Investigation Summary
Flight 4 was a scheduled service from Salt Lake City to Cheyenne. The flight proceeded normally until the final approach phase. The crew was navigating using a series of rotating beacons, a standard method for night mail and passenger flights in the 1930s. At approximately 02:17, the crew communicated with the Cheyenne ground station, indicating they were near the Silver Crown beacon, located about 10 miles northwest of the airport. Shortly thereafter, the aircraft struck the ground on a knoll. The impact and subsequent fire destroyed the aircraft. The investigation focused on why an experienced crew, led by a captain who had flown the route over 100 times, would fly into the ground. A key finding was the state of the cockpit illumination; the rheostat for the cockpit lights was found in the full-bright position. In the era before sophisticated flight instruments and terrain awareness systems, pilots relied heavily on outside visual cues. High-intensity internal lighting would have caused significant glare and 'night blindness'; preventing the crew from seeing the dark, unlit Wyoming terrain as they descended.
Final Conclusions
The Department of Commerce investigation concluded that the probable cause was the failure of the pilot to maintain sufficient altitude to clear the terrain. Contributing factors included the darkness of the night and the high intensity of the cockpit lighting, which reduced the pilots' ability to observe the ground. The aircraft was found to be functioning normally prior to impact, with no evidence of structural or mechanical failure.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Halston A. 'Colly' Collison. Hours cited for Air Mail Service only; total career hours likely higher.
Systems & Failure Modes
Rotating Beacons
Tower-mounted lights used for visual navigation along established air routes during night operations.
Cockpit Lighting Rheostat
A control used to adjust the brightness of instrument and cockpit lights; found at maximum intensity after the crash.
Interesting Facts
- 01Captain Collison was a veteran of the U.S. Air Mail Service and had survived numerous forced landings.
- 02The aircraft was a Boeing 247D (MSN 1698), one of the first modern all-metal airliners.
- 03The crash site was located near the Silver Crown rotating beacon.
- 04Former U.S. President Herbert Hoover was nearly a passenger on this flight but took a train instead.
- 05The nine passengers included Vincent Butler (attorney), Juliet Hillman (socialite), John F. Cushing (President of Great Lakes Dredge and Dock Co.), George H. Miner, Helen Warren (UAL employee), Roy Bane, C. H. Mathews, Carolyn Cathcart, and Robert H. Renebome.
- 06Passenger Robert H. Renebome was discovered to be a fugitive traveling under an alias using another man's ticket.
Safety Actions & Advisories
Night Vision Awareness
The accident highlighted the dangers of internal cockpit glare during night operations, leading to better pilot training regarding light management during approach.