United Airlines Flight 409 - Investigation

Investigation

Due to safety concerns, the CAB accident investigation team —not trained in alpine mountaineering techniques— was unable to visit the cliff location where the DC-4 initially hit. Study of the wreckage that could be retrieved for examination suggested a nose up attitude and an unusually low airspeed of the plane, implying that the plane was attempting a climb at the time of its crash. The reasons for this are not explicitly known, but several theories exist:

• An altimeter indicating an inaccurate altitude, leading the pilot to believe he was higher than he actually was;
• Mountain obscuration by clouds, preventing visual sighting of the mountain peak before it was too late to react to prevent the crash;
• Turbulence, specifically downdrafts, around Medicine Bow peak, pushing Flight 409 into the mountain.

Possible incapacitation of crew by carbon monoxide emanating from a faulty cabin heater was speculated upon based on recovery crew observations that crew bodies appeared 'discolored.' This theory was never proven, and the CAB report specifically states that there was no evidence to support crew incapacitation.

After the investigation of the accessible wreckage was completed, United Airlines requested that the remaining debris be destroyed by the military. Attempts were made to accomplish this, but despite the use of explosives, artillery fire and —according to most sources— napalm bombs dropped from aircraft, complete obliteration of the wreckage was not possible. One source, a 2007 book about the Rocky Mountain Rescue Group, contradicts the assertion that military jets bombed the site with napalm; instead, the book states that the cliff face was mined with explosives that were detonated in the spring of 1956, and the event was tightly controlled and not publicized. Regardless of the disposal method, small fragments of flight 409's airframe and parts of the engines still exist in the area surrounding the crash site.