The details in this blog post originated from a book written by Paul A. Craig titled The Killing Zone – How and Why Pilots Die. I believe that the author created one of the best summaries of the advent of GPS based navigation which is arguably the greatest shift in aviation history. I want to share the information here with you as I found it to be quite fascinating.  What follows is mostly quoted with some paraphrasing here and there for conciseness.

Flight basics

Possibly the most famous and probably the most important book ever written on flying an airplane was published in 1944, which is Stick and Rudder: An Explanation of the Art of Flying by Wolfgang Langewiesche. The book is still in print today and explains how an airplane turns, climbs and glides, and discusses the precisions maneuvers required for license flight tests. Those precision flight maneuvers are still seen as requirements on flight tests today.

The fact is that flight training has not changed much since 1944 and that accounts why Stick and Rudder is both still relevant and yet a classic.

The 1938 book titled, Flight Handbook – The Theory and Practice of Powered Flight, has a chapter on flight instruments. The illustrations and descriptions of the pitot-static system and gyroscopic instruments in that 1938 edition are the same as you would see in flight training books today. The teaching techniques, flight maneuvers, flight instruments, and ground-based navigation taught to pilots did not undergo any significant change for 60 years. Then came the decade of the 2000s, and aviation underwent the greatest shift in its history.

The computer age

Seeming overnight, general aviation flight training entered the computer age and the satellite navigation age all at once. It happened too fast for some. There were pilots who took one look at computer screens in the cockpit and opted out. Some airline captains took early retirement rather than have to learn how to function in the world of automated flight decks. Some general aviation pilots did the same. The new electronics that found their way into general aviation cockpits instantly changed the role of the pilot. For the preceding 60 years, the pilot was the manipulator of flight controls. Now the pilot had also become the manager of information.

The shift

There was a perfect storm brewing in the 1990s that set the stage for the shift. In 1998, flight training companies were operating fleets of training airplanes that were all older than the students who flew them. General aviation training airplanes simply were not being built after the 1970s because of the threat of lawsuits against the manufacturers. Tort reforms in the 1990s removed many of those barriers, and legacy aircraft manufacturers began producing again. Several new manufacturers even entered the market. But building airplanes again did not create the shift. Manufacturers would have just made new versions of old models (and some did exactly that) if it weren’t for breakthroughs in three more areas: the laser ring gyro, the Global Positioning System (GPS), and the radar mapping of planet Earth.

The laser ring gyro

The laser ring gyro was not new technology in 2000. It had been in use in airline and military aircraft, and the actual concept dates back to 1913, when a French physicist, Georges Sagnac, experimented with rays of light moving in opposite directions around a circular turntable. Laser ring gyros are designed to replace traditional mechanical gyros. Laser ring gyros have no moving parts and virtually never fail. Mechanical gyros, such as the ones illustrated in the 1938 Flight Handbook, were the basis of one of the greatest fears of instrument pilots – a vacuum system failure while in the clouds.

The vacuum system sucked air across the mechanical gyros and started them turning. The turning gyro provided the rigidity in space required operate the attitude gyro and the directional gyro. If the vacuum pump failed, the air would stop flowing, and then the gyros would coast to a stop. As the gyros coasted, rigidity would fail slowly, and this easily fooled the pilot’s understanding of the aircraft’s attitude. Many fatal accidents have been the result.

The laser ring gyro had been used as part of an inertial navigation system (INS) during its application with the airlines, the military, and the Hubble Space Telescope. This inclusion with the navigation function made the cost of the laser ring gyro prohibitive for general aviation. Then came the key breakthrough: The laser ring gyro was separated from the navigation function, and the attitude heading reference system (AHRS) was born. The AHRS only attempts to estimate the aircraft’s attitude: roll, yaw, and pitch. AHRS does not estimate velocity, position, and altitude, as would be the case with the INS. The cost of the laser ring gyro dropped, and together with computer generated images, the AHRS made a primary flight display (PFD) possible for civilian pilot use in training. The age of round “steam gauges” was done. The age of the glass cockpit had begun.

Global positioning system

In 1991, Bernard Shaw and Peter Arnett, reporting from the al-Rashid Hotel in Baghdad for CNN, gave the world its first account of the use of the GPS. They reported on the initial bombing that used satellite-guided cruise missiles and “illuminated the night sky.” The original GPS, which had been under development by the U.S. Department of Defense for the previous 18 years, had a scrambled signal so that it could only be used by U.S. military forces. Ultimately, the signal was made available for worldwide civilian use.

The concept of GPS is also quite simple and old-fashioned. GPS calculates position the same way sailing ship captains have done for 400 years – using a time, speed and distance problem. But GPS keeps much better time than the Harrison Sea Clock of 1736 did. The GPS uses an atomic clock. The atomic clock is capable of counting the rapid and dependable cycles of radiation coming from the cesium-133 atom and translating that into intervals of time that are many fractions of a second in duration. The time it takes for a signal, traveling at the speed of light, to complete the distance between a GPS Navistar satellite and a GPS device can be calculated just like a student pilot with an E-6B flight computer calculates ground speed.

If you know the speed of something, and if you can count time, you can determine distance. What once was a military secret is now as commonplace as a phone – in fact, GPS is probably on your phone. The breakthrough: We now always know where we are without paper charts, plotters and guesswork.

February 2000

The last piece of the puzzle that triggered the shift and enabled a revolution in general aviation was completed in February 2000. Before 2000, humankind actually had a more accurate map of the surface of Venus than of the surface of Earth. The unmanned Magellan spacecraft was launched in 1989 and entered orbit around Venus a year later.

Venus is shrouded in clouds, so the surface of Venus had never been seen before. To peer through the clouds, Magellan spent the next four years aiming a downward-facing radar toward the surface and bouncing back images of the terrain below. Radio contact with Magellan was lost in October of 1994, but not before it sent back detailed maps of 98% of Venus. It was later that somebody figured out that we should do the same for Earth. On February 11, 2000, Space Shuttle Endeavor launched on an 11-day radar mapping mission of planet Earth.

The Shuttle Radar Topography Mission (SRTM) used two radar antennas, one inside the shuttle’s cargo bay and the other on the end of a 200-foot arm that extended out from the cargo bay to capture the high-resolution digital topographic database of 80% of Earth’s landmass. Not until the year 2000 did we have a really good look at ourselves.

By 2002, all the components converged: AHRS could give us an affordable computer screen-sized image of an airplane’s attitude, GPS could tell us exactly where we were located over the Earth, and SRTM gave us the view of what we were flying over. This launched the spin-off capabilities of moving maps, coupled autopilots, heads-up displays, ADS-B and synthetic vision. And all this was taking place when light airplanes were being built again for the first time since the invention of the cell phone, laptops, and high-definition television. It was a perfect storm – a perfect storm of opportunity and dread for general aviation and flight safety.

Information management

For years, pilots in flight training were taught to set up their cockpit “like a little office” before they would set out on a solo cross-country flight. Everything you needed, such as charts, navigation log, frequencies, pencil, clock, plotter, and manual flight computer, had to be within reach of the pilot seat. If you left anything in your flight bag and threw the bag in the back, it was the same as leaving it on the ground. Students were taught to use a clipboard with multiple clips and a pencil on a string.

While on the flight, they would have to be everything – pilot, navigator, weather forecaster, and mechanic – so they had to be ready. The progress of the flight would be tracked by spotting landmarks on the ground that had been designated as checkpoints on a paper chart. The ground speed was calculated by timing the intervals between those checkpoints. With the ground-speed information, it was possible to adjust the arrival time if needed and estimate the fuel remaining in the tanks. The wind-correction angle was arrived at using the wind face of the E-6B and by “eyeballing” it.

The only connection to the outside world would be the radio. The “crew” would be anyone the pilot could talk to on the radio, but those people would not be able to help the pilot with basic navigation. The pilot might get some weather information on the radio from a flight service station, but usually that was very scant, and the pilot, already with their hands full, had little time to digest it. It all seems so old and crude now. It must sound like retelling how Columbus navigated to the new world to today’s student pilots. But that was the way pilot training was up until the year 2000.

Now, all those charts are on an iPad. Now, the onboard computer database can tell you exactly what time the sun will set this afternoon at the airport in Merced, California. That might be important new if you were flying behind schedule to Merced and you were not current for night flight – but of little interest when flying a GPS approach into Murfreesboro, Tennessee. Thus pilots must learn to manage an overload of information. Pilots must be able to pick out the information bits that are important at a particular point in time and prioritize the available information into safe decisions. Pilots before 2002 never had enough information and always needed more. Pilots after 2002 have more than is needed and must determine what to keep and what to throw out. We went from famine to feast overnight.

To learn more about the potential technology-shift accidents that resulted and how to “train out” these accidents before they happen, I recommend picking up a copy of Paul A. Craig’s book titled The Killing Zone – How and Why Pilots Die to continue where this post ends.

Please comment. I love to hear from my readers.  Thanks again for coming along for this ride, you make my work worthwhile.

Categories: Interest


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