Variable Geometry Technologies for Electric Aircraft

the fascinating thing about electric aviation is that it has created the possibility of entirely new aircraft designs the likes of which we have never seen before the lightweight yet powerful electric motors can be installed anywhere from the wing tips to the fin tips the need for control surfaces is reduced because turning of the aircraft can be achieved by spinning the motors at different speeds we can use multiple small propulsors instead of a few large ones we can have no wings at all we can recapture energy during landing we can generate energy during flight using solar panels but can we do more we can indeed in this video we are going to learn some novel techniques that can be incorporated by electric aircraft to further improve flight characteristics on this channel electric aviation we aim to bring for you the latest developments from the world of sustainable air travel subscribe today to get all of our updates coming up we will be looking at some groundbreaking ideas that can make electric aircraft go further these shape transforming technologies include hovering wingtips morphing and seamless wings but first let's have a look at a fascinating concept that darpa the defense advanced research projects agency has been pursuing it is called the disk rotor the disk rotor is mounted on top of a compound aircraft and is used to house telescopic rotor blades the blades are extended when the aircraft needs to take off or land and are retracted when the aircraft is in cruise mode this helps in eliminating the drag force substantially during forward flight the patent for this concept was filed in 2010 and it was being applied in the development of a vtol aircraft with 400 knots dash speed although this concept was meant for conventional propulsion systems it is more easily adapted for electric aircraft this is because the complex gear down transmission system to power the rotor blades with a conventional turbine engine will not be needed if instead an electric motor is used furthermore the rotating disc can also be used for recapturing some of the energy that is being lost in pushing the aircraft forward by using the same motor as a generator this concept is of great interest to the modern gyrodyne category electric aircraft that are being developed for urban air mobility even though boeing was awarded the contract by darpa due to the classified nature of this program there is very little technical information available the rotor disc can be used in conjunction with another concept being developed by piersecki aircraft corporation it is the variable incidence wing or the free wing one of the problems of the compound aircraft is that the fixed wings underneath the main rotor come in the way of the rotor downwash this reduces the efficacy of the large rotor during lift-off mode using this technique of making the wing parallel with the downwash nearly eliminates the downward drag and allows larger wings to be installed the pa-890 compound aircraft is being designed on this concept and has a 12.3 meter wingspan piasecki have said that the pa-890 will be twice as aerodynamically efficient as a helicopter in terms of lift to drag ratio the wings will do most of the lifting in cruise mode allowing the rotor speed to be reduced by 70 percent thus reducing the drag substantially the aircraft will have lower energy costs and less complexity than a conventional helicopter the design is also expected to have reduced loads and reduced vibration as well as reduced failure rates however for the variable incidence wing to work the forward propulsor should be housed not on the wing but in the tail section the next concept that is equally fascinating is the transforming rotor system that was used in joby aviation's lotus uav in this concept the two bladed rotors mounted on the wingtip provide the upward thrust during takeoff and landing during the cruise mode the tip rotor blades close like a scissor and become an extended part of the wing in evtol aircraft like the cora that don't have tilt rotors or tilt wings there are often several rotors that are used during the takeoff and landing phase but in cruise mode they serve no purpose other than increasing drag as the current electric aircraft have very limited energy at their disposal the component should be designed to serve more than one purpose where possible this is why joby's lotus design is significant because in cruise mode the folded rotor blades increase the wing area by 15 percent and add to the lift the lotus design took its inspiration from nasa's dos samara uav concept the difference in nasa's design was that it used a single-bladed wing tip rotor this caused structural issues of high cyclic loading and aerodynamic inefficiency the lotus addressed these with the two-bladed configuration incorporating a very similar mechanism that transformed the surfaces from rotor blades to wingtips in seconds according to joby the design is easily scalable for larger aircraft this project unfortunately has been discontinued a lot of people with knowledge of aerodynamics understand there is no single aerofoil shape that is ideal for all speeds and all missions aerofoil shapes differ vastly depending upon the requirement there are airfoils that provide extremely high lift but with a penalty of high drag they have a deep camber and are used for relatively slow moving high payload aircraft on the other hand fast moving jets and interceptors have entirely different aerofoil cross sections with low camber similarly high stability wings cross section have a reflex trailing edge while some airfoils have no camber and are symmetric but what if we were able to change the wing shape as the flight conditions changed for example what if a passenger plane was flying empty to pick up passengers from a destination can we change the wing shape when the aircraft is loaded and when it is unloaded yes now we can over time there has been a lot of research done on the morphing wing technology in 1999 nasa invented the microfiber composite or the mfc the mfc consists of rectangular piezo ceramic rods sandwiched between layers of adhesive electrodes and polyimide film if voltage is implied across it it can bend and distort when the electrical stimulus is removed it relaxes back into its original position using this technology morphing wings have been made that can change into several different types of cross sections depending upon the requirement even without using the complicated mfc material there is another technology that can produce the same effect it is called the distributed compliance material technology that was developed by a company called flexis through the funding of afrl air force research laboratory in the us many of you may have noticed that the actuation mechanism for flaps in the airfoil have several components and hinge joints that not only increase the weight and complexity of the aircraft but also render the wing a discontinuous surface this gap on the wing surface is very disruptive for the flow and results in increased drag through the use of distributed compliance flaps can be created without joints and flexible aviation grade material can be used on the skin of the wing to form a continuous surface the flex foil material by the flexus allows shape morphing for large controlled deformations from -90 degrees to plus 40 degrees the flexfoil also permits discrete spanwise twists to reduce the induced drag and withstand external loads while keeping the wing a single continuous surface aerodynamicists have known for a while that with a continuous wing surface it is easier to increase the lift without increasing the drag the application of flex foil has shown drag reduction in the range of 5 to 12 percent for long range fixed wing aircraft it has to be said though that this technology is applicable for all types of aircraft and not just electric so these were a few of the technologies that electric aviation can benefit from please do use the comment section to inform us what you think about them and also the different voice over and with this the video is concluded if you learn something from this video then please do give it a thumbs up thank you for your attention

Channel: Electric Aviation

Views: 65,878

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Id: O8E6fXYfMy4

Length: 9min 23sec (563 seconds)

Published: Thu Apr 01 2021