If you love this hobby, let me present a problem you may someday face. It is more likely to happen to someone new in the hobby but can also happen to the seasoned pro. You are flying your multirotor or plane and the worst thing happens…you lose signal or orientation; it gets farther away, dips below the treeline; it’s gone. I wish I knew about this simple tip because it happened to me.
I was flying a brand new Titan tricopter with an APM 2.6 flight controller and FrSky Taranis radio. I was back in the hobby after 20 years and it had taken days to get the APM’s parameters correct so it would fly as it was supposed to. I tested the flight modes and Return to Launch (RTL) which seemed to function properly. It flew great and I was full of confidence. I let it get a little too far away and lost orientation. This was not supposed to be a problem. I activated RTL and my Titan began to fly further away…FAST. I panicked and tried to take over control but it was too far and too late.
Many of today’s planes and multirotors carry expensive cameras, electronics, and batteries. I lost over $1,000 when my tricopter went down. With a little advanced planning, finding your model can be made a lot easier. That, however; is another topic for another day. What do you do if you are unprepared like I was? Fortunately, if you own an FrSky Taranis, or other transmitter / receiver combination which has telemetry, you are not totally out of luck.
What I’m about to show you is how to use your Taranis’ RSSI telemetry as a lost model locator. RSSI stands for Received Signal Strength Indicator. The RSSI reading on your Taranis is a logarithmic representation from 0 to 100 of the signal strength your receiver is receiving from your transmitter. The higher the value, the better the signal. At a reading of about 50, you are as far away as your model can safely go; it’s time to turn around.
There are many tutorials on the net to show how to configure telemetry on Taranis. If you haven’t done so already, add RSSI and battery (CELLS) telemetry to one of your telemetry screens and bring it up.
Immediately after the crash, hold your transmitter above your head so the antenna is pointing straight up and look at the RSSI output. If RSSI is anything greater than zero, you know that the model is not too far away and that the battery and electronics of your plane are still functioning.
If RSSI is zero, you may be too far away, or your battery or electronics may have become unplugged; hopefully not. For now, I’m going to assume that you are receiving telemetry.
Case 1: You Receive RSSI Telemetry
Point your transmitters antenna in the direction you saw your model go down and note the RSSI value. Slowly sweep your transmitter antenna side to side from 9 o’clock to 3 o’clock and observe the RSSI value. As your antenna reaches a perpendicular angle (90 degrees) to your model, the RSSI signal will be the strongest (largest) value. When your antenna points in the direction of your model, the RSSI signal will be the weakest (lowest) value, maybe even zero…depending how far away your model is.
Begin walking in the direction of the lowest signal. You will be walking in the direction of your model. As the distance between you and your model grows closer, the difference between your lowest and greatest RSSI signal will grow small. It may even be too small to gauge a proper direction. Look around. You are close. If you don’t find it in the immediate area, switch your radio into range check mode. According to FrSky, while in range check mode, the effective distance of the transmitter will be decreased to 1/30. Begin looking for your model again as you were before. If you are in a wooded area, it is possible that your model is stuck above you in a tree. You can check by sweeping your antenna up and down as well as side to side. Keep moving in the direction of the lowest signal strength. You will eventually walk right into or under it.
Case 2: You Do Not Receive RSSI Telemetry
But, what if you initially do not receive RSSI telemetry? You may not be able to use this technique. Your battery or other electronics may have become unplugged. This is one of reasons you want your electronics properly and securely installed. Or, you may simply be too far away from your model to receive a signal. This is our next case.
STOP. If you are to find your model, you need an accurate heading. Note exactly where you are and find a landmark near where your model went down. If you can, pull up Google Maps and find the landmark and the area you want to search. Move into the area while holding your transmitter antenna straight up. Hopefully, as you close the distance between you and your model, you will begin receiving an RSSI signal.
If not, use Google Maps and stay on your initial heading. When my model went down, it was found much farther than I had initially expected. It was also found completely by chance because I did none of what I’ve outlined above.