The Firefly was a low-wing cantilever monoplane, featuring an oval-section metal semi-monocoque fuselage and a conventional tail unit with forward-placed tailplane. It was powered by a Rolls-Royce Griffon liquid-cooled piston engine, which drove a four-blade Rotol-built propeller. A large chin-mounted radiator was present to provide cooling for the engine. The Firefly had retractable main undercarriage and tail wheel, the hydraulically-actuated main landing gear retracting inwards into the underside of the wing centre-section. This undercarriage was widely-set, a highly useful feature for carrier landings. The aircraft was also fitted with a retractable arrester hook mounted underneath the rear fuselage. The pilot's cockpit was located above the leading edge of the wing while the observer/radio-operator/navigator was positioned aft of the wing's trailing edge. These positions provided better visibility for operating and landing, and both crew were provided with separate jettisonable canopies.