Tandem wing

[1] Compared to the conventional layout, where the tailplane exerts little or no vertical force in cruising flight, both tandem wings contribute substantially to lift.

At high aircraft AoA, this causes the front wing to stall first, allowing safer flight at low speeds than the equivalent conventional layout.

The mechanisms of stability and control for a tandem wing are similar to those for the tail-first or canard layout; the distinction is mainly in the relative size of the forward surface.

[4] However, the larger trim forces available compared to a smaller tailplane or foreplane mean that a tandem design can offer a greater range of trim conditions, and hence of centre of gravity (CG) location than other layouts, which can offer a practical solution where weight loadings and distributions may vary during operations.

However a wide CG range leads to other problems, including a compatible undercarriage layout and safe stalling characteristics.

[1] Having also flown simpler fore-and-aft tandem models of up to 14 feet (4.3 m) in span, in 1903 Samuel Pierpont Langley built a full-size tandem-wing monoplane, the Aerodrome, and launched it from the roof of a houseboat.

Curtiss added floats and made other improvements, enabling it to undertake short hops as a true waterplane in 1914.

But it was not until the next year that his type VI, a wheeled tandem monoplane of broadly similar configuration to Langley's Aerodrome, became the first tandem-wing aeroplane to fly.

[4] Overlapping with Eiffel's work, Stefan Driezewicki developed and wind-tunnel tested an inherently stable tandem-wing design.

The Caproni Ca.60 prototype flying boat comprised a long passenger-carrying hull to which were attached in tandem three stacks of triplane wings from the successful Ca.4 line of heavy bombers and airliners, earning it the nickname "Capronissimo".

The first fully controllable tandem-wing type was the French-built Peyret tandem glider, which won the first British gliding competition in 1922.

However stability issues relating to the variable front wing could lead to lethal crashes in the hands of the novice pilot, and the type eventually fell out of favour.

[10] George Miles saw the tandem Lysander at RAF Boscombe Down and realised its potential as a short-span, short-take-off Naval fighter.

Although the design was rejected, it flew well enough to prompt development of the larger M.39B, a subscale test aircraft for the proposed M.39 high-speed bomber to meet Specification B.11/41.

After WWII, interest returned to the Flying Flea's tilting forewing concept and, with its worst dangers now understood and fixed, designers have continued to develop the idea, typically still for home construction.

Other tandem approaches such as the Delanne were largely forgotten, until David Lockspeiser conceived of his Land Development Aircraft, a low-cost utility transport.

Up-and-coming maverick designer Burt Rutan was working on a low-powered but highly efficient plane for home construction.

The tandem layout offered a low-drag fixed undercarriage installation, by placing the main wheels in housings at the tips of the fore wing and applying anhedral to raise the fuselage high enough for a propeller.

Insects with tandem flapping wings include the Odonata (dragonflies and damselflies), Lepidoptera (butterflies and moths) and some Thysanoptera or Thrips.

Odonata species typically have long, thin wings and can synchronise the flapping of fore and aft pairs in various different modes, allowing them to be both fast and highly manoeuvrable.

By comparison the Lepidoptera have wider wings which are flapped in synchrony and may even overlap in flight, and are better suited to endurance flying.

Some species, such as the band-wing, also have sufficiently enlarged pelvic fins, further back along their bodies, to form a tandem layout.