Elk Mountain DC-3 Accident Report
The following are Ron's hand-typed excerpts from the CAB accident report investigation. Some abbreviation and omissions and lots of typing mistakes are made.
SA-113 / File No. 257-46
Adopted: Dec. 24, 1946 Released: Jan. 6, 1947
UNITED AIRLINES INC. , Douglas DC-3 NC25675 Elk Mountain, Wyoming January 31, 1946
United Air Lines' Flight 14, en route from Boise, Idaho, to Denver, CO. crashed near thetop of Elk Mountain, Wyo. at 0247 MST, Jan. 31, 1946. All 21 occupants of the aircraft were fatally injured and the Douglas DC-3, NC25675, was demolished by impact and fire.
HISTORY OF THE FLIGHT
Flight 14 departed Portland, OR. at 2020 Jan. 30, 1946, with stops scheduled at Pendleton, OR., and Boise, ID. After being serviced at Boise, the aircraft departed at 0007 Jan. 31, 1946, to cruise nonstop to Denver. The original flight plan authorized prior to departure from Boise specified a cruising altitude of 9,000' between Boise and Malad City, ID; 11,000' between Malad City and Rock Springs, WYO.; and 13,000' between Rock Springs and Denver. Until the aircraft arrived over Rock Springs, the flight was conducted without any apparent difficulty. However, as the flight approached Rock Springs the captain requested and received a change of flight plan in order to remain at 11,000'.
Approximately the time Flight 14 reported over Rock Springs, UAL Flight 44, en route from Oakland, CA. to Cheyenne, WYO. transmitted a position report over that station at the same altitude. As the two aircraft approached Sinclair, WYO. at 11,000' the pilots of Flight 44 observed the lights of Flight 14 approximately one mile ahead and apparently on the left side of the airway. The two aircraft appeared to be on converging flight paths and, before reaching Sinclair, Flight 14 was directly ahead of Flight 44. The crew of Flight 44 observed that Flight 14 appeared to pass over the range station at Sinclair, and to take up a heading directly toward Laramie, WYO. Flight 44, meanwhile, maintained a course close to the left hand side of the airway and the pilots continued to watch Flight 14 as it bore to the right in the direction of Elk Mountain. Having encountered scattered to broken clouds at his cruising altitude in an area approximately 30 miles east of Sinclair, the captain of Flight 44 climbed to 11,300' where he was able to cruise above all clouds. From this point the lights of Flight 14 were intermittently visible to the co-pilot of Flight 44 through breaks in the clouds and the aircraft appeared to be approximately three miles to the right of the airway slightly below the cruising altitude of Flight 44.
Shortly thereafter the co-pilot of Flight 44 observed a bright flash off to his right and a red fire which appeared to glow through theclouds. Fearing that an accident had occurred to Flight 14, the pilot of Flight 44 immediately attempted to establish contact with it without success. At approximately the time of the accident UAL Flight 28 was proceeding westward from Laramie at an altitude of 12,000' and also observed the bright red glow from the vicinity of Elk Mountain. Subsequent attempts to contact Flight 14 by ground stations were unsuccessful and it became apparent that the aircraft had struck Elk Mountain.
An aftercast of the weather situation at the time and in the vicinity of the accident indicated that winds aloft were from 300 degrees to 310 degrees, between 50 and 55 mph. A UAL pilot operating over this portion of the airway testified that scattered-to-broken clouds existed at 11,000'. This observer also indicated that there was a definite overcast around the summit of Elk Mountain extending approximately five miles in all directions. Although the clouds were reported to have been 300' in thickness it was estimated that in the immediate vicinity of Elk Mountain clouds could have been between 500 and 1,000' in thickness.
Adverse weather conditions prevailing soon after the accident delayed the arrival at the scene of investigators of the Safety Bureau of the Civil Aeronautics Board. Although several attempts were made to climb Elk Mountain the following day by personnel from local Army stations, the extremely low temperature and heavy snowdrifts made it impossible. Approximately seven days after the accident occurred, a Board investigator was able to reach the scene and to accomplish a cursory inspection of the wreckgae. Because of the impossibility of completing a satisfactory examination due to the heavy snow that covered the wreckage, arrangements were made to return to Elk Mountain during late June at which time most of the snow would have melted at the scene of the accident.
On June 25, investigation of the wreckage was continued under more favorable conditions. With the exception of the left engine, which had rolled over the crest of the hill and into a large snowbank, most of the debris was accessible for inspection. Examination of the seats and the broken seat belts indicated that both pilot and co-pilot were at their respective stations at the timeof impact. Marks of impact on the ground indicated that the aircraft was in approximately level flight at impact. Distinct propeller marks had been cut in the face of the mountain and both wings were torn from the fuselage. The fuselage disintegrated as it slid up the mountain slope for a distance of approximately 200 yards. Some parts of the aircraft continued along the direction of flight over the top of the ridge rolling down the east side.
Inspection of the radio panel disclosed that the ADF receiver was tuned to 235 kcs. at the time of the accident and that the range receiver was tuned to 212 kcs. The frequency of the Laramie radio station is 236 kcs and that of Sinclair is 212 kcs.
A survey of the direction of flight indicates that Flight 14 was on a magnetic course of 80 degrees at the time of impact. Inasmuch as winds of 50 to 55 mph at a relative wind angle of 235 degrees were experienced, it is probable that approximately 14 degrees of wind drift would have been experienced along the course between Sinclair and Laramie. Laramie is on a magnetic bearing of 98 degrees from Sinclair and, if the wind conditions remained constant throughout the course, a magnetic heading of 84 degrees would have been required to negotiate such a course.
The airway eastward from Sinclair parallels the center of the east leg of the Sinclair range to the intersection with the northwest leg of the Laramie range. From this point it bends sharply to the right toward Laramie on a heading of 137 degrees. The distance between Sinclair and Laramie via Airway Green 3 is 88 miles while the distance between the two range stations on a direct course is 79 miles. The point of impact on the southwest corner of Elk Mountain at an elevation of approximately 10,822' is located on a direct line between the Sinclair and Laramie radio range stations. The flight path of the aircraft in the vicinity of the accident had deviated south of the airway a distance of approximately 4 1/2 miles. Elk Mountain represents the highest terrain between Sinclair and Laramie within an area of 15 miles of either side of the direct course. The doglegged airway was designed in order to provide most effective clearance from the high terrain to the south.
Capt. Briggs had recently returned to duty with UAL after a tour of duty of 1 1/2 years with the Army Air Force. Upon return to United he was given six one-way qualifying trips over the route, two as a co-pilot and four as an observer riding the "jump" seat. First Officer Atlas was making his first scheduled flight over theroute.
Investigation of CAA comm. records for the period including thetime at which the accident occurred indicates that all nav. aids including beacon lights and radio facilities were functioning normally at the time of the accident.
That region of WYO. in the vicinity of Elk Mountain is very sparsely settled and no witnesses were located who had either seen or heard Flight 14 from the ground immediately prior to or at the tim eof impact.
The elevation at the top of Elk Mountain is 11,162'. Flight 14 struck the mountain at an elevation approximately 340 feet below that of the crest of the mountain and approximately 180' below the assigned cruising altitude. Such a deviation cannot be considered unusual and could be explained by decrease in the barometric pressure as the flight proceeded eastward and the unusually low temperature encountered in that area.
The magnetic heading required under the conditions of the winds aloft and magnetic variation in the area of Elk Mountain in order to maintain a direct course between Sinclair and Laramie was approximately 84 degrees. Although it has been determined that the aircraft was actually on a magnetic course of 80 degrees at impact, the point of impact was on a direct line from the Sinclair to the Laramie radio range stations, the magnetic bearing of which is 98 degrees. It is unlikely that the same wind direction and velocity would have prevailed at thesurface of Elk Mountain and the actual wind drift experienced by Flight 14 immediatel prior to impact is impossible to determine. It therefore appears that Flight 14 had deviated from the airway in order to maintain a direct course between these two points. This conclusion is further confirmed by the fact that the aircraft ADF receeiver was tuned to the frequency of the Laramie radio range station. Although the possibility may exist that the deviation from the airway had been a result of wind drift, it is apparent that Capt. Briggs was aware of the winds aloft inasmuch as he had navigated without apparent difficulty to Sinclair from Portland, OR. It is extremely unlikely, therefore, that such wind drift was experienced without his knowlege.
Testimonf of pilots operating along Airway Green 3 at approximately the time of the accident and weather data furnished by the Weather Bureau indicate the likelihood that Flight 14 encountered some clouds in the area of Elk Mountain and that at the time of impact the pilot was actually "on instruments."
No evidence was disclosed as a result of examination of the wreckage, inspection of the aircraft's maintenance records or testimony of the pilots of Flight 44 to indicate failure of either the powerplants or the aircraft structure. The request by Capt. Briggs for a change in clearance to permit the flight to remain at 11,000' and the fact that the point of impact was at an elevation reasonably close to 11,000' indicate that he was experiencing no undue difficulty in maintaining his cruising altitude.
Impact marks on the face of the mountain further indicate that the aircraft was in straight and level flight and apparently under control. It must be concluded, therefore, that the pilot maintained a cruising altitude which did not provide adequate clearance over Elk Mountain; that the pilot departed from the normal course along Airways Green 3; and that the aircraft struck Elk Mountain while "on instruments."
On the basis of all available evidence the Boad finds that:
1. The pilots, aircraft, and crew were properly certificated for the flight.
2. An instrument flight plan was authorized for Flight 14, which included a cruising altitude of 13,000' between Sinclair and Laramie, WYO.
3. When over Rock Springs, WYO., range station the captain requested and received approval of a change of flight plan in order to permit him to remain at 11,000'.
4. Until reporting over Sinclair, the flight had been routine.
5. The flight deviated from the prescribed route and followed the most direct course between Sinclair and Laramie.
6. The ADF reciever was tuned to the Laramie radio range station.
7. At 0247 MST, Flight 14 collided with Elk Mountain at an elevation approximately 180 feet below its assigned cruising altitude and 4 1/2 miles south of Airway Green 3, and was demolished by impact and fire.
On the basis of the foregoing the Board finds that the probable cause of this accident was the deviation from the prescribed route at an altitude insufficient to assure adequate clearace over Elk Mountain.
BY THE CIVIL AERONAUTIS BOARD: (signed) Oswald RYAN, Member; Harllee BRANCH, Member; Josh LEE, Member.
Landis, Chairman and Young, Member, did not take part in the decision
Last Modified: 1/1/2008