One of the fundamental challenges of flying RC aircraft is that you are separated from the machine you are controlling. You must assess the health and status of your vehicle from a distance using only limited visual and aural cues – rarely an easy thing to do. Sometimes the first symptom of a failing system is a trail of smoke that inevitably leads to the ground.
RC telemetry systems provide the means to accurately gauge certain parameters of your model during flight. Think of it as a remote dashboard. Do you want to know how hot your motor is running? How about an alarm that can warn you when your model reaches an altitude of 400 feet? Telemetry devices can provide those things and more.
What Telemetry Requires
There are several different ways to receive telemetry data. Some telemetry systems are standalone units with a transmitter/sensor package in the model and a receiver on the ground. For FPV flyers, On-Screen-Display devices take the data from onboard sensors and overlay it on the real-time video feed. The result is something like a heads-up display found in many modern full-scale aircraft. An increasingly popular form of telemetry system is the type integrated into the model's radio system. The pilot's handheld transmitter sends flight commands to the aircraft while also receiving downlinked data. The same onboard receiver that interprets commands also transmits telemetry data. In this way, both the transmitter and receiver are actually transceivers.
The majority of radio manufacturers offer telemetry-capable systems in their lineups. The example that I've chosen to highlight in this guide comes from Futaba. As of this writing, there are three Futaba aircraft transmitters that are telemetry-capable (10J, 14SG, and 18MZ) as well as a handful of receivers. With these systems, their telemetry features are embedded in the S.Bus2 circuitry of the components. That nuance begs a brief explanation of S.Bus2.