Delta wing — triangular aircraft wing design
A delta wing is a triangular planform used on fixed-wing aircraft, especially supersonic types; it provides structural stiffness, internal volume and distinctive vortex lift behavior at high angles of attack.
Overview
A delta wing is a broadly triangular wing planform used on many fixed-wing aircraft. Its simple geometry—broad root and a straight or slightly curved leading edge tapering to a point—gives the configuration its common name. Designers have chosen delta wings for aircraft that must balance high-speed performance, internal fuel or systems volume, structural stiffness and predictable handling. The layout appears on military fighters, interceptors, experimental aircraft and several civil supersonic types.
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Design and aerodynamic characteristics
At supersonic speeds a delta wing can be efficient: a highly swept or slender delta reduces wave drag and can be made thin and stiff to resist high dynamic pressures. At subsonic speeds large deltas may suffer higher takeoff and landing speeds and comparatively low lift coefficients, but they develop strong leading-edge vortices at high angles of attack. These vortices energize the airflow above the wing and produce concentrated, high lift that benefits maneuverability in combat aircraft. Pitch and roll control on many delta designs use elevons, control surfaces that combine elevator and aileron functions.
Variants and features
- Tailless delta: no separate horizontal tailplane; control is via elevons.
- Tailed delta: retains a conventional tail to aid pitch control and low-speed handling.
- Compound or double-delta: a kinked leading edge provides different inner and outer sweep angles to improve lift and reduce drag, especially at low speeds.
- Ogival delta: a curved, continuous leading edge used to smooth transonic and supersonic flow while improving low-speed behavior.
- Delta with canards: small foreplanes ahead of the main wing add control authority and delay stall onset.
History, applications and examples
The delta concept was explored extensively in the mid-20th century as designers pursued reliable supersonic flight. The shape saw widespread use on interceptors and light fighters of that era and later on some strategic and transport types where internal volume or structure was important. Notable examples include several Dassault Mirage fighters, large delta bombers and experimental types, and the Concorde supersonic transport, which used an ogival delta to balance supersonic efficiency with acceptable low-speed handling. Some aircraft combine the triangular wing with foreplanes or tailplanes to overcome the delta's low-speed limitations.
Design trade-offs and modern use
Designers select a delta when the priorities include simple, strong wing structure, space for fuel or equipment within the wing, and good high-speed characteristics. Trade-offs include higher landing and takeoff speeds for many pure deltas and increased induced or profile drag in some flight regimes. Modern fighter designs often use canards, leading-edge extensions or other control surfaces with delta wings to improve agility and reduce the traditional penalties at low speed. For background reading on basic concepts see entries on the wing, the fixed-wing aircraft category, supersonic aerodynamics, fighter aircraft design, and the geometric triangle.
Special Features
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In contrast to conventional wing geometries (such as rectangular wings, elliptical wings or trapezoidal wings), delta wings on aircraft have the shape of a triangle and thus of the Greek capital letter delta (Δ). They have a relatively small airfoil thickness in relation to their wingspan and depth.
The absence of a complete stall represents a special safety aspect. The decrease in airspeed due to a high angle of attack only leads to a steeper stall and a higher angle of attack in a delta aircraft. Consequently, this can be compensated for by sufficient thrust and the aircraft can be returned to a normal attitude such as straight flight.
Delta wings allow a high lift for a short time, but this is bought with a strong loss of energy. The short-term high lift can be used for fast direction changes or back-fall manoeuvres.
The control flaps on the delta wing can replace the aileron function as well as the elevator, the flaps at the end of the wing are then controlled accordingly mixed. Alternatively or additionally duck wings are used. Also the widespread complete tailplane can be combined with delta wings and duck wings.
Range of use
Delta wings are particularly suitable for the supersonic range. Their shape allows a large area in the Mach cone. In the subsonic range, however, they have a higher drag than conventional wings of greater aspect ratio for the same lift. In the higher supersonic range (Ma ≥ 2), small, thin, trapezoidal stub wings with a negative V-pitch like those of the F-104 offer the better lift-to-drag ratio if the accommodation of hydraulics, landing gear, and integral tank can be dispensed with.
Fighter planes are designed for small turn radii and high roll rates in addition to high speed. For small turn radii or high angular velocity a large lift is required, for high speed a small drag. The delta wing is a suitable compromise; it may be thin, heavily swept, of small span, and of large area. The low aspect ratio results in a lower moment of inertia about the longitudinal axis, which leads to a higher roll acceleration. Its long wing root allows a high torsional stiffness.
The high drag in vortex lift mode was used by the space shuttle to dissipate energy in a controlled manner after re-entry. Fighter planes have sufficient thrust to compensate for the losses.
In the field of aeromodelling delta wings are widely used due to their simple construction and stall resistance.
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AlegsaOnline.com Delta wing — triangular aircraft wing design Leandro Alegsa
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