GPS 10 Years Later

It is a cliché, but time does fly when you are having fun. Interesting is fun, and almost nine really interesting years have passed since I got one of the first (if not the first other than a manufacturer) approvals for GPS approaches. The FAA approval is dated 7/25/94. That first unit, a Garmin GPS 155, offered some installation and operational challenges, but after I mastered them it became my primary bit of navigational gear, both for en route and for approaches.

Since getting that unit approved I've changed, evaluated and upgraded units and now have a Garmin GNS 530 and a Bendix/King KLN 94. Several other navigators have been in the panel along the way, but there has always been an approach-approved GPS in my airplane.

The pervasiveness of GPS is evident in the number of approaches that I have flown using various navaids. Since getting that first approval, I have flown, in actual conditions, 65 GPS approaches, 46 ILS approaches, five localizer approaches, one back course localizer approach and one VOR/DME approach. There is still an ADF in my airplane, but I haven't flown an NDB approach since starting with GPS.

A lot of those GPS approaches were overlays of existing non-precision approaches, and I still monitor the raw data from the VOR and DME when flying an overlay of one of those approaches. That reflects no lack of confidence in GPS; it's just that if I happen to have a belt and suspenders, I'll wear them both.

En route, GPS has been the primary navigational aid, though I do still run my trusty King KLN 88 loran. Occasionally I'll monitor some en route navigation with a raw VOR signal, and I am always reminded of how the VOR signal wanders around, where the GPS is completely stable.

A great feature of GPS units is the flight plan function. I know what routes are likely to be approved in the area that I fly the most, and I always use the flight plan function of the GPS and input the plan before takeoff. If cleared as filed, that means that all the en route navigational chores were done in advance. All the autopilot has to do is keep the needle in the middle, and all I have to do is sit and watch as the airplane automatically follows the flight plan. That leaves plenty of time to monitor everything else.

The FAA originally promised a lot on GPS that hasn't yet been delivered. In an exclusive Flying briefing on the subject, FAA officials told us, in late 1994, that there would be 8,000 GPS approaches with vertical guidance in place in five years. There's a big difference between zero, the actual number, and 8,000, but the FAA is plodding slowly toward the implementation of those approaches with vertical guidance. Still, I doubt that GPS will replace ILS approaches in the foreseeable future.

The FAA officials also said there would be no new Category I ILS installations after late 1995. There have been many. Further, the FAA said that the phase-out of VORs and NDBs would start in 2001 and that it had little interest in maintaining loran as a backup. Maybe a few NDBs have been turned off, but the VOR/DME system has hardly started phasing out and loran is still going strong. Certainly the Victor airways system is still 100 percent intact, is in use every day and is likely to stay that way for quite a while.

What the FAA has done well, and on a timely basis, is design and implement a lot of stand-alone GPS approaches, and more are being added on a regular basis. The air traffic control folks are great at approving long en route direct legs, too.

Some flight schools still teach VOR and NDB, usually because they don't have an approved GPS in their fleet, but in airplanes used for travel, GPS has become the standard.

If anything is lacking in GPS it is in pilots taking full advantage of the equipment. I'll digress for a moment here on a point that suggests that at least a few pilots are trying to take too much advantage of the equipment. Handheld GPS units are wonderful devices that are as accurate as the installed ones. They are not "approved" for anything, though they can be used for en route navigation. Just ask the controller for a heading to fly until receiving Los Angeles and fine tune that heading with the handheld GPS.

The trouble comes when pilots try to use handhelds for instrument approaches. They are neither approved nor designed for this, and their databases do not contain the full approach, as is required. And there have been at least two fatal accidents where a pilot was apparently using a handheld to fly a GPS approach in low weather. The only time that should be attempted is in an emergency.

With the installed and approved GPS navigators, a lot of pilots just won't learn all there is to know about using the system, and one veteran pilot told me the other day that he still uses VOR for approaches, where available, because he doesn't like to go to the trouble of setting up the GPS for an approach. That's too bad, because it has so much to offer.

One of the neat features on a GPS approach is the fact that in the final stages of the approach, the GPS gives distance to the end of the runway, not the airport reference. That is fine information, not to be used to cheat on minimums but to heighten situational awareness.

GPS gives a readout of the track being made good over the ground, and this is useful en route and downright wonderful on an approach. The track that we make good is what gets us where we are going, and by flying track instead of heading, all the guesswork is taken out of allowing for wind drift and changing wind. GPS groundspeed is also pinpoint accurate, and the units will calculate the winds aloft for you with great accuracy.

Then there are the maps. There's just nothing quite as helpful as a map showing both your position and the approach that you are flying. The way GPS ladles on information that gives situational awareness was evident one day as I was flying a GPS approach at Batavia, Ohio.

The approach was to Runway 4 and my arrival was from the east. There were numerous other airplanes inbound, but from the gist of the conversation I gathered that I'd be first for the approach. It was set up on both the Garmin GNS 530 and Bendix/King KLN 94. I told the controller I'd take a turn onto final right outside the final approach fix, and he assigned the heading to make that work.

From the assigned heading it was obvious that the controller was indeed vectoring for a turn in just barely outside the FAF. He did a masterful job as I watched the map and the digital readout of the distance the airplane was from intercepting the final approach course. The final heading before intercept was just right.

That could have been done by the controller had I not had a map, but with the map I was in the loop all the way. Without the map, and the other available GPS information, I wouldn't have much other than a full-scale quivering needle until the time it started to come to center, and I likely wouldn't have been comfortable with an intercept that close to the final approach fix.

Later that day, headed back home, the weather appeared that it would be a good idea to set up for the approach. The published portion of the VOR or GPS approach to Runway 9 starts at the 246 radial off Hagerstown (Maryland) at 10 miles. I have that waypoint in the GPS as a user waypoint. My right seat person this day was Drew Kassal, call sign "Doc," a 26-year veteran at Washington Center, and he asked for direct to the 246 at 10. It was approved. I activated the unit for vectors to final and then just flew the little airplane on the map to the 246/10 waypoint symbol where the final approach course was intercepted and the approach flown-in the same manner it would have been done had the controller vectored us to the 246/10.

All that is good and exciting, but the other things that GPS enables, and will enable in the future, are going to bring further evolution to the way that we fly.

The hot avionics item right now is the equipment that delivers weather information, including composite Nexrad displays, to the cockpit. GPS is an integral and essential part of this. It locates the airplane on the map of the weather and shows the track of the airplane in relation to the weather.

Also, when metars and TAFs are called up, the Bendix/King system uses the GPS to give the en route flight plan and destination weather and uses present position to give the location of the nearest weather. When the metars map is selected, where it shows weather symbols depicting VFR, marginal VFR, IFR and low IFR, GPS information positions the airplane symbol on the screen.

The new general aviation ground prox system (called TAWS by the FAA, for terrain awareness and warning system), is all about GPS. The airplane's position in space, both vertically and horizontally, is determined by GPS and is compared with a database of terrain, obstructions and airports. Appropriate warnings are given if the airplane is getting too close to something, or if the sink rate is too high, or if other parameters are exceeded. Fly correctly and you never hear the TAWS speak, except for one thing. It'll tell you when you are "500 above" on every approach just to remind you of where the ground is located. This is also a reminder that it is there waiting quietly, ready to tell you in advance if you are about to do something really dumb.

The use of GPS information as a gyro replacement, or to enhance gyro performance, has been bandied about for a while, and Garmin is first to make some application here, with the handheld GPS 196. This new unit has more features than a panel-mount GNS 530, at a fraction of the price. There's even a screen that shows an HSI, altimeter, airspeed, vertical speed and a turn-coordinator-like depiction, a kind of "partial panel" arranged in the normal pattern of instruments. The screen is big enough to be useful. The database for this unit supports all the instrument approaches, and at first sight it appears to be a wonderful backup should all the lights go out on a dark and stormy night.

Flying with it, though, will convince you that to successfully get an airplane down using nothing but GPS-derived information in this form would take a lot of skill and even more luck, and Garmin forbids using the GPS 196 for actual instrument flying. For one thing, to set up for an approach you have to get out of the instrument panel screen, which wouldn't be practical.

From a flying standpoint of trying to stay right side up using only the GPS 196, the biggest problem is with the simulated turn coordinator information. It shows rate of turn but the update is only once a second because the GPS operates at one Hertz, calculating a new position once each second. That may sound fast, but trying to fly in rough air with something that has that much delay is totally demanding. The only way that I could fly the GPS 196 in simulated instrument conditions was to not move anything until a definite trend was shown on the simulated turn coordinator. To turn, the best way was to make a half standard rate turn and, if things got dicey in the bumps, to go back to a no turn indication and settle down before attempting further turn. The vertical speed indication has quite a bit of lag, too. The "airspeed" indication is actually groundspeed, so that has to be used with a knowledge of winds aloft. The HSI is fine and might even be a little more usable in determining whether or not the airplane is turning than is the simulated turn coordinator. There's no slip/skid indication, so you have to rely on feel for that. I did manage to keep the airplane under control for a half hour and find the airport using the GPS 196 only in simulated instrument conditions.

I would judge the GPS 196 instrument panel display, especially the simulated turn coordinator depiction, as a little crude and difficult to fly. However, the concept is good, and I'll bet we will see a lot of development in the use of GPS-derived information for things other than navigation. If Garmin can integrate these basics into a handheld unit that retails for a $1,000, just think what might come next.

All this sounds good, but there are currently some negatives on GPS. The GPS satellite constellation is said to be at less than 100 percent now, and I think that I can detect that when using handheld GPS units without an external antenna. My little Garmin GPS III used to work perfectly, all flight, every flight, when perched (with Velcro) atop the control wheel of my airplane. Now it only works about half the time in that location and often has to be perched atop the panel to get an adequate view of satellites. Flying with the 196, it lost the signal a few times when mounted on the control wheel with the supplied device. When you are using it to try to control the airplane, a loss of signal is truly a serious business. Even the units installed in the panel flash an occasional RAIM alert more often than before, meaning the accuracy isn't adequate for approaches.

The government that created a system that sent us all scurrying to the avionics store to buy this wonderful stuff doesn't seem to have as strong a commitment to maintaining the system as it had in getting the ball rolling. Nor is anyone able to predict when or how the satellites that are now working perfectly will degrade.

It is said that there are plenty of satellites in inventory, ready to be launched, but there aren't available rides into space for these satellites. And, in the past few years, three launches have been unsuccessful or delayed.

The Defense Department runs the GPS system, and it is obvious that it will take some help from other sources to keep GPS on track to eventually be a sole-source navigational system. The question of electronic jamming of the GPS signals must also be addressed. This affects a lot more people than pilots, too, as the GPS signals are used for timing in internet and cellular communications.

Now you know why Garmin put a VOR and ILS receiver in its popular 430 and 530 navigational systems.

Everyone who has put the effort into taking full advantage of GPS systems sure never wants to go back to the bad old days. But we do have to temper enthusiasm with the reality that the GPS system probably can't ever achieve the reliability of the ground-based systems with their distributed transmitters and diverse technologies. Where in that 1994 briefing the FAA told Flying that the backup system for GPS would be GPS enhanced by local area augmentation and wide area augmentation, that may not come true, at least for a long while. The ILS system will stay around, and the prediction that the shutdown of the VOR system would begin in 2001 not only didn't come true, it likely won't come true in the foreseeable future. The decision that I made to leave the KLN 88 loran in my panel looks better every day.

In reality, the ultimate backup system for GPS might become the ground-based radar system coupled with the retention of some VORs plus the ILS system. And, hopefully, some more satellites will go flying soon.


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