According to Wikipedia: "The E-1 Tracer was the first purpose built airborne early warning aircraft used by the United States Navy. It was a derivative of the Grumman C-1 Trader and first entered service in 1958. It was replaced by the more modern E-2 Hawkeye in the early 1970s. The E-1 was designated WF under the old US Navy system; the designation earned it the nickname "Willy Fudd". Since the S-2 Tracker was known as S2F under the old system, that aircraft was nicknamed "Stoof"; the WF/E-1 with its distinctive radome gained the nickname "Stoof with a Roof." The E-1 featured folding wings for compact storage aboard aircraft carriers. Unlike the S-2 and C-1 in which the wings folded upwards, the radome atop the fuselage necessitated the E-1 to fold its wings along the sides of the fuselage."