Before we look at the specific technology involved in the design of this new Switchblade, we'll discuss exactly how the position of a plane's wings affect its performance.
Unswept wings are efficient at low speeds, providing a great amount of lift compared to the amount of induced drag exerted on the plane. Induced drag is essentially another component of the force that allows the plane to fly. As air flows around the wings, the resultant turning of the airflow deflects the plane up, counteracting gravity pulling the plane down toward the ground. However, some of that force also resists the plane's forward movement, resulting in drag. As speed increases, this drag becomes even more problematic.
As an aircraft approaches and passes the speed of sound, shock waves form (pressure waves heard as a "sonic boom" by observers if the plane is supersonic). These waves create a second form of drag known as wave drag. When a shockwave forms, it changes the aerodynamic profile of the plane. Instead of a streamlined aircraft shape cutting smoothly through the air, this large pressure wave adds a bulky impediment that must be pushed through the air. It's sort of like running into the wind carrying a mattress. Unswept wings are very bad at dealing with wave drag.
Swept wings cut down on drag caused by turbulence at the wingtips. But the real advantage of swept wings comes in supersonic flight -- the configuration cuts down on wave drag by redistributing the shock waves along the plane's aerodynamic profile. They are ideal for these high-speed conditions. Unfortunately, they do not allow for heavy payloads at lower speeds. Swept wings are also inefficient and burn too much fuel to stay aloft, which reduces the range of the aircraft.
So why is the U.S. military bringing back variable-geometry wing technology? Technological advances mean better wing transition mechanisms, advanced wing shapes and computer systems that can control unstable aircraft. The Pentagon has identified a need for a plane that can remain aloft for long periods close to enemy territory, and then switch to a high-speed mode to rush in and deliver a blow before rushing back out at supersonic speeds. These two modes of flight require drastically different wing profiles for maximum efficiency. Northrop Grumman's new Switchblade is unlike any "swing wing" aircraft previously imagined.
Image courtesy Northrop Grumman
In the next section we'll look at the Switchblade technology.