Replacement 2-inch standby altimeter and standby attitude indicator

Effectivity: Learjet M24B/D/E/F, 25B/C/D/F, M28, M29, M31/31A, M35/35A, M36/36A, M55/B/C, M60 aircraft  

ATA: 34 – Navigation 

By: Mark Carter –  Technical Services 

The standby altimeter is required for RVSM operations in all of the above-referenced aircraft. Similarly, many of these aircraft have installed a two-inch standby attitude indicator. A new FAA STC-approved source for replacement two-inch altimeters and two-inch attitude indicators is now available. 

Butler Avionics, Inc./Avcon Industries, Inc. has a solution to modify aircraft with a replacement two-inch standby altimeter or a two-inch standby attitude indicator. A subsidiary of Butler National Corporation, Butler Avionics, Inc., has obtained a Federal Aviation Administration supplemental type certificate (STC) approval for installation of the Mid-Continent Instruments & Avionics MD 23 standby altimeter and standby attitude indicator in Learjet Model 24, 24B/D/E/F, 25, 25B/C/D/F, 28, 29, 31, 31A, 35, 35A, C21A, 36, 36A, 55, 55B, 55C and 60 aircraft. 

The two-inch standby altimeter or attitude indicator retrofit solution is available from Butler Avionics, Inc. of New Century, Kansas, an FAA authorized installation/repair facility. The two-inch altimeter and attitude indicator modifications are available as a kit for avionics/maintenance providers. The modification requires minor wiring changes and should fit within the existing panel location. For additional installation information or an appointment, please call Patrick Hupp at Butler Avionics, Inc., (913) 829-4606. 

For further information, please contact your Learjet Field Service Representative.