The SI Aerospace 2855-01-1 is a Horizontal Situation Indicator (HSI) used in aircraft avionics systems to display navigation information including heading, selected course, VOR/ILS deviation, and bearing data. It provides a combined directional display that helps pilots maintain situational awareness during both VFR and IFR operations.

This unit is commonly found in business jets and certified aircraft as part of integrated flight instrument suites, often paired with attitude indicators, directional gyros, and autopilot systems. The “AR condition” typically indicates as-removed status, meaning the unit is taken from an aircraft without overhaul or repair since removal.

Key features include:

Aircraft HSI navigation display instrument
Shows heading, course, bearing, and lateral deviation
Integrates with VOR/ILS and navigation systems
3-inch or standard panel-mounted avionics unit (configuration dependent)
Used in certified IFR navigation systems
Compatible with AHRS / directional gyro inputs (system dependent)
Designed for cockpit situational awareness and navigation accuracy
As-removed (AR) condition unit – untested since removal
Common in business jet avionics suites (e.g., Citation-class aircraft)