Investigation Summary
United Flight 736 was operating a multi-stop transcontinental service from Los Angeles to New York. At the same time, an F-100F Super Sabre from Nellis Air Force Base was conducting a 'simulated ADF instrument jet penetration' training exercise utilizing the KRAM radio station, which involved a high-speed descent from 28,000 feet. The two aircraft collided at approximately 21,000 feet while the F-100F was in a descending right bank. The fighter's right wing sliced through the DC-7's right wing, leading to a total loss of control for both aircraft. The investigation highlighted a 'see and be seen' failure exacerbated by high closure speeds and cockpit visibility limitations. Specifically, a metal canopy support on the F-100F and a windshield pillar on the DC-7 likely obstructed the pilots' views of one another until collision was unavoidable.
Final Conclusions
The Civil Aeronautics Board (CAB) determined the probable cause was a high rate of near head-on closure at high altitude which, together with human and cockpit limitations, resulted in a failure to see and avoid the other aircraft. The CAB also faulted the Civil Aeronautics Administration (CAA) and Nellis Air Force Base for failing to coordinate activities, allowing hazardous training maneuvers to be conducted within busy civilian airways despite numerous previous reports of near-misses. Notably, while cockpit structural limitations were cited as a factor, the CAB report observed that the view of the fighter from the DC-7 copilot's position was not obstructed by any supporting pillar.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Systems & Failure Modes
Cockpit Visibility
Structural pillars in both the DC-7 windshield and the F-100F canopy were found to have created blind spots that likely hid the conflicting traffic.
Air Traffic Control Coordination
There was no direct communication between Nellis Air Force Base controllers and civilian CAA controllers, despite their facilities being only six miles apart.
Interesting Facts
- 01The collision occurred at a combined closure speed estimated at 765 mph.
- 02Among the fatalities were 13 civilian and military experts assigned to the American ballistic missile program.
- 03The FBI was called in to search for sensitive national security documents carried in handcuffed briefcases by the contractors.
- 04The accident occurred while a CAB hearing on expanding controlled airways was actually in progress in Washington, D.C.
- 05The crash site for the DC-7 was located near Sloan, Nevada, while the F-100F crashed several miles away.
- 06The Douglas DC-7 (N6328C) had a manufacturer serial number (MSN) of 45142 and was manufactured in 1956.
Safety Actions & Advisories
Federal Aviation Act of 1958
The collision accelerated the passage of legislation that replaced the CAA with the Federal Aviation Agency (FAA), giving it total authority over both civil and military airspace.
Positive Airspace Control
The CAB implemented experimental rules barring aircraft without specific clearance from entering designated high-altitude airspace, requiring all such flights to be under instrument flight rules (IFR).
Personnel Travel Restrictions
The military and defense industry adopted rules preventing large groups of technical experts working on the same critical project from traveling on the same aircraft.