THE MARCH OF AVIONICS TECHNOLOGY
Article appeared in Flying Magazine March 2020 by John King
My instructor was in the backseat behind me. He was always yelling at me. This time he was yelling that I needed more rudder when I used aileron. I was a teenager. I thought he was mad at me. I know now he was just trying to be heard over the ambient airplane noise. The airplane was an Aeronca 7AC Champion. It had no electrical system or intercom system, and we had no headsets.
I didn’t think of the airplane as missing anything. The other airplanes on the field were similar. I just thought that was the way airplanes were made. I had no idea of the march of avionics technology I was to witness in my flying future.
Of course, we also had no electronic navigation. We used pilotage, comparing the chart to landmarks; and dead reckoning, holding a heading and speed and keeping track of time. In ground school we learned to draw our proposed ground track on a chart. We drew another line to the destination representing wind direction and speed. We used the lines to plan our heading and time for the trip.
In the early 50s, things became more complicated when the FAA mandated that pilots demonstrate emergency instrument skills for a private pilot certificate. This required airplanes with electrical systems for the turn indicator, and vacuum systems for the attitude indicator and heading indicator.
I didn’t participate personally in this particular technological advance. The airplanes with instruments cost more to fly. I was saving up to go to college. The $8 per hour that I was paying for airplane and instructor was all I felt I could afford. After I soloed the Aeronca on my 16th birthday I decided to stop this outrageous expenditure, and quit flying.
Years later, I resumed my flying in companionship with Martha. We bought a Cherokee 140. It, of course, had an electrical system. It was also decked out with dual nav-com radios. I was introduced to radio communications and navigation. It was a big step up from my days of pilotage and dead reckoning.
When we got our Private Pilot certificates, we got the lust for something faster. We bought a Piper Comanche and set out explore the rest of North America. On our way to Barrow on the North Slope of Alaska we discovered in Fairbanks that we needed more than VOR navigation. We needed ADF to navigate our way any further north. By now I apparently had lost my pre-college frugality. Martha and I laid out the money on the spot to have an ADF installed in our Comanche. ADF had been around a long time and was not really an advance in technology. But to us ADF was new technology that allowed us to go further north.
As we continued to fly the Comanche, we flew more and more IFR. Since we were equally hooked on flying, we had no financially responsible partner when it came to spending for avionics. When Martha and I wanted DME to support our IFR flying, we immediately laid out the funds to put a DME in our Comanche.
When the technology became available in 1978, we sprang to install a King KNS 80 in the Cessna 340 we owned by then. The KNS 80 was referred to as a course line computer. It would electronically move a VORTAC to a new location. Using the signal from a VORTAC within reception, we could navigate to or from the computed position miles away as if the VORTAC were actually in the new position. It was our first experience at being able to navigate by VHF in a straight line as far as 199 miles, without having to go from navaid to navaid. The capability was referred to as area navigation. The KNS 80 could store four preset waypoints so you could quickly switch from one waypoint to the next.
In 1990, Narco Avionics came out with a product for general aviation called StarNav. It took navigation to the next level. StarNav was a multisensor navigation system containing VOR, localizer, and glideslope receivers. It had a database allowing it to automatically tune nearby navaids to provide a continuous navigation solution. We installed StarNav in the old Citation that we had then. As friends of Ed Zimmer, the owner of Narco Avionics, we were beta testers. It was Martha who suggested the name “StarNav.”
In addition to utilizing its self-contained sensors, StarNav interfaced with other receivers including DME and loran. Loran referred to long range navigation. It was originally developed for marine navigation. Loran allowed continued navigation even when we were out of range of VHF signals. Eventually we replaced the loran in our Citation with GPS, which gave us improved position accuracy. StarNav was our first experience with the combination of a database and area navigation for nation-wide automatic navigation. Today, GPS systems combine that capability with a map to routinely provide simple, intuitive navigation.
In its early days GPS wasn’t as useful as it could be because the military dithered the signal for civilian users. This dithering deliberately added 50 meters of error horizontally and 100 meters vertically to GPS signals. This was referred to as “selective availability.” In May of 2000 selective availability was removed, making GPS vastly more precise and practical for civilian use.
On July 10, 2003, the Wide Area Augmentation System (WAAS) was activated for general aviation, covering 95% of the United States, and portions of Alaska. This even further improved the precision of GPS. WAAS works by having ground stations with known positions receive the GPS signal. They then correct any errors and send the correction for the area back to satellites, which then send out the corrected signal. WAAS allows a position fix within 10 feet, 95% of the time.
A WAAS receiver is required for ADS-B Out. With ADS-B every airplane reports its very precise position to all the other aircraft in the vicinity, and to ground stations. With WAAS we can now see the accurate location of every nearby airplane on our screen. This has already proven to greatly reduce the collision rate and save lives.
It is hard to imagine how far avionics has come. Navigation and situational awareness in the cockpit is vastly more precise and easier, and information is incredibly plentiful. Plus, it’s all a lot more fun. Our GTN 725 displays our position, weather and traffic information on the same screen. It is wirelessly connected to our iPads which serve as additional multi-function displays, providing the information available from the panel navigator and displaying it very intuitively. At home our pre-flight preparation supplies us with more copious current information with more immediacy and better detail than was available even to flight service station operators in our early days of flying.
It has been a great journey. Even though I am no longer a sixteen-year old kid, I still have no idea what the future holds. But with the accidental wisdom of experience, I can tell you that change will continue in increments, and that in a few decades we will have arrived in a marvelous new place. I am looking forward to it.