Western Air Lines Flight 34

Investigation

After the discovery of the crash site, the Civil Aeronautics Board (CAB) sent a team of investigators to the area. The team arrived on March 1, but they were limited by the weather conditions, which included freezing temperatures, high winds, and snow. The team first focused on the recovery and identification of the victims, which they completed by March 2. Some of the victims had to be identified from pieces of their clothing, items of jewelry, personal items, and hair samples. The remains were taken to Gillette, Wyoming, where they were placed in sealed caskets, then taken to Casper to be flown home to their families. Investigators on the ground gathered mail that the aircraft had been carrying, and brought anything that was still intact to the Gillette Post Office for forwarding. Due to the harsh weather conditions, investigators were only able to make a limited examination of the wreckage as it was found at the crash scene, then the parts of the wreckage were numbered and identified, and their locations were recorded on a distribution chart, and it was transported to Ellsworth Air Force Base in Rapid City. There, the structural components of the aircraft were laid out on a hangar floor to be studied in greater detail.

Investigators searched over a 20 mi area over the last 30 mi of the aircraft's flight path for any witnesses who may have seen or heard the flight. Because it had been snowing heavily when the plane crashed, there were no eyewitnesses, but investigators identified twelve people who had heard an aircraft flying overhead on the morning of the accident. All of the witnesses described the sound of the aircraft as though it was flying much lower than planes ordinarily flew in the area, but the sound of the engines seemed normal to them. Most of the witnesses described the plane flying in the same general direction, but two of them said they heard it twice in a short period of time and from different directions, as though it had circled.

A two-day board of inquiry was held by the CAB in Denver in May 1954, during which they took testimony from 32 witnesses and investigators. Investigators testified that they could not determine the exact time of the crash, but a watch found in the wreckage had stopped at 10:32. They testified that they had not found any evidence of structural or engine failure in the aircraft before the crash. According to company records, the gross weight of the aircraft was 36990 lb, which was 2144 lb less than the maximum allowed takeoff weight, and the center of gravity was within approved limits.

The aircraft was not equipped with flight data recorder or a cockpit voice recorder. Flight data recorders were not required on passenger aircraft before July 1958, and even then only in aircraft that flew higher than 25000 ft. Further investigation of the wreckage did not turn up any evidence of structural failure or malfunction of the control surfaces, and both engines appeared to have been working. The radio equipment was set to the correct frequencies, the cockpit instruments appeared to be functioning, and the heat and anti-icing valves were found in the operating position. There was no sign of an in-flight fire, the landing gear and wing flaps were retracted, and damage to the pilot seats indicated that both seats were occupied at the time of the crash.

Investigators did, however, discover three small pieces of ice, about the size of a man's little finger, inside one of the engine carburetors at the scene of the crash. The pieces matched the shape of the folds in the rubber boot that was attached above the carburetor intake, but investigators had no way of determining whether the ice was present before the crash, or whether it entered the carburetor after the carburetor and boot had been detached from the engine by impact and was in a position to receive falling snow in the days after the accident. The finding raised the question of whether ice buildup in the air intakes had caused the engines to lose power, but pilots experienced with the type of aircraft testified that the Convair aircraft was designed with a very effective carburetor heat system to fight icing in extreme conditions.

A large amount of attention was paid to the possibility of different types of icing that may have occurred in flight. The weather conditions at the time including the likelihood that heavy icing conditions would have occurred at 17000 ft altitude. Those conditions could have caused icing in the engine carburetors, or on the flight surfaces. The Convair CV-240 was only certificated to fly in light icing conditions. However, pilots experienced with the aircraft reported that the carburetor and wing de-icing systems on the aircraft were very efficient and probably would have dissipated any ice buildup in a short amount of time. Investigators doubted that any ice accumulation severe enough to cause a problem would have persisted long enough to cause such a rapid loss of 12000 ft of altitude, and that the conditions at lower altitudes where the snow was melting as it reached the surface should have helped remove any ice buildup.

CAB investigators evaluated several possibilities that could have caused the crash. One idea was that an in-flight fire could have been the cause of the crash, but investigators found little evidence of a fire. Some pieces of wreckage were found with fire damage but investigators demonstrated that the damage occurred from ground fires after the crash. Another idea was that the crew could have become incapacitated during the flight, but the normal tone of voice of the crew during its last radio report, the lack of evidence of an in-flight fire, and the lack of evidence that the crew had used the oxygen masks in the cockpit led investigators to conclude that this theory was not likely. Investigators also found no evidence that an explosion or other types of sabotage to the aircraft had occurred. There was a possibility that there was a malfunction of the control system in flight caused by ice or another object becoming lodged and later breaking loose at the time of impact. Investigators were unable to find any evidence of such a malfunction, but identified it as a possible cause. They explored the possibility that the cargo that was being transported in the passenger cabin had shifted or become loose and had created a hazard, but investigators concluded that the method of securing the cargo that had been used was adequate and that the company had not previously experienced this type of trouble. None of the witnesses on the ground saw any lightning during the storm and weather records did not indicate that any lightning had occurred. The lack of any marks from a lightning strike on any of the parts of the wreckage suggested that a lightning strike was not a likely cause.

CAB investigators were only able to determine the probable cause of the crash as "a sudden emergency of undetermined origin under adverse weather conditions resulting in rapid descent and impact with the ground at high speed".