During the late 1950s, an improved ASW model, the Gannet AS.4, and its T.5 trainer equivalent were developed. The improvements included the fitting of an up-rated Double Mamba engine. Several were refurbished with new electronics and radar, thus were re-designated Gannet AS.6. During 1958, the Gannet was selected to replace the Douglas Skyraider in the airborne early warning and control (AEW) role. In order to accommodate the systems required for this new mission, the Gannet underwent a significant redesign that saw a new version of the Double Mamba installed, new radome mounted under the aircraft, the tailfin increased in area, the undercarriage lengthened and the weapons bay removed. A total of 44 aircraft (plus a single prototype) of the AEW.3 version were produced. Design The Fairey Gannet is a carrier-borne turboprop-powered aircraft. It was typically operated by a crew of three, a pilot and two aerial observers. The pilot was seated directly above the aircraft's Double Mamba engine and behind the gearbox and contrarotating propellers in a position that conferred a favourable view over the nose for carrier operations. The first observer was seated underneath a separate canopy that was directly aft of the pilot's position. On the production aircraft, a second observer was also present in their own cockpit that was located over the wing trailing edge. This addition disturbed the airflow over the horizontal stabiliser, necessitating the addition of small finlets on either side. The wing of the Gannet folded in two places, forming a distinctive Z-shape on each side, to minimise its space requirements while being stowed onboard aircraft carriers. The first fold was upwards, at about a third of the wing span where the inboard anhedral (down-sweep) changed to the outboard dihedral (up-sweep) of the wing (described as an inverted gull wing). The second wing fold was downward, at about two-thirds of the wing span. The length of the nosewheel shock absorber caused the Gannet to have a distinctive nose-high attitude, which was a common characteristic of carrier aircraft of the era. The Gannet had a sizable internal bomb bay within the fuselage; it was the first British aircraft in FAA service to be capable of storing all its munitions (other than rockets) within an internal bomb bay. Such munitions could include depth charges, sonobouys, homing torpedoes, bombs, markers, and mines. Hard points beneath the outer wings could carry up to 16 Mk.8 or 24 Mk.5