KFC 225 AUTOMATIC FLIGHT CONTROL SYSTEM
KCS 55A Compass System
33
Rev. 0 
Apr/99
12. The glideslope pointers indicate 
the relative position of the glideslope path with respect to the aircraft. (In other words, if the pointers are above the center marker, 
the aircraft is below the glideslope.)
Abnormal Circumstances
If the Warning Flag (HDG) 
appears during operation, the compass card indications will be in error. 
Power may be removed from the KG 
102A Directional Gyro by pulling the 
appropriate circuit breaker. The 
Selected Course, VOR/LOC 
Deviation Bar, the NAV flag, and the 
To/From Indicator will remain in 
operation.
If the Navigation Warning Flag 
(NAV) appears during operation, 
there are several possibilities: (1) the 
NAV receiver is not turned on, (2) 
the NAV receiver is improperly 
tuned, (3) the ground VOR or LOC 
station is malfunctioning, (4) the aircraft is out of range of the selected 
ground station, or (5) the aircraft 
NAV receiver has malfunctioned. 
(The compass card will continue to 
display the aircraft heading even if a 
usable NAV signal is not being 
received.
If the glideslope pointers 
remain out of view during a front 
course ILS approach, wither the aircraft glideslope receiver or the 
ground station glideslope transmitter 
is malfunctioning. Glideslope is usually not available during a back 
course approach. (The VOR and 
LOC course display will continue to
function normally even if a usable 
glideslope signal is not being 
received.)
A continuous large deflection of 
the slaving meter or large discrepancies between the magnetic compass 
and the KI 525A compass card may 
indicate a failure in the slaving system. If a slaving failure should occur, 
the Slave/Free Switch should be 
moved to select the free gyro mode. 
Then, by using manual clockwise or 
counterclockwise corrections, the 
compass can be rotated to the correct heading as indicated on the 
standby compass. The KCS 55A 
system should continue to function 
normally except the heading information will be solely derived from the 
KG 102A Directional Gyro. There will 
be no automatic heading correction 
and periodic adjustments must be 
made manually to correct for precession by reference to the standby 
magnetic compass, as with any 
directional gyro.
Note: It is desirable to disconnect 
the autopilot under the following 
conditions:
1. HDG flag comes into view.
2. System is in fast slave.
3. During manual slaving.
The system has the capability 
to supply the autopilot with an automatic disconnect signal under these 
conditions.
Note: For system limitations in your 
particular aircraft type, refer to your 
Flight Manual Supplement.
KCS 55A Compass System
32
KFC 225 AUTOMATIC FLIGHT CONTROL SYSTEM
Rev. 0
Apr/99
Under some conditions it is possible for the system to stop slaving 
exactly 180 degrees from the correct heading. If this should occur, 
move the “Slave” switch on the 
KA 51B to the unslaved (free) 
position. Rotate the compass card 
±10 degrees from the incorrect 
heading by using the manual rotation switch and then return the 
system to slaved operation. The 
system will then slave to the correct heading.
4. For the free gyro operation, check 
the magnetic compass to determine the correct magnetic heading. Then use the manual slave 
switch to align the system with the 
earth’s magnetic field. Periodic 
checks with the standby compass 
are recommended to check and 
correct for gyro precession.
5. Until a usable navigation signal is 
being received by the NAV system, a red flag labeled “NAV” will 
be visible in the upper left quadrant of the KI 525A Indicator. In 
operation, this warning flag should 
be visible whenever an inadequate navigation signal is being 
received.
6. For normal navigation to or from a 
VOR or VORTAC, set the NAV 
receiver to the desired VOR or 
VORTAC frequency and the red 
navigation flag (NAV) should disappear from view if a usable signal is being received.
7. Rotate the course select knob to 
position the course pointer to the 
desired VOR course.
8. The VOR deviation bar represents 
the selected course, and the relationship of this bar to the symbolic 
aircraft in the center of the instrument visually presents the actual 
relationship of the selected course 
to your aircraft heading. (In other 
words, if the symbolic aircraft on 
the display indicates approaching 
the deviation bar at 45 degrees, 
that is the angle at which your aircraft is actually approaching the 
selected course.
9. To prepare for an ILS approach, 
tune the NAV receiver to the 
desired Localizer frequency. If a 
usable Localizer signal is being 
received, the NAV warning flag 
will disappear.
10. For a front or back course 
approach, rotate the course select 
knob to set the course pointer on 
the inbound Localizer course. As 
with normal navigation (#6 above), 
the LOC deviation bar represents 
the desired course. The relationship between this bar and the 
symbolic aircraft gives a true picture of your aircraft’s position with 
respect to the Localizer course. 
Always setting the course pointer 
to the inbound Localizer course 
provides the correct deviation bar 
sensing whether flying a front or 
back course approach.
11. The glideslope deviation pointers 
should become visible on both 
sides of the display when a usable 
glideslope signal is received. If 
they do not come into view, a 
usable glideslope signal is not 
being received.