Revelation and Call to Action

During the Vietnam conflict, U. S. pilots flying F-4 and F-105 aircraft faced highly maneuverable MiG-17 and MiG-19 aircraft, and the unan­ticipated return of the close-in dogfight demanded maneuverability that had not been required during design and initial entry of the U. S. aircraft into operational service. Unfortunately, aircraft such as the F-4 exhibited a marked deterioration in lateral-directional stability and control char­acteristics at high angles of attack. Inadvertent loss of control became a major issue, with an alarming number of losses in training accidents. A request for support to the NASA Langley Research Center by representa­tives of the Air Force Aeronautical Systems Division in 1967 resulted in an extensive analysis of the high-angle-of-attack deficiencies of the air­craft and wind tunnel, free-flight model, and piloted simulator studies.[1284]

The F-4 experience is especially noteworthy in NASA’s contributions to high-angle-of-attack technology. Based on the successful demonstra­tions of analysis and design tools by NASA, management within the Air Force, Navy, and NASA strongly supported an active participation by the Agency in high-angle-of-attack technology, resulting in requests for simi­lar NASA involvement in virtually all subsequent DOD high-performance aircraft development programs, which continue to the current day. After the F-4 program, NASA activities at Langley were no longer limited to spin tunnel tests but included conventional and special dynamic wind tunnel tests, analytical studies, and piloted simulator studies.

The shocking number of losses of F-4 aircraft and aircrews did not, however, escape the attention of senior Air Force leadership. As F-4 stall/spin/out-of-control accidents began to escalate, other aircraft types were also experiencing losses, including the A-7, F-100, and F-111. The situation reached a new level of concern when, on April 26, 1971, Air Force Assistant Secretary for Research and Development (R&D) Grant

L. Hansen sent a memorandum to R&D planners within the Air Force noting that during a 5-year period from 1966 through 1970, the service had lost over $200 million in assets in stall/spin/out-of-control accidents while it had spent only $200,000 in R&D.[1285] Hansen’s memo called for a broad integrated research program to advance the state of the art with an emphasis on "preventing the loss of, rather than recovering, aircraft control.” The response of Air Force planners was swift, and in December 1971, a major symposium on stall/poststall/spin technology was held at Wright-Patterson Air Force Base.[1286] Presentations at the symposium by Air Force, Navy, and Army participants disclosed that the number of aircraft lost by the combined services to stall/spin/out-of-control acci­dents during the subject 5-year period was sobering: over 225 aircraft valued at more than $367 million. Some of the aircraft types stood out as especially susceptible to this type of accident—for example, the Air Force, Navy, and Marines had lost over 100 F-4 aircraft in that period.

An additional concern was that valuable test and evaluation (T&E) aircraft and aircrews were being lost in flight accidents during high – angle-of-attack and spin assessments. At the time of the symposium, the Navy had lost two F-4 spin-test aircraft and an EA-6B spin-test vehi­cle, and the Air Force had lost an F-4 and F-111 during spin-test pro­grams because of unrecoverable spins, malfunctions of emergency spin parachute systems, pilot disorientation, and other spin-related causes. The T&E losses were especially distressing because they were experi­enced under controlled conditions with a briefed pilot entering carefully planned maneuvers with active emergency recovery systems.

The 1971 symposium marked a new waypoint for national R&D efforts in high-angle-of-attack technology. Spin prevention became a major focus of research, the military services acknowledged the need for controlled flight at high-angle-of-attack conditions, and DOD formally
stated high-angle-of-attack and maneuverability requirements for new high-performance aircraft programs. Collaborative planning between industry, DOD, and NASA intensified for research efforts, including ground-based and flight activities.[1287] The joint programs clearly acknowl­edged the NASA role as a source of corporate knowledge and provider of national facilities for the tasks. With NASA having such responsibilities in a national program, its research efforts received significantly increased funding and advocacy from NASA Headquarters and DOD, thereby revers­ing the relative disinterest and fiscal doldrums of the late 1950s and 1960s.

One of the key factors in the resurgence of NASA-DOD coupling for high-angle-of-attack research from the late 1960s to the early 1990s was the close working relationships that existed between senior leaders in DOD (especially the Navy) and at NASA Headquarters. With these individuals working on a first-name basis, their mutual interests and priorities assured that NASA could respond in a timely manner with high-priority research for critical military programs.[1288]

From a technology perspective, new concepts and challenges were ready for NASA’s research and development efforts. For example, at the symposium, Langley presented a paper summarizing recent experimen­tal free-flight model studies of automatic spin prevention concepts along with a perspective that unprecedented opportunities for implementation of such concepts had arrived.[1289] Although the paper was highly contro­versial at the time, within a few months, virtually all high-performance aircraft design teams were assessing candidate systems.