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|  4.5.3.7.6 Start the roll, pitch, and yaw table tilted 10 degrees, with
the table set for automatic reversing. After five minutes, stop the table,
return it to a level position, and again set the synchro box as specified
in 4.5.3.7.2.
4.5.3.7.7 Record the synchro box angle reading and subtract it from
the reading of 4.5.3.7.5 to obtain the drift.
4.5.3.7.8 Repeat 4.5.3.7.5 through 4.5.3.7.7 with the open end of the
gyro rotor-facing east, south, and west. The gyro is placed in the above
orientations by caging the gyro facing the connector east, south, and west,
respectively, uncaging the gyro, and refacing the connector north. (Note:
Advance the matching synchro 90 degrees for each successive reading and
withdraw the ACR contacts for south and west readings.)
4.5.3.7.9 Creep, in degrees per minute, is 0.25 times the sine of the
latitude; that is, if the latitude is 43 degrees and 50 minutes, the ap-
parent drift is 0.17 degrees per minute.
4.5.3.7.10 Recession, in degrees per minute, is equal to the total
drift for a given period corrected for creep, divided by the time in
minutes for that period. Precession shall not exceed plus or minus 0.1
degree per minute.
4.5.3.7.11 As precession can be opposite to creep, the following pro-
cedure shall be used to ensure that consecutive drift readings are properly
corrected for the effect of creep.
4.5.3.7.11.1 When setting the synchro box in 4.5.3.7.6 and 4.5.3.7.8,
observe the direction in which the synchro is turned to null out the
error. If rotation is counterclockwise, the difference between the sec-
ond synchro reading and the first (observed drift) shall be considered
"positive." If the rotation is clockwise, the difference shall be con-
sidered "negative."
4.5.3.7.11.2 As creep in the northern hemisphere is clockwise, its
value as calculated by 4.5.3.7.9 shall be considered "positive." Creep
in the southern hemisphere is counterclockwise and shall be considered
"negative."
4.5.3.7.11.3 Total precession for a given period is equal to the alge-
braic difference between the observed drift for that period and the cal-
culated creep for the same period.
4.5.3.7.11.4 This completes this portion of the drift check.
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