What Are Airplane Wing Spars and How Do They Work?

As the primary structural member of a wing, wing spars are an indispensable component on fixed-wing aircraft that help explain how they are able to take flight. Whether you are an aircraft owner, operator, or simply an enthusiast, getting to know these core structural components can make a big impact, so we invite you to read on as we discuss what airplane wing spars are and how they work.

In essence, wing spars are the “bones” or structural elements within the wing that form the base framework for the outer plating to be attached. As key structural components, they are designed with the proper curve and dimensions necessary to enable flight. This typically means that they are flat on the underside and curved on top, that way there is less distance for the wind to travel below the wings than above them. Once a plane is heading in a forward direction fast enough, this curved shape creates lift, pushing the aircraft up into the air.

In order to bear the incredible level of force placed on the wings for them to be able to fly, wing spars must be made of material that is both very durable and flexible. Since the wings create vortices and experience great amounts of force from all directions, they must also be able to handle a large amount of tension and compression without snapping. As such, the common materials used for wing spars are strong but bendable materials like wood, metal (usually aluminum), and composites.

Though mostly used in early aircraft models, wooden wing spars can still be found on some recent airplanes, like the all-wood Robin DR400. Made from trees known for their straight, uniform, and long grain, the wood used in aircraft spars must be compressed and glued together to retain the wing’s shape, as well as laminated to increase strength. As a material, wood offers a very lightweight option, but it is also vulnerable to biological attacks and certain weather conditions, two significant setbacks that have placed most of its use firmly in the past.

Aside from wooden slabs, aluminum is another material that has often been used for making aircraft spars. In addition to being lightweight, aluminum is not affected as much by weather and biological factors, but it still requires regular inspections and maintenance checks to ensure its integrity. If even greater durability is desired, there are wing spars made of composites like carbon fiber or kevlar. These materials are often employed in modern airplanes because they have both reduced weight and greater strength.

In addition to different materials, spars may also be designed with different shapes and styles. The three major designs you are likely to see are monospar, box beam, and multispar. Monospar wings have one main spar which provides the bulk of the shaping and structure for the airfoil. This design is rarely used today, but it can offer a very lightweight option for certain wing designs.

More common is the box beam style which has two main spars that are connected to the bulkheads and stringers forming a box shape to make the wing stronger. Lastly, as the most popular option, multispar wings feature two spars, one of which is positioned near the leading edge, while the other is located near the rear part of the wing. This orientation keeps the ribs and skin aligned and helps prevent the wing from twisting.

Altogether, wing spars form a crucial part of fixed-wing aircraft that offers structure and flexibility to the wing’s design. If you are on the search for wing spar parts or other aircraft components, ASAP NSN Parts is your premier source for top-quality components that can stand the test of time. Explore our various catalogs of available parts that have been organized by part type and manufacturer, or make use of the provided search tool to find specific items of interest. Backed by a widespread supply network that reduces lead times, we are well-equipped to find time and cost savings for your part acquisition needs!


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