TM  55-1510-221-10 (2.)  Turn  rate  indicator.  Deflects  to  indi- cate rate of turn. (3.) Inclinometer. Indicates  lateral  acceler- ation (side slip) of aircraft. 3-22. GYROMAGNETIC COMPASS SYSTEMS. a.  Description.  Two  identical  compass  sys- tems  provide  accurate  directional  information  for the aircraft at all latitudes of the earth. As a heading reference,  two  modes  of  operation  are  used:  direc- tional gyro (FREE) mode, or slaved (SLAVE) mode. In polar regions of the earth where magnetic heading references  are  not  reliable,  the  system  is  operated  in the FREE mode. In this mode, the system furnishes an inertial heading reference, with latitude correc- tions introduced manually. In areas where magnetic heading references are reliable, the system is oper- ated  in  the  SLAVE  mode.  In  this  mode,  the  direc- tional gyro is slaved to the magnetic flux detector, which supplies long-term magnetic reference to cor- rect  the  apparent  drift  of  the  gyro.  Magnetic  heading information from both systems is applied to various aircraft  systems  through  pilot  and  copilot  COM- PASS No.1   -  No.2  switches.  There  are  no  circuit breakers  for  the  gyromagnetic  compass  systems.  The circuits  are  protected  by  the  2-ampere  F2  and  F6 fuses on the No. 1 junction box. b. Vertical Gyro A vertical gyro provides line- of-sight stabilization to the weather radar and roll and  pitch  information  to  the  autopilot.  A  FAST ERECT switch at the top of the pilot’s instrument panel (figure 2-29) provides a means for fast erec- tion  of  the  gyros.  Pressing  and  holding  the  FAST ERECT switch will erect the gyro to within 1.0° of pitch  and  roll  within  60  seconds  of  power  applica- tion, and erect to within 0.5° within 2 minutes. Nor- mal  operation  of  the  vertical  gyro  system  will  not require  use  of  the  fast  erect  switch.  The  circuit  is protected  by  the  3-ampere  F22  fuse  in  the  No.  1 junction  box. c. Controls  and  Functions. (1.)   Pilot’s   COMPASS   No.1-No.2   switch. Selects  desired  source  for  magnetic  heading  informa- tion to display on (a.) No. 1 for display. (b.) No.2 for display. pilot’s  HSI  and  copilot’s  RMI. No. 1. Selects   compass   system (3.)    To ing: 1. No.2.  Selects  compass  system 2. (2.)   Copilot’s COMPASS No. I-No.2 switch. Selects desired source for magnetic heading information  to  display  on  copilot’s  HSI  and  pilot’s RMI and INS. 3-28 (a.)  No.1.  Selects  compass  system No. 1 for display. (b.)  No.2.  Selects  compass  system No. 2 for display. (3.)  GYRO  SLAVE-FREE  switch.  Selects system mode of operation. (a.)  SLAVE.  Selects  slaved  mode. Compass flux valve connects to azimuth card. (b.)  FREE.  Selects  free  mode.  Flux valve is not connected to azimuth card. (4.)  INCREASE-DECREASE  switch.  Pro- vides manual fast synchronization of the system. (a.)  INCREASE.  Causes  gyro  head- ing output to increase (move in clockwise direction). (b.)  DECREASE.  Causes  gyro  head- ing  output  to  decrease  (move  in  counter-clockwise direction). d.  Normal  Operation. (1.)  Alignment  procedure: 1. Gyro  compass  slave-free  switch  - SLAVE. 2. (2.)    To 1. 2. 3. Gyrocompass increase-decrease switch - Hold switch momentarily in the direction desired, and then release. This will place system in fast  erect  mode.  The  gyro  will then  erect  at  approximately  30 degrees per minute. While in the fast  erect  mode,  the  HEADING flag (HSI) will be in view. When the HEADING flag retracts from view,  the  heading  displayed  will be the magnetic heading. determine magnetic heading: Gyrocompass  slave-free  switch  - SLAVE. RMI  rotating  heading  dial  (com- pass card) - Read heading. determine  directional  gyro  head- Gyrocompass  slave-free  switch  - FREE. Gyrocompass increase-decrease switch - Hold until the RMI com- pass card aligns with the magnetic heading,  then  release. Read  heading.  The  heading  will agree  with  the  appropriate  HSI.