Owner manual

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

Antenna Stabilization

RDR 2100 PG 3/12/07 3:45 PM Page 35