Although the original idea was to keep the Shackelton AEW.2 in service only until the mid-1980s, the reality was much harsher and they were in flight until the early 1990s, in part because during the Cold War, the northern part of the United Kingdom could not be unguarded under any circumstances.The AN / APS-20 radars from the retired Fairey Gannet were mounted under the Shackelton‘s nose. This radar system had an IFF and VHF communications. The concept consisted of two parts, the airborne and the shipboard, sending signals the first and analyzing the second, which was in charge of air control and deployment of the air defense.AN / APS-20 search radar was projected by the Massachusetts Institute of Technology-Radiation Laboratory under the “Project Cadillac” program in 1944. The main purpose of this project was to equip the American forces with a long-range radar to be used in the planned invasion of Japan, the Operation Downfall. This system was the first airborne early warning radar in the World.This radar had a rotating antenna that was housed in a ventral dome and operated in the S band, (NATO: E band), from 2 to 4 Ghz and was developed by Hazeltine and General Electric. The maximum range was about 460 km with optimal weather conditions and could detect a fighter aircraft at 185 km away.
