Troubleshooting Guide

Solving commonly found errors for copters

Motors Don’t Arm (Double-Flashing Yellow Status LED)

The double-flashing yellow status LED indicates that the drone is failing one of the pre-arming safety checks. The autopilot performs these checks before each flight to ensure that all systems are operating correctly. To see the specific error, connect to a ground station and view the primary flight data display.

Sensor Calibration Error:

If you see a flashing yellow status LED, it’s likely that the sensors did not calibrate correctly during startup. Right after plugging in the battery to your copter, be sure to wait at least 10 seconds before moving the copter at all to ensure proper calibration. IRIS users should also wait 10 seconds before closing the battery door or moving IRIS at all while the internal sensors calibrate and the status LED shows blue and red.

GPS Error:

A common pre-arm safety check error is due to insufficient GPS signal. Your drone requires a strong GPS signal to fly accurately. There are two important measurements of GPS signal required to pass the pre-arm check: the GPS lock (the strength of the signal) and the HDOP (the accuracy of the signal).

A lock is obtained when the GPS receives positioning data from multiple satellites. You can see the status of the lock and the number of communicating satellites on the controller’s flight data display. (For IRIS+ and X8+ only, press and hold the controller’s DN button to view the flight data display.)

IRIS+ and X8+ Controller Flight Data

Connecting to five or more active satellites produces a strong GPS lock. It is possible for the GPS to acquire a lock with less than five satellites, but there is a greater chance of losing the lock during flight with fewer satellites. Generally, a clear of the sky produces the highest satellite count, but it can also depend on your specific location and the time of day. Use this tool to see how many satellites are predicted for your flying location.

Horizontal dilution of precision (HDOP) is a measure of the accuracy of the GPS signal, as opposed to the strength of the signal as measured by the lock. To pass the pre-arm check, HDOP must be below a specified value to ensure accurate GPS measurements. A high HDOP can result from the positions of the satellites, obstructions such as buildings and mountains, atmospheric effects, electromagnetic interference from radio towers or onboard radio transmission equipment, or the time of day. You can receive an HDOP error even with a high number of satellites and an active lock.

To improve GPS signal, move to a more open space with a clear view of the sky and wait for the GPS to acquire an active lock or a lower HDOP. It can take several minutes for the GPS to acquire a lock—possibly up to 10 minutes if the vehicle is at a significant distance from the location where it last acquired a lock.

RC Calibration Error:

If the pre-arm check failure specifies an RC calibration error, use Mission Planner to repeat the RC calibration.

If you do not see any response in the calibration screen from moving the controller sticks, ensure that both the controller and the copter are powered and the copter is connected to Mission Planner. If you still do not see any response, follow these instructions( tutorial) to rebind the controller with its receiver. Do not perform this process unless you see an RC calibration errorand no response from the controller when attempting to recalibrate using Mission Planner.

For IRIS and IRIS+, remove the top shell from IRIS by following the instructions here before starting this process. Turn on the controller, and power the copter normally. Now check the RC receiver (pictured below); if you don’t see a green LED, follow these steps to re-bind the receiver to the transmitter.

1. Disconnect the battery from the copter, and turn off the controller. Ensure that both the on/off switches on the back of the controller are set in the down position. Now hold down the F/S button on the back of the controller, and turn the controller on while holding down the button.

iris rc transmitter bind button

2. Hold down the F/S button on the receiver, and connect the battery while holding down the button.

iris rc receiver binding button


3. Disconnect the battery, and turn off the controller. Then turn on the controller and reconnect the battery. You should see a green light on the receiver indicating that it is connected to the controller. If so (replace the top shell for IRIS and IRIS+), reattempt the preflight steps.

Motors Spin at Different Rates

If the motors spin at different rates, you will need to recalibrate the ESC by following this video tutorial.

Unexpected or Inconsistent Flight Behavior

Step 1: Examine your copter to ensure that the components are undamaged. Verify that the propellers are in the correct order of SF and SFP as shown following. Check that all propellers are attached with the writing on the propellers facing the sky.

iris arm diagram

IRIS and IRIS+ Propeller Order

x8 prop diagram

X8+ Propeller Order

Step 2: Press the safety button until blinking red, and connect the copter to Mission Planner or APM Planner on your ground station computer, and connect the copter to MavLink by selecting Connect. Select Initial Setup and Mandatory Hardware, and perform an accelerometer calibration as shown in this video tutorial. Next, perform a compass calibration as shown in this video tutorial.

Poor GPS performance (IRIS and IRIS+)

If you experience poor GPS performance, it could be caused by interference between the GPS cables inside IRIS.

Step 1: Open the top shell.

Step 2: Loosen the tape holding the two thin gray wires from the FrSKY module. Reposition the wires as shown below, and re-stick the tape to the shell. Then replace the top shell.

rewire antenna arrows


My Copter is Drifting

My copter is drifting


There are a handful of reasons why your copter may be drifting. By following this guide, you should be able to find the the cause and eliminate it.


This guide is compatible with Iris+ and X8+ copters only.



For this guide, we assume that the copter is drifting while in Loiter Mode (GPS and Compass dependency).


Loiter mode depends on a good GPS Signal, which relies on two different factors:


1  Satellites

The number of satellites is used to determine the current position of the Copter. The more satellites, the best accuracy. The best accuracy achievable is 1 meter (3 feet).


This stands for Horizontal Dilution of Precision, which may just be interpreted as the quality of the signal. The closer to 1, is the better. The vehicle will give us a green light as soon as the HDOP is 2.5 which means that we might have an error on the position of 2.5 meters (~7 feets).


Make sure you have nice weather and are clear of metal buildings and other sources of interference prior going through this guide.

Check RC transmitter’s trim levels


Drifting can also be caused by unbalanced “trim” levels.


For stable flight, make sure all the trim indicators are centered. If they are not, use the switches to center them. Each trim switch correlates to the level indicators displayed on the screen. These can be easily get knocked out of position, so simply adjust them back to a level position.



Red: Trim indicators

Yellow: Trim switches

Make sure your trims indicators are centered.


Now that we are confident the trim levels are properly set, the next step is to perform a sticks calibration for the controller.


Resetting controller


It’s possible your controller’s parameters were modified with unexpected results. To reset your controller back to its default values, please follow the Reset Procedure. Then perform a flight test to see if the drifting is still occurring.



Reseting your controller’s default values: 


Let’s perform a radio calibration to make sure that the Auto Pilot knows where the center of the stick is located.

Here’s the process:


If you are still experiencing drifting issues, the COMPASS may be loosing orientation. Perform a compass calibration to see if this fixes the issue:


Load “3DR_YouVehicle.param” Default Parameters


Since none of the preceding steps have solved the issue, we can rule out any problems with the Auto Pilot or the Radio Controller.


Now, let’s try to loading all the default parameters for your vehicle. Check out this video as an example. Remember to select the correct parameter for your vehicle.

  • 3DR_Iris+.param
  • 3DR_X8+_RTF.param
  • 3DR_X8-M_RTF.param
  • 3DR_X8_RTF.param
  • 3DR_Y6A_RTF.param
  • 3DR_Y6B_RTF.param



As a final resource, we will perform an ESC Calibration.


After, do a final test flight.


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