when we look at commercial planes they have more or less evolved into aircraft of a certain shape be it boeing airbus embraer bombardier or many others the tube and wing configuration has prevailed when it comes to large civilian airliners and the reasons are not to do with having the highest aerodynamic efficiency but more about practicality and a design that is production friendly similarly if we look at the emerging evitable aircraft and in particular those meant to be used as an air taxi we are witnessing flying machines of a very specific shape in this video we are going to explore the common design features that define the outlook of the upcoming evitol aircraft so let's begin even a cursory look at the five-seater evitals like joby aviation's s4 vertical aerospaces va x4 the maker by archer hyundai's sa-1 and beta aviation's alaia 250 will reveal common design elements all of them are multi-propulsors they have high gulf wing configuration the presence of a v-tail is also a common feature and barring the alaia all of them have five bladed tilt rotors for the ease of reference let's call this the standard evitol design all of the mentioned aircraft have a maximum takeoff weight in the range of 2100 kilograms to 2800 kilograms and have a payload capacity of 400 to 550 kilograms the range is between 80 to 150 miles and the top speed is between 150 to 200 miles per hour note the difference in range in between these aircraft is mainly because of the different amount of battery energy kept as reserved the lift to drag ratio of these standard evital aircraft is in the range of 12 to 18. now there are other aircraft too in the ataxi ev told category which differ only slightly for instance there is the asx mobi one which is different because it has tilt wings instead of tilt rotors but all the other specs are similar likewise we have the over air butterfly that instead of two or more propulsers per wing just has one large rotor on each wing and has two propulsors on the vtail another aircraft worth mentioning here is the embraer x which is different from the rest in more than one aspect the embraer x has a high wing and a v-tail but also has a ventral fin it utilizes ducted fans instead of open propellers and has a canard wing configuration which distinguishes it from others in its category however it has similar specs of range top speed and payload so why is it that ev tolls are converging towards one particular shape and size what are the aerodynamic advantages of the common features of these aircraft let's address these questions one by one we will first look at the size and capacity it is understandable that size empty weight of the aircraft and the payload capacity are all limited by the energy density of the battery a bigger size or a higher payload capacity in ev toll would require a more voluminous aircraft which in turn would mean not just more weight but much more weight note that as the aircraft scale is increased the weight increases cubically or in other words if we double the size of the aircraft we increase its weight by 8 times we can indeed make an aircraft that is larger and is powered up by battery but it wouldn't be able to go the distance even in their current size the range for most ev tolls is around 100 miles we can try to pack in as much battery as we can but optimization studies have shown that the battery should never make up more than two-thirds of the total weight of the aircraft a higher rate will only decrease the endurance leading to useless weight overpowered systems and higher discharge rates for most evital aircraft today the battery weight is at max one third of the aircraft weight now there is a very simple equation based on first principles to calculate the range of any vetol aircraft which can be used even by people not skilled in maths or engineering the equation says that the range is the product of four factors the first is the battery energy available for cruise or forward propulsion in joules the second is the propulsive efficiency represented by new the third is the lift to drag ratio of the aircraft and the final is the inverse of the maximum take-off weight of the aircraft in newtons the ease of use of this equation can be demonstrated by an example let's say we want to calculate the range of maker by archer the maker has 37 kilowatt hour of battery energy available for cruise which can be converted into joules just by multiplying the value by 3.6 million or 60 times 60 times thousand for propulsive efficiency a conservative value of 0.8 can be used the lift to drag ratio of the maker is 12. the maximum take of mass of the aircraft is 1508 kilograms meaning the weight is 9.8 times 1508 or 14793 newtons the input of these four values in the equation gives the range to be 86 440 meters or 86 kilometers as simple as that archer have mentioned on their website that 37 kilowatt hour capacity is the portion of the battery pack energy reserved for cruise the total battery pack size is 75 kilowatt hour so approximately 50 percent of that portion is used during cruise 12 is kept for hovering mode twenty percent of the energy has been allocated to reserve while fifteen percent accounts for the capacity fade over time and three percent is deemed inaccessible so as not to drain the battery completely to increase the cycle life these percentages are more or less the same for standard ev doles that we are exploring the percentage energy consumption for other type of ev toll can vary for instance on a spectrum on one end we can have the lilium that is optimized for flight during cruise mode and on the other end we can have jaunt aviation's rosa which is more optimized for hover so the twelve percent energy designated for hovering for standard shape ev dole can be as low as five percent for the rosa and can be as high as eighteen percent for lillium the assumption here for lillium jet is that the battery weight is one third of the total weight of the aircraft it would be interesting at this point to look at the conventional tilt rotors and tilt wings that run on jet fuel there are two aircraft that are worth mentioning because of their relatively light weight one was the canadair cl84 dynavort tilt ring with a maximum takeoff weight of 5710 kilograms for vtol an empty weight of 3818kv there's also the augusta westland aw 609 a tilt rotor with a maximum take-off weight of 7620 kilograms and an empty weight of 4765 kilograms the range for these aircraft is 421 miles and 863 miles respectively so the conventional veto aircraft are almost two times heavier than the standard evitrol designs and have four to eight times more range the most successful conventional vtold is the v22 osprey that has an empty weight of 14432 kilogram and a maximum takeoff weight of 21 546 kilograms and a range of 1012 miles this large size is all down to the high energy density of jet fuel so this makes it clear that the size in the standard evitol is limited by the energy capacity of the battery and this brings us to the second common feature of the emerging ev dolls that is the retail empanadas the retail not only has a lower weight compared to conventional stabilizer and fin empanadas but also has less wetted areas so there is less induced and parasitic drag the retail however does require a longer fuselage to avoid undesirable yawing effect referred to as snaking let's now look at the propellers another common theme that runs through the standard ev toll design is the five bladed propellers the five blade props produce higher thrust for the same rpm compared to the three bladed propellers this means that for a certain amount of thrust the five bladed propellers can be spun slower which results in a lower tip speed and in turn lower noise to reduce the noise signature further and he drilled tips are being used these are the reasons that have resulted in joby s4 to register 55 decibels while hovering similarly archer have claimed that their aircraft maker also has a sound signature of just 45 decibels some of the evitals are using two motors to power a single propeller this is done to provide a layer of redundancy in case of a motor failure a more efficient solution however is the one used by asx in their earlier aircraft the mobi-1 v3 they've used core rotating propellers a study has shown that by varying azimuthal spacing between the upper and lower rotor the core rotating rotor can perform better than even contra-rotating rotor therefore if two motors per propulsers have to be kept to provide redundancy then it would be more advantageous to use them for co or counter rotating propellers in the normal operation mode the coaxial configuration not only reduces the noise level but can also lower the power consumption by up to 15 percent so far the tilt rotor has been the choice of most aircraft manufacturers only the mo b1 v3 by asx and the transcend air vy 400 have come up with tilt wing configuration there are advantages of tilt wing over tilt rotor for example the downward from the rotors is not apprehended by a horizontal wing as is the case in a tilt rotor configuration note that the osprey loses 10 percent of its thrust because of the interference from the wing the other advantage is the relatively quick transition from hovering to cruise the cl-74 dynavort for instance was able to take off vertically then accelerate from zero airspeed to 100 knots or 115 miles per hour in just 8 seconds on the other hand the tilt rotor has to build up speed and reach a point beyond the stall speed of the aircraft after which the rotors can begin tilting down the third advantage of a tilt wing is that a single tilting mechanism is required for the whole aircraft which reduces complexity rather than having one for each of the many rotors the tilt wings have a stronger case for electric aircraft as the motors are much lighter compared to engines and so the tilting mechanism for tilt wing doesn't need to be as bulky there are two disadvantages however for the tilt wing configuration first is its susceptibility to gas during hovering because of the large wing area although this problem can be alleviated by using venetian blind wings but that would add complexity to the design the second disadvantage is that if the battery is stored in the wings it will make the wings heavier and this would require a bulkier tilting mechanism and this brings us nicely to our next design feature that is the distributed battery pack system a distributed battery pack system that is spread out is more advantageous than a single large centralized battery pack it not only provides better weight distribution but also allows better heat removal due to larger exposed area and prevents thermal runaway propagation the high gulf wing configuration common in modern ev tools is mainly to provide clearance from the rotors and ease of accessing the aircraft the high wing configuration with batteries stored in the wings also allows a higher center of gravity closer to the plane of the rotor this gives better stability while hovering so there we go we have discussed the common features that have been the choice of so many upcoming evitrol aircraft and hopefully provided the reason for the choice so what do you think the best design should look like do let us know in the comments section and with this the video is concluded if you learn something from it please do give it a thumbs up thank you for your attention