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Requirements for a Backup Attitude Indicator When a GI 275 ADAHRS Is Installed as a Primary Attitude Indicator in Class I and Class II Aircraft
A backup Attitude Indicator is required when an GI 275 ADAHRS is installed in either a Class I and Class II aircraft.
Another GI-275, for example, can be used to serve this purpose.
Select this link for more information on the GI 275.