The US Navy is working to get a $2.3 billion project to develop a GPS-aided landing system for aircraft on ship decks back on track after funding shortfalls delayed initial fielding by six years. Interested companies will be briefed on the revised schedule next month, while the navy plans a new round of risk-reduction flight tests for early next year.


The navy version of the Joint Precision Approach Landing System (JPALS) was to become operational in fiscal year 2007 but is not now expected to come online until at least 2013, says navy programme manager Capt Pete Riester. A land-based version of the system is also being developed for the US Air Force.


How JPALS will be fielded initially - as either a land-, aircraft- or ship-based system - is still under debate, but the basic concept is "more than likely that a [Boeing F/A-18] Hornet must be able to land on one of my carriers," says Riester. Plans to add JPALS to helicopters, cruisers and destroyers have been delayed indefinitely for funding reasons.


Riester's staff has nearly two years to refine the operational plan for JPALS. In April 2006, the programme faces a go-ahead decision to enter a four-year system development and demonstration phase. At that point, says Riester, the navy programme may be merged into the same contract as the USAF version, which has already been awarded to Raytheon.


Although stuck in pre-development, navy JPALS has already achieved several breakthroughs. First, its relative GPS signal technology - linking an F/A-18 and the USS Theodore Roosevelt - completed the first "hands-off" carrier landing three years ago. Last month, ARINC also tested a secure VHF datalink that should permit JPALS transmissions despite jamming attempts.


Baseline requirements for JPALS include transmitting the ship's location out to 370km (200nm), allowing an aircraft carrier to track up to 50 aircraft within 50nm and providing precise location data on landing to within 15cm (6 in). The system is based on the Shipborne Relative GPS (SRGPS) signal which establishes a fixed point on the carrier as the ground-truth for navigation and broadcasts the co-ordinates and error readings to aircraft with JPALS-equipped receivers.


Because the technology can correct for the aircraft carrier's movement in six axes of motion, SRGPS also is considered a prime candidate to guide unmanned air vehicles during formation flying and autonomous refuelling. Sierra Nevada, which designed the SRGPS signal used during the F/A-18 hands-off landing in 2001, plans to perform an autonomous refuelling mission later this year.





Source: Flight International