The Vertical Gyro covered by this specification is a component of the MF-1 Compass, Directional Reference System which is intended for use in fighter, attack, patrol, transport, and cargo type aircraft whose range of operation will be world-wide, including polar regions, as well as all aircraft requiring medium precision heading reference stabilization. This system will provide directional information to remote indicators, electronic equipment, radar equipment, navigational equipment, and furnish directional control for autopilots, bomb directors, automatic approach equipment, and other auxiliary systems requiring directional reference intelligence. The main features of this new system are its precise directional accuracy, compactness, lightweight, reliability, flexibility of application, ease of installation and maintenance, compensation for magnetic deviation, correction for apparent gyro drift, and compass indication stability independent of latitude, as well as permitting the aircraft swing procedure to be accomplished rapidly and accurately.