The Handley Page HP.115 was a experimental delta wing aircraft designed and produced by the British aircraft manufacturer Handley Page. It was built to test the low-speed handling characteristics to be expected from the slender delta configuration anticipated for a future supersonic airliner. The HP.115 was designed during the 1950s as a part of the wider supersonic aircraft research programme that was sponsored by the Ministry of Supply. At the time, both the delta wing and supersonic flight were both relatively recent innovations. By 1956, the Supersonic Transport Committee had been deemed necessary to build a demonstrator to prove that the slender delta wing design was not only suitable for high speed flight but would also be reasonably functional at lower speeds as well. Initially, work centred around an unpowered glider, but it was determined that a self-powered aircraft would be more economic. Accordingly, Handley Page was selected to produce its proposal, the jet-powered HP.115, at the company's Cricklewood facility. On 17 August 1961, the sole HP.115 performed its maiden flight; flight testing of the wing commenced shortly thereafter. A separate research aircraft, the BAC 221, was also built to study the high-speed aspects of the wing research. Over a relatively lengthy period of experimental flying, the HP.115 proved itself to be relatively capable and provided significant data regarding delta wing characteristics during the takeoff and landing phases. The aircraft itself was withdrawn from the test programme in 1974 and subsequently preserved; it is presently on static display at the Fleet Air Arm Museum. The HP.115 had helped validate the properties of the slender delta wing, leading to a similar wing being adopted for Concorde, the Anglo-French supersonic airliner that entered service during the 1970s. Design and development Background Through the 1950s, various studies on supersonic transports (SSTs) suggested that the economics of such designs were far too poor to be practical. Lift is generated in different ways at supersonic speeds and achieving reasonable lift-to-drag ratios requires the wings to have a very short span. This works well at supersonic speeds, but offers very little lift at low speed. In order to make a design that is able to take off and land on existing runways, either the aircraft would have to use wider wings and lose supersonic cruise economy, have enormous engine power, or be extremely large. A way out of this dilemma was presented in Britain by Johanna