedures to avoid icing.”To tell you the truth I’ve never experienced it,” he said of the phenomenon.He doesn’t heat the carburetor during takeoff because it decreases power. The heated air affects the carburetor’s fuel-to-air mixture.However, the procedures for using carburetor heating vary depending on the type of plane, he said.Contact Dennis Webb: 945-8515, ext. 516dwebb@postindependent.com

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