Why Are Airplane Wings Angled Backwards??

why're plane wings angled backwards today most planes have a swept wing design and this helps the plane fly faster but it wasn't always this way let's look back in time and learn how this technology was developed and what we learned in the process back in 1941 most planes were designed with a straight wing and the Lockheed p-38 lightning was no different the straight wing design works well at lower speeds but the p38 was not a slow plane and its engineers quickly discovered that the plane had major control issues in high speed dives on November 5th 1941 a Lockheed test pilot by the name of Ralph Burton died when he lost control of his aircraft this spurred a major investigation headed by an engineer called John stack he employed a special type of photography called schlieren photography to observe the air flow in a high-speed wind tunnel and this is what he saw as air passes over the wing the air over the top of the airfoil accelerates this is how the wing generates lift this means that a wing traveling at less than the speed of sound can actually develop areas of localized flow traveling faster than the speed of sound and shock waves form at these locations the shock waves will reduce the lift and increase the drag on the wing the speed at which shock waves begin to appear is called a critical Mach number and Ralph Verdun reached the speeds during his high speed test dive so why did this cause a crash as the speed of his plane increased even further the airflow from the surface of the wings separated due to the shock wave formation this separated flow actually increased the lift on the tail wing and this combined with the reduced lift on the wing caused the p38 to enter an even deeper dive one that was very difficult to escape from John stack solved this problem in 1943 by placing a special flap under the wing where the flow was not been affected by the shock waves this flap could be deployed during dives and would increase the lift on the wing to maintain proper pitch control over the next decade John continued his work in the development of supersonic flight and was a major driving force for the development of the bell x-1 which was the first manned vehicle to break through the sound barrier in 1947 the bell x-1 was a rocket-powered plane and its fuselage was modeled after a 50 caliber round which was known to be stable in supersonic flight its engineers increased the critical Mach number of the plane by using a very thin wing and a the pitch control issues of the p-38 by raising the tail wing up and out of the downstream airflow of the wing but this plane still had a straight wing the realization that the swept wing may hold the key for high-speed flight came at the end of World War two in 1951 the balik's v was released and as design was mostly based on a captured German prototype the bell x5 had the special ability to change its sweep angle during flight making it the perfect test subject to investigate the aerodynamic advantages of the swept wing let's compare the aerodynamics of the straight wing bell x-1 and the balik's v as it increases its sweep angle air over a straight wing will flow parallel to the cord only this is called a chord wise flow the air that accelerates and creates lift as explained earlier it is this acceleration that reduces the critical Mach number of the plane now let's look at the flow over the bell x5 as it increases its sweep angle a swept wing introduces a new component of flow the span-wise flow this flow runs along the length of the wing and does not accelerate and thus does not affect the critical Mach number by converting some of the airflow into span-wise flow the acceleration of air over the chord is reduced this means the play can fly faster before shock waves begin to form over the wing as the plane increased in speed the pilot could increase the sweep angle doing this converted a larger volume of air into span-wise flow and thus increase the critical Mach number even more this test proved that the swept wing design could delay the formation of shock waves and thus allow planes to fly faster so next time you're flying take a look out the window and admire the engineers of the early 20th century their designs have allowed us to travel across the globe at transonic speeds and hopefully soon regular citizens may break through the sound barrier once again thanks for watching if you want to learn more about the mechanics of the swept wing click on my website here for my next video I'll be discussing the design of wind turbines please subscribe and like our Facebook page below

Channel: Real Engineering

Views: 1,449,885

Keywords: supersonic flight, supersonic, lockheed, P-38 Lightning, Bell X-1, Bell X-5, Shockwaves, aviation, engineering, aerodynamics, swept wing

Id: GXFpLnPpDtY

Length: 4min 5sec (245 seconds)

Published: Tue Mar 01 2016