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.
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.
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.
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(Ardupilot.com 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.
2. Hold down the F/S button on the receiver, and connect the battery while holding down the 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.
If the motors spin at different rates, you will need to recalibrate the ESC by following this video tutorial.
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.
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.
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.
Now that we are confident the trim levels are properly set, the next step is to perform a sticks calibration for the controller.
As a final resource, we will perform an ESC Calibration.
After, do a final test flight.