System Maintenance Manual

Page 7-22 G1000/GFC700 System Maintenance Manual – C90A/C90GT/C90GTi King Air
Revision F 190-00682-01
7.6 GDC 74B Air Data Computer
Original GDC 74B is Reinstalled
No software or configuration loading is required if the removed GDC 74B is re-installed. This does not
include units that were returned for repair as their software and configuration files are deleted during the
repair testing process. Continue to GDC 74B Test (Section 7.6.1).
Original GDC 74B Installed in Opposite Locations for Troubleshooting
No software loading is required if the original GDC #1 and GDC #2 are installed in opposite locations.
Continue to GDC 74B Test (Section 7.6.1).
New Repaired or Exchange GDC 74B is Installed
If a new repaired or exchange GDC 74B is installed, the correct software and configuration files must be
loaded to the unit. See Section 3.9, and then continue to GDC 74B Test (Section 7.6.1).
New GDC 74B Configuration Module is Installed
The correct configuration files must be loaded if the GDC 74B configuration module has been replaced.
See Section 3.9, and then continue to GDC 74B Test (Section 7.6.1).
7.6.1 Air Data Test (GDC 74B and STBY Instruments)
The G1000 system must be maintained in accordance with the G1000 System Maintenance Manual listed
in Table 1-3 and appropriate regulations. When the GDC 74B is tested in accordance with 14 CFR Part
43, Appendix E, note the following exceptions:
• For paragraph (b)(1)(i) Scale Error, use Table 7-1 of this section instead of Appendix E, Table I
• Do not perform paragraph (b)(1)(iv) Friction
• Do not perform paragraph (b)(1)(vi) Barometric Scale Error
The following Air Data Test is to be performed in addition to or in conjunction with any other regulatory
required testing. This test must be performed on both pilot and copilot systems with a calibrated Air Data
Test Set (ADTS) with a combined accuracy/repeatability specification of less than ±20 feet for the test
altitude range. NOTE: Allow both GDC 74B units to stabilize for 15 minutes while powered before
conducting the following tests.
1. Perform pitot static system leak check of each system as specified below. Reference King Air 90
Series Maintenance Manual, 34-00-00.
a. With the pitot-static test set connected to the aircraft, perform a leak test of the aircraft pitot
plumbing at an altitude of 30,000 ft and airspeed of 226 knots. When pitot pressure has
stabilized, verify the cumulative leak rate is 1 knot/minute or less.
b. With the pitot-static test set connected to the aircraft, perform a leak test of the aircraft static
plumbing at an altitude of 30,000 feet and an airspeed of 120 knots. When static pressure has
stabilized, verify the cumulative leak rate is 200 ft/minute or less.
2. Connect the pitot/static tester to the aircraft left and right pitot and static ports. Note that the
standby altimeter and airspeed indicator are connected to the copilot side pitot and static lines.
3. Verify that the PFD1 altimeter baro setting is set to 29.92 in Hg (1013.25 mb).
4. Start PFD1 in configuration mode and navigate to the GRS page. The values for altitude and
airspeed are shown on the AHRS/AIR DATA INPUT table as B ALT and IAS for both
AIR DATA 1 and AIR DATA 2.