Hawker Siddeley Harrier the AV-8C configuration; this programme involved the installation of ECM equipment and adding a new inertial navigation system to the aircraft's avionics. Substantial changes were the Lift Improvement Devices, to increase VTOL performance; at the same time several airframe components were restored or replaced to extend the life of the aircraft. Spain's Harriers, designated AV-8S or VA.1 Matador for the single-seater and TAV-8S or VAE.1 for the two-seater, were almost identical to USMC Harriers differing only in the radios fitted. The Royal Navy's Fleet Air Arm (FAA) operated a substantially modified variant of the Harrier, the British Aerospace Sea Harrier.
Hawker Hoopoe fitted during the short trial period, two variants of the Bristol Mercury were later replaced by an Armstrong Siddeley Jaguar and Panther with an increase in performance. Trials at Felixstowe in 1929 with floats fitted showed that the aircraft was severely underpowered with the Mercury powerplant, requiring the change to the Jaguar engine. Service interest in the type had waned by autumn 1930 although the single prototype continued in development flying with Armstrong Siddeley and the Royal Aircraft Establishment until 1932 when the Hoopoe was scrapped. Hawker Hoopoe The Hawker Hoopoe was a British prototype naval fighter aircraft designed and