A VOR/DME arc is a procedure often encountered in Standard Instrument Departures (SID), in Standard Arrival (STAR) and final approaches to land.
The arc is defined by a distance to the VOR (the DME distance), the turning direction (clockwise or anti-clockwise) and two radials; one entry radial and one exit radial.
The execution of the arc requires often the calculation of anticipations; to enter and to exit the arc.
To enter the arc: the anticipation is estimated in terms of distance, usually in nautical miles; 1/2% x TAS (for a standard 3 degree/sec rate-of-turn) in still air.
To exit the arc: the anticipation is estimated in terms of degrees; 1/2% x TAS x 60 / DME (for a standard 3 degree/sec rate-of-turn) in still air.
The mobile application allows you to determine these anticipations. Have fun!