Big Turn, Little Turns, Big Turn

DME arcs can be problematic for infrequent IFR flyers because, like holding patterns, arcs are not that common. A DME arc simply involves flying a circular course around a VOR/DME or VORTAC station (aka the station) at a specified distance, as if the aircraft were attached to the station on a string. Distance Measuring Equipment (DME) onboard the aircraft displays the distance from the station, though an certified GPS receiver can substitute for DME. It's easy to visualize a DME arc if you have a moving map and many late-model GA aircraft with fancy GPS units will fly a DME arc on autopilot while you sit back and watch. Without a moving map, joining an arc and tracking it accurately is more challenging, but it can be an enjoyable challenge. To that end, here are well-tested techniques for flying DME arcs, with or without GPS.

Anatomy of an Arc

The primary protected area around an arc is quite large (4 miles either side), but during a check ride or proficiency check pilots are expected to remain within one mile of the specified arc distance. Approaches incorporating a DME arc will have at least one minimum altitude to maintain, but altitude step-down fixes may be defined at particular radials along the arc.

DME arc Required Obstruction Clearance

Instructors and examiners often use the term right arc for an arc that keeps the station on the right wingtip of the aircraft, or left arc where the station stays on the left. Air traffic controllers usually refer to the general direction from the station where you will fly the arc, such as "arc Southeast." I've see at least one approach chart use the phrase arc clockwise. With calm winds, the station should remain directly off the wingtip. 

Remote, non-radar environments tend to have instrument approaches that use DME arcs because they help air traffic controllers who lack radar to maintain separation between aircraft. I saw a lot of approaches with DME arcs flying in the Caribbean for that very reason. Arcs also allow pilots to fly on their own navigation and get established on an approach course from en route environment. Consider the KLOL VOR/DME-A approach where you could be arriving via the Lovelock 219˚ or 054˚ radial, which happens to correspond to Victor 6.

Get Ready, Get Set ...

From a proficiency standpoint, flying a DME arc demonstrates your ability to plan and maintain orientation. Here are the basic steps.

1. Get established on the correct radial leading to the arc
2. Fly toward the arc
3. Turn approximately 90 degrees onto the arc
4. Maintain orientation as you track the arc
5. Depart the arc on the appropriate radial

More simply, flying a DME arc consists of:

• Big turn
• Several small turns
• One last, big turn

Consider the three basic navigation equipment set-ups found in most GA aircraft:

• Two CDIs (Course Deviation Indicators)
• One HSI (Horizontal Situation Indicator) and one CDI
• One HSI and one RMI (Radio Magnetic Indicator, G1000's call it a bearing pointer)

If you have two separate VOR receivers, set one to navigate to the arc and the other to the fly the radial or course you'll use to exit the arc. Early editions of the FAA's Instrument Flying Handbook cautioned the reader that DME arcs should not be attempted without an RMI/bearing pointer. That wording was removed several years ago.

Tune your DME to the correct station and identify the Morse code id, remembering that these identifiers are broadcast just twice a minute. Beware of DME units that automatically use a frequency tuned on one of your VOR receivers, sometimes called remote channelling, because it's easy to inadvertently get distance information from the wrong station. When possible, consider manually tuning and identify the DME frequency. If you're using an IFR-approved GPS receiver to fly an arc, you have several options covered later.

Fly to the Arc

In the example shown, the aircraft is Southbound, tracking inbound on the CEC 343 radial toward the 11 DME arc. You could set HSI course pointer is set to exit the arc on the I-CEC localizer with the course needle set to 114 degrees and set the #2 CDI is set to fly to navigate around the arc. In this example the aircraft is headed TO the station to join the arc, but other approaches may have you headed FROM the station to join an arc. The first common mistake pilots make is they lose track of the station's position relative to their aircraft. Don't let this happen.

Some folks get all wound up about whether the radial should be at the top or bottom of the CDI. Keep it simple: Set the top of the OBS so it matches the general direction you need to fly to join the arc, in this case 163 degrees. For an HSI, set the course pointer so the arrow generally points in the direction you need to fly.

The Big Turn


Do yourself a big favor and get established accurately on the arc from the get-go. If you blow through the arc by turning early or late, you've made a lot of work for yourself and you're more likely to bust the 1 mile tolerance. It may sound simple, but you need to clearly understand which way you'll be turning initially to join the arc.

Approach charts are oriented North-up and if you're a Track-up person, the chart representation can seem upside-down: There's no shame in rotating your approach chart to a track-up orientation to help you visualize your situation.

With the chart oriented Track-up, it's obvious you want to turn right and keep the station off the left wing. If you're flustered or task-saturated and you simply guess, you have a 50-50 chance of getting it right. You certainly want better odds than 50-50 when flying in the clouds, right?

Many pilots recall a DME arc as being a series of small turns, forgetting that the initial turn onto the arc requires a big turn - roughly a 90 degree turn. You need to turn right, so look at the heading at the three o'clock position of the HSI or CDI. In this case, you'll be turning to a rough heading of 253 degrees. If you have a heading bug, bug that heading.

A 90 degree change in heading at 3 degrees-per-second takes time so you must to lead the arc to account for the distance covered during the big turn. A rule of thumb is to use 5% of your groundspeed as the lead distance. Assuming your ground speed is 120 knots, start turning onto the arc about 0.6 miles before the arc or when the DME reads 11.6 miles. Depending on winds aloft, your groundspeed may differ significantly from your indicated airspeed, so select the groundspeed readout on your DME and pay attention to it. When your DME reads 11.6, make the big turn.

After the big turn, the course pointer points to station

Turn Ten, Twist Ten

Regardless of which way you turn to get on the arc, stay on the arc by making a series of small, strategic changes in heading while adjusting your OBS or HSI to track your progress. Let's say you are using an HSI to fly the arc, twist the OBS so that you just barely have a full-scale needle deflection in the direction you are flying. Not sure which way to twist the course pointer? It's really simple, same side safe:

1. Determine your current heading
2. Locate that heading on the OBS or HSI
3. Twist the OBS or HSI course pointer so the needle deflects on the same side of the CDI as where you found your current heading

Current heading on same side as course deviation bar = Same side safe

Using an RMI/bearing pointer is much simpler: Just adjust your heading to keep the arrow head of the pointer generally aimed at the station.

While you fly the arc, consult your DME to determine your distance and speed relative to the VOR/DME station. By setting the DME unit to ground speed/time-to-station mode, you can strive to see a ground speed (relative to the station) that is below 20 knots or so. That's taxiing speed and you won't get too far off the arc at those speeds.

If you have a heading bug, use it to track your chosen heading and adjust the bug each time you change heading to remain on the arc.

Let's say after joining the arc the DME indicates 11.2 miles. You're outside the arc and need to turn at least 20 degrees toward the station. Don't be afraid to make an aggressive heading change if you are outside the arc. On the other hand, if you joined the arc and the DME indicated 10.5 miles you are slightly inside the arc and that's not a bad place to be. Maintaining the current heading which should eventually take you back onto arc or turn away from the station by just 10 degrees. Wait 5 or 10 seconds and you should see the DME distance increase.

If the DME distance is within 0.1 or 0.2 miles, fly your present heading and wait for the CDI needle to center. Once it does, twist the OBS another 10 degrees, and consider turning the aircraft 10 degrees toward the station. Whether or not you change heading depends on the winds aloft and what the distance readout says.

Stop the Arc, I want to get off ...

To exit the arc on the desired radial or course, you need to make another big turn. Many instrument approaches with DME arcs depict a lead radial to alert you that your exit is approaching. Just like the turn to join the arc, exiting the arc require approximately 90 degrees of heading change.

This bring up the fact that there are four basic DME arc variations:

• Fly TO the station, join the arc, exit the arc flying TO the station.
• Fly TO the station, join the arc, exit the arc flying FROM the station.
• Fly away FROM the station, join the arc, exit the arc flying FROM the station.
• Fly away FROM the station, join the arc, exit the arc flying TO the station.

Additional Challenges

There are many places (the SF Bay Area being one) where there are few published DME arcs. That means a pilot on a check ride or proficiency check may be asked to demonstrate a made-up DME arc with no charted representation. When flying a made-up arc, your examiner or instructor should have specified either a left arc or a right arc, so figure out which way you'll need to turn to keep the station on the left or right side of the aircraft.

A particularly challenging DME arc can be found in the MTN VOR/DME RWY 15 where you arc right to the runway threshold, complying with various step-down fixes as you go. You'd obviously want to fly this arc very accurately. And if you need to fly the missed approach, you get to fly another arc to the missed approach holding waypoint. I've only flown this approach on a simulator, but would welcome the opportunity to try it in a real aircraft.

The Easy Way

If you're using an IFR-approved GPS receiver to fly an arc, here are your options:

• Load the instrument approach defines the arc, specifying the appropriate transition
• Make the VOR/DME station the current waypoint (proceed direct-to)
• G1000 and G530 can display distance to any VOR station that has been tuned

The obvious choice with most late-model GPS receivers is to load the approach with the appropriate arc transisition and let the GPS guide you.

Practice Makes Perfect

The best way to maintain proficiency with DME arcs is to practice in a simulator or in a real aircraft. Like a good crosswind landing, there's a satisfying feeling to flying a good DME arc. Try it, you'll like it.

Pocket Protector Optional

A calculus professor once told me the only tools a real mathematician needs are a pen, a piece of paper the size of a postage stamp, and his or her brain. That may be the case if one is sitting at a desk, quietly contemplating the theoretical. Controlling an aircraft that is hurtling through the air at two miles per minute or more while simultaneously listening and talking on the radio? That endeavor has the unfortunate side effect of dropping everyone's IQ by several points, which is why pilots have adopted a few tools to help them deal with the flying world's challenging mix of theoretical and practical. One such tool is the E6B calculator.

For older, traditionalist pilots, the E6B is synonymous with "slide rule" and the mere mention of electronic E6B calculators and smartphone apps will get them on their soapbox in a heartbeat, praising the slide rule and preaching against the dangers of new-fangled electronic contraptions. Young upstart pilots, having likely never used a slide rule, may find this attachment a bit odd. Frankly I do too. But even as electronic E6Bs are becoming widespread, there is still a place for the old fashioned E6B slide rule.

Tried and True

The advantages of the E6B slide rule are many: It requires no batteries, it does a variety of calculations, and it is relatively lightweight. The "front" side of the E6B can accomplish a dizzying array of calculations and conversions: Ground speed, distance, time, fuel consumption, endurance, knots to nautical mile - provided the user has been properly initiated. The back side of the E6B, sometimes called the "wind side," is used to calculate wind correction angles and determine winds aloft.

The disadvantage of any slide rule is that in order to use it, the user must provide most of the problem-solving context. In a high-workload environment, user-supplied context is less than ideal. If you don't understand how to arrange the slide rule scales to solve your problem, you won't get very far. Even after you have a grasp on the slide rule basics, you must still use common sense to ensure that your answer is not off by an order of magnitude.

Some might argue that having to provide this sort of context and judgement is the very thing that ensures an understanding level of knowledge about the calculations be performed. That rings hollow to me because in flight what is most desirable is speed and accuracy. It's possible to go through the motions of slide rule calculations, mimicking what you've seen, arrive at an answer (correct or incorrect), and still not understand how you got there. Yet for kinesthetic and tactile learners, the E6B is an ideal tool, probably more so than an electronic calculator. Instructors who are unsure of their student's learning strengths can always have them take one of the many learning style inventory tests available on-line.

In spite of its apparent simplicity, the slide rule E6B is by no means foolproof. Tiny screws hold the main section together. With age, these screws can come loose and if that happens in flight, you'll have an interesting project on your hands. The wind side has a transparent plastic disk that is meant to be marked with a pencil, but that plastic can become cloudy, brittle, and riddled with marks. APR Industries has developed an innovative E6B design that uses a rotating windspeed cursor arm on the wind side so that you don't have to make any pencil marks. Who says you can't teach old dogs new tricks?

If you are up for a challenge, grab the E6B of your choice and try tackling one of the Safety and Flight Evaluation Conference (SAFECON) Practice Exams. 

Flashy and New

There seems to be a endless supply of E6B apps out there for smart phones like the iPhone and the Android. At last count there were over 30 E6B apps at the iTunes store, some included as a feature inside an app. Perhaps creating E6B apps is a rite of passage, like writing your first "Hello world" program.

My favorite iPhone/iPad E6B app continues to be PFMA since it has a very simple, shallow menu structure. You provide the information you know and PFMA provides the missing information. No need to first locate the type of problem you're trying to solve in a complex and multi-layered menu structure. There are a few conversions that PFMA doesn't do and some obscure calculations that are missing, but it's easy to use in flight and a very good deal at $5.99.

For those of you wondering, that other calculator is an ancient HP-16C Computer Scientist that still works flawlessly. What can I say? I love RNP calculators and you never know when you might need to calculate the 2's compliment of a binary number.

Regardless which E6B app you choose, remember you won't be allowed to take your smartphone or other multi-purpose electronic device into an FAA knowledge test session.  Hmm ... Maybe there's life in that old E6B after all. Or purchase one of the dedicated E6B electronic calculators like the ones sold by Sporty's. I still have one of the Sporty's models, though the LCD display has long since given up the ghost.

Required Knowledge?

Like sailors before them, aeronautical navigators aboard airliners of yore used a sextant to plot their position. Thinking about this got me wanting to learn something about celestial navigation, even though it has been supplanted by satellite-based navigation. So in my spare time, I'll be working on building my own (very simple) sextant. When completed, I plan to try plotting my position in a few locations on the ground and compare the results to a handheld GPS or Google Maps on my iPhone. This project is for my own amusement and just because I find it interesting doesn't mean I'll soon be requiring my students to build their own sextants.

Ron wrote a cogent rejoinder to my post about digital versus paper charts, pointing out that most any pilot can blindly follow a magenta line into oblivion if they have lost (or perhaps never learned) basic flight planning and navigation skills. Many instructors might see that lack of skill and interpret it to mean that the pilot needs more training, but a deeper question seems to emerge: "What knowledge should the FAA (and, by extension, DPEs and CFIs) require pilots to demonstrate in the first place?" I believe the answer lies in thoughtfully combining the use of hand calculations, slide rule and electronic E6Bs, paper and digital charts, and paper navigation logs with computerized flight planning.

Tradition versus Progress

There's a undeniable pride student pilots feel once they have mastered basic calculations with an E6B. That's understandable because acquiring slide rule prowess is like learning a magic trick. Your friends are bound to be impressed, especially if the E6B you use is contained on the face of a flashy pilot watch. Pushing buttons on a calculator? Anyone can do that! For my part, I'll continue to teach my students how to use paper charts and a slide rule E6B, but I also won't discourage them from embracing new technology. I never tire of hearing students marvel "So pilots really used to fly this way?"

Is Cross-Country Flight Planning Passé?

The widespread availability of sophisticated GPS receivers, digitized aviation charts, and internet-based weather information is changing the way student pilots are learning cross-country flight planning. The introduction of new technology and techniques always raises questions: Should student pilots be taught to use paper charts, plotter, pencil, and a slide rule E6B or encouraged to switch entirely to electronic charts, calculators, GPS and computer-based weather briefings? Don’t throw out that plotter and slide rule just yet because the best approach to learning the complicated process of cross-country flight planning involves combining old school with waay cool. Here’s the first installment of a multi-part series on the revolution in VFR cross-country flight planning, written with student pilots and their instructors in mind.

Drawing the Line

One of the first steps in cross-country flight planning is to get a rough idea about the general direction and the distance involved. With a current paper chart, just plop your plotter down and draw a course line between your departure and destination airports with a pencil. Sounds easy enough until you need to plan a route that begins on one side of the chart and continues on the other side, which actually provides a good scenario for comparing paper and digital charts.

FAA VFR charts include instructions for extending a course line from one side of a chart to the other using a pencil and a spare sheet of paper, but it's a Catch 22: You determine the magnetic course by drawing a line between the two points, but you can’t draw the course line because the points are on opposite sides of the chart.

One solution is to purchase a World Aeronautical Chart (WAC), which covers a larger geographic area at a scale of 1 to 1,000,000 as opposed to the sectional chart scale of 1 to 500,000. Good luck finding a WAC anywhere but on-line. One could purchase two versions of the same sectional and piece them together, being careful to account for the 2 minutes of longitudinal overlap on each side. You could cut the Gordian Knot by using Victor airways or choosing a landmark that appears within the overlap on each side of the chart. Or you could use your current chart and an expired chart that you just happened to have saved, just don’t mix them up!

Or simply combine paper with plastic: Use a handheld GPS or any of a variety of web sites to determine the magnetic course between the two airports, then use your pencil and plotter to replicate that course. Which approach is best? That's really up to the pilot. The goal in teaching student pilots is not to preserve hallowed aviation traditions for their own sake. Whether a student is using paper or plastic or a combination of the two, the goal is for them to understand what they're doing and why they're doing it. Using a combinational approach with old and new products may actually end up teaching the student to a correlative level of knowledge.

Digitized charts provide a big, mostly seamless chart and you'd think that would make plotting a course line on a digitized chart easier, but plotting a digital course line can be less flexible and more abstract than doing it by hand with pencil and paper. EFB apps like Skycharts Pro and ForeFlight Mobile as well as online planners like FltPlan or FlightAware will draw a course line representation, but your choice of waypoints may be limited to the VFR reporting points, intersections, navigation aids, and airports contained in the application’s navigation database. Some products allow you to define your own waypoints using lat/long, but that's not terribly convenient.

VFR Sectional and Course line using FltPlan.com

Doing the Coursework

With the course drawn on a paper chart, you use your plotter to measure the true course, locate the nearest isogonic line and apply the magnetic variation shown (subtract Easterly variations, add Westerly variations) to determine the magnetic course. If your destination or departure airport has a VOR on the field, get the magnetic course from the compass rose surrounding that VOR. Either way, with a bit of care and attention will provide the magnetic course on a paper chart within ±1˚, though simple arithmetic errors can result if you’re in a rush.

Old school pilots and instructors rightly claim that never drawing a course line on a paper chart can rob student pilots of an important learning experience about Magnetic declination. Yet with the right input data, computers tend to do a faster and more accurate job with arithmetic and geometry than humans: Waypoints entered, the digital course line drawn, determining the magnetic course is a foregone conclusion. A good approach for student pilots is to plan first on paper, then check your results using a digital source.

Go the Distance

Plotters offer a variety of scales and if you mistakenly measure using the wrong scale ... you won’t be the first pilot to do so. So look carefully, choose the correct scale for your chart and line up the correct marks.

Getting the distance on a digitized chart is a forgone conclusion, but errors are still possible. You can enter the wrong waypoint or misspell the waypoint. One tipoff is a digital course line that makes a sudden, severe turn off the edge of the map you're viewing.

If the digital product you are using provides recently assigned ATC routes, remember that these are instrument flight rules (IFR) clearances and these routes may involve altitude requirements that are beyond capability of the average GA aircraft. If you will be flying IFR, remember that there may not be any recently assigned ATC routes for the departure and destination airport that you have chosen.

Some EFB apps are better than others at drawing a course line that is visible, yet doesn't obscure important information.

FFM course line obscures airway radial

SCP course line is more ... subtle

Overcoming Obstacles

With a preliminary course line drawn, consider the appropriate altitudes one could fly. You'd think that pilots would know and apply the hemispheric rule, but it's surprising how many pilots (intentionally or unintentionally) fly WAFDOF (wrong altitude for direction of flight).  Whether you remember "Odd birds fly East" or simply refer to the diagram etched into many kneeboards, do other pilots a favor: Fly the correct altitude for your magnetic course.

Minimum elevation figures are shown on VFR charts and these provide the lowest altitude that will clear the highest charted obstacle within a specific quadrangle by 300 to 400 feet. Depending on how close your route is to that highest obstruction, flying at or just above that altitude may be the safe thing to do or it may be hopelessly foolhardy. I don't know of any app that will make the assessment of a safe altitude for you: You're going to have to use your little gray cells.

Whether you are using paper or digital charts, a nifty course line that goes to your destination won't necessarily keep you clear of special use airspace. One cool feature in SkyCharts Pro is the ability to get information on special use airspace by tapping. Locate the red circle next to an MOA, prohibited, or restricted area and tap twice to get the effective times, altitudes and the frequency of the controlling agency.

ForeFlight offers a similar feature, but it requires more taps to get the same information. ForeFlight does offer a quick way to create or change course lines by tapping and dragging.

Acquire, Combine, Conquer

Paper chart adherents often claim that paper is foolproof because paper charts don’t require batteries, they can be folded and handled, and are less intimidating to pilots who may be less computer savvy. True, but paper charts have some serious disadvantages: They can be torn, damaged, lost, or hopelessly riddled with marks from previous flight planning efforts. Last, but not least, all paper charts eventually expire and become obsolete.

Even before the FAA changed the structure for chart retailers, it was often difficult to get a paper chart unless you planned ahead. With a reduced number of chart retailers, your odds of acquiring a current paper chart at the last minute from a local retailer is tantamount to winning the lottery. A chart subscription is obviously the best bet, but that’s not much help if you’re away from home on a longer trip, need an oddball chart, or you lost your chart a week before it was set to expire.

The chart retailers who remain have to deal with unsold, expired paper charts. Charts have to be printed and physically shipped which adds to the cost and carbon-loading. Old school pilots are familiar with the various paper chart subscription services available through Aeronav or a variety of on-line retailers, but they may not be up-to-speed on the various options for digital charts.

Digitized charts, whether viewed on-line or on an iPad, tablet, laptop or desktop computer can be acquired at a lower cost (some are available on-line for free), they are easy to update, and they can cover large geographic areas without folding, flipping, or ripping. There’s no physical shipping required and no paper to recycle. The disadvantages of electronic charts basically boil down to all the possible failures to which electronic devices are heir to, including screen readability in bright light, software/hardware failures, and drained batteries. There are also some problems with how digitized charts are stitched together, but that really just reflects the limitations with how the FAA generates the charts. Hopefully that process will continue to be modernized and soon we'll see seamless VFR and IFR charts become a reality.

FAA VFR charts can be downloaded to your computer as raster files for free, and a simple, free, and platform-independent solution for viewing them is Google Earth. Follow the instructions in this WikiHowTo  and overlay sectionals and terminal area charts in Google Earth. While this approach has limitations, it does offer pilots the ability to view charts for large geographic areas at little or no cost. You can even do some rudimentary flight planning activities, like determining the course and distance between airports.

Several products are available for the iPad that allow you to access VFR charts, including ForeFlight and Skycharts. The cost of these products varies from $20 per year to $80 per year or more. Like all cockpit resource management issues, one size does not fit all. Both of these apps allow you to create flight plans that will draw course lines on the digital charts and give you magnetic courses, but old school paper chart planning provides more flexibility and, dare I say it, precision.

If you are a Mac user, MacGPS Pro provides another option for importing FAA raster charts. MacGPS Pro lets you define user waypoints, integrate with an external GPS receiver, and measure distances and courses. Similar solutions probably exist for the Windows world, but not being a Windows user, well ...

Paper and Plastic

After a student pilot has been through the flight planning process a half dozen times using paper charts, it's not clear that any more learning is likely to take place by restricting them to old school planning. While I do believe that a students' primary experience should involve pencil, plotter, and paper chart, that doesn't mean they should be discouraged from branching out to the high-tech solutions once they understand flight planning basics. Looking at the strengths and weaknesses of paper and digitized charts it’s easy to conclude that the best approach is to understand and use both. Having a paper back-up strategy in flight is the prudent advice offered by the FAA’s AC on Electronic Flight Bags.

Some pilots may still resist using digitized charts for the understandable reason that they simply prefer holding a chart in their hands. Nothing wrong with that, but charting and flight planning is changing. Time waits for no one, not even old school pilots, so don't be afraid to explore and experiment.

In future installments, I'll discuss how technology is changing calculators, navigation log preparation, and in-flight diversions.

GPS Transition, Part I

If you are a pilot who has avoided flying GPS-equipped aircraft or glass cockpits, you’re not alone. Many pilots, some who are VFR-only pilots, shy away from getting checked out in glass panel aircraft. It’s as if they take one look at a glass panel or read the first pages of a GPS pilot’s guide, get a sinking feeling, and think “This looks way too complicated.” Or they may fly a GPS-equipped aircraft and simply avoid using the GPS for anything but direct-to navigation. Take heart because learning to fly a glass panel or GPS-equipped aircraft is not only doable, these systems offer some important advantages.


A big part of the intimidation factor is that instructors, training courses, and pilot guides often focus on mastering the knob-twisting and button-pushing for a particular brand and model of GPS or worse, they start with nitty-gritty details of how all the components function. The key to learning and then mastering GPS and glass is to start with what you learned about pilotage and VOR navigation, use that as a bridge to learning RNAV concepts, and then you’ll be ready get into the details of the particular model of GPS you plan to use.


Start with the Known


As a student pilot, you undoubtably recall learning to get a weather briefing and then creating a navigation log for your cross-country flights. Most instructors still require student pilots to complete this process using pencil, paper, plotter, a navigation log form and an E6B calculator. The drill goes something like this:

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  Draw one or more course lines on your chart between your departure and destination
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  Determine the altitude(s) for direction of flight based on terrain, airspace and other considerations

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  Using the chart and a plotter, measure the True Course (TC) for each leg
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  Apply the local magnetic variation and determine the Magnetic Course (MC)
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  Determine a planned True Airspeed (TAS)
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  Using the winds aloft forecast, calculate ground speed & a wind correction angle
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  Use the wind correction angle to determine a Magnetic Heading (MH) to fly
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  Apply the compass deviations to determine a Compass Heading (I find this a bit precious)

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  Determine Top-Of-Climb and Time-Of-Descent based on aircraft performance
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  Identify checkpoints along the route and measure the distance for each leg
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  Calculate the leg time and fuel burn for each leg
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  Determine total time and fuel required for the entire trip

If this seems like a lot of work, it is. But it’s a good learning process, too. As soon as the ink is dry on their temporary airman’s certificate, most pilots quickly graduate to using an computer-based flight planner such as the ones offered by DUAT, DUATS, or AOPA. This is smart because it saves time and reduces errors. I like the flight planner that DUAT provides because it has a nice format and it calculates Top-of-Climb and Time-of-Descent, but there are plenty of choices out there.

Whether you create your navigation log by hand or by computer, you’ll refer in flight, make notes on the estimated and actual times of arrival, and update subsequent legs as you gather real-time flight information. This process of dead reckoning is not foolproof: You’re bound to discover some discrepancies in what you planned. After all, the winds aloft forecast is just a forecast.




Old School, meet New School


When navigating via VOR, you either fly to the VOR station or away from the station. Whether you are tracking a particular radial or you simply headed direct to the VOR, this sort of navigation involves basic steps:

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  Tune the frequency of the VOR station you want to use
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  Listen to the Morse code identifier and verify it is the correct station
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  Twist the OBS or HSI course pointer to set the desired radial
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  Choose an intercept heading or determine a direct-to heading
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  Fly that heading and adjust as necessary for winds aloft

When flying on Victor Airways or Jet Routes (course lines connecting VOR stations on the ground), you generally fly away from one VOR and then switch to flying to the next VOR. The point on an airway where you switch from using one VOR to another VOR is called a changeover point.


GPS navigation is sometimes called To-To navigation, not after the little Cairn terrier in the Wizard of Oz, but because you’re always navigation to something called the current waypoint. A waypoint can be anything contained in the GPS database (an airport, VOR, NDB, intersection, computer navigation fix, or user waypoint). At its most basic, GPS navigation involves these basic steps.

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  Press the Direct-to button
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  Enter the name of the waypoint you want to navigate to
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  Confirm you’ve entered the correct waypoint
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  The GPS will display a desired track (DTK) to the waypoint
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  Twist the OBS or HSI course pointer to the desired track (DTK)
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  Fly a heading that corresponds to the DTK and adjust as necessary for the winds aloft

Some of the differences are that with GPS don’t have to listen to Morse code and you don’t have to figure out the correct course since the GPS tells you the desired track. With GPS, pilots can also fly on a desired track that is a course line between waypoints entered in a GPS flight plan. You can even enter waypoints that define a Victor or Jet airway, but more on that later.


Move toward the Unknown


As you apply old school flight planning to GPS navigation, you’ll need to correlate the old school terms to some high-tech terms. Below is an elegant figure from an old Garmin manual that concisely illustrates some core GPS navigation concepts.

Current track (TRK) is essentially the aircraft’s current, real-time magnetic course across the ground. It’s easy to appreciate that calculating TRK by hand in real-time would require significant time and effort. That’s why airliners of yore had dedicated navigators as part of their crew. With GPS, the TRK is automatically calculated, displayed on your GPS screen, and updated in real-time for free. That’s pretty cool.


Desired track (DTK) is either the magnetic course between the current waypoint and the previous waypoint in your GPS flight plan or, if you pressed the direct-to key, it is the magnetic course from your current position to the current waypoint. GPS receivers with a moving map usually show the desired track as a magenta line. Glass panel systems with an electronic horizontal situation indicator (HSI) will automatically set the course pointer to the the DTK. Without an electronic HSI, you will need set the course pointer or OBS to the DTK, just like you would do when tracking a VOR radial.


Track angle error (TKE) is not used by most pilots, but it is the difference between the desired track (DTK) and the current track (TRK). If the DTK and the TRK both read 060˚, you are either on the magenta line or you are paralleling that line. If DTK and TRK differ, TKE can tell you if you are diverging from or converging to intercept the DTK.


Cross-track distance (XTK) tells you the lateral offset (usually in nautical miles) between your current position and the DTK. When XTK is zero or near zero, you’re on the DTK.


A full-scale deflection of the CDI or HSI needle can mean different things, depending on the current GPS course sensitivity. The three sensitivities are ENR (enroute), TERM (terminal), and APR (approach). A full scale needle deflection means the XTK is 5 nautical miles when in ENR mode, 1 mile in TERM, and 0.3 miles in APR (again, there are other possible approach sensitivities we're leaving out for now).


So what about updating the old school navigation log and dead reckoning? The GPS will continuously calculate the time and distance to the current waypoint, leaving you time to focus on other tasks like looking for traffic, evaluating the weather, and talking with ATC. If you still want to create a navigation log and update it in flight, by all means do so. Dead reckoning is a skill and if you don’t use it, you’ll lose it.


What about the magnetic heading and the wind correction angle? You don't really need them to stay on course because the GPS calculates the DTK and TRK in real-time. As for winds aloft corrections, you simply fly a magnetic heading that will keep you on the DTK. Many glass panel aircraft will even calculate and display the winds aloft for you in real-time.


What about the leg time and fuel consumption? GPS and glass panel systems that are aware of your fuel consumption can display the estimated time en route for each leg as well as the estimated fuel burn for each leg, too.


While all of this information is waay cool, it’s important to remember that having GPS on board won't keep you from running low on fuel, flying into restricted airspace, crashing into a mountainside, or flying into a thunderstorm. You still have to use your little gray cells, otherwise flying wouldn't be much of a challenge, would it?


How you go about accessing the above-mentioned GPS information on a particular brand of GPS will vary, but rest assure that this information is available in virtually all aviation GPS receivers. There really needs to be more discussion of these basic concepts in the FAA's Instrument Flying Handbook and in all GPS pilot guides.


Some other important and often-overlooked GPS concepts that are common across different models of GPS receivers are Waypoint Sequencing, Turn Anticipation and GPS flight plans.  We’ll examine at these in GPS Transition, Part II, so stay tuned.