Johns Hopkins study declares augmented GPS OK for ‘stand alone’
AOPA and ATA ask FAA to accept results, turn to transition issues
The eagerly awaited Johns Hopkins study of Global Positioning System risks and capabilities has affirmed that augmented GPS can “satisfy the performance requirements to be the only navigation system installed in an aircraft and the only service provided by the FAA for operations anywhere in the National Airspace System.”
“The FAA should now move ahead to transition planning according to the specific recommendations of the Hopkins report,” said Carol B. Hallett, president and CEO of the Air Transport Association, and Phil Boyer, president of the Aircraft Owners and Pilots Association. ATA, AOPA, and the FAA were co-sponsors of the Hopkins study.
The associations representing airlines and general aviation called on the FAA to proceed with two additional geostationary reference signals, a national GPS plan, and a management commitment to developing system improvements and user procedures.
The Johns Hopkins Applied Physics Laboratory report said a 24-satellite GPS constellation with the Wide Area Augmentation System (WAAS) including four geostationery reference signals can satisfy all U.S. requirements for oceanic navigation through Category I precision instrument approaches.
The study also said a 24-satellite system with four geostationery signals, WAAS, and the Local Area Augmentation System (LAAS) can satisfy all precision approach requirements through Category III with no improvement needed in the GPS satellites already aloft. For Category II/III approaches, airports would require two ground-based LAAS pseudo-satellites (“pseudolites”) and other enhancements.
Risks to GPS from natural, man-made, and hostile radio interference were all judged to be manageable. Unintentional interference theoretically could occur from television broadcasting on Channels 23, 66, and 67, whose harmonics could interfere within line-of-sight range.
Lesser radio interference risk was also possible near business band VHF (taxi dispatch) broadcasts and the military’s few over-the-horizon radar installations. Aircraft on-board interference was also cited as possible but can be handled with antenna technology.
Intentional jamming was a risk area, but the study found that planned GPS avionics are designed to recognize it. Johns Hopkins said such threats can be managed. “Technologies are emerging that can greatly reduce vulnerability to GPS signal jamming,” the study said.
Sunspot and atmospheric problems were judged to be either non-factors for augmented GPS or extremely limited in effect.
The study called for development and implementation of operational procedures to handle these manageable issues. Johns Hopkins said the FAA should (1) firmly establish the size and characteristics of the GPS and geostationery satellite constellation, (2) specify a timetable for improvements, (3) refine correction methodologies, and (4) develop regulations and monitoring to prevent interference.
In response, AOPA and the Air Transport Association called for:
- Rapid implementation of WAAS and two additional geostationery signals,
- Collaboration with the user community on a national GPS plan,
- Greater civilian control in the management of the GPS system, and
- Accelerated implementation of procedures/policies to produce early operational benefits.
ATA President and CEO Carol B. Hallett commented, “This study clearly shows that with the proper investment and improvements, GPS will become the navigation system for the twenty-first century. This investment will include two more satellite transponders, and ATA will work to help make this a reality.”
AOPA President Phil Boyer added, “With many of the technical issues answered, the entire aviation community—the airlines, general aviation, the military, and the FAA—must now turn full attention to planning the transition phase. Agreement on costs, timing, and user acceptance will determine the timeline for planning out the critical implementation phase.”
FAA Administrator Jane Garvey said the FAA is “encouraged” by study results.
“I am pleased we were able to work with AOPA and ATA to reach consensus on where we’d like to go with GPS. More cooperative efforts will be necessary in the future to reach the goal of GPS navigation, and we’re committed to making that happen,” said Administrator Garvey.
The Johns Hopkins study sought to determine the performance capabilities of the Global Positioning System and augmented GPS, and its risks as the only method of radio navigation provided by the FAA or in use aboard aircraft.
The Air Transport Association represents leading airlines. Its member carriers transport over 95 percent of all passenger and cargo traffic in the United States.
The 340,000-member AOPA represents non-scheduled flying known as general aviation. AOPA members comprise 56 percent of the nation’s 616,000 pilots and own 75 percent of the 187,000 non-airline aircraft in the United States.
January 29, 1999