DESIGN DESCRIPTIONThis is the Airbus A390D, an advanced next generation multi-purpose drone, with VTOL (Vertical Take-Off and Landing) and STOL (Short Take-Off and Landing, when flying in horizontal fixed wing mode) capabilities,
a hybrid design created through the merging of design elements from both multi-rotors and fixed-wing aircraft.
Inspired by flying wing aircrafts, quad rotor drones and traditional biplanes, the A390D is a combination of both of them.
Its fuselage is the main wing, enabling the entire craft to generate lift, potentially reducing the size and drag of the wings and optimizing the volume of the drone. Although the main central wing-body has is relatively low aspect ratio, thanks to the combination with higher aspect ratio wings located in x position, hovering motors covers acting as winglets, and correct position of the Ruddervators (V-Tail), induced drag residual vortex are reduced drastically, and Oswald factor estimated is 1.2. Thanks to this features, the overall size of the aircraft is really compact compared with other drones with similar performance.Following the simplicity concept as one of the main targets, it has the minimum required rotors, 4 lifting motors/rotors, and one motor is used for forward thrust in the fixed-wing flight mode, located in front, blowing air directly over the wing-body, thus generating additional lift, and allowing to take off as a normal fixed wing plane in a very short track.
Regarding the quadrotor drone influence, it has an internal structure similar to this type of drone: the main carbon fiber multi layer structure, and four structural elements connecting with the wings, in which are located de hovering motors.
The wings are based on sandwich structure, with slim sheet of carbon fiber, filled with high tensile strength foam, and exterior vinyl wrapping (white).
Its overall style is similar to a biplane, with the cruise propeller located in the front, main landing gear located slightly forward the center of gravity, and double wings, but these are located in tandem position, lightly swept.
As the aircraft must operate in extreme weather conditions with temperatures varying from -30 to 55ºC, it has a cooling system which consists in an inlet in the front side just under the propeller, with ducts for battery cooling in hot environments. These can be be sealed in cold weather conditions, to avoid LiPo battery failure.
The name of the aircraft, A390D has been selected following the Airbus numbering system, so, as the last plane released was the A380, next is 390, and “D” means Drone.EXPLANATION OF DESIGN DETAILS
As the plane must be as simple as possible, and it should have landing gear for conventional fixed-wing take-off and landing, in addition to vertical take-off, the A390D has a landing gear similar to other systems used in classic biplanes and small planes like Cessna, it consists in two main wheels located slightly forward of the center of gravity, supporting almost all the weight of the aircraft, covered with a fairing to improve aerodynamics, and instead of one small wheel at the rear end, two wheels are located in this position, supporting just a small part of the total weight, connected to the respective servos of each Ruddervators at the rear for steering capabilities when the drone is on the ground.Conventional fixed-wing take-off and landing should be performed when possible, as this take-off mode is more energy efficient than vertical take-off.“Waterproofness”
To be able to operate safely flying with moderate rain, all the electronic components are located inside the fuselage like a conventional plane (no servos outside). The motors are waterproof and dirt resistant.
For better ship-ability, the four wings can be disassembled, and placed together with the main wing-body. Landing gear can be unmounted and saved inside de cargo bay. The resulting size is very compact (1.5m long and 0.8m wide). As the wingspan is not too large (2m) the entire drone is relatively easy to transport without disassemble.Payload and cargo concept
Payload size is 450 x 350 x 200mm, is coincident with the center of gravity, and it’s accessible from top and inferior sides, just by opening the hood in the top of the drone, or a gate located at the bottom. The system to secure the payload in the right place avoid shift during flight is very simple, the walls of the container are covered with inflatable mechanism, immobilizing the payload, regardless of size or weight. If the payload size is close to the cargo bay, the inflatable mechanism can be easily removed. Payload can be interchangeable with payload bay of same size and same interface.Ease of handling
The main behavior feature of the A390D is its neutral stability.
Naca 4418 airfoil has been used for the main wing-body y and naca 4415 for the wings.
Directional stability is controlled by 2 Ruddervators (V-Tail) located a the rear end of the drone.
Pitching control is outstanding in this aircraft, thanks to the multiple surfaces controlling longitudinal stability: as the 4 wings have it characteristic tandem configuration, these act as Elevons as well (control surfaces that combine the functions of the elevator and the aileron). Rear ruddervators also add elevator function.
When the aircraft is performing vertical lift-off and landing, ailerons are down to reduce wing surface and optimize propeller airflow during hovering.
In horizontal cruise flight, hover propellers are locked parallel to the flight direction to reduce drag.
Center of gravity is coincident with center of lift, but can be adjusted by displacing the batteries longitudinally.
Weight and size
19.96 kg empty. Total weight loaded is 25 kg. Wingspan 2m (0.8m when unmounted) length 1,5 m.Fail safe components to prevent catastrophic failure
XL96 Skycat parachute, located over the gravitycenter, inside the hump of the drone, and X55 launcher.
The system is covered with a breakable plasticsheet, that breaks when the parachute is deployed.
Safety provisions: limit time on ground with rotors spinning
Propellers stop spinning almost immediately afterturning off the motors, but to add additional safety provisions a contactbreaker can be placed in the rear end of the drone (in the area clear ofpropellers) for safety of the operator during loading and unloading operations.Performance
The Airbus A390D has a payload capacity of 5 kg, and a range of 65 km. Cruise efficient speed is 100 km/h (28 m/s). Estimated maximum burst speed is 158 kmh (44 m/s).
Maximum Thrust generated by the horizontal flight motor is 15.8 kg (close to 2/3 of the total weight of the loaded aircraft as proposed). Combined thrust generated by the 4 hovering motors is 50.4 kg (2x total weigh of the loaded aircraft).
As it has power reserve, it can deliver payloads to closer range at higher speed, also change flight direction and hard maneuver in case of emergency.Components List
Cruise flight motor: E-Flite 1x Power 360 Brushless Outrunner Motor, 180Kv , up to 6000w http://www.e-fliterc.com/Produ...
Cruise flight rotor: 1x Mejzlik carbon fiber propeller 22 x 14
Although the recommended propeller for this motor are 24 x 10 to 25 x 12, with 22 x 14 propeller is achieved the calculated efficient cruise speed and maximum thrust
Hover motors: 4x T-Motor U11 120 KV up to 4000w and 12,6 kg of thrust. http://www.rctigermotor.com/ht...
HOver Rotors:4x T-Motor Carbon fiber propeller 27 x 8.8, recommended for the T-Motor U11. http://www.rctigermotor.com/ht...
Batteries: 2x Tattu 26000mAh 22.2V 25C 6S1P Lipo Battery Pack, connected in series to get 44.4V http://www.gensace.de/capacity...
The rest of the components and internal equipment are already provided, or are standard components.Calculations
Motors and Propellers has been calculated and checked by several RC plane design tools.
Surface Areas calculated and checked by surface modeling software.
To calculate the center of gravity, it has been considered that, the empty aircraft without internal equipment or motors, has a center of gravity slightly backwards the intersection of the wings (main landing gear is located in an advanced position over the CG, but the secondary landing gear an V tail affects slightly more in the opposite direction).
To balance CG, the cruise flight motor and camera system are located as close of the nose cone as possible, generating a torque of 0.8 kgm, and the rest of the internal equipment is located in the rear position, behind the cargo bay, generating a torque over the GC of the emplty drone of 0.6 kgm.CG final position is x=679 mm (considering coordinate origin in the tip of nose cone)Surface Calculations:Wing Area
= 0,149 m2; 4 wings = 0.596 m2
Central wing (Body) area = 1.03 m2
TOTAL WING AND BODY-WING AREA = 1.626 m2
Vertical Tail Surface
= 0.079 m2; 2 vertical tail= 0.158 m2
As the tail surface has an angle of 127º from the horizontal plane, 127ºsin = 0.79; 0.158 m2 multiplied by 0.79= 0.125 m2
Control Surface Area for Yaw
=0,026 m2; 2 vertical tail = 0.052 m2
As the tail surface has an angle of 127º from the horizontal plane, 127ºsin = 0.79; 0.052 m2 multiplied by 0.79= 0.041 m2
Horizontal Tail/Canard Surface:
as the aircraft has a tándem wing setup, each wing is part of the horizontal/canard surface, plus the rear ruddervators.
Vertical Tail Surface= 0.079 m2; 2 vertical tail= 0.158 m2
As the tail surface has an angle of 53º from the horizontal plane, 53ºcos = 0.6; 0.158 m2 multiplied by 0.6= 0,095 m2
TOTAL HORIZONTAL TAIL/CANARD SURFACE = 0.596 m2 + 0.095m2 = 0.69 m2
Control Surface area for Pitch
: as the aircraft has a tándem wing setup, each wing is part of the horizontal/canard surface, plus the rear ruddervators.
4 wings surface control surface = 0.11 m2
Tail control surface = 0.027m2 multiplied by 2 = 0.054 m2
As the tail surface has an angle of 53º from the horizontal plane, 53ºcos = 0.6; 0.052 m2 multiplied by 0.6= 0.031 m2
TOTAL Control Surface area for Pitch= 0.031 m2 + 0.11 m2 = 0.14 m2