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|  MIL-D-70789A (AR)
accepted within the first 3.5 minutes of Normal Align, bit 5 of
STATUS character S1 shall be reset and bit 4 of STATUS character
S1 shall remain reset. When both bits 4. and 5 of STATUS
character S1 are reset, the proper operator response will be to
command RESTART, and update position.
3.5.3.1.2 Normal alian. In the Normal Align mode, the DRU
shall automatically align the navigation coordinate frame by
determining the direction of the gravity vector and
gyrocompassing. Normal Align shall be accomplished without entry
of external orientation data. The DRU shall enter the Normal
Align mode automatically after power turn on unless the last
shutdown was accomplished with a STORED HEADING SHUTDOWN command.
The DRU shall also enter the Normal Align mode on receipt of the
RESTART command (30.3.3) if the DRU is stationary (see 30.3.3 for
exceptions). Otherwise, bit 6 of ALERT DATA character D3 shall
be set and the DRU shall remain in the present mode. Bit S of
STATUS character S1 shall be set and bit 4 of STATUS character S1
shall be reset when the DRU enters the Normal Align mode.
During the first 3.S minutes (maximum) of Normal Align, and only
during the first 3.5 minutes (maximum) of Normal Align, if
excessive vehicle motion is detected or the vehicle prematurely
proceeds on its mission, bit 3 of ALERT DATA character D2 shall
be set, bit 5 of STATUS character S1 shall be reset, and bit 4 of
STATUS character S1 shall remain reset. (When both bits 4 and 5
of STATUS character S1 are reset, the proper operator response
will be to command RESTART.) After the first 3.5 minutes
(maximum) of Normal Align have been completed, bit 4 of STATUS
character S1 shall be set and bit 5 of STATUS character S1 shall
remain set until Normal Align is completed.
STATUS bit S3/1 shall be set when the DRU determines normal align
attitude data is valid (within 3 sigma of the specified
accuracies) for use by the prime system.
If Normal Align is completed with the vehicle parked at one
location the DRU shall meet the survey accuracies specified in
3.6.1.1. The vehicle may move after being in the Normal Align
mode for 3.5 minutes (maximum). In which case, bit 2 of STATUS
character S1 shall be set after each 3 minutes, 45 seconds of
travel until a maximum of 15 minutes, plus 30 seconds for each
travel period, of align time have been accumulated with the
vehicle stopped.
Vehicle stops of less than 30 seconds or periods in which motion
disturbances are present shall not count toward align time. If
Normal Align is completed at the next vehicle stop, the DRU shall
meet the survey accuracies specified in 3.6.1.1. If Normal Align
is completed at more than one subsequent vehicle stop, or if
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