The Saga of the Driggs (Idaho) GPS Approach

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If you think mastering the user interface of an approach-certified TSO C129 GPS is tough, just try getting a new GPS approach! Case in point: the new GPS-A approach at Driggs, Idaho, a popular fly-in destination on the western edge of Grand Teton National Park. In this article, an aircraft owner and pilot based at Driggs documents his incredible two and a half year struggle to get a GPS approach commissioned, published and flyable. Believe it or not, getting the FAA to design and approve the approach turned out to be the easy part! Persuading Garmin to fix their software so it will recognize the approach turned out to be the real stumbling block. Is the ordeal over yet? Hard to tell.


Driggs, ID Driggs, Idaho, is in southeastern part of the state, northwest of Jackson Hole, Wyoming, and on the opposite side of the majestic Teton range. The short, scenic Teton Pass provides easy highway travel between Driggs and Jackson (most of the year, at least), and many find Driggs an attractive alternative to the congestion and high prices that have characterized Jackson in recent years. In the winter, some of the best skiing in the West can be found in the Tetons; in the summer, the Teton River offers perhaps the best fly fishing on the planet.

U59 airport diagramThe Driggs Municipal Airport (U59) is a nice facility with a 7300-foot lighted runway and a friendly FBO (Teton Aviation Center). Its major shortcoming both for fly-in visitors and for pilots like me who are based in the area has been the lack of an instrument approach. Because of Driggs' mountainous location, none of the terrestrial navaids in the area were suitable for getting into or out of Driggs on the gauges.

But with the advent of GPS and the availability of approach-certified GPS receivers, almost every airport should be able to have an instrument approach, right? Well, yes, but it's not as easy as it looks. This is the story of the unbelievably frustrating 18 months that I spent trying to get a GPS approach for Driggs.

First, we deal with the FAA...

Approach plateThe FAA Flight Procedures Office in Seattle took a little over a year to design and draft the new Driggs GPS-A approach. I expected that. By July 1996, they told me that the new approach was ready for prime-time, that had been sent to Oklahoma City for publication, and that commissioning was imminent. Little did I know that it would be another eighteen months and a few dozen phone calls later before I could try flying that approach.

The first hitch was that although the approach had been drafted, turned out that the FAA had no approved criteria for instrument departures without the use of terrestrial navaids. It took eight months and constant pressure to resolve that problem. Then it turned out that while all this approach design work had been going on, the FAA forgot to get the airspace around the airport reclassified from Class G to Class E as required, and this threatened to delay things for many more months. Fortunately, the there was a scheduled FAA fly-in event at Driggs in July 1997 that generated some internal pressure on the bureaucrats to get things sorted out relatively quickly. Political pressure from Idaho congressmen and Vice President Gore's office may have helped, too. There were a few more complications, too, like getting the FAA to flight-check the approach, and meeting the requirement to get a dual altimeter system (or AWOS-1) installed at the FBO to provide an approved altimeter setting.

But finally, an honest-to-god approach plate for the GPS-A approach at Driggs arrived with my November 6, 1997, revisions. On November 7, I decided to go try to fly the approach. Guess what? My approach-certified TSO C129 Garmin GPS-165, updated with the very latest Jeppesen NavData card, told me that there were no instrument approaches at U59. Wonderful!

...and then, with Garmin!

Garmin GPS165I called Garmin technical support and was told that my GPS-165 did not have the latest software that would allow it to fly stand-alone (non-overlay) GPS approaches. I FedEx'd my GPS-165 and two others to Garmin for a software transplant.

A few days later, Garmin tech support called to say that the new software was installed, but the receivers still couldn't find the Driggs GPS-A approach because that approach was not on the Jeppesen NavData cards. The receivers (with their new software) were shipped back to Driggs, and Garmin said they'd check with Jeppesen on why the Driggs approach was not on the datacard.

GarminAfter several days, having heard nothing from Garmin, I called Jeppesen directly to find out what was going on. Jeppesen told me that the Driggs approach was not on the datacard because Jeppesen had received instructions from Garmin not to include any circling GPS approaches on NavData cards prepared for Garmin receivers!

A call to the NavData guru at Garmin revealed that Garmin's software developers never anticipated that there would be any GPS circling approaches (there are presently 37 such approaches in the U.S.), and that they did not provide a "data type" in the software architecture to accept such an approach. That's why Jeppesen was instructed not to include GPS circling approaches in their datacards for Garmin receivers.

Garmin GPS155I escalated the issue to a higher level at Garmin. I was told that redesigning the GPS-165 software to accommodate circling GPS approaches was a big deal that would take at least many months, perhaps a year, and that Garmin was not prepared to commit to doing it at all! Apparently memory space is so tight in the GPS-155 and GPS-165 that such a change might not be feasible. I was also told that the reason Garmin designed the software the way they did was that they had been assured by the FAA that all stand-alone GPS approaches would be the straight-in variety. Garmin also said that any software change would require a 20,000 page "Fault Tolerance Specification Test" (#DO-178) that could take months to accomplish.

Finding a workaround

Garmin suggested that the easiest way around the problem was to persuade Jeppesen to mis-label the approach as a straight-in approach (GPS RWY 21) instead of a circiling approach (GPS-A) so that the Garmin software could deal with it.

JeppesenI called Jeppesen. They said they'd be happy to re-label the approach provided they could get the FAA to authorize this in writing, and that they'd even be willing to do this relabeling only on Garmin datacards so that other manufacturers' GPS receivers wouldn't be affected.

The FAA, however, was unwilling to authorize such an intentional mislabeling of the approach, even on a temporary basis, insisting that the problem should be fixed in the Garmin software. While I had to agree with this in principle, it was clear that I was not going to be able to take advantage of the hard-fought Driggs GPS-A approach unless some workaround could be found.

Meantime, I started making calls to other GPS manufacturers to find out whether they had similar problems with the Driggs approach. The results: AlliedSignal (Bendix/King) and NorthStar checked the KLN-90B and M-3 and said they handled the Driggs approach fine. II Morrow verified that their boxes could handle the approach too. Trimble tried it on their model 2000 and 2101 GPS receivers and found they could not call up the Driggs approach (but they didn't know why not). Later, Trimble said that it wasn't a software problem, but that Jeppesen had been stripping GPS circling approaches off their datacards, and that Trimble would instruct Jeppesen to stop doing so in future revisions.

Numerous calls to various FAA people all over the country made it clear that nobody wanted to be the one to take responsibility for approving the intentional mislabeling of the circling approach as straight-in. I got "vectored" from one FAA office to another, and from one person to another. Each time, I was told "I'm not sure why you were told to call me. You really should be speaking to X."

Yes, Virginia, there is a Santa Claus!

FAAFinally, I talked with FAA's national resource specialist on GPS hardware, Jim Treacy (ANM-103N), who seemed genuinely concerned about finding a solution to this predicament. After considering several alternatives, Treacy concluded that the best interim solution was to relabel the Driggs approach as a "VOR-A" overlay approach, and then creating a fictitious VOR that would be NOTAMed permanently out of service. Leave it to the FAA to come up with a solution like that! I wasn't complaining, though. It was wonderful to finally talk to someone in the FAA who actually looked for solutions and not obstacles.

Treacy emailed several FAA offices concerning our plight at Driggs, and asked for comments on several possible workarounds, including relabeling the approach as GPS RWY 21, relabeling it VOR-A GPS with a phantom VOR NOTAMed out-of-service, or creating a "Special Approach Procedure" for Driggs.

As of December 1st, I was told that the FAA had agreed to approve the relabeling of the approach in order to make it work with the Garmin receivers, but I don't yet know precisely which approach will be taken nor what revision date will contain the changes. But I finally feel like the problem is going to be resolved somehow, and soon. At least for Driggs. As for the other 36 airports with GPS circling approaches, I'm not sure what will happen.

After two and a half years of waiting, it's about time!