Installing Mission planner Hardware in a fixed wing aircraft

Project overview
To get the benefits of mission planner on a asw28 2.5m motor glider, a few important hardware setup details will allow for a better preforming aircraft. This installation of a mission planner based flight controller will allow for autonomous soaring, where the aircraft automatically senses lift and trys to stay in that thermal. Another feature that mission planner allows for is return to home, and with a large sailplane, some thermals can take them out of sight.

Figure 1. Stock asw 28 sailplane

Aircraft current status:
The aircraft is currently a stock ASW 28 v2, it has a motor and esc/bec combo, with 6 servos. The 6 servos actuate the ailerons, flaps, rudder and elevator. With the independent servos for the ailerons and flaps, it allows for the aircraft to use crow on landings. Crow is where the ailerons both move upward and the flaps drop down, this causes an immense amount of drag, which aides in the landing of the aircraft.

Hardware to be installed
To allow for full functionality of mission planner and ardupilot a few components need to be added. These consist of a flight controller, a pitot tube, a sbus reciever, and a gps. For the flight controller a matek systems F405, this was because the full pinout of a pixhawk flight controller was not required for this installation. Using the F405 saves on cost and weight over a standard pix hawk. For the pitot tube a Matek analog airspeed sensor was selected, as it paired well with the f405 flight controller. The receiver to be installed is a frsky r9 slim plus, this was to allow for a increased control link distance, as it is a 900mhz setup. Finally a gps was selected to be paired with the system and a matek M8Q-5883 GPS Module was used as it has the addition of a compass which can allow the aircraft to have redundant compasses, one internal on the flight controller and the external gps on.

Mounting the electronics 

The flight controller was installed into a 3d printed mount then the 3d print was glued into he upper deck of the fuselage, this can be seen in Figure 2. The flight controller has to be as close to the center of gravity/ center of lift as possible as it will sense the movement of the aircraft more accurately.  Next was installing the pitot tube, this created some problems as mounting it in the wing could create issues with taking apart the aircraft, and with a 2.5 meter wingspan its hard to transport without taking it apart. The decision was made to install the pitot on the fuselage, which can create some problems when the propeller is on as the airspeed will be faster as it is getting prop blast as seen in Figure 3. This is only a slight issue as the throttle is only used for climbing the aircraft or return to home, which uses the gps for speeds with a few modifications in mission planner. Speaking of the gps, it needs to be mounted facing the sky to acquire satellites. It also needs to be placed away from any transmitters or magnets as they can interfere with the signal. For these reasons it was placed behind the canopy on top of where the wings join. Finally the receiver needs to be installed, this also needs to be away from anything transmitting, or large metallic objects like the battery and the motor. For this installation the receiver was put in the tail section of the blow-molded fuselage, with the antenna on the outside of the aircraft.

Figure 2. A flight controller mounted in its 3d printed holder in the fuselage

Figure 3. The propeller blast can interfere with the pitot tubes readings (right red part) 

Conclusion
Many different precautions have to be taken when setting up a uav, as there are many things that can interfere with each others operation or that can provide false readings. The next steps for this uav are to got into mission planner to install arduplane and do all the proper calibrations to prepare it for flight.