Aircraft control has always been a challenge for pilots. The problem lies in the fact that it requires a high level of skill and experience

Fly By Light and Morphing Wings: A New Way of Aircraft Control

Aircraft control has always been a challenge for pilots. The problem lies in the fact that it requires a high level of skill and experience. This makes it very difficult for new pilots to master the art of flying. Since the creation of the biplane Wright Flyer over a hundred years ago, aircraft flight control systems have undergone substantial development. The Flyer 1 was controlled using wires and pulleys that bent and twisted the wood-and-canvas wings essentially warping them and then adjusting the rudder to assist with turning. The pilot’s left hand was responsible for controlling the elevator as they lay on their stomach on the aircraft’s lower wing. In the coming decades, the primary method of control was mechanical consisting of a series of cables, rods, and pulleys. In the next stage of development, the fly-by-wire concept was introduced in some military aircraft from the 1930s through to the 1950s. In 1968 the Concorde became the first commercial airliner utilizing a fly-by-wire system albeit an analog one. It wasn’t until 1988 when Airbus released the A320 that a digital fly-by-wire system had been introduced. This is the standard still in use today, almost 40 years later. There have been only two aircraft that briefly conducted tests with fiber optic cables but no other advancements have been made. However, considerable research has gone into morphing wings. Similar to the Wright Flyer that utilized wing twisting, morphing wing technology explores a whole new dynamic of aircraft flight control and wing redesign. Combining fly-by-light and morphing wings can result in much lighter aircraft with much more responsive control. In this paper, we will explore the utilization of a new concept, fly-by light, the replacement of traditional wiring with fiber optic cables, and morphing wing, active wing shaping.

 

Background

History and Design of Fiber Optic Technology

            The use of light to transmit messages can be dated back to as early as the 1790s, long before man had even made any significant attempts at a flying machine. Two French brothers invented the first optical telegraph by mounting a series of lights on towers and having operators send messages using these lights from one tower to another. Over the course of the following two hundred years, major developments would be made. Between the 1970s and 1980s telecommunications companies began deploying fiber optics in an attempt to modernize their network infrastructure. In 1997 the Fiber Optic Link Around the Globe, a single cable that spanned the globe became operational and was the foundation upon which the Internet was developed. Two decades later fiber optics can be found in the operations of several industries primarily networking, telecommunications, and even medical.

Fiber optic cables are quite similar to electric cables but their internal makeup contains several optical fibers usually made of either glass or plastic that transmit light. The light carries the data signals and in the cables, it can achieve speeds between an astonishing 180,000 to 200,000 kilometers per second.

 

 

 

 

Advantages and Disadvantages of Fiber Optic Cables over traditional Copper Wiring

There are several pros and cons of fiber optic installations but for the context of this paper, we will pay more attention to those that have the largest effect on aircraft design.

Advantages

            Size. Fiber optic cables can have a cross-sectional area as much as 30 times smaller than that of their copper counterpart but still be able to transmit up to 4.5 times as much data.

Weight. In addition to the cables being smaller, they also weigh significantly less and can translate to hundreds of pounds worth of savings in a typical airliner installation. Their lighter weight also makes them easier to install.

Interference. A huge driving force for military applications is the fact that fiber optic cables are completely immune to electromagnetic interference. As warfare modernizes, having a jet that can still fly at faster speeds without disruption to its control system from electromagnetic attacks would be a significant tactical battlefield advantage.

Cost. These cables are primarily made with glass and the raw materials for the manufacture of glass are cheaper and more readily available than that copper.

Faster Speeds. Fiber optic cables transfer data at a speed a little slower than that of light, roughly 31%, and light moves at 300,000 km/s.

Greater Bandwidth. This ensures a higher data transfer rate, therefore pilot’s command passes rapidly from the aircraft cockpit to control surfaces which ensures smooth aircraft maneuvering.

Disadvantages

            Expensive Installation. Special training and test equipment are required to install fiber optic cables and they are not as strong as copper wires.

Very susceptible. The cables are very easy to damage during installation and maintenance activities.

Difficult to Splice. The fibers are difficult to splice and bending them too much can cause them to break.

 

 

 

 

 

 

 

 

 

 

 

Morphing Wing Design

            The concept behind wing morphing is the ability to actively change the planform or twist the wing to achieve the most efficient configuration during all flight conditions. It is a futuristic approach to variable geometry aircraft. A few fighter jets have been designed that have wings that can sweep rearward in flight. The most popular example is the F14 Tomcat. Wings that are straight are very efficient for low-speed flight and swept wings are more efficient for high-speed flight hence the implementation of this technology. However, that technology solved problems at that time and was not a sustainable path for development. It would have resulted in bigger, heavier, and more complex designs. So as time passed and propulsion and control systems developed, there was no longer a need for variable sweep wings.

Weight has always been and will always be a major design consideration. For years researchers have been trying to deform wings as an alternative to movable control surfaces but the mechanical devices used to achieve this added significant weight changes that canceled any aerodynamic advantages obtained. Also, it added another layer of complexity to the design and maintenance process because the more things that move means that there are more things that can break.

The advent of morphing wings promises much lighter wing structures. Instead of having multiple movable sections like flaps, slats ailerons, and spoilers the entire wing will be one movable structure. By affixing small high-torque motors to each wing tip the entire wing could be twisted to achieve the desired flight characteristics or movement. Modern jets are constructed using composite materials and so too will morphing wings. A joint effort between NASA and MIT has begun experimenting with tiny lightweight units that will be assembled in a lattice framework to form the entire wing unit. Each piece is quite sturdy and the final shape can be configured as necessary to achieve an overall wing design. Think of it like building blocks with Lego blocks. Initial research so far utilizes tiny robots that are designed to build the structure from the inside out. This modular construction allows for mass production of the tiny subunits and the utilization of artificial intelligence and robotics can complete the assembly process. Current production composite wings are made with the use of large, expensive machinery and precise layering of the materials. After that, there needs to be hardening and curing time. So not only will there be weight reductions by employing this technology but the manufacturing process will be cheaper and faster. Also, because of its modular design, repairs and replacements will be much easier and faster.

 

 

 

 

 

 

 

 

 

 

 

Practical Applications

Implementation

            A common concern for the application of the morphing wing technology is that there would no longer be a place to store fuel. However, the first practical use would be in drones. The MIT-NASA team has already constructed a small prototype wing mounted on a fixed stand demonstrating how the actuation would look and work. Combining the morphing wing with an active stabilization system powered by artificial intelligence and utilizing fiber optic cables for signal commands from the central processing unit to the wing actuators will result in seemingly instantaneous corrections to flightpath and attitude disturbances.

After its application in drone technology, it can gradually be tested in aircraft systems. In an attempt to preserve the Earth and reduce the effects of climate change, more manufacturers and startups have begun research and development of electrically and hydrogen-powered aircraft. In the case of electrically powered aircraft, a fuselage-mounted propulsion system and much larger batteries may be used while still achieving a high payload would be possible due to the reduced weight of the wings as well as with the use of the much lighter fiber optic installation.

For hydrogen-powered aircraft, the fuel, hydrogen is best stored in cylindrical containers. Therefore, a wing would not necessarily be the best place to put those but rather somewhere in the fuselage. The engines may still be mounted on the wings because of the increased strength of the design.

 

 

Performance Improvements

            Wind tunnel tests of the scaled models so far have shown that the flexible wing technology pretty much equals that of a rigid wing of the same size and shape but does so at ten percent of the weight. For reference, the wings of a Boeing 747 weigh roughly 95,000 pounds. If morphing wing technology is used that would translate to an impressive 86,000-pound reduction. Throughout the entire performance envelope, the model wing not only performed just as well as the rigid wing but revealed some advantages that were not previously considered during design. One of these is proverse yaw. As we know adverse yaw is the tendency of an aircraft to yaw to the outside of a turn. Proverse yaw is the tendency of an aircraft to yaw into the turn thus resulting not only in sharper but coordinated turns. There were also noticeable reductions in drag. In the flat or 0-degree flap configuration, the rigid wing boasted a slightly lower drag coefficient. However, in the 10-degree flap range which corresponds to a tip twist of 4 to 6 degrees, the drag coefficient of the flex wing was about half that of the rigid wing.

Next-generation fighter aircraft can take advantage of the morphing wing’s and fiber optic cable’s overall weight reduction and use this to carry more armaments. The speed improvements of data transmission due to the optical fibers will result in a much faster control response and maneuverability will be increased due to the ability of the entire wing to move. Faster turn rates and sharper turns may not seem like much but in dogfights, a split-second advantage over the opponent can be the difference between life and death or winning and losing a battle in contested airspace.

 

 

Conclusion

We have explored traditional means of aircraft control, how they have evolved, and prospects for the future. Fiber optic cables will more than likely be the first of these two to be implemented in real-world scenarios. Gulfstream attempted a few tests a little over a decade ago with their GV testbed and Airbus experimented with the EC 135 helicopter but neither has managed to implement them on production model aircraft. The size and weight advantages coupled with the reduced cost of the cables will have slight but noticeable performance improvements and a decrease in cost per installation.

Morphing wings on the other hand are a derivative of variable geometry wings. We have explored their composition and design and it is based on a lattice framework of small, sturdy pieces that are arranged together to form the wing structure. The overall structure is very strong but due to it being comprised of multiple small pieces, it is very flexible. The subunits may be mass-produced and the modular construction enables easier and faster replacements of damaged or worn parts.  Weight is the most significant advantage over traditional wings but the drag reduction with the wing twisted to a corresponding degree of flap deployment is in excess of 50%. Scaled models and wind tunnel testing has been done but the world is yet to see a real-world practical application. The introduction of morphing wings in commercial aviation will be able to open an entire universe of new possibilities that are only limited by our minds. The sky is truly the limit.

 

 

 

References

Chakravarty, A., Berwick, J. W., Griffith, D. M., Marston, S. E., & Norton, R. L. (1990). Fly-by-Light Flight Control System Technology Development Plan Final Report (No. 19900005795). National Aeronautics and Space Administration.

Gui, A. What Are the Fiber Optic Cable Advantages and Disadvantages? (2018, October 18). Fiber Optic Cabling Solutions. com/what-are-the-advantages-and-disadvantages-of-optical-fiber-cable.html”>https://www.cables-solutions.com/what-are-the-advantages-and-disadvantages-of-optical-fiber-cable.html

History of Fiber Optics. (2020b, October 14). Timbercon. https://www.timbercon.com/resources/blog/history-of-fiber-optics/

Jenett, B., Calisch, S., Cellucci, D., Cramer, N., Gershenfeld, N., Swei, S., & Cheung, K. C.

(2017). Digital Morphing Wing: Active Wing Shaping Concept Using Composite Lattice-Based Cellular Structures. Soft Robotics, 4(1), 33–48. https://doi.org/10.1089/soro.2016.0032

 

Lite, T. (n.d.). 7 Advantages of Fiber Optic Cables Over Copper Cables. Retrieved November 6, 2022, from https://blog.tripplite.com/7-advantages-of-fiber-optic-cables-over-copper-cables/