Aircraft Spruce & Specialty is now carrying the Castleberry Instruments & Avionics attitude indicator, which is an approved substitute for the previously mandated rate of turn indicators in Part 23 aircraft operating in Part 91 and less than 12,500 pounds. (This substitution is based upon the FAA Advisory Circular AC91-75, which promotes the installation of a backup attitude indicator.) But, even better, it's a suitable backup for Experimentals with glass panels.
The internally lighted electric attitude indicator replaces the turn and bank and is a straightforward installation in the same panel location, according to AC Spruce. It will fit a standard 3.125-inch instrument mount; the erecting knob passes through one of the mounting holes. The unit has a standard inclinometer and a failure warning flag to indicate loss of gyro rpm. When used with the Castleberry Emergency Power Unit (Model EPU 28-24RMT), this instrument offers a margin of insurance in case of an aircraft electrical power failure.
The Castleberry AI is available in either 14 volt (P/N 10-02823) or 28 volt (P/N 10-02824) and sells for $2095; the Emergency Power Supply (P/N 11-05822) is $1685. Both units may be purchased online at Aircraft Spruce & Specialty.