Few aircraft in history have gained the iconic status of the McDonnell Douglas F-4 Phantom II. This versatile jet, known for its prowess in a variety of conflicts, was a staple in many air forces of the world. Of the many variants it came in, the F-4E which the US Air Force aircrew affectionately called the “Rhino” stood out with its powerful General Electric J79 engines, capable AN/APQ-120 radar, and an internal M61 Vulcan cannon.
In the late 1960s and the early 1970s, a batch of F-4E and RF-4E Phantoms was delivered to Israel, which it designated as “Sledgehammer.” These saw very good use by IAF pilots against Soviet-exported fighters flown by neighboring Arab nations. The RF-4E variant could carry precious reconnaissance capabilities, be it limited. Israel had no high-altitude spy planes, like the SR-71 Blackbird or U-2 Dragon Lady; likewise, requests for Martin RB-57F Canberra were being refused time and again by the US State Department.
Things took a turn for the worse when emboldened by the Soviets, Egypt began establishing a sophisticated network of surface-to-air missile sites. The threats for Israeli pilots continued to grow, and by mid-1970, several Phantoms had been lost to these SAMs. The need for a much more capable reconnaissance platform became urgent.
Enter General Dynamics with a proposal to convert existing F-4Es into a new variant capable of Mach 3+ speeds. This ambitious project aimed at satisfying Israel’s reconnaissance needs while countering the Soviet MiG-25R Foxbat-B recon aircraft, which had begun operating from Egyptian bases during the early 1970s. With its powerful Tumansky R-15 engines, the MiG-25R was capable of Mach 2.83 and even Mach 3.2 in emergencies making it virtually impossible for the F-4 to intercept.
General Dynamics’ ideas completely transformed the F-4E design by incorporating two large conformal tanks carrying 2500 gallons of water apiece for PCC. The system would inject water into the engine inlets, and through evaporation, cool down the air going into the engines, with especially notable thrust improvements high up. Similarly, redesigned intakes, larger scoops, and vortex generators would enhance flow. The reshaped F-4, given the F-4X nomenclature, would see its sustained speed above Mach 3.
Despite this bright idea, the US Air Force quickly shelved the project in favor of the forthcoming F-15A. The State Department was also cool about the idea as it felt that the exporting of such advanced technology could compromise the strategic balance, placing the SR-71’s dominance at risk. General Dynamics now offered an unarmed reconnaissance version, the RF-4X, fitted with a HIAC-1 LOROP camera in an attempt to avoid these problems.
In 1974, Israel loaned a single F-4E to General Dynamics for mockup and prototype work. However, from the complexity of the PCC system to the abandonment of support by the USAF, the project never achieved problem-free status. Being in a financially incapable position to pursue the program on a solo basis, Israel could not go it alone, so the RF-4X was laid to rest.
Although the F-4X itself never took to the air, it found life after death. Israel continued to search out improved reconnaissance capabilities and eventually modified three Phantoms into the RF-4E(S) variant, which was similarly equipped with the HIAC-1 camera. These planes, nicknamed “Tsalam Shablul” or “Photographer Snail,” remained on active duty with the IAF until their retirement in 2004.
The story of the F-4X is but a takeaway in the long history of the relentless pursuit of military aviation technological advancement, even when insurmountable challenges had to be overcome.