Instruction Manual

Instructions for Continued Airworthiness 190-01190-11 Rev. 1
for G500H in Robinson R44 Series Rotorcraft Page 16 of 20
2. Loosen the four Phillips thumbscrews with a screwdriver.
3. Gently lift the GRS 77H from the mounting plate (if the supports for the mounting plate are
removed, the GRS 77H must be recalibrated)
2.7.2.2 Installation
1. Place the GRS 77H on the mounting plate, ensuring the orientation is correct.
2. Fasten the unit to the plate using the Phillips thumbscrews. Recommended torque is 22-25 inch
pounds.
3. Visually inspect the connectors to ensure there are no bent or damaged pins. Repair any
damage.
4. Connect the connector to the GRS 77H, ensuring that each slidelock is secured on both sides.
Original GRS 77H is Reinstalled
If the original GRS 77H is reinstalled, then no software loading is required. This does not include
units that were returned for repair as their software and configuration files are deleted during the
repair testing process. Reference Table 2-3 to determine whether recalibration is required.
New, Repaired, or Exchange GRS 77H is Installed
If a new, repaired, or exchange GRS 77H unit is installed then software must be loaded per Section
5.4.2 of the G500H STC Installation Manual. Reference Table 2-3 to determine whether re-
calibration is required.
GRS 77H Configuration Module is Replaced
If the GRS 77H Configuration Module is replaced, the GRS 77H must be re-calibrated. Reference
Table 2-3.
2.7.2.3 Return to Service
After removing and reinstalling the GRS 77H, the following return-to-service checks should be
performed.
1. Power up the G500H system with the GDU 620 in normal mode.
2. Verify that the GDU displays valid heading and attitude within approximately one minute. Note
that heading can remain invalid if the magnetometer is near a large metal structure such as a
hangar wall or if the magnetometer is close to a large ground power cart.
3. Verify that no unexpected alerts are present. If alerts are present, troubleshoot using Section
2.6 of this ICA.