Tuesday, December 7, 2010
The Evolution Of Navigation
Flying from A to Z is no longer as simple as it used to be. It’s simpler.
MODERN TECHNOLOGY. GPS units such as the Garmin G96 make dead reckoning a distant memory.
My first airplane, a Globe Swift GC-1B, had a Narco VHT-3 Superhomer, an antediluvian, tube-style, crystal-controlled com with 12 channels that could occasionally transmit a signal across the ramp. I carried another dozen crystals for additional frequencies in those days and could remove crystals I didn’t need and substitute appropriate ones. The com could also serve as a basic VOR nav receiver.
My Swift also boasted a Bendix T12D ADF that worked on alternate Thursdays when the moon was full. Actually, the T12D was probably a good, basic unit—mine was just old and tired.
Automatic direction finding was the simplest and most complex form of radio navigation. It was simple: All you had to remember was the needle always points directly at the station (okay, not always). Navigating by ADF was almost idiotproof inbound to the station. The bad news was that low-frequency signals are susceptible to many forms of static interference, and navigating away from the station was problematical.
Today, ADF is out of style. That’s okay in a world of copious VORs and reliable GPS signals, but it can be more than a little scary in the mid-Pacific when GPS blinks and you’re still 1,000 miles from a small island with an NDB, and you have no ADF on the panel of a new airplane and no positive way to find land.
In the not-so-good-ole days, the prevailing navigation method for general aviation was most often point and shoot. General aviation’s alleged fat cats rarely were; and aircraft owners often couldn’t afford exotic VHF/LF avionics. Dead reckoning and pilotage more often were the rule. You simply plotted a course and flew by reference to time-speed-distance, or you pointed the nose at the nearest landmark you could see, then picked another visual cue in the same direction and continued the process until you found your destination.
It was pretty simple stuff. When the radios weren’t obliging, DR/pilotage worked most of the time, and it even directed Lindbergh to Paris 83 years ago. It even routed me to Shannon, Ireland, from Gander, Newfoundland, Canada, 33 years ago on my first ferry flight.
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