(Updated) ADFs, NDBs, and VORs: Non-GPS Instrument Flying

VOR and NDB are navigational aides. This guide will teach you the basics of how to use them in MSFS2020 with a tutorial.

VORs and NDBs: How to fly like it's 1949

Introduction: What are VORs and NDBs?

VORs and NDBs are navigational aides. They both work by broadcasting radio signals.

"VOR" is an acronym for Very High Frequency Omnidirectional Range. It is a short range system capable of fixing an aircraft's position relative to the VOR beacon.


The above image is the ICAO symbol for a VOR station on aeronautical maps.

An NDB is a Non-Directional Beacon. It broadcasts a simple and relatively long-range radio signal which can be intercepted by a radio direction finder. The direction finder simply points towards the beacon.


The above symbol is the ICAO symbol for an NDB station on aeronautical maps.

You can use a mixture of NDBs and VOR stations to get a positive fix on your position without using GPS. Together with dead reckoning, you can navigate without relying on VFR or GPS - given you have a head for mathematics and are able to fly straight.

VOR

1: Aircraft travelling towards the VOR station. 2: Aircraft travelling away from the VOR station. 3: Aircraft flying above the VOR line. 4: Aircraft flying below the VOR line. 5: Aircraft flying to the right of the VOR line. 6: Aircraft flying to the left of the VOR line.

The aircraft's position relative to the VOR station is shown on the VOR indicator. Through some electrical wizardry, your aircraft's VOR indicator shows whether you are on the left, right, above, or below the VOR station's "line" travelling along a particular direction.

VOR stations placed at the end of runways will also often be able to take you down a glide path in the direction of the station. This gives you a capacity to perform instrument landing.

NDB and your ADF

Your aircraft's Automatic Direction Finder will probably look a bit like this. In this picture, the aircraft is flying a course due north directly to the NDB. As a result, the ADF needle points due north.

The Automatic Direction Finder will point in the direction of Non-Directional Beacons. Non-Directional Beacons (NDBs) are essentially radio stations. You can tune into them with your Automatic Direction Finder and it will point straight to the station.

This is useful if an airport or particular location has an NDB station: you can just fly straight towards the signal as indicated by the ADF and eventually you'll get there.

However, that is not an efficient way of flying as you'll make dog-legs jumping from signal to signal. Instead, the best way is to plot a course direct to your destination and, en route, fix your position on a map with by using two radials from NDBs. You can also fix your position using VOR radials.


Fixing the approximate position of an aircraft by reference to the radials from two NDB stations. The left station indicates ~135°. The right station indicates ~270°.

In order to fix one's position:

• Set the compass surrounding the ADF to your heading.
  
• Read direction in degrees to NDB
  
• If ° to NDB <180°: calculate (° to NDB) + (heading)° + 180° to find radial. Trace this on the map from the NDB.
  
• If ° to NDB >180°: calculate (° to NDB) + (heading)° - 180° to find radial. Trace on the map from the NDB.
  
• Repeat with a second station.
  
• The point where the two radials intersect is your rough position.

By using this to chart your progress along a flight plan, you can use speed and distance formulae to calculate the effect of wind on your speed and direction by judging where you are against where you should be. You can then calculate an appropriate new course to compensate.

How to calculate wind speed correction angle:

• (Wind direction)° - (course)° = 𝑥
  
• 𝑥 multiplied by (windspeed) divided by (true airspeed) = (wind correction angle)°

NDB/ADF at Bristol EGGD

Let's use VOR and NDB in-game. Select a Cessna 152 and find the Bristol International Airport in the United Kingdom (EGGD).


EGGD. You can turn on the necessary IFR and NAVAID details in the options at the bottom of your screen.

If we examine the airport closely, we see that the airport itself is marked by the central crosshair symbol. Flanking it to the west and east are two stations - one western one named IBTS and the eastern one IBON.


EGGD. West of runway is IBTS. East of runway is IBON. South of runway is the NDB codenamed BRI.

Click on IBON to open the station's information panel - revealing the frequency of the station to be 110.150Mhz. Make a note of the frequency.


IBON frequency is shown as 110.150Mhz.

Click on the BRI Non-Directional Beacon to reveal the frequency. It is 414kHz.


The NDB BRI, shown as 414kHz.

Begin a flight in your Cessna 152 some distance east of EGGD.


Start around here, due east of the airport, with lots of distance to spare. Set weather to a sunny and calm day.

Turn the Cessna due west and fly a course of 270°. Get the speed down to a steady rate and keep straight and level. You should see Bristol airport straight in front of you.

Tune the ADF (on the right of the cockpit panel) to receive the BRI NDB at 414. Do so with the three knobs for each digit.


The ADF indicator is the instrument second in from the right-hand side of the cockpit instrument panel, while the ADF signal input is below (reading 414). - Click to maximise.

In the above picture, the ADF is tuned and receiving BRI at 414. The aircraft is flying due west, and the direction to the NDB is shown on the ADF indicator's yellow needle as straight ahead. We can see clearly out of the window that the airport is, indeed, straight ahead. If we perform the calculation to get our radial, we take the direction to the NDB from our course (0°, because we are flying straight towards it) plus our heading of 270°, minus 180°, totalling 90°. Our radial is about 90° from the station: we are just about exactly due east of BRI.

The limitations of NDBs are that they don't carry any inherent information on your position on a map, or distance to the target, or your height. They only tell you where the NDB is in relation to your aircraft.

To fly like a 40s pro, use weather information to keep your barometric pressure correct on the altimeter, fix your position regularly on a map by referencing two or three NDBs (with rapidity), and get used to speed and distance formulae to calculate journey time and speed.

VOR at Bristol EGGD

Continuing on, we also tune our VOR receiver to the VOR station IBON at the eastern end of runway 27. The frequency of IBON was 110.150mHz.


The VOR indicator shows we are on course with IBON for runway 27 at EGGD.

See the above image to examine how we tune the VOR receiver. Use the upper right-hand (NAV) part of the radio stack. The two-stepped knob will allow you to change the second (STANDBY) frequency to 110.15. Once you have inputted 110.15, hit the <-> button to switch the USE and STANDBY frequencies. The VOR indicator will then spring to life and indicate where you are relative to the IBON VOR station.

IBON's "line" traces a gentle slope at 270° towards the start of EGGD runway 27. Follow the VOR indicator and make a landing based on what it tells you about your position.


A closeup of the VOR indicator, tuned to IBON at 110.15. It shows the aircraft is very slightly to the left of and somewhat above the exact course towards IBON.


VOR indicator shows we are too high.

Here the horizontal line on the VOR indicator tells us we are flying higher than the perfect approach as described by the VOR signal. We should go lower to fix it.


The VOR indicator shows we are on track.

Here the horizontal and vertical lines intersect at the centre point. We are proceeding directly towards runway 27 at a good angle of descent, and so long as we don't stall or have a heart attack, we should be able to make a comfortable landing.

Summary

You can use VOR and NDB information in all weathers as a manner of keeping your course and making "instrument-inspired" landings in poor weather or at night. It's not as immediate or easy-to-use as GPS, yet offers a fascinating challenge and a real dip into how it felt to fly in days gone by. It's a step up from dead reckoning and VFR!

Remember to take a note of relevant frequencies for NDBs and VORs before you fly as you can't access them in-game once you have begun.

I believe the more modern aircraft can use NDBs and VORs as well as / instead of GPS, but you'll need to know how to use glass cockpit things for that. As I'm solidly trapped in the 1930s I unfortunately can't help you there, but the principles will be the same.

Be thankful we've got ADFs - the key word in there being automatic direction finder - as opposed to manual radio direction finding. Co-pilots in early airlines would crank a radio antenna around until they get a fix on a radio station, then make a note on where it is, and repeat rapidly enough to get a useful fix. Battling against communication technology, storms, rain, wind, hail, snow? That's tricky business. Pilots flying C-47 Skytrains/Dakotas from Newfoundland to the United Kingdom would use sextants to measure the stars and find their position.

Bugs

I've noticed that NDBs and VORs occasionally fail to work. I don't really know whether that's because I'm stupid, or because the game "forgets" they exist. Either or both could be true. Luckily, we have GPS to save us if things start breaking :)

Advanced Documentation: Approach Charts for NDB/VOR

If you've grasped the essentials of VOR and NDB, we can apply our foundation knowledge to a realistic scenario: using flight charts to make a pattern instrument landing. Instrument landing (or ILS) flight charts exist for every major staffed airport. Even unstaffed airstrips usually have charts. It's a bit like driving a motor car in the correct lanes through a complex junction - it's essential, or you might end up crashing!

This is a hobbyist flight chart for simulations of Bristol International Airport EGGD. It is specifically written for using NDB with DME (Distance Measuring Equipment).



Don't be frightened by its complexity - it is there to help you.

For context, we will briefly summarise the documentation commercial pilots use to navigate to an airport and land safely:

• 1 - Pilots use approach charts. These describe exact GPS waypoints with precise altitudes and directions. These take an airliner from cruise to the airport.
  
• 2 - Pilots use airport charts for specific approaches. They describe precise flight paths, altitudes, and other procedures to land at a specific runway. These usually use GPS waypoints and VOR/DME. These take an airliner onto the runway, and is the type of chart supplied above.

Regarding Point 1 - there is no way to perform approaches reliant on standard waypoints without using GPS. Pilots not using GPS must substitute chains of VORs and NDBs. This must be illustrated in a flight plan and pilots must inform controllers en route.

Regarding Point 2 - Some airports do not have NDBs, and some lack VOR. EGGD is suitable for our purposes as it has both. It also has specific instrument approach charts for using NDB and VOR for landing. Some airports may not have NDB or VOR approach documentation. In these cases, landing is dangerous unless under VFR conditions.

We'll go through each part of the chart.

• Communications frequencies are at the top. Use these to tune into the tower, approach, ATIS, and other essential services. We also find the altitude of the airport - "AD ELEVATION 622" "THR ELEVATION 601". EGGD slopes downwards to the west, so the highest point is the start of Runway 27 at 622 feet ASL (above sea level). The lowest point is the start of Runway 9 at 601ft ASL.
  
• Further down is the map. We see the airport itself is the box-like object in the middle with several lines and boxes springing out of it. Surrounding landmarks are also illustrated. The lines and boxes describe flight paths and frequencies respectively, and are what we are most interested in.
  
• Below the map is the "RECOMMENDED PROFILE" table. It describes a descent gradient of 5.2% - or 320ft/nm. That is to say, you should descend at 320ft per nautical mile.
  
• Below the "Recommended Profile" chart is a side-view of the flight path described in the big map above. It has a box in it labelled "MAPt NDB(L) BRI" - or "Missed Approach Point" - for use if you overshoot or abort landing.
  
• Below the side-view is a chart. It shows the "Obstacle Clearance Attitude/Height" for different types of aircraft. Aircraft are grouped here by category of speed - A is less than 91kt; B >91kt & <121kt; C >121kt & <261kt; D >141kt & <166kt. Our Cessna is Category A. The OCA basically instructs us in Category A not to do the landing procedure below 960ft altitude (359ft above ground level).
  
• The bottom part has advisories and instructions. We don't need to think about those.

We're going to try using the chart to fly a proper instrument approach. A major part of the procedure is the use of "DME", or "Distance Measuring Equipment". DME almost always a feature of VOR stations. It simply states how far away the VOR station is. Unfortunately, our Cessna 152 doesn't have DME in-game! Modern pilots (and the aircraft in-game) use GPS systems to display VOR DME. As far as I know, their analogue equivalents are not found on any MSFS 2020 aircraft except the Douglas DC-6.

We have to use GPS if we want to use DME (Distance Measuring Equipment) unless you are flying the Douglas DC-6. Please refer to the manual/instructions for your aircraft of choice for using DME. You can use speed and distance formulae to gain a close approximation of distance from a VOR without DME.

We'll go step-by-step, referring to the chart at every point:

1. Fly at 3000ft ASL directly over NDB on course 094°. We are instructed to do so by the two maps: top-down shows the angle in degrees, as does the side-view, along the flight path (the big blue line) labelled "(CAT A, B)".
   
2. Fly along this course until you reach 8nm from the beacon - your GPS's DME will indicate this distance, or otherwise you must gauge the distance by performing speed/distance calculations or using VFR. We see this from the top-down map and side-view map: the blue line describes a journey along 094° until "D8", or "Distance 8 nautical miles". As you go, descend gradually to 2500ft ASL.
   
3. At D8 and 2500ft ASL, turn steadily left to a heading of 263°. This is the curve in the top-down map. Do not lose or gain height in the turn. This is shown in the side-view map - the blue line does not descend as it turns back on itself.
   
4. You want to finish your turn facing directly 263° before reaching a distance of 5.8 nautical miles inbound.
   
5. At D5.8, begin descent - follow the path described by the VOR. Land.

If you decide to abort, the chart helpfully describes what to do. Follow the dotted line leading from the airport on the top down and side-view maps - it shows 263° heading, and the "MAPt NDB(L) BRI" missed-approach box tells us to climb straight away to 3000ft ASL, and then, at a DME distance of D4.7, turn right and repeat the whole procedure.

Summary of ILS Flight Charts

Flight charts exist to give specific instructions about where and how to land at an airport. Look out for the following things on any ILS flight chart:

• Contact frequencies with the tower, control, ATIS, and other essential services.
  
• Frequencies for NDB and VOR facilities.
  
• Flight path with course in degrees. This will be illustrated in a map.
  
• Altitudes along the flight path. This will be described on the maps and written information.
  
• Missed approach vectors and altitudes - and sorted by aircraft category.
  
• Basic landmarks for visual confirmation of position in good weather.

We have looked at an ILS flight chart for use with NDB and DME. There are many others - the most common are GPS approaches.

Good luck and happy landings!

Glossary

ADF - Automatic Direction Finder. The instrument in your cockpit that points straight towards an NDB. Provides LNAV information.

AGL - Above Ground Level.

ASL - Above Sea Level.

ATIS - Automatic Terminal Information Service. A radio service provided at airports. Describes weather conditions and barometric conditions for your altimeter.

DME - Distance Measuring Equipment. An instrument (or part of a GPS display) that shows distance to a VOR or NDB. Helps with LNAV.

FL - Flight Level. An altitude metric for high-altitude flight. Used for commercial aviation above a certain altitude when the literal distance to sealevel or ground is unimportant. It is typically 1013.25 hPa or 29.92 inHg. Height in thousands of feet are written/spoken as whole integers - 5, 10, 15, 20, 25, 30, etc.

GPS - Global Positioning System. Provides easy LNAV data. Advanced GPS systems also show groundspeed, true airspeed, course corrections, and other useful features. GPS can plot a straightforward path to your destination effortlessly - the "magenta line".

GS - Groundspeed. A true measurement of distanced travelled over time based on speed and distance formulae.

IAS - Indicated Airspeed. The speed at which the air rushes past - as measured by your pitot tube.

ILS - Instrument Landing System. Methods for landing an aircraft without needing to look out of the window.

LNAV - Lateral Navigation. The ability to distinguish where you are on a compass relative to a certain point.

NDB - Non-Directional Beacon. A radio station that can be pointed towards by your aircraft's ADF (Automatic Direction Finder). Provides LNAV information.

MAPt - Missed Approach Point. Described on ILS charts to help guide pilots in the event of a failed approach/landing.

OBS - Omni-Bearing Selector. A system on your aircraft that calibrates which vector (direction) you would like to take towards or away from a VOR.

QNH and QFE - Query Nautical Height and Query Field Height. Reference settings for altimeters that are, essentially, ASL and AGL respectively. QNH describes the barometric setting for reference against sea level. An aircraft sitting in Bristol Airport EGGD, with its altitude of 600ft ASL, would read 600ft on the altimeter when set to pressure QNH. QFH describes the barometric setting for reference against the "field" or ground. An aircraft sitting in Bristol Airport EGGD, despite being 600ft above sea level, would read zero on the altimeter when set to pressure QFH.

RNAV - Random Navigation. A method of modern GPS-reliant flying (the "magenta line").

TAS - True Airspeed. The actual speed at which your aircraft is moving through the air (without the margin of error given by a pitot tube).

VNAV - Vertical Navigation. Your VOR provides VNAV information in the "horizontal line" describing whether you are above or below a glidepath.

VOR - Very High Frequency Omnirange Station (VOR). A radio station that describes an aircraft's position in relation to it, and along a specified line of approach. Provides LNAV and VNAV information.

[Quicosse]

Excellent: Easy to undersatand.

[Duke Flapjack]

I loved flying VOR in FSX occasonally. It was fun trying to use a more complicated navigation than "set nav to GPS and turn autopilot on."

[OG Alcoholic Stepdad]

VOR is still required on your FAA exam, it's a necessary back up.

[richardotoolemetta]

I have been teaching instrument flying since the 1960's and this was an awesome piece of work. Thanks for the effort that was put into making it so comprehensive.

[Gipper]

Technology is killing the spirit of aviation adventure. NDB's and VOR's are foolproof and indispensable tools for all weather flying, and this guide is also a valuable tool for those needing to try this kind of flying. Great job. Marked it amongst my favourites.

[RetroO]

tf is this bull sh#t

[Dank Williams]

Good guide, can't wait for someone to do a B-17 or similar type aircraft for this game so we can have proper historical flying. Crossing water and that anxious wait to pick up that VOR/NDB signal is what flight sims are all about!

[m@X_1$_3P1K_1245]

as an actual pilot this is a better explanation that most things ive read/watched abt vor's

[Von_Carraghan]

Thank you!