The Handley Page HP. 75 Manx was a British experimental aircraft designed by Handley Page that flew test flights in the early 1940s for possible transport, bomber and fighter aircraft projects.
The Manx was named after a breed of stub-tailed cats from the Isle of Man.
Design and development
The Manx was built to participate in a flight research program investigating problems associated with tailless aircraft. The partially-swept wings supported the vertical stabilizers of a twin tail, with elevons for pitch and roll control.

Construction of the prototype was subcontracted to Dart Aircraft of Dunstable. There were serious issues encountered early in the development phase that caused a delay in the testing program. After it was delivered in 1939, redesigns had to be made because the Manx was too heavy, and there were also structural integrity issues with the main spar.

An unorthodox aspect of the Manx design incorporated into the aircraft was that the main undercarriage was retractable, while the nose gear remained fixed.
At a later stage of development, it received a fairing covering the wheel for aerodynamic streamlining.

Taxi tests began in early 1940, but inspection revealed serious deterioration of the wing structures, which required extensive repair.

The HP.75 had an 18-ft long teardrop-shaped fuselage housing a pilot and a rearward facing observer. It was dwarfed by huge wings with a span of whopping 39 ft. Each wing consisted of a straight section near the fuselage and a swept section featuring an elevon and ending with a wingtip rudder. The wingtip rudders were supplemented by a small central fin on the fuselage.

The aircraft was powered by a pair of 140-hp de Havilland Gipsy Major II air-cooled engines. The powerplants themselves were located in the center fuselage between the pilot and the observer. By means of flexible drive shafts they drove a pair of two-blade propellers mounted on the wings’ straight sections in a pusher configuration.

Another unorthodox design solution applied by the Manx’s creators was the jettisonable tail cone. In case of emergency, the observer would get rid of this aircraft part to bail out as quickly as possible.

At last, the prototype performed a ten-minute long maiden flight in June 1943. It didn’t last longer because the aircraft lost the canopy mid-air. Luckily, the pilot managed to make a safe landing. Overall, 31 flights totaling 17 hours were performed until April 1946. The aircraft proved to be significantly underpowered. It had a top speed of 146 mph and ceiling of mere 10,470 ft. The HP.75 also suffered from serious vibration issues. Despite all these shortcomings, test pilot Robert Kronfeld said that, compared with other tailless aircraft, the prototype was “a success in several ways and well worthwhile developing".

The sole example built was scrapped in 1952.











Specifications (HP.75 Manx)
General characteristics
Crew: two, pilot and flight test observer
Length: 18 ft 1 in (5.5 m)
Wingspan: 40 ft 0 in (12.2 m)
Wing area: 246 sq ft (22.9 m2)
Empty weight: 3,000 lb (1,361 kg)
Gross weight: 4,000 lb (1,814 kg)
Powerplant: 2 × de Havilland Gipsy Major 4-cyl. inverted air-cooled inline piston engines, 140 hp (100 kW) each
Performance
Maximum speed: 150 mph (240 km/h, 130 kn)
Service ceiling: 15,000 ft (4,600 m)