(Jimmy of the Clue Crew reports from Kadena Air Base in Japan.) The 30-foot rotating dome on top of the AWACS E-3 is a highly advanced version of this system first implemented in England in the 1930s
These Air-Controlled Interception aircraft were the first to 
merge two ... of advanced and specialized aircraft, including the U.K.'s Fairey ... a 
rotating 30-foot-diameter radar dome mounted above the fuselage,... [DOC] [TLE] E-3 Sentry (AWACS) - GlobalSecurity.org [PAR] The E-3 Sentry is an airborne warning and control system (AWACS) aircraft that 
... is a modified Boeing 707/320 commercial airframe with a rotating radar dome.