The number of wings indicate whether it is a monoplane, biplane or triplane. Somerville installed the devices on his early biplane and monoplane designs. The resulting design was a twin-engined, low-winged monoplane with a retractable tailwheel undercarriage. The Cessna 305A was a single-engined, lightweight, strut-braced, high-wing monoplane with a tailwheel landing gear. The Boeing 720 is a four-engined low-wing cantilever monoplane. It is a conventional, low-wing cantilever monoplane with fixed tailwheel undercarriage. The aircraft was a high-wing cantilever monoplane with a fixed undercarriage. The Ju 87 was a single-engined all-metal cantilever monoplane. The DC-10 is a low-wing cantilever monoplane, powered by three turbofan engines. The Avro Anson was a twin-engine, low-wing cantilever monoplane. It was a single-seat, all-metal, low-wing cantilever monoplane with aft-retracting main undercarriage. The XFR-1 was a single-seat, low-wing monoplane with tricycle landing gear. The aircraft, a Vickers R.E.P. Type Monoplane, was to be flown by Francis Howard Bickerton. The airframe was a one engine two-seat monoplane, with a metal-covered frame. The Model 3000/T-6 is a low-wing cantilever monoplane with enclosed tandem seating for two.