Accident at Near Hanksville, Utah, 21 Aug 1947

Accident narrative

On August 21, 1947, a Curtiss-Wright Commando Model C-46E operated by Slick Airways crashed into a ridge of Blue Bell Knoll Mountain, 40 miles southwest of Hanksville, Utah. The two pilots and one passenger were killed, and the aircraft was destroyed.

**The flight** The flight originated at Willow Run Airport, Ypsilanti, Michigan, on August 20, 1947, with its destination Burbank, California. Following a scheduled landing and crew change in Denver, Colorado, Captain Marvin George Vaughan and First Officer Robert Humes departed at 0406. Herbert V. Preeg was carried as a non-revenue passenger to obtain factual data for a story on air freight.

The flight plan specified that they would proceed in accordance with visual flight rules at 14,000 feet to Eagle, Colorado; 12,000 feet to Grand Junction, Colorado; and 10,000 feet to St. George, Utah. The proposed airspeed was 180 miles per hour, and the time en route was computed to be 4 hours and 40 minutes.

**The sequence of events** The flight proceeded normally, reporting over the Eagle radio range station at 0447 at 14,000 feet. At 0552, the crew reported over Grand Junction at 12,000 feet, descending to 10,000 feet. They reported over Hanksville at 0558 at 10,000 feet, estimating their arrival over Bryce Canyon at 0627. This transmission was received loud and clear, with no indication of mechanical trouble.

Around this time, a CAA communicator on duty at Hanksville observed the aircraft flying between the radio range station and Mt. Ellen. He stated the aircraft appeared to be flying normally and was below a layer of clouds. Approximately 12 minutes later, the aircraft crashed into a ridge of Blue Bell Knoll Mountain. Witnesses in the vicinity stated that clouds obscured the mountain tops at that time.

**What the investigation found** The wreckage was located 100 feet below the mountain ridge at an elevation slightly over 10,000 feet, on a magnetic bearing of 228 degrees from the Hanksville radio range station. The precipitous and rocky terrain formed a U-shaped canyon opening eastward. Investigation disclosed that the aircraft had flown into this canyon through the opening as it progressed on its westerly course.

The airplane had practically disintegrated on impact. Evidence indicated a flash fire occurred when the aircraft struck the ground, but none of the structure had burned and there was no evidence of fire prior to impact. The complete disintegration meant little could be learned from the wreckage itself. However, ground observations and position reports indicated the airplane had been flying on course without difficulty. Aircraft records showed it was loaded within allowable limits, properly maintained, and airworthy.

The Board noted that while the flight had been proceeding on course from Hanksville at 10,000 feet under visual flight rules, instrument weather conditions existed at 10,000 feet in the vicinity of the crash. The terrain the aircraft struck was above the flight's cruising altitude. According to the Slick Airways Operations Manual, instrument flight over this area should have been conducted at 13,000 feet.

Considering that the mountain tops were obscured by clouds, the aircraft was observed flying below the clouds, no mechanical difficulty was reported, and the airplane was observed flying normally on course, the Board concluded it was logical that the airplane was flown into clouds and into terrain above its cruising altitude.

**Probable cause** Upon the basis of all available evidence, the Board determined that the probable cause of this accident was "the continuation of the flight into instrument weather conditions over mountainous terrain at an altitude too low to clear the mountains en route."