Am looking for building a Fixed Wing UAV for Aerial mapping and performing it based on my own research. Your suggestions are most welcome to correct myself in building it. 

AIM

To assemble a Fixed wing UAV for Aerial Mapping with 2.5 - 3 hours endurance

REQUIRED PARTS

1. Skywalker X8 (2122mm) airframe

2. TURNIGY Plush 60amp Electronic Speed Controller

3. Aeronaut CAM carbon 12x6.5 folding prop blades, Aeronaut 36mm Precision Spinner for 5mm shafts, 38mm Aluminium centre piece, Folding Propeller Blade Stopper

4. X8R 8/16Ch - FrSky S.BUS ACCST Telemetry Receiver

5. Digital Air Speed Sensor And Pitot Tube Set

6. Turnigy TGY-225MG Analog High Torque Servo 26g – 2

7. Turnigy Aerodrive SK3 - 3542-800kv motor

8. Pixhawk 2.1 autopilot

9. Taranis X9D Plus transmitter

10. HERE GPS

11. 22,050 mAh Li- ion battery – 2

13. Carbon Fiber sheet (1 Roll – 4 x 6)

14. Balsa Wood 

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I am continuing my fabrication process.

Please suggest me if anything needs changes or modifications

Airframe 

Checked for all Parts

  1. Pair of Wings with Elevons and Wing joiners
  2. Fuselage top and bottom parts
  3. Canopy
  4. Two Carbon Rods to Strengthen wings
  5. Two carbon rods to join Wings to the fuselage
  6. Push pull rod setup for Elevons movement
  7. Motor Mount

Every part separately weighed

Airframe Fabrication

1. Elevons cut out from both wings to avoid its damage during reinforcement process of wing

a) Elevons just joined with the wings by thin line foam.

b) Using Paper cutter or Surgical Knife cut made on that thin line to separate elevons from wings

2. Reinforcement of Fuselage parts with carbon fiber sheet

a) Fuselage bottom part covered with carbon fiber sheet by cutting carbon fiber sheets into required pieces and labelling over fuselage horizantally to get good finishing

b) In the above figure, the carbon fibre sheet over that rectangle block removed to put a plywood (come along with Airframe kit) in that block to avoid damage of airframe during landings

c) This portion covered separately because following horizontal pattern over this area gives bad finishing.

After labelling carbon fiber sheet, the surface ironed using iron kit for expansion of carbon fiber sheet so that wrinkles made during labelling of sheet corrected

d) Fuselage upper part covered by Carbon fiber sheet. Because of the curved surface this part was covered by cutting carbon fiber sheet into horizontal strips and labelled for better finishing

e) Winglets also covered with carbon fiber sheet. For curved surface, sheets labelled as stripes and for flat surface sheet labelled and cut according to the shape required

f) Finally that surface ironed to avoid wrinkles while labelling.

3. Reinforcement of Elevons

a) Elevons strengthened by balsa wood to avoid damage while flying. Balsa wood cut in to dimensions of elevons to glue it permanently at the bottom surface of elevons by using Z-Poxy.

b) Elevons also fully covered with carbon fiber sheet to make it more strengthen. After that, elevon surface ironed using iron kit.

4. Reinforcement of Wings

a) To place the carbon fiber rod on the wing, cut made using surgical knife at the bottom surface of the wing in exact dimension of carbon fiber rod.

b) Then carbon fiber rod inserted into the wings and glued with Z-poxy to stick it permanently.

c) Over the rod fiber tape sticked to ensure more grip.

d) To continue with wing reinforcement servos for operating elevons should be fixed before covering the wings with carbon fiber sheet. For that servo`s has been balanced for its torque before fixing it to the wings.

e) Before placing the servo, balsa wood glued using Z-poxy to strengthen the surface to fix the servo

f) Then servo placed and fixed with Hot glue and wires fitted into the cut provided for it and servo connector to Autopilot left out.

g) Over the servo and wire also fiber tape sticked to ensure more grip.

h) Wing flaps fixed to the wings using Z poxy. Except the place (approximately marked in the above figure) for rectangle plate which joins wings to the fuselage all other surface glued with Z-poxy to fix the flaps.

i) Wing bottom surface covered with carbon fiber sheets by cutting sheets into stripes.

j) Whole bottom surface covered with carbon fiber sheet and extended upto the leading edge.

k) Over the surface of servo also balsa wood sticked using double side tape, to avoid its damage during landing.

All these process of wing reinforcement followed for another wing also and finally both the wings look as in below figure.

5. Winglets joined to wings

a) Z-poxy applied at wings place were the winglets are fixed and also at the winglets place were it is attached to the wings.

b) Then winglets placed and holded for few minutes to set.

6. Reinforcement of Canopy

a) Before covering canopy with carbon fiber sheet it is sticked with velcro tape wherever required to fix it with fuselage as shown below.

.

b) Carbon fiber sheets cut into square pieces and labelled over the whole canopy.

c) Then the canopy surface was ironed to avoid wrinkles because of the Velcro tapes.

Fuselage upper part also sticked with velcro tapes to hold the canopy as shown above.

7. Attaching Wing Joiners to the Wings

a) Wings surface where the joiner need to be attached applied with z-poxy and the wing joiners counterpart also applied with Z-poxy

b) Then Wings placed over table and holded tightly then the wing joiner attached with care and checked in order to align the wing joiner`s hole through which the carbon fiber rod runs to join wing and fuselge

c) And check also done to avoid Z-poxy applied over servo wires, wing joiner clips during work process. And all the extra fluid of z-poxy wiped out.

The same process followed for another wing also.

After wing joiners set with the wings, the trainling edge of the wings also covered with carbon fiber sheets as shown above.

8. Attaching X-Ray sheet strips to elevons

To fix the elevon to the wings also for its required deflection X-ray sheets cut into strips and attached to the elevons

a) 6 x-ray sheet strips 3 for each elevon been cut

b) Slots to insert the x-ray sheet strips into the elevons made in equal distances at the attaching surface of elevons as shown in above figure

c) Then the strips inserted and applied with Z-poxy to fix it permanently.

Fabrication process finished and followed by that placement of components as follows

9. Placing components in Airframe Fuselage compartments

a) Weightless foam pieces were stuck using hot glue gun at the fuselage bottom part compartments to level place the plywood (3 compartment plywood dimensions refer to below figure) on three compartments

Plywood 1 (dimension)

Plywood 2 (dimension)

Plywood 3(dimensions)

b) Ply woods are cut with mentioned dimension and filed using wooden filer for required dimensions in order to fix it.

c) Plywood parts including motor mounts covered with Carbon fibre sheet

9A) Fixing Airspeed Sensor

a) The inlet of airspeed sensor placed at bottom fuselage nose part by facing the inlet out of the airframe

b) Then hole made in between the first compartment and second compartment of the fuselage bottom part using soldering machine to pass the air speed sensor tubes refer figure below

9B) Fixing Battery

a) Batteries checked for placement at the first compartment of fuselage

a) Another hole made to in between first and second compartment to pass the battery Y-cable to connect with power module and ESC.

c) Power module to power Pixhawk autopilot and ESC connected to Y cable (its another end connected to battery) at one end and with ESC at other end using extension wire.

Mounting Motor

a) Motor mount (1) stuck with plywood motor mount (2) using Z poxy.

b) Motor mounted to motor mount using screw (4 Screw and nut) (3) and this whole setup placed on the fuselage back in the place provided for motor using Z poxy.

c) Another plywood mount (4) stuck with frame as opposite to motor mount setup to fasten motor mount screws with nuts.

d) To avoid damage of Fuselage bottom part during landing a plywood piece stuck with the bottom surface in the place provided for that using Z-poxy.

9D) Placements and Connections of ESC

a) ESC fixed adjacent to motor using double foam tape and connected to Motor (clockwise rotation)

b) To power ESC, wire from Power module connected to ESC to pass this wire hole made between second and third compartment of fuselage using surgical knife.

Placement and connections of Receiver

a) Receiver placed at the right side of the third compartment of fuselage where ESC placed. Antenna from receiver should be left out of the airframe to get signal from ground.

b) Connection between Autopilot and Receiver to get signal from transmitter--- the connection wire (3 pin) from SBUS of receiver to RCIN of Autopilot (Pixhawk) to pass this wire hole made between second and third compartment of fuselage using surgical knife.

9F) Placement of Autopilot

a) Autopilot placed at the second compartment of fuselage near to centre using double side foam tape

b) Autopilot`s direction of Arrow (marked in the case) should face vehicle front while placing it

Placement and Connections of Power module

a) Power module is placed at the second compartment of the fuselage in order to supply power to Autopilot and ESC from battery (placed using Double side foam tape)

b) One end of Power module connected to Battery Y- cable(1) and another end to the ESC power extension wire(2) and the third connection from power module is to Autopilot power port (using Pixhawk`s Power cable) (3)

Placement and Connections of GPS module

a) GPS need to be fixed over the stand which comes out of the upper part of fuselage open to air (checked for this placement and 2 holes made at the upper part of the fuselage to fix the GPS stand and to pass the GPS wire to connect to Autopilot GPS port)

Placement and Connections of Telemetry radio 433 Mhz

a) Telemetry (Air Module) placed at the second compartment of fuselage and its antenna left outside the airframe. To let the antenna out of the airframe hole made at the Upper part of the fuselge

b) It (Air module) is connected to Autopilot to get Telemetry data from autopilot so that drone will be linked to GCS.

c) Ground module of Telemetry radio connected to GCS (Mission Planner)

Discussion Continues...

I am continuing the discussion with connections of components...

9J) Purpose of Y-cable connection

a) Connection between ESC and Servo (to power servo)

b) Connection between ESC and Autopilot (to send throttle signal to ESC-motor)

c) Connection between Servos and Autopilot (to send signal to servo)

Discussion continues with connections check...

9K) Connections Checks

  1. Checked whether above mentioned connections are done perfectly before Connecting from battery to Power module
  2. Started from Install firmware to the Autopilot by connecting autopilot to Mission Planner (Video) (This can be done before placing Autopilot or either after placing) (here done before placing autopilot)
  3. Connection between autopilot and Mission planner terminated.
  4. Telemetry radio connected to mission planner to receive data from autopilot
  5. Connection between Battery to Power module done
  6. All Mandatory Hardware calibration done

                1. Accelerometer Calibration – Completed

                    a) Under Initial Setup | Mandatory Hardware,  from the Accel Calibration left-side menu.

                  b) Clicked Calibrate Accel to start the calibration. Mission Planner will prompted to place the vehicle each calibration position.

                  c) The calibration positions are: level, on right side, left side, nose down, nose up and on its back. After the calibration process completed, Mission Planner will displayed “Calibration Successful!” as shown below.

               2. Compass Calibration

                  a) Under Initial Setup | Mandatory Hardware, Compass selected. Flight controller configuration selected as Pixhawk/PX4 to automatically enter the most important configuration information for my board

            b) Normally no need to change any of the “General Compass Settings” or compass specific values (i.e. “Compass #1” section), but I wanted to confirm that the Enable compassesand Obtain declination automatically boxes are checked

            c) Onboard calibration carried out, clicked the “Onboard Mag Calibration” section’s “Start” button

            d) Buzzer attached to flight controller given a single tone followed by short beep once per second

            e) Holded the vehicle in the air and rotated it so that each side (front, back, left, right, top and bottom) points down towards the earth for a few seconds in turn as the vehicle is rotated the green bars extended further and further to the right till the calibration completes

            f) successful completion of calibration three rising tones emitted and a “Please reboot the autopilot” window appeared and autopilot rebooted, before arming the vehicle .

         3) Radio Calibration

           a) Connected the autopilot via USB and turn on your RC transmitter. Verified that the transmitter is bound to the receiver (the receiver displays a solid green light) and the correct model for your vehicle is selected.

           b) Mission Planner’s INITIAL SETUP opened | Mandatory Hardware | Radio Calibration IRC receiver (Rx) and transmitter (Tx) are bound is confirmed, by the green bars moved when the transmitter sticks moved.

              c) Clicked on the green Calibrate Radio button in the lower right of the window.

              d) Mission Planner will displayed a prompt to check radio control equipment is on, battery is not connected, and propellers are not attached. Selected OK.

                  e) Moved the control sticks and toggle switches on the transmitter to their limits of travel and observed the results on the radio calibration bars. Red lines appeared across the calibration bars to indicate maximum and minimum values

                f) Selected Click when Done when all required channels are set at the minimum and maximum positions. Mission Planner shown a summary of the calibration data.

                   4. ESC Calibration

                      a) Started with the autopilot powered, but with the propeller removed

                      b) switched to MANUAL flight mode

                      c) Moved the throttle stick on transmitter to maximum

                      d) At this stage the ESC/motor doesn’t given beep to indicate that it is in ESC calibration mode.

Calibration failed – worked on it to rectify the reason.

                      e) This process (a to c) repeated several times for checking but no positive result.

                      f) Once checked with PPM encoder, but this also doesn`t worked.

                                                                                          Solved:

  • Safety switch not fitted to the system when while doing the calibration steps. So we ignored the step “disable the safety switch (if fitted)”. But in our case it was enabled even if the switch is not connected to the autopilot.
  • After many trials, again while checking the calibration steps it was found out.
  • After disabling the safety switch the ESC/motor given beep to indicate that it is in ESC calibration mode.Typically it will be 2 or 3 quick beeps, but the motor won’t turn.
  • Now the throttle stick lowered rapidly to zero. The ESC given beep to indicate it has accepted the new calibration range.
  • Now slowly the throttle raised and checked that the motor response correctly to the throttle movements

9L) Center of Gravity Check

After completing placement of all component temporarily, Centre of gravity is maintained or not checked.

a) Without any permanent sticking the fuselage upper part and the wings attached

b) Then the whole setup lifted and hold at finger tips on a point of both the wings.

c) If the CG is maintained the setup will be balanced in all axis. But in our case the Airframe weight concentrated towards nose direction because of the weight of battery.

d ) To overcome this issue battery placement planned to change as one cell at first compartment and another cell at the third compartment. Notice Velcro sticked at first and third compartment for battery placements also Y-cable also extended in order to connect both the battery cells.

e) The carbon fiber sheet over the plywood compartments also removed because it is coming out whenever a components taken out from the surface of it.

9M) Attachment of GPS Stand

a) Before fixing GPS stand the plywood part of second compartment altered for leaving space for camera. Notice plywood cut done.

b) Now GPS stand attached to the plywood by drilling holes on it to pass through the screws for GPS stand placement.

9N) Attachment of Airspeed sensor Inlet and Its board (Permanently)

a) Airspeed sensor inlet permanently fixed to the fuselage nose part using Z-poxy

b) Airspeed sensor board (1) connected the inlet tubes (Large wire to upper port and small wire to bottom port) and placed at the second compartment.

9O) Placement of components changed for maintaining CG

10) Fabrication process carried out after completing placement of components

 

10A) Attachment of Composite strips to fuselage and wings (to hold fuselage and wings)

a) A strip of composite material cut to insert to the wings cut and checked for its dimensions

b) Strips taken out of wings after making sure its dimensions, permanently fixed to the fuselage as shown above using

Z-poxy

c) This strip remaining portion inserted into wings while attaching wings and fuselage.

10B) Attachment of top fuselage part and bottom fuselage part

a) Z-poxy applied at the joining surfaces of the fuselage parts and joined by placing top fuselage part over bottom fuselage part.

b) To hold them together masking tape rolled at required place as shown in figure also weight placed on the fuselage for tight fit.

c) Fiber tape sticked at joining places of fuselage parts like nose area and top surfaces as shown above to ensure more grip.

10C) Attachment of Wing joiner’s counterpart to the Fuselage

a) Carbon fiber rods to hold the wings to the fuselage inserted through the holes for checking proper alignment to the holes in wing joiners.

b) Then wing joiners and the surface of fuselage to attach the wing joiners applied with Z-poxy and joined together as shown below.

a) Same work carried out for another side of fuselage to attach wing joiner to it.

10D) Attachment of elevons to the wings

a) Elevons attached to the wings by making cut in the wings in order to insert X-ray sheet strips attached to the elevons.

b) Before inserting, strips glued with Z-poxy and then attached.

c) Fiber tape sticked in between wings and the elevons to ensure their holding.

d) Over the fiber tape, Carbon fiber sheet sticked in between the wings and elevons.

10E) Attachment of control horns on elevons

a) Control horns have pin type of projection at its bottom. On that Z-poxy applied and pinned on the elevon surface and push pull rod placed as shown above.

b) The fuselage rear part on both sides carbon fiber sheet sticked.

View after complete Fabrication of Airframe

10F) Carbon fiber sheet finishing using Air Blower

a)Carbon fiber sheet covered over airframe especially at the fuselage top and bottom part found to be coming out without adhering to the surface.

b)For that all carbon fiber covered surface treated to proper finishing using air blower. (Hot air from blower expands the carbon fiber sheet and make it to adhere to the surface.

11) C.G Checked again for this whole setup 

CG checked after changing placement of battery as shown below.

a) Total weight including camera has been weighed, it is 3.83 kg.

b) Then checked for CG. By holding the wings at finger tips and checked for its balance. But for this placement also CG not maintained. So placement need to be changed.

12) Change of component placement for CG maintaining

a) Battery placed in between first and second compartment of fuselage and secured using cable ties

b) Position of Autopilot, Receiver and Power module also shifted to third compartment of fuselage

c) Then position of GPS mount, Airspeed sensor board remains at the second compartment fuselage

d) CG checked whether it is maintained or not.

After changes, the placement of components as follows (refer to above figure)

1. Nose of Fuselage – Airspeed sensor inlet

2. First compartment --- No components

3. Between First and Second Compartment --- Battery (Both the cells)

4. Second compartment --- GPS mount (top of it out the airframe GPS), top surface of second compartment (inwards) Radio (air module), Air speed sensor board.

5. Third compartment --- Autopilot, Power module, Receiver, ESC and maximum wire connections between components and autopilot runs through this compartment.

6. Rear of Fuselage --- Motor mounted and also Propeller.

According to this placement CG is maintained/airframe is balanced while holding wings on fingertip.

For this setup CG location is calculated.

1374 (x) = 71 (11.5) + 66 (19) + 419 (32)

x   = 11.26 cm

 13) Final Check and changes needed

a) Placement of components fixed as mentioned above.

b) Battery velcro changed

c) Carbon fiber sheet on airframe blow dried using airblower for finishing.

d) After all nessecary changes, the system components checked again for its working to proceed to First flight phase.

 

14) GPS Hardware Problem

a) At that time of first flight test preparation, GPS gone in to hardware problem (refer to video).

b) For this Autopilot and GPS sent to the vendor for its replacement.

Problem solved

  1. It was checked by the vendor, but GPS was working while they are checking. (refer to video)
  2. So they sent back the same components.
  3. We checked it again with our setup it was working perfectly (Refer to video)
  4. But what was the reason it was not working before we couldn’t able to figure out. Vendor said that any wire connections might be the problem (we don’t agree with that reason, because we checked many times for the connection while the GPS was not working

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