FPV Drone Build Problems Troubleshooting

You have finished your latest and greatest drone build and you are getting ready to maiden it, there are few things to consider to make your maiden more enjoyable and successful and also avoid FPV Drone Build Problems. In order to be more concise the following troubleshooting guide addresses general hardware issues and configuration issues on Betaflight / Cleanflight / Butterflight based flight controllers that may also apply for other flight controllers with slight modifications.[vc_row][vc_column][vc_single_image image=”1862″ img_size=”large” alignment=”center” onclick=”link_image”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

Before maiden flight

You can avoid or trace most of the fpv drone build problems happening on maiden flight by following the simple checklist outlined below.

Soldering

You should be sure that all your solder joints have the liquid silver look and are reliable. Bad solder joints may cause the FC, RX, ESC or Motor to loose power, prevent the signal from the fc to reach to the ESC or sbus signal from the RX reaching the FC.
If you are new to soldering and not exactly sure how to improve your skills, be sure to check the Learn how to Solder like a Champion! article for some great soldering tips and tricks.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_single_image image=”1865″ img_size=”large” onclick=”link_image”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

Motor screw length

Take care to use appropriate motor screws depending on the arm thickness, in order to prevent the screws touching the motor windings and damaging the motor. Usually you will receive two sets of motor screws intended for 3mm and 4mm thick arms. Nowadays in the time of naked bottom motors it is really easy to check if the screws are too long just make sure that you do, also some manufacturers are already putting a plastic shield between the screw hole and the windings in order to protect the windings from the screws.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_single_image image=”1868″ img_size=”large” onclick=”link_image”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

Motors are spinning freely when mounted on the arm

Sometimes, if the motor is not properly centered, the C-clip may be rubbing on the side of the arm and prevent the motor from spinning freely.  Aligning the bottom bearing with the hole on the bottom of the arm would solve this issue.
When building with already used motors you should check if all the shafts are straight and there are not any C-clips or retainer bolts missing. In addition, when you try to spin them by hand they should spin freely, otherwise that could be a sign of debris between the magnets and the stator, bent bell, loose magnet or bent motor bottom.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

Proper motor order and rotation

Check for proper connection between the ESC signal wires and the flight controller by following the flight controller motor order. When using 4in1 ESC double-check the wire order on the JSD-SH connectors, not all ESC/fc combinations have the same motor order. You could check if the motor layout and configuration is correct in the motors tab in Betaflight configurator.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

Flight controller orientation

Be aware of the flight controller orientation  and change the flight controller configurator options accordingly.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_single_image image=”1872″ img_size=”large” onclick=”link_image”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

Rx binding

While in the flight controller configurator you can also check if the Rx is binded and configured properly and also if the channels are mapped correctly

Proper propeller placement

Take your time when mounting the propellers. Once you have learned how to mount them it may seem as a straightforward process, but even the pros could make a mistake on a race event.
In the newer firmware versions for the flight controllers, there is an option to reverse motor rotation (screenshot from betaflight switch) and while this is good for keeping the camera lens clear and better gate crash handling, you may get confused sometimes, especially if you own multiple rigs with different motor rotation settings.

Flight controller overloaded

In some rare cases some of the available configuration settings may cause the FC processor to be overloaded and prevent you from arming the FPV drone. This never happens with the default firmware settings, so unless you were experimenting with loop times and/or gyro sampling rates you will never experience this issue.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_single_image image=”1877″ img_size=”large” onclick=”link_image”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

ESC / Motor / Propeller combination

It is worth mentioning that In some cases FPV Drone build problems could be caused by components not matched properly, especially motor / ESC  / propeller combination.  Some combinations may activate the ESC overload protection or in worst-case scenario cause the motor or the ESC to overheat and burn.
Before ordering specific motor / ESC combination you should do some research and at least check the motor static thrust test results on websites like Mini Quad Test Bench or EngeneerX Youtube channel.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][ultimate_ctation content_alignment=”ctaction-text-left” ctaction_background=”#ffcd32″ ctaction_background_hover=”#ffbf00″ enable_icon=”enable_icon_value” icon=”Defaults-info-circle” icon_size=”55″ text_color=”#4d4d4d” ctaction_padding_left=”20″ ctaction_padding_right=”20″ text_font_size=”desktop:24px;” text_line_height=”desktop:30px;” ctaction_link=”url:https%3A%2F%2Fwww.youtube.com%2Fuser%2FEngineerX%2Fvideos||target:%20_blank|”]As EngeneerX states: in flight, Amp draw is approximately 25% to 35% lower than thrust stand readings. Also the small 800-1600mAh LiPos used as flight packs can’t sustain nor supply such high discharge rates.[/ultimate_ctation][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

FPV System wiring

There are few things to consider when wiring your camera and video transmitter that could help you get better quality video feed.

• If possible, power your camera from the video transmitter or use the camera pads on your flight controller in order to reduce the noise in your video feed
• The video signal wires going from the camera to the video receiver should be as short as possible and not crossing near or touching electronic noise inducing components, such as ESCS, radial inductors, etc.
• Take care that the camera and the video transmitter have a common ground. This could prevent the osd flickering on high throttle for some flight controllers
• If you aren’t planning on using an OSD then wire the video signal from the camera directly to the video transmitter
• Isolate the video transmitter SMA connector from touching the carbon frame by using a double-sided sticky foam tape
• Use a low ESR (equivalent series resistance) capacitor of minimum 25 volts and 200uF

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FPV System checkout

One last check before heading out to maiden your FPV Drone is to test that your FPV feed is working properly, double-check that the video transmitter and receiver are on the same frequency and your video transmitter antenna is not damaged or loose.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

Troubleshooting FPV Drone build problems after maiden flight

FPV Drone not arming

So you are out in the field ready to maiden your new FPV Drone and guess what, that thing won’t let you maiden it, since it is not arming at all.
If you have followed the above checklist thoroughly there is small possibility for this to happen, but anyway if your newly built FPV Drone is not arming, this is a sign of one of the following issues:

• Check that the rx power wires aren’t broken
• The rx is not binded
• Rx channels not mapped properly
• Throttle not at zero or min_check too low
• If enabled, the accelerometer is not calibrated (check Betaflight stick commands for in field calibration)
• High cpu load

A beeper connected on the flight controller could help when solving this issue. All flight controllers have a specific beeper codes for things like those that rx is not linked with the tx, the tx is off, throttle is not at zero position etc.  You can find the beeper codes for flight controllers based on Betaflight / Cleanflight firmwares in the official Betaflight FAQ here.

 

FPV Drone shooting up to the sky or jumping at you and trying to kill you

Things like this usually happen as soon as you arm your FPV drone and throttle up.
Most of the times the source of the “shooting up” thing are excessive vibrations coming to the flight controller, which tries to overcorrect and it seems like it is not responding to throttle commands at all but you can steer it and disarm it. Soft mounting the flight controller or finding and eliminating the source of the excessive vibration solve this issue.

Flipping out or jumping at you immediately after arming it means ether wrong motor order, motor direction or propeller placement.
You can check the motor order and direction in the corresponding configurator software for your flight controller.

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Death rolls & brownouts

Most of the times you could do a simple maiden flight, test hover your FPV Drone build do some light punch outs and not experience any problems.  However, when you start to fly FPV you may experience your FPV Drone flipping and/or falling out of the sky.

In this case, it is advisable to try to fly few more times in order to gain some more insight into this problem. Try to remember the side that your FPV drone is flipping, whether it is random or specific side and if it happened while doing hard maneuvers; the throttle percentage was near maximum or minimum. This may point out if the problem is with only one motor/ESC combination or if it has something to do with the motor timing, motor idle speed or ESC firmware.

Flipping on the same side would definitely mean that either the ESC or the motor on the arm that is dipping are damaged and problematic. The easiest solution in this case would be to inspect them for damage or bad solder joints. If you cannot find any damage, you should at least reflow all solder joints on that arm and test if the issue has been resolved. If the issue persists, it is advisable to replace the ESC or the motor.

Joshua Bardwell has recently posted a great video explaining how to diagnose a bad motor by using Blackbox logs:[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_video link=”https://www.youtube.com/watch?v=ZccPV8Ucl2g”][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]If your FPV Drone build problems are manifested as flipping on random sides or just falling out of the sky that could be a sign of one of the following issues:

Wiring or antenna problems

Flight controller loosing power mid flight, receiver failsafe or loose connection on the sbus pad. These three look similar since the motors disarm and your FPV Drone drops like stone. In case of a failsafe, you may get an RSSI warning if your rx/tx has such feature.
You should recheck the solder joints and most important all wires for continuity. Be aware that sometimes when using JST connectors with silicon-coated wires the wire may be broken at the crimping point.

Wrong motor timing

You may be able to hear the wrong motor timing as audible motor stutter while doing hard maneuvers and cause motor desyncs. The motor timing is an ESC setting that briefly defines the motor’s electromagnetic coils firing time. Lower value means that it will fire earlier and thus produce more RPM while higher value fires later and produces more torque but reduces the RPM. Generally, when experiencing desync issues it is advisable to increase the timing while checking if the problem persists.
Some of the newer ESCs especially the ones based on BLHeli_32 have automatic timing feature that measures the demagnetization time and keeps the timing as low as possible without causing demagnetization issues.
Be sure to check the BLHeli manual if you need more info about motor timing

Motor stalling

Another issue that could cause random flips or so called “death roll” is motor stalling during hard maneuvers caused by low digital_idle_percent value when using Dshot protocol. The solution in this case would be to increase this value. In my experience, setting it to 7 or 8 solves this issue. You can read more about setting this value and setting Dshot ESC Protocol on Betaflight here

Voltage spikes

Voltage spikes generated by motors braking when using damped light that are overloading some of the electronic components on the flight controller thus causing unpredictable behavior. Most of the time this is prevented by using a minimum of 25V 200uF capacitor by bridging the main battery power terminals

No signal ground on the ESCs

Not using the ESCs signal ground wire which is strongly recommended to be grounded on Dshot ESCs

ESC firmware is not up to date

Sometimes using newly released ESCs could mean that the firmware could have some bugs that may cause issues, so it is advisable to check and update to the latest stable firmware version

FC not playing well with other components

In some cases the flight controller may not “play well” with some ESC types or on certain voltage. I have had a flight controller that worked perfectly on 3S batteries and my drone was dropping of the sky when I tried to fly it on 4S batteries. Another one was not working reliably on some ESCS and it has replaced with newer revision. So be sure to check if other fellow pilots have had the similar experience.

It is worth noting that analyzing the blackbox logs if you have them could prove helpful when troubleshooting FPV Drone build problems. You do not have to be good at analyzing blackbox logs to notice if the culprit is one motor/ESC or if it is happening randomly.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

FPV Drone build problems with the video feed

White lines

White or clear lines in video feed is sign of electronic noise and it could be fixed by adding a capacitor to the main battery terminals

Dark lines

Dark lines in the video feed are sign of either having the video transmitter needs more power than provided or in come cases it may be a sign of a faulty video transmitter or camera, you could test this by powering the video transmitter directly from the battery leads.

Jello

Visible jello or shaky video feed could be a sign of loose camera screws, loose camera sensor inside the camera casing or loose or defective camera lens. You should check and tighten the all screws, try adding some sponge or hotglue between the camera sensor board and the camera back cover and replace the camera lens. If none of the above helps, then the issue has something to do with either defective motor bearing, problematic motor shaft, and bent motor bell, bad propeller or tuning issues.

FPV feed interference

Video feed breaking out on small distances usually means that you have either defective antenna or antenna lead, broken SMA connector on the video transmitter, faulty video transmitter or even having selected a wrong channel frequency on your goggles that is near the one that the video transmitter outputs on.

If you want to read more about FPV Drone problems and solutions regarding the video transmitter and fpv camera, visit Oscar Liang’s article dealing with this issue here

 

When assembling your FPV Drone, even if you are eager to finish it as soon as possible, take your time and do the things thoroughly, this could help you later on to spend more time in the air and less time troubleshooting FPV Drone build problems. Although this article is relatively long, it is scratching the essentials of the problems and I certainly hope that you will find it helpful both as a checklist for issues that may appear during assembly and as a troubleshooting guide after your maiden flight.

Let me know if you have anything to add by commenting below.