Flexible wing
A wing that deforms in flight for control or storage.
A flexible wing is an aircraft wing or airfoil that changes shape while in flight. Early pioneers used this property for control: the 1903 Wright Flyer twisted its lightweight wing tips to steer, a method the Wrights patented and others copied. As engine power and speed increased, the forces required to warp wings grew too high, and the technique was largely abandoned by 1914. Other early experimenters, like Gustave Whitehead, designed collapsible wings that folded away like a fan, aiming to solve storage and transport problems for vehicles like flying cars.
In flight, all wings flex naturally under aerodynamic and inertial loads—a phenomenon called aeroelasticity. Most aircraft designs try to minimize this by making wings as stiff as possible, but some have used it intentionally. The Horten brothers’ flying-wing gliders of the 1930s had wing tips that bent upward in flight to act as stabilizers. Later, the Short SB.4 Sherpa, developed by Geoffrey T. R. Hill in the 1950s, used an aeroisoclinic wing that controlled flexing to maintain handling at all speeds. Similar aeroelastic tailoring later became necessary for safe forward-swept wing designs.
Since the 1960s, flexible wings have dominated hang gliders and ultralight aircraft. In 1948, Francis and Gertrude Rogallo created a collapsible kite that used tension lines and air pressure to keep a constant shape in flight. Francis Rogallo, working at NASA’s Langley research center, developed the concept into designs for crewed aircraft, including a space vehicle re-entry system. After talks in 1959 and 1960, his ideas spread, leading to the Rogallo delta wing and the paraglider, both used for kites, hang gliders, and ultralight aircraft (some with backpack engines). Despite testing, NASA never used Rogallo wings for spacecraft descent. The Rogallo wing itself evolved into a double-delta “parawing” with struts to maintain its planform, while the parafoil became a fully collapsible, double-skinned wing held open by air pressure from the front.
In the 21st century, new flexible yet strong materials have renewed interest in using wing deformation for control. A flexible flap has been test-flown on a Gulfstream III, and such surfaces work by smoothly altering shape to deflect airflow, reducing drag compared to hinged control surfaces, which create gaps and vortices.
- First powered aircraft with wing warping
- 1903 Wright Flyer
- Year rogalo kite developed
- 1948
- Year rogalo talks spread
- 1959-1960
- Key people
- Wright brothers, Gustave Whitehead, Horten brothers, Geoffrey T. R. Hill, Francis and Gertrude Rogallo
- Example modern test aircraft
- Gulfstream III
- Example human powered ornithopter
- UTIAS Snowbird (2010)
Lore & Background
Early pioneer aeroplanes such as the 1903 Wright Flyer used the flexible characteristics of lightweight construction to control flight through wing warping. Others made collapsible wings for folding away, such as the flying car designs by Gustave Whitehead. The Wright Flyer used wing warping for lateral or roll control, twisting one wing tip to increase its angle while twisting the other to reduce it. However, as engine powers and air speeds rose, the forces needed to operate controls increased, and by 1914 warping was all but abandoned.
Aeroelasticity is the natural tendency of any wing to flex under aerodynamic and inertial loads. Most designs seek to minimize effects by making the wing structure stiff, but some have used it to advantage. The Horten brothers' flying-wing gliders of the 1930s had wing tips that flexed upward to act as stabilizers. The aeroisoclinic wing, developed by Geoffrey T. R. Hill in the 1950s and flown on the Short SB.4 Sherpa, attempted to control flexing to maintain handling. Similar aeroelastic tailoring was later applied to experimental forward-swept wings.
In 1948, Francis and Gertrude Rogallo developed a flexible kite that could be collapsed for storage. Their design used tension lines and aerodynamic forces to stabilize and control the wing. Following talks in 1959 and 1960, the Rogallo delta and paraglider designs were soon used for kites, hang gliders, and ultralight aircraft. The parafoil is fully collapsible and double-skinned, held in shape by air pressure from in front.
Reader's Guide
Flexible wings have significantly influenced aircraft design across multiple eras. The Wright brothers' wing warping system provided the first effective control on a powered aircraft, enabling the first flight. Although abandoned by 1914 due to increasing control forces, it established a principle later revisited. Collapsible wings, predating powered flight, addressed ground storage and transport, as seen in Gustave Whitehead's flying car attempts.
Since the 1960s, flexible wings have dominated hang glider and ultralight aircraft designs, with the Rogallo wing and paraglider becoming widespread. The Rogallo wing, evolved from Francis Rogallo's 1948 kite, uses struts to maintain planform while relying on air pressure for its conical profile. The parafoil, fully collapsible and double-skinned, is held in shape by incoming air. Although tested for spacecraft descent, no Rogallo types have been used by NASA.
In the 21st century, new flexible and strong materials have renewed interest in using flexing for control. A flexible wing flap has been test flown on a Gulfstream III. Benefits include reduced aerodynamic drag compared to hinged control surfaces, which disrupt airflow and generate vortices. For smaller craft, smart control systems combine with flexible technologies to create articulated wings mimicking bird flight, including human-powered ornithopters like the UTIAS Snowbird of 2010. The technology is known as morphing wing, smart airfoil, or adaptive compliant wing.
Did You Know?
- The 1903 Wright Flyer used wing warping for lateral control by twisting wing tips.
- Gustave Whitehead developed collapsible wings for a flying car design.
- The Rogallo wing was originally developed as a flexible kite in 1948 by Francis and Gertrude Rogallo.
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