Garmin GPS 155 TSO Turns 25

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We take it for granted today, but 25 years ago a GPS navigator approved for non-precision instrument approaches was big thing—and Garmin’s GPS 155 TSO was the first to be approved under TSO-C129 A1.

There’s reason for Garmin to look back on Feb. 16, 1994, with some pride. After decades of abundantly analog navigation solutions bridged by Loran, the steady guidance of GPS was a small miracle. And even though we had enroute-qualified GPS navigation before, the idea of letting the GPS take us all the way to the runway was just a little out there. Even if it was just to follow an overlay of existing VOR or NDB approaches.

The development and certification of the GPS 155 TSO “pioneered the development for initiatives such as NextGen,” says Carl Wolf, Garmin’s vice president of aviation sales and marketing. “As we recognize this significant milestone in aviation, we thank our loyal customer base and dedicated associates who make these achievements possible, and look forward to celebrating many more for years to come.”

Viewed from today’s perspective, the GPS 155 TSO seems primitive, with its dot-matrix display and before-there-were-touchscreens control menu logic. But it demonstrated the capabilities of GPS-based navigation that would be fully grasped and leveraged by general aviation in the years to come. It’s worth remembering that it was just four years after the 155 that Garmin introduced the GNS 430.