UAS FOCUS, LLC

MAINTENANCE MANUAL

TechMerlin C8 Multi-Rotor UAS

(3D Robotics X8 UAS)

This Document Must Be Kept, At All Times, With:

TechMerlin sUAS Serial Number:_____________

Date of Issuance:_____________

V. 7.2015_1
Maintenance Manual

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V. 7.2015_1

Log of Revisions

Revision Information

Rev. # & Date Pages Revision Description

Signature

Printed Name & Title

Maintenance Certification 

Department

Revision Date:____________
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TABLE OF CONTENTS

Section Page

1 Routine Maintenance Schedule 4

2 Interim Maintenance Procedures 4

3

Connect Flight Controller, Download Logs and Check for 

Anomalies 5

4 Inspect all Frame Parts and Wiring 5

5 Check Motors 5

6 Update Firmware 5

7 Propeller Replacement 5

8 Calibration 6

9 Calibrate Radio Control 6

10 Select Flight Modes 6

11 Failsafe 6

12 Calibrate ESC’s 7

13 Test Motor Rotation 7

14 Test Fly 7

Appendix A – Motor Replacement 8

Appendix B – TechMerlin Air Worthiness Checklist 10
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Routine Maintenance Schedule for TechMerlin C8 Multi-Rotor UAS

Routine maintenance interval on the TechMerlin C8 Multi-Rotor UAS (“TechMerlin”) is 

performed after every fifty (50) flight hours. The routine maintenance procedures begin on 

page 5 of this Maintenance Manual.

Interim Maintenance Procedures

Between routine maintenance intervals, in order to maintain the TechMerlin in a safe and flight 

worthy condition, it is our best practice for the Operator to perform the following procedures after 

every ten (10) hours lf fight time:

1. Visually inspect the TechMerlin for any obvious maintenance issues. If any obvious 

maintenance issues are noted, the TechMerlin should be taken out of service and 

promptly returned to the Maintenance Department for the appropriate repairs.

2. Clean the TechMerlin, using compressed air to remove any dust or dirt which may have 

accumulated on the aircraft.
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50 Hour Maintenance Procedures

3. Connect Flight Controller 

o download all logs 

o check for anomalies

4. Inspect all frame parts and wiring for continuity

a. If any breaks are discovered replace the noted parts and any complementary 

sub assemblies

5. Check all motors for proper operation. If motors are not operating properly, replace as 

per instructions in Appendix A.

6. Firmware update to latest UAS Focus ratified firmware

o Update made via Focus Mission Planner

o Install firmware

Select your frame type to install firmware. Listen for the tone once firmware 

installation is complete. You may need to perform the extra step below to 

complete installation. 

7. Propeller Replacement

o Supplies (8) Propeller adapters, (4) SF Propellers, (4) SFP Propeller

o Remove the rings from the propeller package. Select the ring with the smaller 

internal diameter, and insert it into the back of the propeller hub. 

 

o Select the propeller adapters and the longer screws provided with the 

adapters. Do not use the x-shaped plate. Apply threadlocker to the three small 

screws included with the propeller adapters (less than one drop covering four 

to five threads). Attach an adapter to the top of each motor. 

o Your X8 uses SF and SFP propellers. These propellers are labeled on the 

package and on the propeller itself. Add SF and SFP propellers to the motors 

shown in the diagram below with the writing on the propeller facing towards the 

sky. The right propeller order and orientation is critical for your copter to fly 

correctly. Add the spacer above the propeller, and secure the nut tightly on top. 

This will be a tight fit; apply pressure and twist the propeller onto the shaft. 

 Important Note: Ensure that the writing on the propellers for both top and 

bottom motors faces the sky. 
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X8 propeller order diagram

8. Calibration

o Launch Wizard

 Calibrate accelerometer

Follow the prompts to complete accelerometer calibration. Make sure 

to rest the copter in each position for a few seconds before moving to 

the next position. 

 Calibrate compass

Follow the prompts to complete compass calibration. 

o Battery monitor

Select 3DR Power Module for both options to enable battery monitoring using 

the power module.

9. Calibrate radio control

Ensure that your RC transmitter and receiver are bound before performing 

calibration. Turn on your RC transmitter, and select Calibrate Radio. Select 

Calibrate to start, and move the sticks and switches on your transmitter to all 

possible positions. Check to see the red bars stop at the extremes of each control. 

When each channel has a correct minimum and maximum limit set by the red bars, 

select Click when Done to complete. 

10. Select flight modes

Move the switches on the transmitter, and assign a flight mode to the greenhighlighted entry for each position of the switch.

11. Failsafe

Failsafes are pre-programmed behaviors that can be assigned to your copter in the 

case of specific failure conditions. Configure or verify that throttle, battery, GPS, 

and ground control station failsafes are set per UAS focus specifications
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12. Calibrate ESCs

With props removed, turn the radio on and set the throttle setting to maximum. 

Connect the powers supply or battery, after a series of beeps the flight controller 

will flash red, yellow and blue, confirming that it is in calibration mode. Disconnect 

the battery, after a few seconds reconnect the battery and wait for the beeps to 

stop. Move the throttle position to the minimum setting and for two more 

confirmation beeps. Now raise the throttle slightly and all the motors should spin.

13. Test Motor Rotation

Once you have verified that the motors spin at the same rate, check the direction 

of rotation for each motor: clockwise (CW) or counterclockwise (CCW). The motors 

should spin in the directions shown below for X8-m

Correcting motor rotation: If any of the motor rotations need to be reversed, undo 

the steps of this build until you can access the connection between the motors and 

ESCs. To reverse the order of a motor, switch two of the cables connecting the 

motor to the ESC. In the example below, one order of motor-to-ESC wiring 

produces one direction of rotation and the other produces a reversed rotation. 

clockwise rotation wiring

 

counterclockwise rotation wiring

14. Test Flight. Before returning the TechMerlin to service, perform a test flight and 

complete the TechMerlin Air Worthiness Checklist contained in Appendix B of this 

Manual.
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APPENDIX A

MOTOR REPLACEMENT

1 Assemble bottom motor

Align two holes in the bottom of the motor with two holes in the motor plate. Apply threadlocker to two 5 mm bolts, and secure the motor to the plate from below. This motor will attach to the underside of the arm, 

so orient the motor so that the cables will protrude as close as possible to the hole in the side of the arm. When applying threadlocker, use less than one drop, and cover only four or five threads where the bolt 

connects with the motor. Make sure to insert the bolts into the holes in the bottom of the motor and not into the slots where they could interfere with the motor. 

2 Attach top motor to arm

Place a motor plate on top of the arm with the short end of the plate facing towards the end of the arm. Place the motor on top of the plate, and align the two small holes in the motor, plate, and arm. Orient the 

motor with the cables as close as possible to the hole in the side of the arm. Apply threadlocker to two 5 mm bolts (less than one drop covering four or five threads at the end of the bolt), and secure the motor and 

plate to the arm from below by accessing through the two large holes in the bottom of the arm. Make sure to insert the bolts into the holes in the bottom of the motor and not into the slots where they could 

interfere with the motor. 

3 Thread motor cables through the arm

Now you'll thread the cables from both motors through the arm. First, thread the cables from the top motor through the hole in the side of the arm, and use a piece of tape to label the cables so that you can 

distinguish between the top and bottom motor cables. Once you've labelled the top motor cables, thread the bottom motor cables through the hole in the arm. 

 
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4 Attach bottom motor to arm

Place the assembled bottom motor against the bottom of the arm with the short end of the plate facing towards the end of the arm. Apply threadlocker to the ends of the two 25 mm bolts (less than one drop 

covering four or five threads at the end of the bolt). Place a 19 mm hollow spacer between each of the pairs of holes in the two motor plates. Place the 25 mm bolts through the motor plates and spacers, and 

secure from below with a metal nut. 

 
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APPENDIX B

TechMerlin AIR WORTHINESS CHECKLIST

This checklist specifies the guidelines by which each TechMerlin is deemed airworthy prior to 

being placed into service after routine maintenance. Each procedure is performed by the systems 

technician and test pilot, and verified for quality assurance. 

TechMerlin Serial Number: ________________ Test Flight Date: ________________

Flight Location: __________________ Temperature: _____ (F) Wind Speed/Direction: _______

I. Manual Flight Testing

1. Electrical Systems Verification

 a. Magnetometer Calibration: Mag cal has been performed. _______

 b. GPS: GPS system performance has been verified._______

c. Connectors: All connectors have been secured and function properly under load. ____

2. Mechanical Systems Verification

a. Blade Tracking: Blades are in track and system is balanced.______

b. Transmission: All transmission components have been inspected. Drive train has been 

inspected for unusual wear during break-in process, and alignment of components checked._____

3. Engine Functionality

a. Engine start has been tested ____ times and is working properly_____

b. Engine has been run for _____hours, successfully: _____

II. Auto – Flight Testing

1. In-Air Engagement: Aircraft has been engaged in auto with successful Navigation System

maneuvers performed in accordance to test plan.

2. Max Forward Flight: Aircraft has been tested at ________ k/ph

3. Auto Take-Off: Aircraft has been configured for auto take-off, and has performed _______ times 

successfully. _______

4. Auto Landing: Aircraft has been configured for auto landing, and has performed _______ times 

successfully. _________

III. Camera Platform and Camera (if installed)

1. Camera platform integration has been checked and platform performance verified_______.

2. ________________camera has been integrated and evaluated for in-air performance_______

IV. Full Gross / Full Term Flight

1. Unit has flown full term under full gross payload.______. 

2. Unit has flown ___ hours single flight duration, and ___ total hours full term in-air testing.
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CERTIFICATION

I certify that TechMerlin, Serial #__________, has been verified as flight worthy. All specifications have 

been met and the unit is cleared for in-service flight. 

Pilot Signature Technician Signature Verified By Signature

Print Name Print Name Print Name

Date Signed: Date Signed: Date Signed: