Arinc has successfully demonstrated a classified VHF datalink during flight trials of a jam-resistant precision approach and landing system under contract to the USAir Force's Electronic Systems Centre.
Claimed to be undetectable, the VHF link provides global positioning system error correction data to incoming aircraft using the local area differential GPS (LDGPS) system - developed to counter GPS jamming signals broadcast by an enemy to interfere with precision-guided munitions, which could also affect an aircraft's navigation system.
The trial, conducted on 5 April at Holloman AFB, New Mexico using an air force Beech C-12J communications aircraft equipped with LDGPS, included 18 runway approaches while GPS jamming was active.
Tom Sanders, Arinc director of satellite navigation and air traffic control and landing systems, says that while the VHF signal could in theory be jammed, "in practice we've never seen someone target a landing system. The VHF signal is an undetectable radio link, the technology of which gets classified real quick".
The LDGPS is resistant to jamming because it uses five GPS receivers on the ground, one in the air and the correctional VHF link. Each GPS receiver is able to avoid jamming by identifying and ignoring the incoming jamming signal, which would be a powerful broadcast on the commonly used L2 GPS frequency.
The LDGPS project is part of the US Department of Defense's Joint Precision Approach and Landing Systems programme, which aims to develop a next-generation capability for the USAir Force and US Navy. Full system development for JPALS is scheduled for 2006.
Arinc is also working on the US Navy's shipboard relative GPS demonstration system for the service's next-generation CVN 21 aircraft carrier.
Source: Flight International