A Flying Wing is an aircraft which has no definite fuselage. Similar designs are called Blended Wing aircraft, especially when there is no clear distinction between wing and fuselage.
In the olden days reducing drag was one of the important factors because we did not have highly efficient engines that can give enough thrust. In most modern designs, there is significant drag generated due to the large internal volume of the fuselage. Thus by creating a more blended aircraft, there is a lesser distinction established between the fuselage and tail, and therefore drag is eliminated.
One of the first flying wings to be developed was the “Northrop N1M”, by Jack Northrup, around 1941. Later there were several developments done to get heavy bombers like YB35 and YB49 up in the air. Interestingly, however, the idea of the flying wing was presented much before 1941, by engineers like Hugo Junkers, Boris Ivanovich, Charles Fauvel, Alexander Lippisch, and the Horten brothers.
Some notable Flying Wing Designs
The German Horten Ho 229 was the world’s first twin jet, pure flying wing. There are various instances in the past where people have tried to incorporate flying wings in place of fighter jets, especially the Northrop corporation during the end of world war 2.
The YB-49 was a jet-powered heavy bomber created by Northrop Corporation for the USAF. In 1948 the USAF ordered for a full production of these bombers. But only two months later, all flying wing contracts were cancelled without explanation, and all the remaining airframes were scrapped. And a new Convair B-36 program was initiated.
Northrop’s flying wing program may have been terminated due to technical difficulties or political influence during those times between Convair and the USAF. But still, the exceptional qualities and advantages of a flying wing were proved almost 30 years later when the B-2 spirit was designed.
What are the Advantages of Using Flying Wing Aircraft?
Consider the joint of the fuselage and the wing, it contributes a lot to interference drag. Unlike conventional aircraft, in flying wings, the crew, payload, fuel storage unit gets incorporated into the wings. Hence, the need for a fuselage is eliminated, reducing the interference and parasitic drag considerably.
We can also eliminate the drag contributed by the empennage in conventional aircraft. By eliminating the fuselage and empennage we also make the aircraft lighter. Also, if we consider a pusher configuration during design, the wings can be kept away from prop wash which reduces drag. Since the engines can be located above the wing and the aircraft does not require complex high lift devices, this configuration results in a much quieter aircraft. By implementing all these features, we can reduce fuel consumption and increase the overall efficiency of the aircraft.
Better performing control surfaces:
In conventional planes, ailerons are used to roll, and elevators are used for pitch control. Elevators are placed on the tail which gives enough tail arm length to provide the required torque to pitch the aircraft. But we can achieve the same effect in flying wings by sweeping the wings backwards.
Now both ailerons are far behind the Centre of Gravity and can be used for pitch control when moved together. At the same time, they can also be used to roll the aircraft by moving them in pairs, one up and the other down. This combination of elevators and ailerons is called elevons.
For better directional stability and yaw control we can incorporate Split rudders, differential thrust or Vertical stabilizers on the wing.
In conventional aircraft, lift is created by the wings and the payload is concentrated at the fuselage. This creates a lot of stress at the joints where fuselage and wings meet. On the other hand, in a flying wing, the payload is distributed throughout the wing which creates lift throughout the span and thus reduces wing flex and structural stress.
Flying Wing Aircraft are stealthier:
Flying wing designs have a low Radar Cross Section (RCS), which gives them the stealth property. RCS is the measure of how detectable an object is by radar, which was the crucial part in the design of the famous B-2 Bomber also called the “Stealth Bomber”.
What are the demerits of using a Flying Wing Design?
Advanced Airfoil Development required:
For incorporating payload and crew inside the wing, the wing thickness must be considerably high. In airfoils with such high thickness, lift will be limited so you must trade-off between the two.
Flying Wings have a more complicated design:
In flying wings, the functions of an empennage must be fulfilled by the wing. Pitch stability must be provided to the wings by incorporating sweep, Aerodynamic or Geometric twists or reflex airfoils. The pitch can be adjusted by trimming the elevons. The wing sweep can also cause the tips to touch the ground while rotation during takeoff. Incorporating all of these features into the final design becomes a very complex task.
A pusher configuration is inherently unstable:
Also, most of the flying wings that we see have a pusher configuration. This is used to reduce the wing profile drag due to the prop-wash over the wing section. Pusher configuration on wings obstructs the wing trailing edge, thus reduces the total width available for control surfaces such as flaps and ailerons. Generally, a high thrust line is required to provide enough ground clearance for propellers while pitch rotation during take off. Which can cause pitching with a variation of thrust. Also to provide enough clearance, prop diameter may have to be reduced (loss of efficiency) or landing gear made longer and heavier.
Though listing out advantages and disadvantages might make it seem like a simple task, designing a BWB or flying wing is a real practical challenge. Shared experiences of pilots who have flown flying wing say that the aircraft has a high tendency to Dutch roll. Wings can have stability issues if not appropriately designed. Although the flying wing designs have a lot of technical difficulties to overcome, I believe Flying wings and Blended Wing Body designs are a marvellous creation and one day, might have the potential to become a breakthrough for commercial aviation.
Written by Vishnu Latheesh for AeroMIT
Edited by Rahul Alvares