BendixKing IN-862A System RDR-2100 - Manual (Page 41)

DURING TAKEOFF
Since there is no advantage in having the antenna tilt level while at low
altitudes, raising the antenna tilt to clear ground returns caused by gyro
acceleration error will result in satisfactory radar operation. Tilt can then
be readjusted as the vertical gyro stabilizes. Turns during climb-out,
while pitch acceleration error exists, will also cause a stabilization error in
the roll axis.
SHALLOW-BANKED TURNS
If the aircraft is held in a shallow bank attitude, gyro precession will
cause ground returns to appear. This can be overcome by raising the
antenna tilt 1 or 2 degrees until the aircraft is out of the turn and the gyro
has stabilized. In addition to any gyro error, radar stabilization is further
affected by antenna mechanical limits of ±30 degrees.
STABILIZATION LIMITS
Stabilization limitations of the antenna beam may be exceeded during
aircraft maneuvers. These limitations are mechanically fixed at 30
degrees from zero degrees. Combinations of pitch/roll and tilt which
exceed this limitation will diminish stabilization effectiveness. Pitch/roll is
a complex quantity, not an arithmetic sum. However, as a rule-of-thumb,
for small pitch angles, the sum of tilt and bank angles being less than 20
degrees, is within limits.
If the pilot changes the aircraft attitude so as to exceed the combined tilt,
pitch and roll limits (±30 degrees) of the radar’s stabilization system, the
message, “STAB LMT”, will appear at the lower right corner of the dis-
play during the time the limit is exceeded. Please note that during por-
tions of the antenna sweep, the calculated antenna elevation angle may
not exceed the limit. Therefore, the “STAB LMT” will not be displayed.
The “STAB LMT” message will disappear completely when the aircraft
attitude is restored to within the system’s operational limits.
Gyro precession may be experienced during take-off or prolonged air-
craft maneuvers such as rapid descents, etc. Precession error may
Effective Date: 9/98 RDR 2100 Pilot's Guide: Rev 1
37
Antenna Stabilization
RDR 2100 PG 3/12/07 3:45 PM Page 37