Several photos of the F-4’s used in early composite rudder testing at St. Louis. Boron and Beryllium epoxy rudders were both tested.
The above photo shows “Old 122” (YRF-4C 62-12200) in “Agile Eagle” configuration with the Beryllium rudder installed during April 1967. Adding leading edge maneuvering slats to F-4’s was evaluated during flight tests known as Project Agile Eagle. And it should come as no surprise that multiple flight test configurations were run at the same time! McDonnell made 45 rudders which were installed on F-4 fighters for service evaluation.
Also included is a Flight International article from June 7, 1973 on Boron Composites. This lists which aircraft used/tested boron componets and a background on Boron development.
Credit: Ramp “122” photo from FFRC Photo Collection

