BendixKing IN-862A System RDR-2100 - Manual (Page 39)

ANTENNA STABILIZATION
CRITERIA
Automatic antenna stabilization, as employed in today’s weather avoid-
ance radar, consists of an electro-mechanical means of maintaining a
selected beam scan relative to the earth’s horizon during moderate air-
craft maneuvers. To accomplish this, a reference is established by the
aircraft’s vertical gyro, usually a component of the auto pilot or integrated
flight control system.
Any aircraft may experience a noticeable amount of gyro drift during
extended periods of turning flight. If you do encounter a vertical gyro
which precesses abnormally during maneuvering flight (as evidenced on
the artificial horizon in either pitch or roll) but subsequently precesses to
normal attitude during straight and level flight, degrading gyro perfor-
mance is indicated. This type of poor gyro performance does not usually
result in a catastrophic gyro failure, but rather a continued gradual degra-
dation.
PITCH ERRORS
As the aircraft accelerates during takeoff, the gyro will precess in pitch.
As soon as the aircraft speed becomes steady, the accrued pitch error
will start diminishing. Average time required for the gyro to stabilize after
takeoff will vary with acceleration time and rate. Acceleration and decel-
eration on approach can also cause the gyro to precess slightly. This
precession problem is greater on jet aircraft because of their rapid accel-
eration capabilities.
TURN ERRORS
If a turn is accomplished after takeoff while the gyro is off vertical due to
takeoff acceleration, the pitch error will be translated into the roll axis and
will be observed as a roll attitude error when compared to the natural
horizon. The roll error starts disappearing the moment the aircraft
resumes straight and level flight.
In turns made with less than a 6 degree bank (for example, intercepting a
VOR with a shallow cut), the gyro continues to sense the lateral acceler-
ation (lateral force) and, as a result, precesses in the same direction as
the bank. If the turn is continued at the same indicated bank angle, the
actual bank assumed by the aircraft will steepen at the same rate the
gyro is precessing. When the aircraft is returned to straight flight and
brought to wings level via the turn-and-bank indicator or the natural
horizon (if visible) the roll error accumulated during the turn will be
observed on the horizon indicator and will remain for a period of time
unless a fast recovery technique is employed.
Effective Date: 9/98 RDR 2100 Pilot's Guide: Rev 1
35
Antenna Stabilization
RDR 2100 PG 3/12/07 3:45 PM Page 35