aviation Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot air ...

, stagger is the relative horizontal fore-aft positioning of stacked

wings A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expre ...

in a

biplane A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer, used a biplane wing arrangement, as did many aircraft in the early years of aviation. While ...

triplane A triplane is a fixed-wing aircraft equipped with three vertically stacked wing planes. Tailplanes and canard foreplanes are not normally included in this count, although they occasionally are. Design principles The triplane arrangement may ...

, or multiplane. An aircraft is said to have ''positive stagger'', or simply ''stagger'', when the upper wing is positioned forward of the lower (bottom) wing,NACA technical report No.310
''Wind Tunnel Pressure Distribution Tests on a Series of Biplane Wing Models'' (July 1929), p.17. Retrieved on 8 February 2009. Examples include the

de Havilland Tiger Moth The de Havilland DH.82 Tiger Moth is a 1930s British biplane designed by Geoffrey de Havilland and built by the de Havilland Aircraft Company. It was operated by the Royal Air Force (RAF) and other operators as a primary trainer aircraft. ...

or Stearman. Conversely, an aeroplane is said to have ''negative stagger'' in unusual cases where the upper wing is positioned behind the lower wing, as in the

Sopwith Dolphin The Sopwith 5F.1 Dolphin was a British fighter aircraft manufactured by the Sopwith Aviation Company. It was used by the Royal Flying Corps and its successor, the Royal Air Force, during the First World War. The Dolphin entered service on th ...

Beech Model 17 Staggerwing The Beechcraft Model 17 Staggerwing is an American biplane with an atypical negative wing stagger (the lower wing is farther forward than the upper wing). It first flew in 1932. Development At the height of the Great Depression, aircra ...

. An aircraft with the wings positioned directly above each other is said to have ''unstaggered'' wings, as in the Sopwith Cuckoo or

Vickers Vildebeest The Vickers Vildebeest and the similar Vickers Vincent were two very large two- to three-seat single-engined British biplanes designed and built by Vickers and used as light bombers, torpedo bombers and in army cooperation roles. First flown ...

Measurement

The value sometimes expressed as a distance, ''s'' say, but it may also be written as a fraction or percentage of the 'gap' (distance ''g'' between wings), i.e. ''s''/''g''. It may also be presented as an angle equal to tan⁻¹(''s''/''g''). The

Gloster TSR.38 The Gloster TSR.38 was a single-engined three-seat biplane designed as a naval torpedo/spotter/reconnaissance aircraft in the early 1930s. It did not reach production and only one was built. Development Gloster built what was at first known ...

had a stagger of 0.91 m and a gap of 2.0 m, so the stagger might be written as 0.91 m, 0.455, 45.5% or 24.5°. ''s'' is the distance from the leading edge of the upper wing along its chord to the point of intersection of the chord with a line drawn perpendicularly to the chord of the upper wing at the leading edge of the lower wing, all lines being drawn in a plane parallel to the plane of symmetry.

Effects

As a general rule, there is a tendency for the upper wing to contribute a greater proportion of the total lift than the lower with positive stagger, and less with negative stagger. Increase in positive stagger also tends to move the center of pressure forward on the upper wing and backward on the lower wing. When unstaggered, the centers of pressure for upper and lower wings are almost coincidental. Lift comes from having air at a lower pressure above the wing than below. In the case of aircraft with more than one wing, one above the other, the higher pressure below the upper wing and the lower pressure above the lower wing will tend to equalize and so reduce the lift available. The closer together the wings are the more dramatic is this effect. The effect can be reduced by either increasing the gap between the wings, or moving one forward of the other. As increasing the gap may introduce other undesirable effects, stagger is usually applied to reduce the loss of lift. Positive stagger is by far the most common, as this positioning of the upper wing(s) allows better visibility for the crew as well as increased aircraft longitudinal

stability Stability may refer to: Mathematics *Stability theory, the study of the stability of solutions to differential equations and dynamical systems ** Asymptotic stability ** Linear stability ** Lyapunov stability ** Orbital stability ** Structural sta ...

, aerodynamic efficiency and maximum lift.NACA technical report No.70
''The Effect of Staggering a Biplane'' (September 1921), pp.1,3,4. Retrieved on 9 February 2009.

References

{{reflist Wing configurations

Measurement

Effects

See also

References