TM 1-1520-240-MTF
4-58
c. Perform GPS system Start-Up procedure.
Ensure four (4) satellite measurements
(SAT) are being used and estimated
position error (EPE) is 50 (meters) or less
with keys loaded or 200 (meter) or less with
a cold start.
d. Fly helicopter over surveyed test course
consisting of two (2) waypoints used as
checkpoints (CP) a minimum of 20KM
apart.
e. To minimize errors in establishing positions
over the checkpoints (CP), the altitude shall
be the lowest compatible with safety
standards.
f. If checkpoint (CP) information was not
entered through the data loader during
Start-Up, with the Mode switch set to NAV
enter checkpoints using the CDU.
g. Set Mode switch to NAV.
h. Depress GPS/DOP select button on HSI
Mode Select Panel.
i. Set Data switch to MSN. Depress waypoint
key (WP) until > is displayed in upper left
corner of display (meaning destination
mode). On Page 1, ensure that an arrow (²)
is in front of Doppler Only (DOP ONLY) and
GPS Only (GPS ONLY), on lines 3 and 4
respectively.
j. Set the Data switch to OPT.
(1) Select the Doppler backup mode on
Page 1, Line 1 (* Back-Up displayed).
(2) Slew (µ) down to Page 3.
