Precision Landing System Ready for Takeoff

After many years of technology refinement, the USAF's Electronic Systems Center-led land-based increment of the Joint Precision Approach and Landing System (JPALS) is poised to progress to the system development and demonstration (SDD) phase. The system uses the Global Positioning System, or GPS, to enable...

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After many years of technology refinement, the USAF's Electronic Systems Center-led land-based increment of the Joint Precision Approach and Landing System (JPALS) is poised to progress to the system development and demonstration (SDD) phase.

The system uses the Global Positioning System, or GPS, to enable accurate and reliable landing guidance for approaches, including those conducted in low-visibility conditions. It is, in fact, designed to provide precision approach and landing for all the military services in any weather and for virtually any mission, according to USAF Lt. Patrick Ris of the 853rd Electronic Systems Group, the ESC deputy program manager.

The Navy is the Pentagon's lead service for the joint program, and because of its specific needs, the sea service has fully funded and moved its maritime-based increment of the program forward. Now the USAF seems ready to do the same, according to Brian Pierce, a contractor supporting the program. "The technology is ready, and users are beginning to see all the advantages," Pierce said.

Those advantages include equipment and cost reductions. JPALS requires only one ground station per airfield, whereas the instrument landing system, which is now predominantly used, requires one ground station at each end of every runway on an airfield. The one JPALS ground station also may cover all other airfields within a 20 nautical mile radius.

The JPALS system uses datalink receivers on board the aircraft to connect with the ground station. The ground station, being in a fixed location, can constantly measure the ever-changing error factor inherent with GPS and transmit it to the aircraft. Navigation processing equipment onboard the aircraft incorporates the information to increase the accuracy of the aircraft GPS position.

JPALS then uses waypoints provided from the ground station to construct an approach path between the aircraft and touchdown point. The pilot can fly this approach using standard cockpit instruments, or JPALS can be coupled to the aircraft autopilot to perform "hands-off," auto-coupled landings, according to Pierce.

The system allows approaches to be changed easily. It also allows touchdown points to be moved.

"In a hostile environment like Iraq, it's easy to see what a huge advantage that would provide," Ris said.

To help Air Force operators realize the benefits of switching from ILS to JPALS, the 853rd team and contractors with ARINC Engineering Services set up a two-day informational event hosted by Boeing in Seattle earlier this year.

There, two dozen military observers boarded a new Qantas Airways Boeing 737-800 at Boeing Field for a demonstration of an advanced commercial satellite landing system that resembles JPALS.

During the flight, the Boeing 737 successfully completed 15 approaches at five different airfields in the Seattle region. A number of veteran Air Force pilots took turns in the co-pilot seat, Pierce said. "People who came in with reservations came away sold."

The demonstration was the latest in a series of events aimed at both wringing out and showing off the technology, according to Bob Norwood, who supports the program as a contractor.

In October 2007, the ESC group participated with many others in a field experiment held at the FAA's Technical Center at the Atlantic City International Airport. There a so- called man-pack version of JPALS, integrated on the fly by ESC, MITRE and ARINC engineers, was tested.

Using just two backpacks worth of equipment set up not at the runway but at a nearby ball field and then in a salvage yard more than a mile from the runway, operators provided precision approach to Atlantic City airport, and later, to Ocean City airport, 12 miles away. "There's lots of interest now," Pierce said, noting that, combined with an ever- clearer joint service need, that interest should help deliver successful results for the program.

JPALS began, more than a decade ago, as a program designed to meet the emerging needs of an aviation system perceived to be moving away from instrumentation-aided landing systems. It's still envisioned as the system of the future, and in fact such systems are being delivered at a far greater pace than ILS systems.

However, neither the FAA nor the International Civil Aeronautics Organization, which governs worldwide aviation, have yet mandated such a switch.

"We've really been able to work at it and get a much better understanding of the system," Pierce said. "Now we're very confident that we're ready to go forward."