To recommend the essential minimum safe performance requirements for gyroscopically stabilized Directional Indicating System, primarily for use with turbine powered subsonic transport aircraft, the operation of which may subject the instruments to the environmental conditions specified in paragraph 3.3. This recommended practice covers the requirements for gyroscopically stabilized Directional Indicating Systems, which will operate as a 1 \mD/hour latitude corrected, free directional gyro or as a slaved gyro, magnetic compass with 1/2\mD accuracy.