Radionav Sim HD Lite is a free iPad radio navigation training app. The map shows a VOR or an NDB station and an aircraft. You can move them around with your fingers, and change the aircraft’s heading using two fingers.
You can choose any instrument for the control panel and see how the indication changes on your RBI, RMI, VOR or HSI when the aircraft moves. The premium version contains two instruments and more tools to help pilots and flight instructors work on their radio navigation skills.