Waypoints: Before the magenta line

Two decades of GPS guidance

March 6, 2014

Thomas B. HainesAn important anniversary passed in mid-February without fanfare. Today we fly GPS-guided flight plans from right after takeoff through the cruise phase, into the terminal area, and down the instrument approach without much thought, enjoying precise lateral and vertical guidance to within in a couple of hundred feet and a half mile of the runway in all sorts of weather; it’s all kind of humdrum. But just 20 years ago GPS approaches were cutting edge stuff—and not very slick, either.

February 13, 2014, marked the twentieth anniversary of the Garmin GPS 155 receiving FAA Technical Standard Order (TSO) authorization. With that the GPS 155 and its monochromatic text display became the first device to meet FAA TSO C129 A1 standards, allowing a pilot to navigate by GPS through all phases of flight, including—most important—through a non-precision instrument approach procedure. GPSs for en route IFR use had been around for a few years, following closely on the heels of the approval of IFR lorans.

And while the idea of flying a GPS approach using a text display and a swinging needle seems quaint (or perhaps frightening), this was the culmination of years of work by the FAA and the industry. A group of pilots at AOPA and a Beech Bonanza A36 owned by the association led a testing program with the FAA Technical Center that paved the way for IFR GPS as far back as 1992. The Bonanza was sent to the FAA center in Atlantic City for a major installation of test gear, including a tracking ball on its belly that allowed an old Nike air defense radar and missile guidance system to latch onto the airplane from afar to watch its progress through a series of test flights. An FAA technician worked a pallet full of gear in the back while another sat in the right seat to oversee the pilots from AOPA and elsewhere as they flew hundreds of approaches, guided by a Northstar M2 IFR Loran/GPS.

The testing was a moderate success, identifying numerous software changes needed to help pilots fly the procedures more accurately. In addition, the signal monitoring showed the need for additional corrections to the GPS signal in order to get position information precise enough to fly something close to precision approach minimums, which was the ultimate goal.

After the creation of the TSO and much testing, the FAA declared GPS ready for prime time shortly after the Department of the Defense announced GPS initial operational capability in December 1993. Garmin shot out the door with the certified GPS 155 only a couple of months later and the race was on for air superiority among various GPS manufacturers. Some in the competition—such as Northstar, Magellan, and Trimble—don’t exist anymore, at least not in the aviation space.

I remember heading to Garmin’s headquarters near Kansas City to fly one of the very first IFR GPS approaches ever in Garmin’s Mooney. The flight was inspirational and later that year, when I spec’d out the equipment for our 1994 Better Than New 172 Sweepstakes project airplane, a GPS 155 was at the top of the stack. With the gear installed in the summer of 1994, we flew then-FAA Administrator David Hinson and the media on IFR flights to Runway 5 at Maryland’s Frederick Municipal Airport, one of the first GPS approaches in the system.

The desire for precision approaches—with vertical guidance—continued as the FAA moved forward with the Wide Area Augmentation System (WAAS), a combination of ground and satellite-based signals that provided the GPS receiver in the airplane with a correction factor to improve the accuracy of the signal, allowing more precise guidance.

While that system was in development, Garmin and others continued to evolve their product lines. The Garmin GNS 430 came out in 1998, combining for the first time an IFR GPS with a VHF communication transceiver and VHF navigation receivers for VOR, localizer, and glideslope—and the all-important moving map and its now familiar (and relied upon) magenta line. When WAAS was finally declared operational in 2003, a new phase of development occurred, allowing for vertical guidance to or near Category I minimums. Without the need for ground transmitters, the FAA moved ahead quickly with the development of hundreds of new instrument procedures to many more runway ends, improving safety and access to many airports.

Following along on a day-to-day basis, development of the air traffic control system seems glacial, but viewed from the perspective of a couple of decades, the advancements are significant and quite monumental. Our flying will never be the same again—and thank goodness for that.

Editor in Chief Thomas B. Haines has been writing and reporting for AOPA Pilot since 1988—and flying since 1977.

Email thomas.haines@aopa.org

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Thomas B. Haines

Thomas B Haines | Editor in Chief, AOPA

AOPA Editor in Chief Tom Haines joined AOPA in 1988. He owns and flies a Beechcraft A36 Bonanza. Since soloing at 16 and earning a private pilot certificate at 17, he has flown more than 100 models of general aviation airplanes.