GPS - going beyond 'Direct-To'

June 1, 2004

Bruce Landsberg has served the AOPA Air Safety Foundation as executive director since May 1992.

Thousands of pages have been written on the marvels of GPS. Two decades ago only the military knew about it. VOR/DME was king in the continental United States and if you were really on the leading edge, loran was a cumbersome device that did allow point-to-point navigation. The early GPS units were clunky to use but relatively simple in concept. Enter the latitude and longitude, being careful not to transpose numbers, and voilà — time, bearing, and distance to the destination was yours. That was then.

IFR GPS is now the mainstream navigation system for most new cross-country aircraft. These new aircraft still come with VOR and ILS, but these systems are almost afterthoughts. Well, not quite — nothing beats a good ILS on a foggy low approach, but for en route nav and nonprecision approaches, the GPS is tough to top. Regardless of the value of GPS, however, VOR, DME, and ILS will be with us for quite a while. While new GPS satellites are scheduled for launch in this decade, VHF equipment will be a primary nav source well into the future.

The first GPS nonprecision approaches were published in late 1993 as GPS overlays of conventional approaches. The FAA has made steady progress adding GPS approaches, and by 2002 some 3,400 standalone GPS procedures were on the books — some to airports that previously had no approaches at all. These approaches are usually recognized by the so-called "standard T" and require no procedure turns. The pilot selects the initial approach fix that is closest to his en route course and appends that to the flight plan. The units then sequence beautifully through the waypoints right to the end of the runway. It's the best way to go unless you get vectored to final. New units allow that; older ones may allow vectors but may not be quite so obvious as to how the program will bypass the intervening waypoints.

AOPA has been a strong supporter and promoter of GPS from its inception. It was immediately obvious that the ability to go direct at any altitude, with no intervention from the ground, was a major advance and safety benefit. The AOPA Air Safety Foundation has been involved in transitioning pilots to the system for more than a decade. In the mid-1990s we offered hands-on training with IFR GPS units at seminars around the country to learn as much about the systems as we could while providing a service to the early adopters. We could only take 15 students at a time and it was very labor intensive. Now there's a new ASF free seminar traveling around the nation to help pilots get beyond just punching in the destination. Visit the Web site, click on the Free Seminars button, and select GPS: Beyond "Direct-To." The new ASF "Safety Advisor: GPS Technology" for better use of GPS is also available, both in print and online.

Back in the dark ages of the early 1990s, the marketplace was in its infancy and innovation reigned supreme. There were five manufacturers building IFR-approved units. The FAA elected not to require a standard pilot-machine interface so each manufacturer could evolve whatever worked for the company. The knobology could be complex, and some of the human factors left much to be desired.

Two IFR GPS manufacturers are left, for the moment, and there has emerged some thread of commonality as to how GPS units should interface with pilots. For the owner-pilot and others who have a monogamous relationship with an airplane, it is merely a matter of learning that particular unit and working through a 200-page manual. If you fly multiple aircraft with several different units, then life is a bit more complex. Even then, if you understand the general approach to IFR GPS there is hope, if not quite deliverance. ASF's new seminar highlights the common points and gives examples of how to get the most out of your system with some degree of confidence.

If you're flying just one GPS unit and you've got the six core functions wired, stop reading here. But if you have multiple GPS relationships and are unable to commit to just one, much as you'd like to, read on. I'm not going to gush over how easy it all is. Anything is easy if you study it long enough. That's where the manual and the self-training CDs come in.

Learning to manage multiple units isn't hopeless, either, so we've tried to take a very pragmatic approach. Just because a unit has 51 functions and optional software upgrades to do even more doesn't mean you have to learn them all to get IFR functionality. Remember that VOR allowed you to go from A to B and shoot the approach. GPS can do exactly the same and take the flight anywhere, not just to VOR-equipped locations.

Everybody quickly figures out Direct-To, and it's a primary function. But for IFR utility you'll need to learn basic flight plans — that's just stringing together waypoints. Approaches are mini flight plans that are appended to your main flight plan when air traffic control or you figure out which one is applicable toward the end of the flight.

Let me digress momentarily to note that ATC is sometimes very helpful, but sometimes controllers are part of the problem. When a single-pilot flight arrives in the terminal area, it's really helpful to know in advance what's going to happen and then stick with it because the GPS units, or rather the human operators, have difficulty making last-minute changes quickly.

The American Airlines Boeing 757 accident in Cali, Colombia, was a classic in this regard (see " Safety Pilot Landmark Accidents: High-Terrain Tangle," April 2001 Pilot). A last-minute change caused the crew to reprogram its flight management system. While the pilots were dealing with the box, situational awareness slipped away, the aircraft headed for the hills, and ultimately struck one of them. American and many other airlines changed their approach to dealing with the "magic" and recognized the complexity that automation introduces under certain circumstances. The same thought process should apply to general aviation. Plan the approach and ask ATC as early as possible what you can expect, or request what you want based on the landing airport wind conditions and approaches available. As always, look over the approach charts in advance so you're not trying to read, fly, and program simultaneously.

Another core function for the IFR pilot is the ability to intercept a bearing to or from a particular waypoint. When you're in GPS mode and ATC tells you to intercept the 347-degree radial to the Hamiston VOR, it's good to know how to get there without becoming totally bumfoozled.

Do you know how to select an approach, execute a missed approach, and how the holding function works on the GPS unit or units you use? All these skills are important and within the capability of the average pilot, but not without some effort to learn.

If the approach is an overlay or has a VOR on the field, it's a really good idea to back up the magic with "raw VHF." There are a few gotchas that require us to be attentive when using localizers and back courses. A favorite trick of local pilot examiners is to select a back-course approach that has a step-down fix based on a VOR that is located off the airport but with the GPS distance readout based on the airport reference point. There is a several-mile difference that could put the flight into an obstruction. Many a pink slip has been issued on this one.

The new "GPS: Beyond 'Direct-To'" seminar addresses lessons learned, including a depiction of possible accident scenarios. Is the equipment to blame? The "magenta line from God," as the active course on GPS is sometimes described, is only as good as the programming and thinking that generated it. Everyone has heard of GPS trips through restricted airspace or ATC-controlled airspace with the pilot happily oblivious to everything. FAA certificate action, remedial training, and a hassle for all concerned are the outcomes. More serious situations involving controlled flight into terrain usually occur at night. GPS, like any tool, must be used intelligently and there is suspicion that some pilots are not following the rules that VFR requires after dark.

The flip side is that the GPS gear, properly used, may well have prevented many more airspace incursions and accidents. Those saves don't hit the accident reports. How many saves are there? My bet is a lot! For example, a Cessna 172 pilot experienced icing in instrument weather conditions. Unable to maintain altitude, he descended below radar coverage in mountainous terrain. Using a handheld GPS receiver and sectional charts, the pilot was able to land at a nontowered field that had no instrument approach. This pilot was extremely lucky and probably wished he or she had made a better assessment of the weather before the flight. Happily, GPS contributed to a way out of what could have been a fatal situation. Of course this method of escaping near-certain disaster is anything but bulletproof and not recommended.

Engine failures or other in-flight emergencies can be handled expeditiously with the Nearest feature on many of the units. In more than a few cases, an immediate diversion guided by GPS has orchestrated a happy ending. It would be nice if we could just push a button and be given the ability to use all the GPS features. Attending the new ASF seminar on using GPS won't solve all the problems, but it will help you develop a strategy.


If you have a GPS-save story or a miscue that you'd like to share, please e-mail it to asf@aopa.org. We will preserve anonymity.