Local Motors Airbus Cargo Drone Challenge

Transcription

1 Local Motors Airbus Cargo Drone Challenge Small, efficient, secure Author and designer: Sergio González Fernández (Local Motors user Sergius ) Updated May 25, 2016

2 Contents Summary... 3 Introduction... 5 General design... 5 Details... 5 Landing gear... 5 Waterproofness... 6 Modularity/Versatility:... 6 Handling... 9 Weight... 9 Fail safe (air)... 9 Safety provisions (ground) Dimensions Structure Airframe (fuselage, wings, tail) Equipment (batteries, motors, actuators) Avionics Landing gear concept Payload Interior dimensions and securing cargo Frame sheet Base data Drag Stability Extra views Appendix A: Frame sheet Appendix B: Hermes UAV operations manual

3 Summary General design: an efficient VTOL tandem wing. 4+1 big props, minimal interference between components Detail: Landing gear: tricycle type, nose LG + main LG attached to 2 nd wing wingtips Waterproofness: rubber sealants in joints, waterproof materials and motors Modularity/Versatility: nose dome, wings, LG, VTP, motors arms, equipment, motors, props and cargo bay (attached with spring buttons) easily taken apart. Handling: easy to transport and fit in reduced spaces Weight: CG aligned with motors, payload, IMU and parachute, < 25 kg, structure allowed up to 7 kg, carries around 1 extra required payload weight Fail safe (air): all kinds of redundancy, anti-collision, mission control planning and anticatastrophic failure software readiness Safety provisions (ground): safety switch to arm/disarm drone, RGBW LED indicator, optional props protections Dimensions: each wing is 2 m long, divided in 2 parts, fuselage is 1.7 m long and 0.9 m high with VTP and LG Structure Payload Frame sheet Airframe (fuselage, wings, tail): all secondary parts joined to main fuselage CFRP frame with screws and nuts able to be taken apart Equipment (batteries, motors, actuators): 4 hover motors and 1 cruise pusher required with their adapted propeller, ESC and the necessary batteries Avionics: correctly integrated and centered boxes given in the requirements Landing gear concept: three CFRP straight bars with wheels (steerable NLG) Interior dimensions and securing cargo: cargo bay has required dimensions and a fairing around that completes the fuselage aerodynamic shape. It is secured by an antislip floor plus elastic bands. It s released by sliding 4 spring buttons below Base data: 4 to 6 kg of payload at 30 m/s with a medium CL Drag: low drag increases range (or payload weight) 3

4 Stability: stabilizing wings shape and position, NP at 15% behind the CG gives enough stability 4

5 Introduction Hermes is a VTOL UAV able to deliver 4 to 6 kg of payload to 100 or 60 km in 60 to 40 minutes with an optimal configuration. It has a very simple configuration, cheap and easy to manufacture and able to change its whole payload bay to adapt its mission. It is relatively small for its takeoff weight. It is the small brother of the Mercury design (thus the name). General design The whole aircraft is designed with many years of experience from aerospace design guidelines, focusing on this special payload and an overall simplicity. An oval fuselage is shaped around the equipment of the UAV, keeping its wetted area and front area reduced to decrease drag. It contains the avionics, miscellaneous equipment, batteries and payload. The nose is a clear translucent spherical dome that houses the camera, able to look straight down to the ground (-90 deg.) up to 50 degrees up from the horizon without distortion or darkening. Tandem wings with 2 meters of wingspan crosses the front and rear fuselage avoiding payload and equipment, the empennage is a single vertical tail (shark fin shaped). It is also considered to divide the VTP it in two surfaces and attach it to the main landing gear rods but they might crack with hard landings. 4 motors pull the plane upwards in hover mode, attached to the wing tips with reinforcements. They are perfectly placed around the CG and integrated with the wings to keep stability high. Depending on the mission, the payload bay can carry multiple types of equipment: agriculture monitoring, infrastructure inspection, humanitarian missions (fast and heavy duty delivery), firefighting control, ground observation for law enforcement or coast control, transport of medical items, 3D terrain reconnaissance, weather monitoring The name comes from the Greek god, their quick messenger and emissary, patron of invention, trade, roads, boundaries and travelers among others. The colors are taken from the ambulances in some hospitals around the world which have yellow and blue as primary colors. Details Landing gear The landing gear is a simple tricycle type except that the 2 main wheels and their vertical rods hang from the 2 nd wing wingtips. Being fixed avoids moving parts that can cause problems and it is not a big issue added to the parasite drag as it won t fly over 200 km/h. It is located far apart from the payload bay hatch (but equidistant to balance the weight when touching ground), allowing an easy extraction of the module from below and from the back, It is designed to be as short as the payload unloading process allows for minimizing parasite drag. The landing gear increases not just the safety but also the versatility of the UAV. If one or both departure and arrival locations count with a small runway the UAV itself can carry 1.3 kg more 5

6 of payload (reduced batteries) and if the lifter motors (not even their arms) are unscrewed to act as a plane, it saves 2 kg more. Weight saving can also be transformed in more batteries and an increased range/autonomy. In case the clients want to remove the landing gear (easily unscrewed) to reduce drag force and increase autonomy, they must have a proper landing station or trust the controller to perform always a soft landing on the UAV belly fairing (cushioned payload bay recommended for fragile cargo). The landing gear can be much lower (or higher) if needed depending on the landing station. If the unloading process is automated and from below, the station may not require such a high frame. The wheels are thought to have cowlings on the upper side to reduce interference drag. Waterproofness The exposed surfaces are mainly made of composite materials and plastics that withstand the rain effects or even a dive in water with rubber sealants in every small joint and wire hole. The major material, present in the fuselage and aerodynamic surfaces, is fiberglass reinforced polymer, whose epoxy resin can stand water on its surface. All hatches have rubber sealants too. All landing gear materials, as stated in the structure part, work well under moisture and rain environments. The motors are tested again water and dirt by the manufacturer, as expected from the exposed air data probe and parachute elements. Modularity/Versatility: The payload bay is completely removable with its own fairing. It can be enlarged to the tail and can be accessed easily from the belly and from the bottom tail. It is encased into small rail holes from bottom to top and from left to right of the fuselage and secured with 2 spring buttons on the sides. The payload bay can carry the batteries too, so the swap operation just requires unloading the bay, unplugging the batteries wires, plug the new ones and attach the new bay. This is another optional feature offered to the client. 6

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8 The whole middle fuselage frame can also be replaced for other applications, although it requires detaching the main structure. This allows changing its wing, lifter motors with arms 8

9 and landing gear if necessary (keeping the front frame with avionics and the rear frame with empennage and pusher motor). Besides, every motor and propeller can be changed with just a screwdriver. For shipping purposes it is enough to remove the wings and the motors arms and put them between the landing gear. The fuselage with the air data antenna and the rear propeller is shorter than 2 meters. If it needs to be even more packed the VTP can be removed too, making it 40 cm lower in height. Properly packed it is estimated that 4 Hermes packed in this configuration can be fitted in a regular transport van (E.g. Hyundai I800) as the Mercury. Mercury transport example, very similar dimensions but 2 wings of 2 m each Handling The drone can be lifted with ease by the forward arms in the wings by 2 people. The nose and tail are good support points too. It can be tilted to lay on its tail to allow and easy access to the payload in the belly fairing. Weight The MTOW is set to <25 kg and the structure weighs below 7 kg. The heaviest parts are in the CG or close to increase stability. Wings are almost equally placed at the sides of the payload, with enough static margin to leave out the tail surfaces that delay the neutral point. Lifter motors are away from the CG in all directions to keep stability in take-off and landing. The main CFRP structure (density = 1.66 g/cm 3 ) weighs 1.6 kg with a plate thickness of 2 mm, the glass fiber cover (density = 1.52 g/cm 3 ) weighs 2.8 kg and the rest of components as motors arms and landing gear weigh 1.6 kg, summing up to less than 6 kg. Fail safe (air) To prevent crashes in case of one or more motors failure, propeller separation, power loss or bird strike, an automatic deployment parachute and launcher are provided, apart from the installation of a landing gear that allows an emergency landing with just the pusher motor or even gliding. This landing gear absorbs better the force of a hard landing than typical multirotor skids. The high aspect ratio of the wing grants a good gliding ability to this UAV apart from the excellent lift to drag ratio. In any case, the batteries are segregated in the system, so if one battery fails it just affects 2 hover motors at most, or just the cruise motor. As it is not 9

10 supposed to fly over water in accordance to its range, no floating devices or water skis are designed. The own software of the flight control computer has a failsafe option that starts a controlled landing in case it detects a low voltage in any of the batteries, if the signal with the ground control station is weak/lost, if the mission parameters are lost or if the UAV has entered too much inside a restricted geo-fence. The controlled landing will be performed in hover mode if hover batteries have enough charge and all 4 motors are operative. If any of the hover motors fail, the UAV will execute a conventional landing with the cruise pusher motor and if no motors are operative and the parachute can t be deployed (worst case scenario) the UAV will glide to the ground with just the assistance of the control surfaces. Every emergency case will be notified to ground control. Mission control must plan the route in advance to study the possible obstacles the UAV might find. To avoid mid-air collisions with buildings, trees or other UAVs, apart from creating navigation routes as in large aircraft transport, the UAV can be built with a small sonar/infrared sensor and/or a TCAS (Traffic alert and Collision Avoidance System) in conjunction with other RPAS. Safety provisions (ground) Propeller protections are avoided because another system replaces them, with the related reduced parasite drag and harder manual payload access from the side. It consists of a safety switch located below the nose that prevents the rotors to spin via a connection to the flight control computer. However, the protections are designed by the manufacturer and are optional for the client, who might want to install them if the UAV is going to be operated by people and not an automated system. These protections will be efficiently shaped for reduced drag, keeping similar parasite drag as the propellers alone would cause. The fuselage has indications in the hatches providing the instructions to handle the equipment. An RGBW LED light next to the safety switch will indicate personnel in ground when the drone is ready to be safely approached. In this location it doesn t dazzle people close to it but still illuminates enough reflecting on the ground. Red means the UAV is armed and executing the mission, green means it is ready to be operated by ground personnel, blue means safety switch is on and it is safe to load/unload it. The LED will be flashing white during the mission to act as an anti-collision beacon, especially for nighttime operations. When the UAV is unpowered the LED will be off. The whole walk-around time is less than 15 minutes. More info on pre-flight checklist manual attached as an appendix. 10

11 LED and safety switch below the nose Dimensions Structure Airframe (fuselage, wings, tail) Semi-monocoque structure: CFRP lightweight frames, decks, bars and spars provide the necessary strength in torsion, flexion, traction and compression along the longitudinal fuselage axis, along the wingspan, empennage and lifter motors arms. Vertical and horizontal decks are 11

12 joined with plastic joints and metal screws. The main fuselage airframe and hatches are covered with 5 mm of fiberglass, CFRP is avoided in the cover because it shields the radio signals. The aerodynamic surfaces are made of hot wire cut foam blocks (EPP or EPO) reinforced internally and externally with CFRP. The 4 semi-wings divide the wing loading so the each one doesn t have to flex a lot and motors arms are held tighter. Straight and conventional shapes make the manufacturing and versatility very easy. The parts of the fuselage are attached with joints between the bars, as well as all the aerodynamic surfaces and their spars. A monocoque or bone-shaped structure is not considered now as it inhibits modularity and is harder to manufacture. 12

13 This model incorporates a tandem wing which has no interference with the internal equipment/structure at all and allows an easy access to the payload from below. Both wings have a swept angle to delay the CG position because placing the first wing rearward would interfere with the payload, the IMU or the parachute. The angle they have back is not random, it gives the perfect static margin integrated with the position of the motors and their arms from the wing tips to be evenly placed around at the sides of the CG (so all motors lift at the same power value). The first one is above the second one, to correct the downwash effect and reattach the flow to the upper skin of the second wing with its high pressure flow from the lower skin (pictures below by Henri Mignet gives an idea). This has very good longitudinal stability results. They have a dihedral angle too, the first one is positive and the second one negative (so it would stall first and thus correct the pitch automatically). This decreases even more the interference and with the airflow and added to the swept back angle gives a lot of stability. The whole second wing can be trimmed in pitch angle to adapt to the weight, size and position of the payload and batteries. 13

14 The position of the motors focuses always on safety (structural, flight stability or effects to ground personnel) and ease of handling. They are screwed to small carbon arms in the wing tips. No additional surfaces like winglets or strakes are added as they don t increase the overall efficiency of the UAV at this flight mode and speed. They reduce the induced drag increasing the parasite drag, complexity and manufacturing costs, so they are not considered for the base version. The VTP has the necessary volume for both static and dynamic stability, it is far from the ground to avoid hits in case of a tail strike in a bad balanced or hard landing, it leaves enough space for deployment of the parachute, which is tilted 20 degrees to the right side, and it isn t affected by any turbulent flow from forward elements (fuselage, wings or motors). The control surfaces can be trimmed even easier by turning a screw in the servo control rod, changing its leaver arm length. The fuselage shape, while being easy to manufacture and built with divisions from the rest of structural elements, is slender enough to keep drag low, shorter than 2 m, has soft transitions between its elements, allows good air flow for the pusher motor and keeps the center of gravity in the same plane section for lift and thrust. The 4 motors are fixed with short carbon bars to the 4 wing tips. This way they don t create any interference in the wing (as seen in a typical pressure distribution along the wingspan). In fact the little arms in the wing tips act as winglets, a barrier to prevent high pressure air from going to the low pressure region in the upper skin. Equipment (batteries, motors, actuators) Many batteries are needed to power the cargo drone. It is estimated that 5 LiPo batteries need to be carried to give energy to the motors and rest of systems. Each one is mah capacity, 20C discharge, 6S cells and 1.6 kg heavy. Battery efficiency is kept low (155 W h/kg), even if the manufacturer says it is higher in order to be conservative and because the efficiency when it is installed is reduced. To make it fly, 4 motors attached to the outboard wing lift 25 kg at standard conditions and one pusher motor in the rear end gives the necessary cruise speed (150 km/h) to gain wing lift and to overcome drag. Lifter motors chosen model is T-motor U10 kv100 (400g each), from the efficiency series, giving 8 kg force maximum thrust each. The pusher motor is the U8-10 kv170 (239 g), giving a maximum thrust of 4.7 kg force. U8 PRO specifications are missing from the manufacturer website but they might be even better except for heavier weight. All motors 14

15 have the same carbon fiber propeller from the same manufacturer (28 x 9.2 inches) which provide their peak thrust to weight efficiency (~10). They all work well with a 6S or 12S battery pack. Carbon fiber propellers give the best efficiency and need to rotate slower than wooden propellers. U10 motors need a 30A ESC (4 x 44 g) in case they run at maximum voltage (44.4 V with the 12S batteries), because the maximum current will be 24.4 A). U8 pusher maximum current with 22.2 V (6S batteries) will be 23.8 A, so another 30A ESC is needed for cruise. If the pusher uses 12S batteries, it is recommended to install a 20 x 6 wooden propeller instead of the CF one. Sharing the propellers and ESC for all 5 motors allows a good interchangeability. The hover propellers are set parallel to the symmetry plane when the cruise mode begins to reduce their parasite drag. The hover motors have cowlings around them for the same reason but the cruise motor doesn t, as it will be running for more than 30 minutes between half and full throttle and may overheat even with air inlets. It is recommended by the manufacturer not to cover it and it is designed with its own patented self-cooling shape. U10 (lifters) and U8 (pusher) specifications 15

16 30 A ESC inside carbon tube Every propeller is attached to the shaft with the adapted assembly provided by the manufacturer, the same assembly of bedplate they provide to screw it to the structure. In the case of lifters, the arms that hang from the wings are reinforced to resist the motors force on the edge they are screwed at. In the case of the pusher, it is attached to a strong flat frame at the rear end of the fuselage. The rear end can house an internal combustion engine if the UAV user wants to extend its range/autonomy at the cost of carrying fuel instead of batteries. Lifter motors are placed higher than the wings to avoid interference drag, to increase stability and to avoid sucking dust, sand or small rocks. In case of uncontained blade liberation, none of the blade would cause a catastrophic failure thanks to their location. 4 actuators (rotary servomotors) are used, one for each aileron in the first wing for roll, another actuator inside the fuselage moves both the second wing ailerons symmetrically (acting as elevators for the pitch) and 1 more in the rudder for yaw. Ailerons controlled symmetrically can act as flaps for landing and take-off in conventional flight mode. That sums up to 4 control channels, plus 5 other channels for the motors. One more channel is needed for manually deploying the parachute, another one for manually controlling the transition process and some extra ones to additional actions like arming the drone or overriding the safety switch. Actuator below the wing moving the aileron 16

17 Additional power sources are being studied to recharge batteries during flight: an electric generator driven by the cruise motor inboard axis, solar panels on the wing upper skin, vortex/bladeless wind energy generators, autorotation landing that takes energy when descending either in kinetic (inertia can be used for an emergency landing as in an autogiro) of electric form (KERS style, to recharge batteries with the necessary power for a soft landing). Another system in development which can be implemented to this operation is a selfrecharging UAV. It has connections in the landing gear that create a bridge between a battery charger in the landing station and the batteries electrical system, automating the charging operations of the drone. It can be charged by induction too when it approaches the landing base like cell phone wireless chargers and it works very fast. This combined with an automated unloading/loading process turns the whole operation completely unmanned. Avionics The center of gravity axis is shared by the payload, the battery pack, the inertial measurement unit (IMU) and the parachute, all of them accessed from top or below. The IMU can go inside the structure of the wing between spars or a bit forward to avoid interference. The rest of equipment provided in the requirements has its own reserved space in the nose (the camera inside the translucent dome as well as the air data probe and antennas) and the forward fuselage, which helps taking the CG forward and reduces the wiring among elements. Transmitting and receiving antennas (flight control, video, GPS) will be placed as far apart as possible once they are known, so the interference and signal noise doesn t represent an issue. Landing gear concept The landing gear sticks are made of fiberglass straight bars (or CFRP), bearings are made of stainless steel and wheels are made of rubber. The nose landing gear wheel has a free rotation 17

18 axis which doesn t increase weight significantly and allows turning in a possible taxi phase. The bars are directly joined with the structure frame and the wing spars, transmitting the landing force effectively. Payload Interior dimensions and securing cargo Payload bay is designed to be a bit larger than the required dimensions. When the payload boxes inside the cargo bay are smaller than these requirements they are secured by many possible means, taking into account they won t be heavier than 6 kg. From simpler to more complex: a rough rubber floor on the bay module that prevents shifting of the CG along axis X and Y could be enough, viscoelastic polyurethane foam (memory foam or LRPu), cable ties, elastic strings and finally a mechanism of plates that move along rails with springs (similar to universal battery chargers or sliding cellphones, 2 plates below press the boxes along the Y axis and 2 plates above press it along the X axis). Inside the enabled boxes for the client, vertical and horizontal plastic separators are included to place each item evenly spaced and unable to shift (e.g. blood samples, syringes, medicines ). CG shifting won t be an issue. 18

19 The cargo bay is removed by sliding 4 spring buttons on the belly of the UAV, next to the corners of the module, 2 at a time. 19

20 Frame sheet Base data Every time a performance value is fixed, it s in the mind of the designer being conservative with the numbers, with safety margins to reduce future errors and added design cost during the project. This is referred mainly but no limited to: battery specific energy, efficiencies, structure and equipment weight, dimensions, wing surface, lift and drag coefficients. Every value is rounded and increased/decreased to the safety side. Ignition kit s frame sheet is attached at the end as an appendix. The main figures are these: Payload Mass m Payload = m TOM m empty = 4.07 kg for 100 km 5.98 kg for 60 km Cruise Speed v cruise = 30.6 m/s Speed equals 110 km/h. These aspects are explained in the appendix. 20

21 Drag Parasite drag is obtained from Digital DATCOM formulas, Roskam and Raymer methods, mixing this geometry with coefficients coming from laminar and turbulent Reynolds tests as well as form and interference factors of several aerodynamic shapes. FFwing1 1, CD0wing1 1,23946 FFwing2 1, CD0wing2 1,23946 FFrud 0, CD0rud 0, FFfus 1, CD0fus 3, FFnacs 7, CD0nacelle 0, FF LG 5, CD0 LG 0, The optimal lift coefficient for minimal drag is 0,43 but obviously for a negative pitch angle around 2 degrees down. This is the CL and gliding angle the UAV might have to boost its autonomy. Total induced and parasite drag sums the total cruise drag and thrust required by the motor to overcome it. CD0 0,011 Stability The center of gravity can be easily changed moving the battery pack along the longitudinal axis. By design it is placed close to the payload, a bit behind to improve its access from the side, but there s a lot of space below the first wing and inside all the rear half of the fuselage, making it more able to be shifted. In addition, the neutral point could be set much backwards with a little change in the first wing position or the second wing pitch to increase the longitudinal stability. 21

22 Apart from all the explanations given in the Structure-Airframe part about how this wings control stability, the longitudinal stability is calculated. Lift coefficients for the wing surfaces are obtained with Digital DATCOM formulas, their relative position and geometry. They are dimensionless, referred to the dynamic pressure and the wing surface. In addition, the interference of the first wing over the second one (downwash) is obtained too with empirical formulas and coefficients. It is negative because the wing flow decreases the relative angle of attack of the tail. 22

23 CLα and dεdα results and comparison CLα1 4, CLα2 4, dεdα advanced calculation NEGATIVE dεdα (DATC -0,36367 All the geometry put together with their lift coefficients and downwash effect gives the neutral point position, or combined center of lift. Neutral Point xnp 0, m from root chord 0, m from nose 1, % Center of Gravity xcg 0,542 from wing root 0,692 m from nose 1,7344 % Static Margin SM (%) 0, A positive static margin means the neutral point is behind the CG, making the UAV selfstabilizing in pitch (statically stable). Over 10% is already enough stability. This is checked with the value of the total moment coefficient (values between -0.8 and -1.5 are adequate). 23

24 xpn 0, αtrim δetrim CLαtotal 7, ,06429 CMα -1, ,21544 VT 1, ,36658 CMδE -7, ,51773 Thrust (N) 12, ,66887 CMThrust -0, ,82002 δetrim (rads and degrees) -0, ,06429 rad deg This chart shows how the potential tail should be pitched up or down to compensate the lift created by a virtual wing lifting from the NP. In this case it is just a value to check how displaced is the CG related to the NP and how big the correction should be made (not a problem with the actual numbers). As the CG is a bit further of the center of pressure, the second wing might need to pitch the UAV up to compensate the moment. This small pitching is used to balance the thrust vector around the CG too. In the case of tandem wings this doesn t apply as both wings generate lift and more or less the same so if the CG is between them both of them have positive lift. Last calculations give the needed negative angle for the tail to compensate all moments. It is less than a degree because the lift and weight forces are very close to each other in the wing. The chart in the right gives additional notions of tilting the tail in case the wing is pitched up to increase lift. For example, if the UAV must fly slower to save battery weight, the wing will need to have a higher lift coefficient to compensate the decrease in speed. Tilting the wing up 2 degrees for example will give much more lift but the tail must be tilted down 3.7 degrees, as seen in the chart. 24

25 Extra views 25

26 Appendix A: Frame sheet Airbus Cargo Drone Challenge Frame Sheet Sergio González Fernández (User Sergius) Version... V 2.00 Last Update Aircraft Data: Green cells are calculated by formulars or are given (not changeable) requirement values e cells are specific to the design entry; mandatory to be filled out by the participant as delivery item Blue cells are optional delivery items Aircraft name : Hermes General Requierements Description Symbol Value Unit Comment Maximum Take-Off Mass mmtom = 25,0 kg Shall stay below 25 kg Air Density r= 0, m MSL and ISA+20 C Geometry Data: Description Symbol Value Unit Comment Wing Span b = 1,9 m For each wing. No need to consider them separat c = 0,3125 Aspect Ratio AR = 6,08 - For each wing Wing Area Sref = 1,1875 m² Twice each wing surface Wing Loading (fixed wing mode) m/sref = 21, kg/m² kg/m² recommendation Disc Loading (rotor disc) m/sprop Lift = 15, kg/m² kg/m² recommendation Lift Propeller Area per Lift Propeller Sprop Lift = 0,397 m² Lift Propeller Diameter Dprop Lift = 0,711 m Cruise Propeller Diameter Dprop Cruise = 0,7112 m Cruise Propeller Area per Cruise Propeller Sprop Cruise = 0,40 m Number of Propeller for Hover npropeller,hover = 4 - Number of Propeller for Cruise npropeller,cruise = 1 - Fuselage Length Lfuselage= 1,77 m Fuselage Diameter (max. Diameter) Dfuselage= 0,32 m Vertical Tail Surface Svertical tail = 0,054 m² VTP Vertical Tail Leaver Arm to CoG lvertical tail = 0,93 m VTP Horizontal Tail/Canard Surface Shorizontal tail = 0,59375 m² 2nd wing Horizontal Tail/Canard Leaver Arm to CoG lhorizontal tail = 0,86 m 2nd wing Control Curface Area for Pitch Scontrol,pitch = 0,057 m² 2nd wing Control Surface Leaver Arm to CoG for Pitch lcontrol,pitch = 1,09 m 2nd wing Control Surface Area for Roll Scontrol,roll = 0,057 m² 1st wing Control Surface Leaver Arm to CoG for Roll lcontrol,roll = 0,69 m 1st wing Control Surface Area for Yaw Scontrol,yaw = 0,011 m² VTP Control Surface Leaver Arm to CoG for Yaw lcontrol,yaw = 0,98 m VTP Mass and Balance Data: Description Symbol Value Unit Comment Structural Mass (wing, fuselage, empenage, nacelles, ) mstruct = 7 kg Avionics Mass (see ignition kit) mavionics = 3,4 kg PDF values sum 3,26805kg, default was 3,4 Flight Control Actuation mactuation = 0,55 kg Electric Motors and Controllers Mass (for hover) mmotors,hover = 1,776 kg 4 x T-motor U x Turnigy multistar 30A ESC Electric Motors and Controllers Mass (for cruise) mmotors,cruise = 0,68 kg Turnigy multistar 30A ESC Propellers Mass (for hover) mpropeller,hover = 0,4 kg 4 x T-motor 28x9.2 CF Propellers Mass (for cruise) mpropeller,cruise = 0,1 kg T-motor 28x9.2 CF Battery Mass mbattery = 4,610 kg Additional Mass for Installations minstallations = 0,5 kg mass for wiring, installations, etc. Empty Mass å mempty = 19,016 kg Payload Mass d = mmtom - mempty = 5,98 kg Center of gravity location x-location xcog = 0,69 m From the nose. (Payload at 0,65 m) y-location ycog = 0 m z-location zcog = 0,09 m Height from the center longitudinal axis (X) of the 26

27 Efficiencies: Description Symbol Value Unit Comment Efficiencies for Hover Flight Electrical Motor Efficiency (incl. Motor controller efficiency) helect. motor = 88% Figure of Merit FOM = 0,6 - Battery Efficiency hbattery = 97% Power Management and Distribution Efficiency hpmad = 99% Efficiencies for Cruise Flight Electrical Motor Efficiency (incl. Motor controller efficiency) helect. motor = 88% Propeller Efficiency hpropeller = 82% Battery Efficiency hbattery = 97% Power Management and Distribution Efficiency hpmad = 99% Aerodynamics: Description Symbol Value Unit Comment Oswald Factor e = 0,867 - Zero Lift Drag Coefficient CD0= 0, Cruise Lift Coefficient CL Cruise= 0,46 - Induced Drag Coefficient CDi Cruise= 0,01 - Lift to Drag Ratio L/DCruise = 19,34 - Static Margin SM = 15% Component specific Energy: Description Symbol Value Unit Comment Battery Specific Energy wbattery = 155,0 Wh/kg Aircraft Range Performance Estimation: Description Symbol Value Unit Comment Required Cruise Thrust Tcruise = 12,7 N Cruise Speed vcruise = 30,6 m/s Range drange = 60,0 km Required Cruise Power Pcruise = 558,0 W Hover nz nz= 1,1 - Required Hover Power Phover = 4775,5 W Required Power for Avionics PAvionics = 93,0 W previously 91W, without ADS Cruise Time tcruise = 37,7 min including 5 min reserve Hover Time thover = 2,0 min 2 min Hover time is required Battery Energy Ebattery = 571,6 Wh Some values are left unchanged, like the structure mass, the efficiencies, battery specific energy and installation, actuation and avionics masses (although avionics mass seemed to be a bit lower in the ignition it). The wingspan is that of each wing as it is used to calculate the aspect ratio (6 each wing, they don t sum up), but the surface must be multiplied by two as it is used to calculate lift and drag. Wing and disc loadings are obtained from the dimensions of their elements, not the other way around. They are later checked to be between the recommended values. The wing surface is set to be enough to lift the MTOW at the desired cruise speed but not so big in order to keep a low drag and reduced size. The propellers are big as they give the highest efficiencies with the chosen batteries for the recommended motor by the manufacturer. Their masses are introduced in the mass section. CD 0 is adapted to the one calculated. 27

28 Cruise speed is set to fit the required payload (more speed, more battery weight, less payload) but also the lift coefficient required by the wing. Flying slower requires a higher CL which can only be achieved by certain complex (cambered) airfoils. In this chart (set for a range of 60 km) it s shown what CL might be needed at a given speed and how much payload the UAV could carry. Going for a CL value of 0.46 (not pessimist neither optimist), the UAV should fly at 110 km/h to carry 6 kg. If the aircraft can achieve a real higher CL value (for the whole aircraft, not just the wings), it should be able to carry more payload by flying slower. It always depends of what we have, how much does out payload weigh and how quick we want to arrive. v(km/s) v(m/s) CL Pcruise Ebatt Wbatt Payload 80 22,2222 0, , ,946 3, , , , ,844 4, , ,7778 0, , ,743 4, , ,5556 0, , ,641 4, , ,3333 0, , ,539 4, , ,1111 0, , ,438 5,1245 5, ,8889 0, , ,336 5, , ,6667 0, , ,235 5, , ,4444 0, , ,133 5, , ,2222 0, , ,031 6, , , , ,93 6, , ,7778 0, , ,828 6, , ,5556 0, ,6 858,726 6, ,7 Payload weight comparison for a 60 km mission 28

29 Appendix B: Hermes UAV operations manual Preflight inspection checklist (at base level), 10 min 1. Check batteries voltage, for each one if they are segregated (avionics equipment, VTOL and cruise motors, camera ) 2. Flight equipment visual inspection (walk around) (UAV unpowered, LED off): a. Controller/Transmitter check for damage b. Structure check: i. From nose to tail and from top to bottom, no apparent cracks ii. Wings and control surfaces are intact, no leading/trailing edge or wingtip damage iii. Same for empennage surfaces iv. Landing gear presents no damage or deformation c. VTOL motors arms hold tight to the wings d. All 5 motors turn freely, are tightly screwed to the structure e. Propellers are correctly attached and don t have any scratches, dents, bending or chips 3. Connect power to autopilot 4. Connect power to avionics 5. Check-ins from Ground Station a. Check telemetry b. Check RC signal c. Check avionics connection d. Check compass e. Check level horizon f. Check GPS g. Check airspeed h. Check altitude i. Check mission uploaded to flight control computer: vertical take-off, transition, cruise, transition back and vertical landing 6. Check safety switch off, check arming is secured 7. Turn safety switch on (UAV safe and powered, LED on blue) 8. Check response of control surfaces is correct in direction, time and speed 9. Check auto-stabilization from gyroscopes 10. Connect power to motors (UAV on stand-by, LED on green) 11. Close and secure all access hatches (avionics and camera bay, batteries 1&2 bays, payload bay) 12. Bring UAV to take-off zone 13. Check operation zone is cleared from people, animals and obstacles 14. Check the weather conditions, avoid flight in too windy conditions, heavy rain, snow, hail 15. Check the take-off, landing and route locations don t enter in the reserved space for airports according to the country s legislation 29

30 16. Check possible wireless networks and antennas interference 17. Arm UAV (UAV armed, LED on red and flashing white) 18. Start mission VTOL to cruise transition phase Cruise to VTOL transition phase Cargo transport mission: Arrival destination checklist (at client level), 5 to 15 min. (some steps are optional) 1. Bring replacement batteries (charged) (UAV armed, LED on red and flashing white) 2. Disarm UAV (UAV on stand-by, LED on green) 3. Turn safety switch off (UAV safe and powered, LED on blue) 4. Check safety switch off, check arming is secured 5. Bring UAV to unloading zone 6. Open batteries 1&2 hatches 7. Disconnect power to motors (UAV unpowered, LED off) 8. Extract batteries (discharged) 9. Open payload bay hatch 10. Extract payload and put aside 11. Insert replacement batteries (charged) 12. Open avionics hatch 13. Check batteries voltage, for each one if they are segregated (avionics equipment, VTOL and cruise motors, camera ) 14. If UAV encountered problems during operation, such as hazardous weather or hard landing: a. Follow step 2 from preflight inspection checklist (Flight equipment visual inspection) 15. If voltage is not enough: a. Disconnect power from autopilot and avionics b. Change their batteries c. Follow steps 3, 4 and 5 from preflight inspection checklist 16. Follow steps 6 to 12 from preflight inspection checklist (UAV on stand-by) 17. Arm UAV 18. Start mission 19. Remove payload from unloading zone 20. Connect discharged batteries to charger 30