Top 50 Navigation Innovations

From paper charts to satellites in space, Flying's Top 50 Navigation Innovations counts down to the single most noteworthy navigation innovation of all time.

50. Bonfires It took remarkable courage to fly the early airmail routes in open biplanes in the years right after World War I. The fleet of de Havilland D.H. 4s used for such duty were known as “flying coffins” because of their poor safety record. Eighteen pilots lost their lives between May 1919 and the end of 1920 flying over the Allegheny Mountains from New York to Chicago. The federal government was about to scrub the airmail service, prompting the head of the Post Office Air Service, Otto Prager, to stage a dramatic cross-country flight that would impress Congress, the president and the public. In March 1921, four D.H. 4s took off across the country to deliver mail from New York to San Francisco in record time. The stunt succeeded, delivering the mail in an astounding 33 hours and 20 minutes and saving the air service. But the pilots who flew the route couldn’t have done it without the predominant navigation aid of the day: bonfires tended along the route to guide the airmail planes at night and in low visibility. (Photo courtesy of Silvan Smith) Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

49. Celestial Navigation For thousands of years, travelers venturing out beyond the realm of identifiable landmarks have called upon the assistance of celestial bodies to help them find their way. By measuring the angles between their visual horizon and those celestial bodies above, sailors, landgoers and, eventually, pilots could compare those figures to the known location of those stars, planets or the moon at a given time, and thus deduce their location on Earth. The method relied on spherical trigonometry and astronomical know-how, but demanded little in terms of physical equipment, requiring, at the very least, the help of a sextant, an almanac and a timepiece. While celestial navigation left plenty of room for human error, it became a more accurate practice over time, helping pilots take aviation to new heights during everything from the dawn of aviation to the Gemini space missions. Lest you think celestial nav is an antique discipline, you should be aware that the United States Air Force Academy conducted courses in celestial navigation well into the 1990s, though graduating pilots were no longer given a sextant to carry in their flight kit. (Photo courtesy of Mike Lewinski) Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

48. Microwave Landing System (MLS) The microwave landing system was a big idea that never made it, though why it didn’t is more an accident of history than an indictment of the technology. MLS uses an array of microwave signals to transmit a 3-D course to MLS receiver-equipped aircraft approaching the airport. Unlike ILS, MLS is easy and relatively cost-effective to install, and it can handle numerous arrivals from different points, unlike ILS, which relies on a single localizer course to funnel all approaching aircraft. While MLS looked primed to take off in the early ’90s — it was developed in the early 1970s — that never happened, as GPS/WAAS came on the scene with its promise of precision approaches with absolutely no infrastructure, a promise it has since fulfilled. There are today no MLS approaches in the United States and just a few around the world. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

47. RMI (Radio Magnetic Indicator) Before the dawn of GPS and glass cockpits, the process of determining your location while on an NDB or VOR approach proved a sometimes-cumbersome process. The introduction of radio magnetic indicators, however, provided a powerful boost for situational awareness during such a time-intensive phase of flight. By supplying an aircraft’s heading in conjunction with its relative bearing to an NDB or VOR radial, the RMI essentially combined two instruments into a single unit, negating the need for pilots to digest readings from multiple sections of the panel and link the relationship between them. Thanks to the compass card technology behind RMIs, pilots could get all this information in one spot, without having to do the math in between. Due to their relatively high cost, RMIs were at first more heavily used in airliners and other high-end aircraft than in smaller airplanes, but over time their cost came down and they wound up leaving their mark on an increasingly user-friendly navigational scene. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

46. IFR Databases Even the greatest GPS receiver or flight management system in the world isn’t worth much without an internal IFR database. Chock full of the necessary fixes, approaches, routes, departures, arrivals and all the other coded information that allows us to fly from point A to B and on to point C with the press of a few buttons, the IFR database transformed how pilots fly. It’s safe to assume that Capt. Elrey Jeppesen never could have imagined that the aeronautical chart company he founded in 1934 would go on to pioneer IFR database technology, but that’s exactly what happened in the early 1970s with the introduction of Jeppesen NavData for the then-new flight management systems being installed in Boeing airliners. Today, we take the IFR nav database almost for granted — unless it’s expired, that is. We have Capt. Jepp to thank for that, as he laid the decades’ worth of groundwork needed to make Jeppesen NavData a reality. Related: - Jeppesen, Garmin Team To Cut Cost of Data Updates
- IFR Flight Prep: A Whole New Game Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

45. Barn Top Markings Little more than two decades after Orville Wright’s 12-second flight changed the world, air travel had already become a viable means of getting from one town to the next. While widespread standardized charting had not yet materialized, pilots created other means of finding their way, including the use of large visual markings painted atop the roofs of barns, train stations, skyscrapers and other buildings. The markings varied in size and form, but often featured the names of nearby towns, airports, directional arrows to guide low-flying pilots toward them and, in later cases, lat and long info. In 1926, the U.S. government commissioned a number of organizations to increase the number of markings, with the desire to have at least one every 15 miles. To that end, some 13,000 markings graced the tops of buildings before the United States’ entrance into World War II, a conflict that triggered the eradication of the navigational aids near the coasts, due to fears that they would aid in enemy navigation were the United States ever invaded. In the following years, the growing use of charts and radio navigation eliminated the need for the visual signals. (Photo courtesy of Missouri State Archives) Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

44. Radar Vectors While pilots are not always happy about “getting vectored” as a traffic separation tool, we know that vectoring technology, in the grand scheme, is our friend. Using radar, controllers can direct traffic to fly in any direction their hearts desire or, more often, that regulations dictate in order to keep traffic legally separated, to sequence aircraft for arrival, and to direct airplanes onto the final approach course of an instrument approach. While radar initially began as a tool used in terminal areas, the extensive benefits of the technology soon became evident, prompting its widespread implementation at en route air traffic control facilities throughout the nation during the 1960s. While giant rotating radar installations are expensive and maintenance intensive, the in-cockpit equipment requirements are minimal — pilots need only a transponder, and if primary radar is available, not even that. Thanks to their convenience and efficiency, radar vectors remain one of the most widely used tools by controllers in today’s national airspace system. Related: - Fly VFR like IFR Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

43. Velocity Vector A velocity vector, also called a flight-path vector, or FPV, shows where the airplane is actually going and is the sum of all the forces acting on the airplane. The velocity vector takes into consideration not only the heading and winds, but also the angle of attack of the airplane to determine its path, taking the guesswork out of navigation. Velocity vectors have traditionally been used on head-up display systems in the military, but are becoming more common in general aviation airplanes with the recent introduction of synthetic-vision displays, which have become increasingly available with integrated flight decks. A symbol that looks like a miniature airplane cross section — a circle with lines on either side — indicates the FPV, and all the pilot needs to do is place the symbol over the targeted location on the screen, and voila! That’s where the airplane will go. Related: - EVS and SVS: The future of your PFD? Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

42. Lighted Beacon Airways The limitation of bonfires as a form of navigation became evident during an early transcontinental airmail flight on Nov. 22, 1921. One of the participating pilots, Jack Knight, flew through the night, but as he approached Iowa City the bonfire crew had gone home. An airport watchman who heard the airplane lit a flare, and Knight landed successfully just as his fuel ran out. The flight led to Congress approving a $1.25 million appropriation for lighted airways. The first route was established in 1923 from Chicago to Cheyenne, Wyoming, with 289 beacons and 39 lighted landing fields along the route. Along the airways, 53-foot towers with rotating beacons were generally located at 10-mile intervals (they were closer in the mountains and farther apart in the plains) with course lights below flashing an identifying Morse code. This form of navigation was limited by weather conditions, and the lighted airways were later replaced with radio navigation. However, lighted beacon airways are still in operation in the mountains in Montana. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

41. Great Circle Navigation In the early days of aviation, pilots took a cue from the mariners who preceded them and developed their routes with the help of great circle navigation. Thinking of the Earth as a perfect sphere, pilots were able to determine the shortest distance between two points by connecting the dots on a globe and theoretically slicing the Earth through the center to create a great circle. To travel along that circle, however, pilots would be forced to make continual heading corrections to make sure they stayed on course. To solve that problem, they instead followed a rhumb line, which was a segmented part of the circle that intersected meridians at a consistent angle, making it much easier for pilots to set and follow a constant heading. Not only did great circle navigation help Charles Lindbergh cross the Atlantic in 1927, but it set the fundamental basis for the routes we use today to traverse the globe. Related: - Jumpseat: Blue Moon
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40. The DG (Directional Gyro) Thanks to the invention of the artificial horizon and the turn coordinator, early pilots could tell when they were turning and where they were flying in relation to the horizon. What they didn’t know, because magnetic compasses were so finicky and hard to use, was exactly what direction they were headed — until the directional gyro, frequently called the “heading indicator,” came along, that is. Based on the same principles used to create the earliest nautical autopilots, the directional gyro relies on a small disk rotating at high velocity to indicate directional changes of an aircraft in flight. As the aircraft turns this way and that, the spinning disk retains its original orientation, allowing it to provide an accurate heading and making it less vulnerable to the directional errors that continually plague a magnetic compass in flight. To maintain its accuracy, all the instrument requires is the occasional fix of slight drift error. Thanks to that reliability and consistency, the directional gyro provided a critical aid to pilots flying by reference to instruments, an aid that has proved its enduring value for decades since. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

39. Airport Beacons The ability to navigate to and locate airports at night was first accomplished with bonfires and flares in the early days of flight. This primitive method started to be replaced in the 1920s, when rotating beacons identified airports as part of a growing lighted airway system in the United States. Rotating white lights were placed at certain navigation locations and at airports along the airways. While lighted airways have been replaced by more sophisticated navigation aids, rotating beacons are still used at airports that allow night operations. Alternating colors are used to distinguish between civil land airports (green and white), seaports (yellow and white), heliports (green, yellow and white) and military airports (green, white and white). Airport beacons are also activated when the weather conditions at the airport are below the minimums for visual flight rules. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

38. Chart Subscriptions For obvious reasons, pilots need current charts, and while government chart-making organizations regularly updated their materials, it was again Jeppesen that established the chart subscription model. The company’s original plan was to provide its pilot-customers with updates on the same 28-day cycle as used by aviation chart data organizations around the globe. The result was the subscription update. Pilots with a Jepp subscription would simply get new charts with updated information, which they would then update in their chart binders. Jeppesen’s method of naming and numbering procedures made the update process, if not quick, then at least comprehensible. In the mid-1990s, the company launched JeppView, a digital product that took the pain and fuss out of updating. A few years later, Jeppesen introduced Electronic Flight Bag access, and numerous manufacturers of cockpit-mounted multifunction displays made use of Jeppesen approach charts for inflight display of instrument procedures, updated through database subscriptions. Today, a few other companies provide navigation database updates, including some, like Seattle Avionics, that refine and disseminate government nav data to app and EFB developers. Related: - Jumpseat: My New Antique
- iPad App Review: Jeppesen Mobile FliteDeck
- Aspen Announces Geo-referenced Chart Feature
- Jeppesen, Garmin Team To Cut Cost of Data Updates
- Killer App: Jeppesen Mobile TC Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

37. Omega Initially developed and tested in the early ’60s as a means of oceanic naval navigation, Omega was one of the first systems to take navigation coverage from the regional level to the global scale. The hyperbolic radionavigation system determined a vehicle’s location by measuring changes in the reception of low-frequency signals as it made its journey. The system relied on eight fixed transmitting stations around the world, which worked to provide an object’s location within an accuracy of 1.5 to 4 miles. To utilize the system, a pilot had to input his aircraft’s location before takeoff so the system could compare that location with the position of the transmitting stations. Omega didn’t become fully operational until the early 1980s and was shortly overtaken by the more effective Loran system and eventually GPS, but nonetheless paved the way in opening up navigation to new accuracies and new worldwide distances. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

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**36. The Coupled Autopilot
** The advent of autoflight came only 10 years after the Wright brothers’ first powered flight, though for decades autopilots were tools not directly related to navigation but to airplane control. Sperry Corporation, now a part of Honeywell, pioneered virtually all autopilot development for decades and throughout the 1930s continued to improve upon the state of the art. By the early 1940s, in support of the war effort, Sperry had developed autopilot coupling, a technique that allowed the system to not only keep the airplane on pilot-established headings and rates of climb or descent but also to tie it to radio navigation courses. Through the course of continual development, this led over time to the eventual development of today’s fully coupled autopilots, which can fly entire three-dimensional flight plans with curved segments and even missed approaches. Today, modern navigation and autoflight are two sides of a technological coin. Related: - Learn from the Autopilot
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35. Loran “Loran,” which stands for LOng RAnge Navigation, was a concept developed by British scientists during World War II and improved by scientists at MIT shortly thereafter, giving it a range of 1,200 nm and an accuracy of a few hundred feet. Loran receivers were popular in general aviation for a short time before more accurate GPS receivers supplanted them. Loran uses ground-based stations that transmit low-frequency signals. The timing between known stations (mounted on tall towers) is used to calculate the position of the receiver, carried on the airplane or ship. Loran has a few noteworthy advantages over GPS. In addition to being an independent GPS backup, its high-power, low-frequency signal is virtually unjammable, and Loran is far less expensive to maintain than satellite-based nav like GPS. Despite this, Loran C, the latest fielded version, was shut down by the United States in 2010. An improved version, eLoran, is under private development and heralded as a critical GPS backup, though it has not been adopted yet by the United States or widely elsewhere. Related: - Loran C Signals to Go Silent Next Month Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

34. IFR En Route Charting Like many aviation charting products, the evolution of IFR en route charts was a gradual process, as these specific charts borrowed heavily from mapping, data and symbology that had been used in previous products. At the same time, the concept behind IFR en routes, conceived during the creation of the first en route radio navaids, is brilliant: Put on the charts only that information that the instrument pilot needs to see and nothing else. The underlying philosophy — that all you need are the gauges, nav radios and a good map to get you to the approach — is central to IFR flight. Interestingly, the elegance and simplicity of paper en routes also led to instrument pilots using them exclusively, even for VFR flying, and led then to the creation “de-clutter” technology on moving maps that lets pilots get rid of extraneous mapping details on their electronic moving map displays. Today, pilots can get IFR en route charts in electronic form from any number of app developers and makers of electronic flight bags. Related: - IFR Insight: Planning for the Arrival
- IFR Flight Prep: A Whole New Game Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

33. International Coverage With the jet age, airline travel had become a truly international affair, and it was critical for operators to have not only current and accurate charts for their home country but for everywhere they flew. Charting pioneer Jeppesen again saw an opportunity and began to expand its coverage areas, eventually expanding to serve the entire world, allowing one-stop shopping for its thousands of airline customers. Jeppesen also established industry standards for aeronautical information, so pilots could depend on common symbology and presentation on all of their charts. While Jeppesen dominated in international charting, international flight-planning services, another critical component of international navigation services, saw offerings from Universal, Honeywell with its Global Data Center, and Rockwell Collins with its Ascend service, all of which provide extensive flight planning, trip planning, international coordination, destination services and more, giving long-range flyers, both of commercial and business aircraft, the tools to navigate the airways the world over. Related: - ForeFlight Expands Into Canada
- SkyVector Unveils Worldwide Charts
- Garmin Expands Euro Charts for Aera GPS Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

32. NDB/ADF When they were adopted half a century ago, nondirectional beacons (NDBs) were smart technology. They were cheap to install, had good range and were particularly good over water. The technology was limited in a number of critical ways, however. An NDB approach is, as the name says, nondirectional. There’s no course or distance information, as there is with VOR/DME, so pilots have to figure wind correction into the NDB solution, use other means of determining their distance from the station (like timing or intersecting radials of a VOR) and make do with very high MDAs. Improved in-cockpit displays, RMIs in particular, helped a little, but pilots generally dismissed NDB approaches as little more than “airport finders.” Today NDBs (in the form of marker beacons), long-range navaids and, to a limited extent, primary approach navaids, still exist, though they have been made largely obsolete by GPS. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

31. IFR GPS receivers Garmin introduced the first IFR GPS receiver, the GPS-155, in 1994, five years after the GPS constellation became operational and (not coincidentally) the same number of years after two former Bendix/King engineers, Gary Burrell and Min Kao (the genesis of the name, Gar/Min!), founded the company in Lenexa, Kansas. Four years later, in 1998, Garmin turned the aviation world upside down by introducing the GNS 430, a panel-mounted IFR GPS receiver with a color moving map and built-in nav and comm radios. It’s hard to think of any single advance in air navigation that changed the way pilots fly more than the IFR GPS, and the GNS 430 played a big part in ushering in that new era, capturing, along with the larger, follow-on GNS 530, a huge share of the market. Today, a host of avionics makers offer IFR GPS receivers to fit every budget. Besides providing GPS departure, arrival, vertical nav and approach capability, the technology allows you to file direct and fly a straight line as far as ATC and your fuel reserves will allow. Related: - Garmin Navigators: Back to the Beginning
- Bidding Farewell to the Garmin GNS Line Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

30. TAWS While pilots don’t often think of terrain awareness as being a navigation utility, it is arguably one of the most important advances in navigation technology since the dawn of aviation. After all, going direct and, hence, off airways, is only a good thing if you don’t run into anything along the way. Terrain avoidance technology is a recent development, which started with radar-altimeter-based ground proximity warning systems. These were “dumb” systems that could look down and warn if the ground began to rise up, but they didn’t know if rapidly rising terrain lay ahead. The development of worldwide terrain databases and “enhanced ground prox” products by Honeywell (AlliedSignal at the time) ushered in an era of smart terrain avoidance that has nearly eliminated controlled flight into terrain accidents of commercial aircraft. Today, TAWS systems are in most commercial aircraft, and prices have come down to the point that powerful TAWS products are available even on cheap portable tablets. Related: - Garmin Gets Okay for TAWS
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29. Approach Lighting Developed in the 1940s, approach lighting systems help guide pilots horizontally and vertically to the runway and are particularly helpful when transitioning from instrument conditions to visual flight for landing. Horizontal guidance is generally provided by patterned rows of lights extending as far as 2,400 feet from the runway threshold. The most common system is the Medium Intensity Approach Lighting System with Runway Alignment Indicator Lights (MALSR), with about 900 installations in the national airspace system. Sequenced flashing lights in the centerline called Runway Alignment Indicator Lights (RAIL), sometimes referred to as the “rabbit,” help guide the pilot to the centerline. Vertical guidance lighting systems are arranged such that the pilot sees a red light when below the glidepath and white light when above it. The Precision Approach Path Indicator is the most common with a row of four lights. The FAA is in the process of replacing incandescent bulbs used in ALS systems with more reliable LED lights. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

28. RNP While not well understood by most pilots, RNP, which stands for “required navigation performance,” is an increasingly important navigation technology. RNP isn’t a hardware standard but a performance standard that in essence guarantees that an airplane can fly procedures to within certain levels of accuracy while monitoring its own performance. The naming of RNP standards is based on margins of nautical miles or fractions thereof. RNP 10, for example, has an accuracy of 10 miles, while RNP .1 is good down to a tenth of a mile. The standards are for three dimensions, which mean that RNP-equipped aircraft can fly procedures both laterally and vertically; this includes curved approaches. Using RNP, airlines — Alaska Airlines pioneered the use of RNP approaches into difficult airports in its home state — can craft special procedures allowing access to airports nestled in mountainous terrain or gain preferred routing into airports in congested airspace. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

27. WAAS/LPV Approaches While GPS breathed new life into the concept of area navigation, it wasn’t until the introduction of WAAS that satellite navigation fulfilled its promise. The FAA’s wide area augmentation system provides additional accuracy and integrity to GPS, allowing for tighter course-keeping capability. The granddaddy of all WAAS-based navigation improvements is LPV, which stands for lateral precision with vertical guidance. It’s a mouthful, but what WAAS LPV provides is a set of RNAV GPS approach minimums that match the capability of many Cat I ILS approaches, down to a 200-foot decision height and half-mile visibility. Today, WAAS LPV approaches are available at more than 1,500 airports comprising well over 3,000 individual approaches. What’s best about WAAS LPV from the FAA’s and airport operators’ points of view is there is no need to install and maintain expensive ground equipment. Pilots love it because all they need is an IFR-certified GPS receiver with WAAS capability and something to display it on and they’re in business. (Photo courtesy of Науменко Егор) Related: - How Do You Fly an LPV Approach?
- WAAS–Based Approaches Now Outnumber ILS's Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

26. GPS Overlays In the early 1990s, not long after the use of GPS was established in general aviation airplanes, the potential for more accurate instrument approaches was realized. An easy way to implement GPS approaches was to simply overlay them over already established non-precision approaches. Course guidance for these approaches was provided through instrument-approved GPS systems. The addition of “or GPS” was added to the title of thousands of VOR, VOR/DME and NDB approaches indicating that they were approved for use with a GPS receiver. Many of these approaches still exist today. While lower minimum altitudes were not allowed with these early GPS approaches, GPS overlays provided much clearer position awareness than their predecessors and they validated the use of the new technology for terminal approach procedures, which allowed GPS to be quickly implemented into the system. Related: - Keeping Track of Your Altitude
- GPS 10 Years Later
- Be Prepared for the Missed Approach Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

25. HF (High Frequency Radio) Charles Lindbergh crossed the Atlantic Ocean without HF, but aviators who make the journey today along the North Atlantic Tracks need to have a way to stay in touch with ATC out over that lonely body of water. Shortwave HF radio has global coverage, making it perfect for long-distance flights over large bodies of water or uninhabited regions. Besides talking with ATC, Arinc provides oceanic aeronautical services over HF radio to assist with ground and flight activities, relay messages to dispatch, and deliver position reports. While HF was extremely important during its early use, these days there are other ways to keep in touch when far from home, including the global Inmarsat and Iridium satellite networks, as well as FANS 1/A (future air navigation service), which provides datalink ATC communications over the Atlantic and Pacific oceans, all but eliminating the need for long-range HF radio communication. Related: - Oceanic Airspace
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24. Whiskey Compass The liquid-filled or wet compass, commonly referred to in aviation as a “whiskey compass,” is a device that pilots use to determine the airplane’s approximate heading. It was a critical component of air navigation for the first many decades of flight. A 300-plus-year-old instrument developed first for ships, the wet compass damps the movement of the mechanism and protects the movement from harm. Among its many problems, the wet compass is a backward affair. The part that is pointing south is labeled “north” and the part that is trailing toward the north says “south,” and when it turns, it does so only after false starts and stops. Even “north” and “south” are mere starting points, giving you your magnetic and not your true heading; corrections are made based on local magnetic deviation. There are turning errors as well, lead and lag errors, and whiskey compasses can be thrown off by magnetic fields in the cockpit. Despite their inaccuracies and obsolescence, the FARs still require these instruments. Related: - Flying Lessons: Technology Tales
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23. Runway Lighting Runway lights first appeared in the early 1930s as a means for pilots to more easily identify the actual runway area. In those days, burning flares were used to outline the edges of the runways, which is why runway lights were also referred to as flare paths. Today’s runway lighting systems are not only more sophisticated but also more reliable than the old flares. White lights line the edges, red lights are seen at the departing end, and green lights indicate the approach end of the runway. Yellow lights mark the edges of the final 2,000 feet or half of the runway (whichever is less) at airports that have instrument approaches. Some runways with precision approaches have additional centerline, touchdown zone, land and hold short and taxiway lead-on lights, to name a few. There are high-, medium- and low-intensity runway lights (HIRL, MIRL and LIRL), and the pilot can often select the desired intensity by clicking the push-to-talk button a set number of times. (Photo courtesy of Craig Mills) Related: - Winter Weather's Dirty Half-Dozen
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22. Government Charting While the history of powered flight goes back to 1903, it would be two decades before the advent of official aeronautical charts of any kind, and until then pilots relied on handmade maps, road, topographical and maritime charts. The first official aviation-specific charts were military ones consisting of airport diagrams and topographical “strip maps” 80 miles wide for commonly flown Army routes. Aviation-themed road maps by Rand McNally were popular, as were maps from aerial photographs. By 1935, the first sectional maps appeared, and mapping standards were being established. World War II created a need for worldwide charting, and a number of now-familiar formats were born, including the world aeronautical chart, planning charts and approach charts, formats that were used around the world. Today, aeronautical charting has moved heavily into the digital realm, and the U.S. government (along with dozens of other governments and private entities around the world) supplies not only paper-based charts but also the data from which private companies create a multitude of navigation solutions. Related: - Garmin 696 With Geo-Referenced Approach Charts
- WingX Pro Adds New Features Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

21. Jeppesen Charting Although aviation-specific charting had been around for a few years before Elrey Jeppesen started jotting down notes in his little books while on his airmail flights, earlier aerial charts suffered from spotty coverage and sparse data. It was for simple self-preservation that Jeppesen began taking note of important topographical, runway, weather and airport information while flying the mail. Once word spread of Capt. Jepp’s charts, requests from fellow aviators started pouring in. In 1934, he established a company selling his “Airway Manuals” for $10 each. Jeppesen went on to develop the first comprehensive set of instrument flying charts for private, commercial and military customers. In 1947 the company worked with the FAA to develop a set of standards and procedures for instrument approaches, which are still in use today. Although a number of other major players have entered the electronic chart market since those early days, “Jepps” are still recognized as the gold standard in paper charts and the foundation of a company that has become a global supplier of navigation data from charts to navigation databases and even to total tablet-based navigation solutions. Related: - Jeppesen Reinvents the VFR Chart
- EASA Approves Jepp iPad Chart Apps Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

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20. Four-Course Range Unless you’re an old-timer in aviation, you might have no idea what the term “four-course range” is or that it even pertains to navigation. The precursor to VOR, the four-course range was the predominant navigation system used by pilots in the 1930s and 1940s. Pilots navigated by listening to Morse code signals that would tell them to fly left or right to join a specific airway. The tone would go solid when they were on course. As VORs gained popularity, the four-course range radio station network gradually was phased out. It disappeared for good in the 1970s. While it might seem like an antiquated way to navigate, four-course range was downright high-tech compared with the method it replaced. Before radio stations were erected, airmail pilots flying after World War I navigated across the country by flying between light beacons and, before that, bonfires along their route. (Photo courtesy of the Airways Museum & Civil Aviation Historical Society) Related: - Unusual Attitudes: Weather or Not
- Seeing Clearly Through Glass Cockpits Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

19. Terminal Radar Initially known as RAdio Detection And Ranging Equipment, terminal radar provides critical safety functions for separating fast-moving aircraft and is still very much in use today. Radar was originally a product of British development during World War II and first became operational at American airports in the early 1950s. The technology works by sending out electromagnetic waves from an antenna, which then partially bounce off airplanes in the air as they encounter them before returning to a receiver. As the remnants of the original electromagnetic waves return, their strength, along with the amount of time it took for them to go from the transmitter to the receiver, are used to determine an aircraft’s location. The system provides an invaluable visual picture to air traffic controllers, who can see where aircraft are located as they approach and depart busy airports. What initially began as terminal radar would soon expand to much larger expanses of airspace, providing vital information that made air travel both easier and safer. Related: - Flying VFR Like IFR Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

18. RNAV (Area Navigation) Area navigation, or RNAV for short, is simply a method for navigating from any one point to any other without those points being defined by navaids. Today’s GPS is an example of RNAV technology. But it is not the first. Area nav was first developed in the 1960s by the FAA, and RNAV routes were published, giving pilots with the proper gear an approved way to fly IFR off airways. The first RNAV receivers were navigators that derived a direct course using lat/long and radial and distance from a VORTAC or VOR/DME. Using triangulation, an RNAV navigation unit allows a properly equipped aircraft to safely and accurately fly IFR routes that otherwise wouldn’t have been possible. Users of units like the Bendix/King KNS-81 could see groundspeed, distance and time from the station and could even create user waypoints, known intriguingly as “phantom waypoints” or “phantom stations,” though defining them took a bit of doing, as the pilot needs to enter a bearing and distance off a known VOR. Such RNAV units didn’t have a long life span, as Loran and, later, GPS took their place, as they provided greater ease of use, better long-range nav capability and more features. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

17. The Chronograph There’s a good reason why the pilot’s watch is the status symbol of serious aviators everywhere. Since the early days, time has been used by pilots as a vital aid to navigation. The precise measurement of time is how we know that the Wright brothers’ famous flight at Kitty Hawk on Dec. 17, 1903, lasted 59 seconds. An error in timekeeping probably had something to do with the disappearance of Amelia Earhart and navigator Fred Noonan in July 1937. And not surprisingly, the entire GPS constellation that we use for primary navigation is one of the most precise forms of timekeeping ever devised. Even today, time is still important in fixing our position, determining the missed approach point on non-precision approaches and letting us keep tabs on how much fuel is left in the tanks, despite what the gauges might be reporting. And besides, a big honking pilot’s watch (think Chuck Yeager’s famous Rolex Submariner) just looks cool. Related: - Finally, Pilot Watches Designed Just for Women
- Flying Gift Guide: Breitling Transocean chronograph
- Hamilton Khaki Flight Timer Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

16. DME (Distance Measuring Equipment) First tested in the 1940s, distance-measuring equipment revolutionized a pilot’s ability to pinpoint his exact location in the air. While it has since been supplanted by GPS, DME’s accuracy and ease of use long remained unparalleled in the realm of navigation. The technology works by sending out a unique radio signal from an aircraft to a nearby ground receptor, which in turn sends the signal back to the DME. The equipment then uses the propagation delay to calculate the aircraft’s position, as well as its groundspeed and estimated time of arrival at the station. DME has advanced over the years, and today promises accuracy that can be within 0.1 nm in some cases and no less than 3 percent off in terms of total distance. While a boon for VFR pilots, the technology proved particularly useful to IFR pilots, providing invaluable information while on approach. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

15. Inertial Navigation Like much navigation technology, inertial navigation systems (INS) were first developed during wartime, specifically in the early years of World War II. Robert Goddard and Werner Von Braun both worked on systems to autonomously guide rockets, for atmospheric and suborbital flights, using basic gyroscopes for guidance. The early systems were only somewhat accurate, but as computing and gyroscopic technology improved, systems became far more accurate. Eventually, computing power progressed to the point that gimbal gyros were no longer needed, resulting in so-called “strapdown” sensors. Advancements in the math of guidance calculations were also key. By the 1950s, inertial navigation was introduced into intercontinental ballistic missiles and, within the decade, into long-range military and commercial aircraft, which would have to enter their starting position before a flight in order for the system to track their progress. INS units were somewhat unreliable (current ones much less so), but commercial aircraft were outfitted with multiple units in part for redundancy but more for increased accuracy, using averaging. By the early 1980s, the more accurate and reliable ring laser gyroscope replaced mechanical INS units. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

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14. Ring Laser Gyro Electromechanical inertial navigation systems (INS) with spinning gyros brought long-range nav into the jet age; solid-state ring laser gyros (RLGs) made inertial guidance common. The technology is right out of the space age: A pair of lasers rotating in opposite directions allow the system to sense microscopic changes in the airplane’s movement, which in turn allows the system to track the airplane’s movement very precisely. RLGs have several notable advantages over conventional inertial guidance systems. They are light in weight and they are remarkably reliable — they often outlast the life of the airframe, as they have no conventionally moving parts. Invented in the early 1960s, RLGs weren’t cheap or producible enough to be introduced for almost two decades. Still, they quickly took over the market. There are today tens of thousands of these units in service. While one might imagine that GPS and WAAS have made RLGs obsolete, that’s not the case; instead, state-of-the-art systems use GPS for improving the accuracy of the RLG system. Related: - The Real Glass Cockpit Question Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

13. iPad One of the greatest story lines of the march of navigation progress has been the democratization of safety technology with increasingly cheaper, more powerful and more widely available safety utilities. Nowhere has this progress been as visible as with the Apple iPad, the tablet that exploded in popularity only a few years ago both in the mass market and in aviation. Applications like ForeFlight and Jeppesen’s Mobile FlightDeck allow pilots to use their iPads as portable full-color primary flight displays, hooked up with GPS to track their progress over terrain-enabled moving maps, while displaying geo-referenced approach charts. If situational awareness is the holy grail of navigation, then the iPad and modern apps have given that ability to the masses of pilots. Related: - We Fly the iPad
- iPad Pilot Safety Alert
- Five Reasons Pilots 'Need' the New iPad
- iPad, avPad
- Pilots Give High Marks To ForeFlight 5.0 Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

12. VOR (VHF Omnidirectional Range) VOR easily ranks as one of the most important navigation technologies of all time. Its biggest contribution to aviation was in giving us our national “highway” system of Victor airways and jet airways. Deployed in the United States in 1946, the national network of fixed ground radio VOR beacons quickly became the air navigation standard around the world. The engineering behind VOR is quite ingenious: A VOR ground station sends out a master signal while a highly directional secondary signal that varies in phase 30 times a second is compared to the master. By comparing the secondary and master signals, the VOR receivers in our airplanes can determine bearing to the station, providing 360 pilot-selectable courses to and from a given station. Currently, there are around 3,000 VOR stations in use around the world. Related: - FAA Plans Major Reduction in VOR Coverage
- Garmin's New Take on VHF Radios Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

11. WAAS (Wide Area Augmentation System) While GPS has changed the way we navigate since its civilian advent some 25 years ago, the technology was limited in accuracy in part because of intentional degradation of the signal by the DoD (called “selective availability”) and by errors introduced by the signal passing through the atmosphere. WAAS (Wide Area Augmentation System) is a form of what has come to be known as Satellite-Based Augmentation System, or SBAS. It uses known sites to compare satellite signals and sends those corrections into space, where always-visible satellites share that correction information with users with WAAS-enabled GPS receivers. The result is accuracy that is many times better than GPS, around 3 feet laterally and 5 feet vertically. The takeaway: WAAS has enabled precision satellite-based approaches, allowing pilots to fly with great precision to thousands more runway ends than were previously served by ground-based precision approaches. Related: - Avidyne Launches IFD540 Touchscreen Navigator
- First Regional U.S. Passenger Airline Completes WAAS Flight
- WAAS Gets Solar Storm Protections Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

10. HSI (Horizontal Situation Indicator) The mechanical HSI uses a combination of instruments and indicators to give pilots a rough approximation in plain view of where they are in relationship to their course. The mechanical HSI, while somewhat antiquated by flat-panel standards, represents the pinnacle of mechanical flight instrumentation. While we refer to “electronic HSIs,” which mimic the workings of the “steam gauge” version, the term does a disservice to the ingenious Rube Goldberg complexity of the mechanical version. Central to the workings of the HSI are the heading indicator, the course deviation bar (which shows the course as input by the pilot), the deviation index (to show right or left of course) and the glideslope indicator (showing on, above or below the glideslope for the approach chosen). Perhaps the biggest benefit of using an HSI versus separate localizer/glideslope and heading indicators is that the instrument scan is simplified. The HSI is one-stop shopping for pertinent flight information. Related: - Bendix/King's low-cost electronic HSI Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

9. HUDs (Head-Up Displays) Head-up displays are just what they sound like: displays of critical flight information that pilots can look at on a see-through window while continuing to view the outside world ahead through the windscreen. HUDs have military aircraft origins dating back to World War II. They enhance situational awareness and eliminate pilot transition from head-down to head-up flying, thought to be a major risk factor when transitioning from instrument to visual reference on low approaches. The first HUDs for commercial aircraft use were developed during the 1970s in the form of Rockwell Collins’ Head-Up Guidance System (HGS), which combines a head-up display with a computer-driven display of flight information projected onto the glass, to give the pilot essential flight information and guidance that is “conformal” with the outside world throughout all phases of flight. A recent Flight Safety Foundation study found that nearly 70 percent of all takeoff and landing accidents could have had a more positive outcome with HGS technology. In recent years, tremendous advancements of HUD technology have been made, including the addition of synthetic and enhanced vision, and with new optical technology, it is now possible to bring HUD to smaller aircraft by eliminating the need for overhead projectors. Related: - Head-Up Displays Prevent Crashes
- WSJ Recognizes Rockwell Collins' HUD Innovation
- Going Direct: HUD vs. Combined Vision
- Google to Release Head-Up Glasses Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

8. Pilotage and Landmarks When airplanes were first made, the only way for pilots to navigate was to look outside and read the landscape to figure out their location and the direction in which to continue flying. This form of navigation is commonly known as pilotage. Before aeronautical charts became common, road maps were very useful tools for early pilots, who could use easily defined landmarks such as roads, rivers and railways to verify their position and navigate from one town to the next. Aeronautical charts made pilotage easier by differentiating various elevation levels by colors and topographical contour lines and by including landmarks such as water tanks, towers and power lines. But with the increasing use of GPS and moving map displays, where pilots can simply look at the screen to find out where they are and where they need to go, pilotage is quickly becoming a lost art. Related: - Practice Pilotage
- Getting From Here to There
- In The Clouds Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

7. Flat Panels (PFDs) A PFD, or primary flight display, is an electronic display of the typical flight parameters: attitude, airspeed, altitude, heading, vertical speed, turn-and-bank and yaw — information traditionally displayed by many separate analog instruments. A PFD condenses the flight information into one screen, using vertical tapes to show airspeed and altitude data, making it easier for the pilot to scan and interpret the information. Situational awareness, particularly during upset attitudes, is also enhanced by alerts (whether color coded or audio), which were not possible with round gauges. Navigation data is often also incorporated into the PFD, further enhancing situational awareness. Many modern PFDs also display a synthetic vision image of the outside environment overlaid by primary flight information. Basic PFDs were introduced in electronic flight information systems (EFIS) in commercial jets in the late 1970s. Today, airplanes from single-seat general aviation airplanes to massive commercial jetliners incorporate advanced PFDs into full glass cockpits, mostly using easy-to-read and reliable LCD screens. Related: - PFDs for Piston Airplanes: They're Here!
- MFD to PFD: Upgradable Displays for Homebuilts, LSAs From Garmin
- Bendix/King by Honeywell KFD 840
- EVS and SVS: The future of your PFD? Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

6. Flight Management System The Flight Management System changed the way pilots fly for the better by allowing for the input of entire flight plans, from departure to cruise to arrival, with automatic sequencing from one leg to the next. The first FMS was developed by Sperry Flight Systems (now part of Honeywell) to take advantage of the VOR/DME RNAV routes that started appearing in the 1970s. Sperry’s FMS for the Boeing 767 and 757 used a microprocessor and internal navigation database to compute aircraft position using a combination of RNAV and inertial reference system inputs. The Sperry FMS also offered a rudimentary form of VNAV, allowing for efficient climbs and descents. FMS grew in popularity in the 1980s as systems from Rockwell Collins, Honeywell and Universal Avionics hit the market. The popularity of GPS brought FMS capability down to the general aviation masses with low-cost products from Garmin, Avidyne, Bendix/King and others. Related: - Avidyne Entegra FMS900w
- Eclipse Receives Avio IFMS STC
- Flying Pro Line Fusion Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

5. AHRS/ADAHRS The attitude and heading reference system has revolutionized aviation. It’s what made Garmin G1000 and a lot of other amazing cockpit technology possible. Similar to the chip that is embedded in your smartphone to tell it which way is up and which way is sideways, an AHRS consists of micro sensors that provide heading, attitude and yaw information. The technology replaces traditional gyroscopic instruments with a single unit that provides incredible reliability and accuracy. The reliability part of the equation is a lifesaver, as digital “gyros” have all but eliminated a chronic cause of fatal accidents: loss of control following gyro failure (mostly due to vacuum pump failure) while IMC or at night. All modern integrated cockpits use AHRS technology, with the most sophisticated avionics adding an air-data computer to transform the AHRS to an ADAHRS. The air-data computer adds airspeed, altitude and OAT to the mix, digitizing those inputs. Not only are microelectromechanical (MEMS) AHRS systems super reliable, they’re affordable too, meaning everything from a multimillion-dollar bizjet to a budget LSA can fly with the technology. Related: - Garmin G1000 Primary Flight Display
- We Fly Dynon's New D1 Pocket Panel
- Garmin Adds Capability to G500, G600 Avionics Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

4. Handheld Navigators Probably the most significant improvement to the life of the hobbyist aviator since the introduction of the sectional chart in the 1930s, the handheld navigator has changed the safety picture for the better since its introduction 30 years ago. Early handheld navigators by Narco (HT-830), Bendix/King (KX 99) and Sporty’s (A300) used VHF signals for guidance. Soon, handheld Loran navigators by Northstar, Trimble and Garmin took over the market. The real breakthrough came in the early to mid-1990s, with the introduction of handheld moving map navigators with increasingly sophisticated features, including extensive databases with obstacles, terrain and procedures. Eventually, the true handheld became rare, as larger, more powerful and heftier portables, like Garmin’s GPSMap 696, came to the fore. Today handheld/portable navigators from a variety of manufacturers offer all of these features and traffic alerting and weather via ADS-B. With the advent of the iPad Mini and small-form-factor units from other manufacturers running sophisticated navigation apps, the age of the multifunction handheld navigator is upon us. Related: - Garmin GPSMap 696
- Bendix/King AV8OR Ace
- Flight Guide Introduces Traffic Alerts on iPad
- WingX Pro7 Synthetic Vision Comes to iPhone
- DeLorme Introduces inReach at AirVenture
- Garmin 796: We Flight It First Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

3. The Sectional The map that pilots of three generations grew up using for their basic navigation needs has looked largely the same for more than 70 years. It wasn’t the first topographical map widely produced, however; that was the 80-mile-wide “strip map,” which was introduced in the mid-1920s and covered popular military routings. The sectional, with a scale of 1:500,000, was launched in the early 1930s in an effort to cover the entire country, a mammoth effort that took more than seven years to complete. The benefits of the sectional chart are immense. Sectionals cover the entire country, so pilots can go where they want, and they feature a wealth of critical pilotage information, including cities, roads, railways, obstacles, visual waypoints, airspace limits and much more. They also give pilots critical, graphical and textual information on terrain height and minimum altitudes, as well as a wealth of airport information, from runway length to beacon information, all of it presented in an elegant, compact form that (usually) keeps the base map clearly visible. With the advent of digitally derived electronic maps, some fear the sectional’s days might be numbered. We’d be surprised. Related: - Unusual Attitudes: The Most Lost I Ever Got...
- Flying VFR Like IFR Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

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2. ILS (Instrument Landing System) It’s safe to say that commercial aviation could not have evolved as quickly as it did without ILS. First tested in the late 1920s, the precision instrument navigation concept made its real debut on Jan. 26, 1938, when a Pennsylvania Central Airlines Boeing 247 carrying a full load of passengers landed in a snowstorm in Pittsburgh using only the ILS signals for guidance. Since then, the ground-based instrument approach system has become the worldwide standard for bringing precision landing capability to airports throughout the world — even allowing properly equipped airplanes at airports with the most sophisticated Cat IIIc ILS capability to land in zero-zero weather conditions. Decision height of a more typical Cat I ILS is 200 feet, matching the capability of the latest satellite-based RNAV WAAS LPV approaches. Still, ILS remains the predominant precision instrument approach system in the world, allowing aircraft to safely reach their destinations, even in the poorest weather conditions. Related: - Sporty's SP-400
- The Short-Final Scud Run
- IFR Training Before the Rating Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

1. Global Positioning System (GPS) GPS, launched by the U.S. Department of Defense in 1972, is a technology that has revolutionized navigation not just for aviation but for the entire world as well. The system is architecturally simple, consisting of a constellation of satellites beaming their signals earthward, where they are monitored and adjusted if necessary. Our receivers get data from multiple satellites and figure out where we are based on the time the signals take to arrive. Our airplanes’ motion, including track and speed, are derived from the change in signals. GPS receivers became widespread in GA in the early 1990s. Since then, the technology has revolutionized how we fly, as companies have introduced sophisticated and affordable FMS systems based on GPS, allowing us to fly precise departure, en route, arrival, approach and missed approach procedures, with more capabilities to come. Related: - The Future of GPS in Aviation
-** GPS 10 Years Later** Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

The countdown doesn't have to end there. Check out Flying's Top 100 Airplanes list of the most influential aircraft of all time. Get exclusive online content like this delivered straight to your inbox by signing up for our free enewsletter.

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