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PRIMUS
r
880
Digital
W
eather
Radar
System
A28-1146-102-00
Radar Facts
5-19
Some vertical gyroscopes have provisions for deactivating the
roll-erection torque motor (whenever the airplane banks more
than approximately 6_) to reduce the effect of lateral
acceleration during turns. To some extent, stabilization error is
displayed in the radar image after any speed change and/or turn
condition. If the stabilization system seems to be in error because the
radar begins ground mapping on one side and not the other, or
because it appears that the tilt adjustment has slipped, verify
that aircraft hasbeen in nonturning, constant-speedflight long enough
to allow the gyroscope to erect on true earth gravity.
When dynamic and acceleration errors are taken into account,
maintaining accuracy of 1/2 of 1_ or less is not always possible. Adjust
the antenna tilt by visually observing the ground return. Then, slowly
tilt the antenna upward until terrain clutter no longer enters the display,
except at the extreme edges. If ground display is observed on one side
but not on the other, the stabilization system is somewhat in error, but
it is probably impossible to adjust it more accurately.
Pitch and Roll Trim Adjustments
The PRIMUS
â
880 is delivered from the Honeywell factory or repair
facility adjusted for correct pitch and roll stabilization and should be
ready for use. However, due to the tolerances of some vertical
reference sources, you may elect to make a final adjustment whenever
the radar or vertical reference is replaced on the aircraft, or if
stabilization problems are observed in flight.
The four trim adjustments and their effects are summarized in table
5-4.