Summary of Interface Testing of the Digital AN/ASN-123 Tactical Navigation Avionic System in the SH-3H Helicopter

This paper presents excerpts of tests performed during the Technical Evaluation (TECHEVAL) of the digital AN/ASN-123 Tactical Navigation (TACNAV) system as installed in the Sikorsky SH-3H Sea King helicopter. The AN/ASN-123 TACNAV system is a computer-based display designed as a direct replacement for the AYK-2 analog navigation computer and the Mark-6 (MK-6) navigation plotter group. The system consists of a 32K-word digital processor, cockpit and Sensor Operator (SENSO) input control units, and a cockpit-mounted 51 square inch digital display screen. This is the first time a digital avionic system with the capability to monitor not only its own Built-In-Test (BIT) but also the status of other avionics on board has been introduced into a Navy helicopter airframe. Inadequacy of the helicopter navigation sensors feeding information to TACNAV degrades TACNAV system navigation accuracy. The navigation sensors on the SH-3H helicopter are fixed-wing sensors of early 1960 vintage. Growth potential of the TACNAV system is addressed for system installation into other helicopter airframes, notably the SH-2, as well as monitoring other avionics and electromechanical functions aboard the helicopter. Selected navigation tests, such as overwater navigation and bias correction which were designed at the Naval Air Test Center (NAVAIRTESTCEN) to test the accuracy of the AN/ASN-123 TACNAV navigation installed in the SH-3H helicopter, are discussed. Additionally, variables which affect the results of the navigational tests and environmental tests are addressed.