Boeing Field to Cheyenne Flight Disappearance and Crash (N1648M)

Flight Details and Departure Conditions The flight originated at Boeing Field in Seattle, Washington, with Cheyenne, Wyoming, as its first scheduled stop. The crew included Captain Lawrence B. Crawford, First Officer Maxwell F. Perkins, and Stewardess Marie Davis. Before departure, the aircraft received 738 gallons of fuel and 20 gallons of oil, resulting in total onboard quantities of 1,020 gallons of fuel and 60 gallons of oil. The crew completed the pre-flight inspection. At departure, the aircraft's gross weight was 45,401 pounds, exceeding the maximum allowable gross weight of 45,000 pounds for passenger operations by 401 pounds. However, the load distribution remained within prescribed center of gravity limits. ## Weather and Flight Plan A United States Weather Bureau briefing at Boeing Field indicated en route weather with scattered to broken clouds becoming overcast, with tops estimated at 12,000 feet. The Cheyenne Terminal Forecast called for scattered clouds at 15,000 feet and visibility greater than 15 miles. The briefing also forecast icing conditions in clouds and precipitation above 6,000 feet along the route, with cloud tops between 10,000 and 14,000 feet MSL. Captain Crawford filed an IFR flight plan, approved by the Civil Aeronautics Administration Air Route Traffic Control in Seattle, requesting a cruising altitude of 13,000 feet to Cheyenne via Airways Green 2, Blue 12, Blue 32, Red 1, and Green 3. The proposed airspeed was 200 mph, with an estimated elapsed time of five hours and six hours and forty minutes of fuel aboard. Denver, Colorado, was listed as the alternate airport. ## Disappearance and Search The flight departed Boeing Field at 0050 and made required position reports without mentioning irregularities. It reported over Malad City at 13,000 feet at 0358 and estimated Rock Springs at 0445. No further radio contacts were made. Attempts by CAA radio stations and other aircraft along and bordering the proposed route to contact the flight were unsuccessful. A widespread search was conducted under the supervision of United States Air Force Air Search and Rescue units. Five days later, the wreckage was found eight miles west of Fish Haven by the pilot of a reconnaissance aircraft. All 40 occupants were killed. ## Official Findings The Board determined that the probable cause was the inadvertent descent into an area of turbulence and icing, which prevented the flight from regaining a safe altitude. Findings noted that light to moderate turbulence and light rime ice were present in cloud tops at cruising altitude, while moderate to severe turbulence and moderate to heavy icing existed at lower altitudes. Ice found on the wing had formed in flight. The crew had been adequately briefed by the U.S. Weather Bureau on route weather before departure. All major aircraft components were identified, and wreckage examination showed no evidence of malfunction, failure, or fire prior to impact. Both engines were developing power at impact. All navigation aids along the route were reported normal. The accident occurred within the airway and slightly to the left of course.