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PRIMUS
R
660 Digital Weather Radar System
A28–1146–111
REV 2 5-19
Radar Facts
Wallowing (Wing Walk and Yaw) Error
A condition where the greatest intensity of ground targets wanders
around the screen over a period of several minutes should not be
confused with antenna mounting error. This phenomenon is caused by
the tendency for many aircraft to slowly wallow (roll and yaw axes
movement) with a cycle time of several minutes. The erection circuits
of the gyro chasing the wallow can intensify the effect of wandering
ground targets. IRS–equipped aircraft are less likely to show this
condition.
Roll Gain Error
If, when the aircraft is in a turn, you see ground returns on one side or
the other that are not present in level flight, the roll gain is most likely
misadjusted. The procedure in table 5–4, and figures 5–21, 5–22, and
5–23 can help you identify this type of problem. Figure 5–24 shows a
total lack of roll stabilization in a turn.
ROLL STABILIZATION (WHILE TURNING) CHECK
Once proper operation is established in level flight, verify stabilization
in a turn using this procedure.
Step Procedure
1 Place the aircraft in 20° roll to the right.
2 Note the radar display. It should contain appreciably no
more returns than found during level flight. See figure
5–24.
3 If returns display on the right side of radar indicator;
the radar system is understabilizing.
4 Targets on the left side of the radar display indicate the
system is overstabilizing. See figure 5–23.
NOTE: Proper radar operation in turns depends on the accuracy and stability of the
installed attitude source.
Stabilization in Turns Check Procedure
Table 5–4