There’s got to be a reason why aeroplanes have gone from low altitude, low speed performance all the way to high altitude supersonic flight. Our guess is that it has something to do with the development of the wing, and here’s why…
Looking back on early aeroplanes, while the fuselage shape has tended to stay the same or similar, it's undoubtedly the development of wings that has changed the way we fly. Early aviators and engineers have studied the phenomenon of flight in nature probably since the dawn of time. Obviously there’s limited evidence to substantiate such a claim, but it’s particularly amusing to imagine cavemen running around, flapping their arms and wondering why they couldn’t take off like the birds around them. Of course, now we know from scientific advancements that it was the size, shape and aerodynamic properties of these birds’ wings which allowed them to fly, and the lack thereof which meant humans couldn't. So how has wing shape in aviation advanced over time in order to combat drag and accommodate fuel efficiency? We thought we’d take a gander into the many realms of wing shape. While it’s not extensive, we think our research will give you a pretty good idea…
The term ‘aerofoil’ refers to the cross-sectional shape of a wing. Whereas in a natural being such as a blackbird, the shape may be more curvature, the shape of an aerodynamically engineered wing is more bowed. This allows air to flow around the shape of the wing freely, unlike with the wing of a bird which pushes the airflow down during flapping for it to stay aloft (as funny as it would be to see an aeroplane flapping across the sky).
In an attempt to combat issues with the initial design of an aerofoil, the supercritical aerofoil was conceptualised in the early 1960s by NASA scientists. Research showed that when using a supercritical wing shape, cruising speed could be increased along with fuel efficiency and flight range. When compared to the more traditional aerofoil features, the new supercritical design offered a flattened upper surface, a highly cambered or curved aft section and greater leading edge radius. Although initially regarded as ‘radical’, the design has since been rolled out as a common replacement for the early designs and is now used on most modern commercial aeroplanes.
A swept wing design has become the most common in use for high speed jet aircraft. Sweeping the wings makes the wing feel like it's flying slower. That, in turn, delays the onset of supersonic airflow over the wing - which delays wave drag and thus improves performance and efficiency.
Early designs were based on the idea that two parallel wings would facilitate a lighter yet stronger structure than a single wing. It was considered that these two wings could be supported with two light wires rather than with a single, thicker wooden part. The structural advantage of the biplane construction is the two wings, vertical struts and wires which form a deep light beam, which is more resistant to bending and twisting than a single wing. The biplane era lasted until the 1930s, when design philosophy was eventually adapted to take full advantage of thin sheet metal manufacturing techniques by using a monocoque or semi-monocoque structure.
Monocoque vs Semi-monocoque
The monocoque design relied largely on the strength of the skin or covering to carry the primary loads, which meant that it was only effective on aircraft up until a certain level, weight or size. Semi-monocoque designs, on the other hand, also use a stretched skin technique, however this is then reinforced by an underlying structure which shares the weight of the load. Different portions of the same fuselage may belong to either one of two classes, but most modern aircraft are of semi-monocoque type construction.
Wood and fabric
First aircraft designs utilised wood as a material. Wood possesses a high strength-to-weight ratio when used in laminate structures and is resistant to adverse environmental conditions if it is first subjected to a specific preservation treatment. However, after many years of wooden aeroplanes, the use of such a material began to be phased out for the use of metals, which have higher strength-to-weight ratios for lightweight structures and corrosion resistant structures for longevity.
Metal began to be used in aircraft as engineers sought to overcome challenges in strength and wind resistance, which only increased as speeds improved with the development of engines. The best-known early use of metal aircraft was in World War I, with Fokkers employing welded steel tube fuselages. Aluminium-covered Junkers are known as the world’s first all-metal fighter planes. All-metal aircraft construction became increasingly popular from 1919 to 1934, with the most common constructions being aluminium or aluminium alloy with fabric-covered surfaces.
Metal’s strength and durability eventually enabled manufacturers to develop aircraft that were easier to design, assemble, and repair, and lighter than the previous generation of wooden structures. All-metal planes were not immune to the elements, with engineers working to overcome hazards including corrosion and metal fatigue.
Exotic metals and composites
By the late 1940s, research into high-speed aviation produced experimental aircraft which were capable of supersonic flight. Extreme speed requires equally extreme strength and thermal resistance to boot, which led to the development of aluminium alloys and the use of exotic materials.
- Advanced carbon-carbon composites
- Silicon carbide ceramic coatings
- Titanium-aluminium alloys
- Titanium alloys reinforced with ceramic fibres
Well, there you have it. Wing shape over time has progressed from the straight wood and fabric biplanes to the swept back semi-monocoque carbon composites structures that are used now. It’s a wonder when we consider the leaps and bounds of improvements that have been made in such a short time, and it makes you think…where could we end up in the future?