AN/ASN-128B/C Doppler Navigation Set

The AN/ASN-128B/C Doppler navigation set integrates a global positioning system (GPS) receiver with a self-contained Doppler navigation.

The AN/ASN-128B/C provides continuous velocities, navigation, and guidance information. When both Doppler and GPS are available, the GPS accurately initializes and automatically updates Doppler present position. If the GPS signal is lost, the Doppler continues to provide accurate velocities for hover and navigation; if the Doppler is in memory, the GPS continues to provide accurate present position. In either case, navigation continues uninterrupted.

System installation and aircraft modifications have been minimized by embedding a Trimble one-card GPS receiver into the signal data converter unit.

AN/ASN-128B/C Features

Contains an embedded GPS receiver (military and civilian-only code units are available).
Automatically selects Doppler navigation when GPS is not available.
Converts existing ASN-128s to ASN-128B/C.
RTA, line-replaceable unit installation, and existing helicopter cabling is unchanged.
Contains MIL-STD-1553 interface in the computer display unit of the ASN-128C.

AN/ASN-128B/C Computer Display Unit (CDU)

Enhanced display and control capabilities, high-throughput CPU, and expanded memory for growth.
Provides data entry capability with four-line, 64 alphanumeric character display.
Displays all navigation and GPS data.
Displays UTC, high-resolution latitude and longitude data, GPS test mode status, crypto key status, estimated position error, and number of space vehicles being tracked.
Expanded memory for greatly increased processing capability with new 10 MIPS.

Steering Hover Indicator (optional)

The Steering Hover Indicator Unit (SHIU) has two modes of operation. In the navigation mode, the SHIU provides the pilot with a display of ground speed, distance-to-go, and left-to-right steering information to the destination selected on the CDU.

In the hover mode, the three pointers indicate the values of three orthogonal components of aircraft ground velocity (along heading, across heading, and vertical). By flying the aircraft to maintain these displayed values at zero, the pilot can hover the helicopter without visual reference to the ground.