When your RC plane flies out of transmitter range some of them are setup to start a slow bank so that it hopefully flies closer to you and you can reacquire communication. What if that fails and the plane comes crashing back to earth? This Lost Signal RC Alarm & Lost Plane Finder project will help you in this case. When your transmitter is not connected the buzzer will sound so you can find it a bit easier. Construction is a nice and compact point to point solder construction which means no PCB is needed.