Vandling / Global NDB-2 aircraft navigation unit teardown

More aircraft avionics to take a look at again. This time we have a Global NDB-2 which is an optional unit for the GNS-500A navigation system commonly fitted to private business jets. This unit is a “databank” containing coordinates and other information for over 20,000 airports and airfields worldwide. It consists of a main unit and a removable memory unit which can also be upgraded via floppy disks. Yeah this thing is old – dates from the early 1980’s.

The memory unit contains a Z80 CPU with an EPROM containing the firmware, 64Kb of RAM and 256KB of battery backed SRAM for storing the database. The main unit consists of 2x ARINC-429 interface boards, a CPU board and a DC-DC converter. The CPU board is powered by a Motorola 6809 CPU and has three RS422 interfaces, two of which go to the rear panel and the other to one of the ARINC boards.

I also dumped the EPROMS and ran them through a disassembler to get Z80 and 68xx assembly code. They can be downloaded here.

The Vandling NDB-2 system is now obsolete and is no longer used for active aviation navigation. The system’s obsolescence is a result of the decommissioning of its underlying technology in favour of modern satellite navigation. Here’s a breakdown of why the system is obsolete:

The end of the Omega navigation system: The Vandling NDB-2 was a data bank for the Global GNS-500A, a navigation system based on the worldwide VLF/Omega network. After the more accurate Global Positioning System (GPS) became fully operational, the Omega network was permanently shut down on September 30, 1997. Without the radio signals from the terrestrial Omega beacons, the GNS-500A and its NDB-2 data bank became non-functional for navigation.
Replacement by GPS: The aviation industry has almost entirely transitioned to GPS and other modern satellite navigation systems. Compared to Omega, which had an accuracy of only a few kilometres, GPS offers pinpoint accuracy within a few meters.
Lack of support and spare parts: The components that made up the NDB-2 and the GNS-500A, including the early computer processors, are no longer produced. This teardown of the NDB-2 unit reveals it to be a piece of vintage electronics, confirming its age and the impracticality of repair.
Phasing out of ground-based navaids: Following the widespread adoption of satellite technology, aviation authorities like the FAA have been decommissioning many ground-based navigation aids, including the non-directional beacons (NDBs) and VORs that preceded GPS.

While some individual non-directional beacons (NDBs) remain in service for very specific purposes, the large-scale VLF/Omega network used by the NDB-2 and GNS-500A has been shut down for nearly three decades.

Photos of the boards