December 1956 Bob Ericson was flying U-2A (56-6690) at 35,000 feet when he suffered an oxygen failure. As he began to pass out, the aircraft went out of control. Ericson managed to open the canopy, and parachute to a safe landing on the Navajo Indian Reservation in Arizona.
Article 341 was modified for a series of radar cross section (RCS) tests called Project RAINBOW. Lockheed attempted to reduce the RCS of the U-2 using radar-absorbent materials.
Another U-2, Article 344, was strung with piano wire of varying dipole lengths between the nose and wings of the aircraft to reduce the radar signature. These methods created extra drag with a resultant penalty in range and altitude. The U-2 aircraft modified under Project RAINBOW were known as "dirty birds" because they were not aerodynamically "clean."
April 1957 During a Project RAINBOW test flight, Article 341 suffered a flameout at 72,000 feet due to airframe heat build-up. Pilot Robert Sieker's pressure suit inflated, but his helmet faceplate failed and he lost consciousness. The aircraft stalled at 65,000 feet and entered a flat spin. Sieker revived at low altitude and attempted to bail out. Without an ejection seat, or enough altitude for a safe manual egress, Sieker was killed. His body was found near the wreck, with his parachute partially deployed. More information here.
An AEC information booklet called "Background Information on Nevada Nuclear Tests" published in 1957) gave a cover story for the Watertown operation. It stated that the National Advisory Committee for Aeronautics (NACA) was operating U-2 aircraft at the Groom Lake site "with logistical and technical support [from] the Air Weather Service of the U.S. Air Force to make weather observations at heights that cannot be attained by most aircraft." At that time, the aircraft were unpainted except for fictitious NACA markings in the event that one of them was lost off-site.
The AEC conducted a safety experiment with an XW-25 warhead just five miles northwest of Groom Lake in Area 13. Called Project 57, the test was part of Operation Plumbbob. The device, with a design yield of one to two kilotons, was involved in a simulated accident without a nuclear detonation. The test spread plutonium over 895 acres. More information here.
May 1957 AEC Radiological Safety Officer Charles Weaver, Oliver R. Placak, and Melvin W. Carter participated in two meetings held at Watertown. The film Atomic Tests In Nevada was shown and discussed during two meetings. Watertown personnel were briefed on nuclear testing activities, radiation safety, and the possibility of radiation hazards from the Operation Plumbbob test series. Before leaving Watertown, the AEC men met with two Air Force officers, Col. Jack Nole and a Col. Schilling, and Richard Newton to discuss arrangements for radiation monitors to visit the airbase whenever fallout was anticipated in the Watertown area.
Shot BOLTZMANN, a 12 kiloton blast, was fired from a 500-foot tower on northern Yucca Flat. Watertown personnel were required to evacuate the secret base to avoid fallout.
June 1957 Two minor atomic blasts, FRANKLIN and LASSEN, were fired at Yucca Flat. CIA pilot classes finished training. The U-2 test operation moved to North Base at Edwards AFB, California. Operational U-2 aircraft were assigned to the 4028th Strategic Reconnaissance Squadron. 4028th SRS commander Col. Nole led the first of two three-ship U-2 formations from