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Weather information provided the crew at McChord AFB supported their evaluation of the briefing, that the flight could be accomplished VFR at least until reaching southeast Idaho, where lowering ceilings were forecast to occur later in the day and if this deteriorating condition existed on reaching southeastern Idaho, the pilot had planned to refile in the air. On the basis of the briefing a VFR flight plan was filed. There is no evidence to indicate that the crew received any further weather information following departure from McChord AFB. At departure from Boeing Field, the official weather observation showed in part, 2,500 scattered, estimated, 12,000 overcast, visibility 15 miles.
However, based on all available weather information, including testimony of inflight and ground witnesses throughout the Seattle area, it is concluded that due to an approaching warm front over the Pacific, cloud conditions lowered relatively rapidly during the early afternoon. It is believed that prior to reaching the accident site the aircraft would have encountered a cloud deck increasing rapidly from scattered to broken to overcast with the base near 5,000 feet, top merging with an overcast whose base was in the 8,000 to 9,000-foot range, tops around 14,000 feet. Under these conditions, it is obvious that the higher elevations of Mt. Rainier would not have been visible to the pilot.
Light to occasionally moderate turbulence was likely to have been encountered en route with light icing in clouds or precipitation above 5,000 feet.
Although the briefing did not include information regarding icing and turbulence it was considered to be adequate. However, the Weather Bureau area forecast which was utilized in the briefing was inaccurate inasmuch as the general conditions encountered by the flight shortly after departure were not forecast to occur until after dark.
With regard to the aircraft's flightpath, there is no way of determining whether the pilot had in some manner incorrectly identified airway V-4 as being the 125-degree radial of the Seattle VOR or had erred with respect to the specific location of Mt. Rainier relative to the 125-degree radial directional as well as by position, the PDI's were found set at approximately this radial, and the crew had reported being on V-4 (at 1417), the first possibility is considered the most probable. In either case the lack of proper correlation of the aircrafts position with respect to obstruction terrain along its flightpath is apparent.
All communications with the Seattle ARTCC, including the last transmission seconds before impact, were considered to be normal and revealed nothing to suggest any aircraft or flight crew distress.
Although the pilot reported VFR conditions climbing through 10,500 feet, the facts and testimony developed during the investigation most substantively support that instrument flight conditions prevailed during the last portion of the flight, and that the aircraft collided with the mountain while being
