Boeing Stearman biplane

Biplane – a fixed-wing aircraft with two main wings stacked one above the other. The first aircraft to fly, the Wright Flyer, used a biplane design, as did most aircraft in the early years of aviation. While a biplane wing structure has a structural advantage over a monoplane, it produces more drag than a similar unbraced or cantilever monoplane wing. Improved structural techniques, materials and the quest for greater speed made the biplane configuration obsolete for most purposes by the late 1930s.

  • interplane strut is an aircraft airframe component designed to transmit lift and landing loads between wing (mainplane) panels on biplanes and other aircraft with multi-wing designs. They also maintain the correct angle of incidence for the connected wing panels and are often braced with wires. Interplane struts designs employ streamlined struts made from spruce or ash. More modern or higher performance aerobatic biplanes often feature metal interplane struts. Struts are usually braced by “incidence wires” running diagonally between pairs of struts.
Wright Flyer first flight 1903

Wright Flyer 1903 – first powered, manned controlled flight. The aircraft ran 40 feet along a wooden starting rail on level ground and then rose into the air. It flew 120 feet in 12 seconds. This was the first flight in history in which a machine carrying a man had raised itself by its own power into the air, had flown forward under control without a reduction in speed and had landed at a point as high as that from which it had started.

Pitts S1s Aerobatic biplane

What’s the problem?
Trade-offs in performance aerobatic airplane design.

  • Ask – What is the best design for a performance aerobatic airplane? Why are some of the special characteristics needed? How can these be achieved? Aerobatic maneuvers put a lot of stress and strain on a plane performing loops, rolls, spins and high speed passes. They need to be light and powerful as really strong to withstand the forces that are applied to the plane structure.
  • Imagine – What materials are strong and light? What forces are applied to each part of the plane in an aerobatic performance? How can the design of the airplane improve the performance? Aircraft built with two main wings can usually lift up to 20 percent more than can a similarly sized monoplane of similar wingspan. A biplane can have a shorter wingspan which tends to afford greater maneuverability.
  • Design, Build – Struts and wire bracing of a typical biplane form a box girder that permits a very light but strong and rigid wing structure.
  • Improve – Modern materials that are stronger and lighter, provided more options for performance aerobatic plane designs.

That’s engineering

  • strut – a structural component designed to resist longitudinal compression. Struts provide outwards-facing support in their lengthwise direction, which can be used to keep two other components separate

Engineering ideas

  • transmit, load, lift, angle of incidence, brace, diagonally, drag, cantilever, maneuverability

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