Delta wing
Although long studied, it did not find significant applications until the Jet Age, when it proved suitable for high-speed subsonic and supersonic flight.
[1] At the other end of the speed scale, the Rogallo flexible wing proved a practical design for the hang glider and other ultralight aircraft.
It can be built stronger, stiffer and at the same time lighter than a swept wing of equivalent aspect ratio and lifting capability.
This both enhances its weight-saving characteristic and provides greater internal volume for fuel and other items, without a significant increase in drag.
However, for a sharply-swept delta wing, as air spills up round the leading edge it flows inwards to generate a characteristic vortex pattern over the upper surface.
For intermediate sweep angles, a retractable "moustache" or fixed leading-edge root extension (LERX) may be added to encourage and stabilise vortex formation.
[4] Such conical leading edge droop was introduced on the production Convair F-102A Delta Dagger at the same time that the prototype design was reworked to include area-ruling.
Here, a shock body beneath the wing creates an attached shockwave and the high pressure associated with the wave provides significant lift without increasing drag.
This helps maintain lift outboard and reduce wingtip flow separation (stalling) at high angles of attack.
Techniques used include: The main advantages of the tailless delta are structural simplicity and light weight, combined with low aerodynamic drag.
[10] A lifting-canard delta can offer a smaller shift in the center of lift with increasing Mach number compared to a conventional tail configuration.
The patent included a broad-span biconical delta, with each side bulging upwards towards the rear in a manner characteristic of the modern Rogallo wing.
[24][25] During the latter years of World War II, Alexander Lippisch refined his ideas on the high-speed delta, substantially increasing the sweepback of the wing's leading edge.
[26] Following the end of hostilities, the DM-1 was completed on behalf of the United States and the shipped to Langley Field in Virginia for examination by NACA (National Advisory Committee for Aeronautics, forerunner of today's NASA) It underwent significant alterations in the US, typically to lower its drag, resulting in the replacement of its large vertical stabilizer with a smaller and more conventional counterpart, along with a normal cockpit canopy taken from a Lockheed P-80 Shooting Star.
The outbreak of the Second World War brought a halt to flight testing of the Pa-22, although work continued for a time after the project garnered German attention.
[29][30] Following the war, the British developed a number of subsonic jet aircraft that harnessed data gathered from Lippisch's work.
Whereas the Vulcan was a classic tailless design, the Javelin incorporated a tailplane in order to improve low-speed handling and high-speed manoeuvrability, as well as to allow a greater centre of gravity range.
[32] Gloster proposed a refinement of the Javelin that would have, amongst other changes, decreased wing thickness in order to achieve supersonic speeds of up to Mach 1.6.
[33] The American aerodynamicist Robert T. Jones, who worked at NACA during the Second World War, developed the theory of the thin delta wing for supersonic flight.
[38] A subsequent experimental aircraft, the Fairey Delta 2 set a new World air speed record on 10 March 1956, achieving 1,132 mph (1,811 km/h) or Mach 1.73.
In contrast to the classic tail-mounted elevators, the canards add to the total lift as well as stabilising the airflow over the main wing.
During the 1960s, this configuration was considered to be radical, but Saab's design team judged that it was the optimal approach available for satisfying the conflicting performance demands for the Viggen, which including favourable STOL performance, supersonic speed, low turbulence sensitivity during low level flight, and efficient lift for subsonic flight.
Notable examples include the multinational Eurofighter Typhoon, France's Dassault Rafale, Saab's own Gripen (a successor to the Viggen) and Israel's IAI Kfir.
[54] Multiple proposed successors, such as the Zero Emission Hyper Sonic Transport ZEHST), have reportedly adopted a similar configuration to that Concorde's basic design, thus the Delta wing remains a likely candidate for future supersonic civil endeavours.
Although tested but ultimately never used for spacecraft recovery, this design soon became popular for hang gliders and ultra-light aircraft and has become known as the Rogallo wing.
