VOR / NDB navigation help

[UKJim 502]

Hi, 

 

So I have a quick question really regarding VOR/NDB navigation. In most small GA aircraft there exists a GPS system that you can follow to get to your destination etc etc. But I want to get flying properly without the GPS and only with instruments.

 

My understanding at the moment ...

 

Tune NAV radio to a VOR frequency and a gauge will change pointing an arrow in the direction and whether you are flying to or from the point. I am not sure why on most tutorials it says change the OBS? Any help here would be good.

 

The other way is to tune the ADF frequency of an NDB into the radios and a gauge will have a single arrow on it - flying with the arrow pointing straight up will take you to the NDB beacon.

 

So to summarise...

 

With VOR method - why do I need to change the OBS setting?

 

When I reach my last VOR/NDB - how do I know where the airport is if it does not have a beacon on the airport? Is it a case of looking on a map and working it out from the VOR? Does it tell you on airport charts from nearby VOR's?

 

Hope this all makes some sense - I want to learn a little more about how pilots do this in real life because at the moment I am just using radios to get to last VOR enroute and then working out from a map what direction I need to fly to get to the airport.

 

Thanks,

Jim 

[Andrew Godden 945]

Hi, 

 

So I have a quick question really regarding VOR/NDB navigation. In most small GA aircraft there exists a GPS system that you can follow to get to your destination etc etc. But I want to get flying properly without the GPS and only with instruments.

 

My understanding at the moment ...

 

Tune NAV radio to a VOR frequency and a gauge will change pointing an arrow in the direction and whether you are flying to or from the point. I am not sure why on most tutorials it says change the OBS? Any help here would be good.

 

The other way is to tune the ADF frequency of an NDB into the radios and a gauge will have a single arrow on it - flying with the arrow pointing straight up will take you to the NDB beacon.

 

So to summarise...

 

With VOR method - why do I need to change the OBS setting?

 

When I reach my last VOR/NDB - how do I know where the airport is if it does not have a beacon on the airport? Is it a case of looking on a map and working it out from the VOR? Does it tell you on airport charts from nearby VOR's?

 

Hope this all makes some sense - I want to learn a little more about how pilots do this in real life because at the moment I am just using radios to get to last VOR enroute and then working out from a map what direction I need to fly to get to the airport.

 

Thanks,

Jim 

 

Jim,

 

OK, so let's see if I can really confuse you. 

 

Firstly, with a VOR, the VOR indicator registers your direction of flight relative to the VOR, that is, whether you are flying TO or FROM the VOR.  You set the OBS / CRS (course) to either determine what bearing you are relative to the VOR, which is indicated by the "needle" being centered or to fly a heading on that bearing by keeping the "needle" centered.  The important thing to remember here is whether you are flying TO or FROM the VOR because the bearing might be a reciprocal bearing, that is +/- 180 degrees.  For example, if the VOR indicator is indicating TO, and you set the OBS to 120 degrees and fly that heading with the "needle" centered, you are flying on a heading of 120 degrees towards the VOR.  As you pass over the VOR, the "needle" will swing and the VOR indicator will change to FROM in which case it is now on a bearing of 300 degrees.

 

The ADF / RMI is more basic.  The needle points direct to the location of the NDB.  If you set the ADF / RMI bearing to your heading, then the needle indicates the bearing to the NDB.

 

In relation to an airport without an NDB or VOR, you determine the bearing from the NDB or VOR to the airport and use the instruments to navigate on a heading to the airport.  Plan-G is an excellent flight planning tool for this if you aren't already using it.

 

If you have your flight realism settings set to realistic, you will also get what is known as "gyro drift".  The easiest way to reset this is by pressing "D" and the keyboard.  This should be done regularly on long flights, say every 30 to 60 mins.

 

The Learning Centre in FSX gives a reasonably good explanation on NDB / VOR radio navigation techniques.

 

I hope this helps and good luck. 

 

Cheers

Andrew

[allardjd 1,853]

Quote

why do I need to change the OBS setting?

 

The best way to think of the VOR is in terms of radials. Radials can be thought of as a series of signals emanating from the ground station. Though they are continuous around the VOR, think of them as a series of 1 degee pie segments. Tuning the OBS makes the receiver sensitive to one of those 360 segments and the CDI (Course Deviation Indicator, the arrow) deflects toward it, not necessarily toward the station.

 

Try a mental experiment here. You're directly north of a VOR you have tuned on NAV1.

 

If the OBI is set for 0 the CDI will be centered with a FROM indication - you are directly on the tuned radial.

If the OBI is set for 010 the needle will be deflected right because the tuned 010 radial is to the right, again with a FROM indication.

 

If the OBI is set for 350 the needle will be deflected left because the tuned 350 radial is to the left - also with a FROM indication.

 

One significant difference between VOR and ADF is that the orientation of the aircraft, i.e. the heading, makes no difference in the panel display on the VOR. In any particular location, the VOR display will be the same no matter which direction the AC is pointing. Everything on the display is about the aircraft's position relative to the station and the heading of the aircraft is immaterial to what is displayed.

 

With the ADF, the needle points to the station and changing the AC heading affects the display - if the station is ahead, the needle points up; if it's behind, the needle points down. Unlike the VOR, Everything on the ADF display is about the station's position relative to the aircraft - the heading of the aircraft does affect what is displayed.

 

Quote

When I reach my last VOR/NDB - how do I know where the airport is if it does not have a beacon on the airport?

 

An airport in some reasonable proximity to a VOR station necessarily lies on one of the VOR radials. You find the airport by determining which radial it lies on (i.e. in which direction it is located from the VOR station), tuning the appropriate radial on the OBI and using the CDI to fly outbound (FROM) along that radial until you are near the airport. Charts or lookup references are used to determine which radial is appropriate. Some aviation sites list bearing and distance from nearby navaids.

 

Note here that it is just as easy to fly a radial FROM a VOR as it is to fly one TO the VOR. When navigating between VORs it's common to fly FROM the one behind you until close enough to receive the next one, then fly TO that one.

 

There are a lot of details that I've glossed over or ignored here, but this should answer your specific questions.

 

One thing to note about flying to an NDB with the ADF - it sounds simple but try it with a stiff crosswind and you'll soon see one of the major complications. Flying a VOR radial directly to or from the staion is a lot easier in a wind than trying to track directly to or from an NDB with the same wind

 

John

[Andrew Godden 945]

Jim,

 

Obviously John and I where on your case at the same time.  Between our two responses, hopefully it will make NDB / VOR navigation easier to understand for you.

 

Cheers

Andrew

[allardjd 1,853]

With apologies to Rudyard Kipling...

 

"There are nine and sixty ways of describing VOR's ways, and every single one of them is right!"

 

John

[Gunner 69]

Have a look at this, Jim.

 

http://www.luizmonteiro.com/learning_vor_sim.aspx

 

 

[UKJim 502]

The explanations were bang on guys - thanks a bunch! So I understand ADF navigation just fine and the limitations (wind)

 

The VOR I see as a point with lines coming out of the center (radials) - I tune the nav radio to the VOR frequency and then I set the radial in the direction I wish to go - say towards the VOR. This will show the needle centre if I am on the right radial and it will say 'TO' as I am going towards the VOR.

I can pass the VOR and this will change to FROM - but I will still be lined up to the same radial.

 

Now - do I simply get the radials that I need to set from maps (Plan G)?

 

What kind of range do VOR's transmit?

 

Thanks for the help it's great - I always get interested in things like this it's a curse sometimes

[allardjd 1,853]

Quote

I can pass the VOR and this will change to FROM - but I will still be lined up to the same radial.

 

Yes, but you can change the OBI as you pass over the VOR and turn to the new heading. You'll then track it outbound with a FROM indication.

 

Quote

Now - do I simply get the radials that I need to set from maps (Plan G)?

 

Yes, or from sites like SkyVectors, FlightAware or AirNav. Usually this is done during flight planning. You should know long before reaching the VOR whether a turn is necessary and what the new heading is. That's what they mean by, "...being ahead of the airplane."

 

Quote

What kind of range do VOR's transmit?

 

VORs come in three flavors - High, Low and Terminal. In FSX the ranges are, I think, 105, 60 and 38 NM, respectively. In the real world it's a little more iffy but as long as you're high enough they click right in at those exact distances in the sim.

 

You can find out what type a VOR in FSX is by bringing it up on the map view.

 

John

[brett 2,316]

PlanG will give you the approximate distance when you hover you cursor of the VOR or NDB, something that FSX does not give you.

 

You can see the VOR radials on most charts. The QDM: Range and Bearing feature in PlanG is also a big help. Right click on center of VOR and pick QDM form the popup/direction is shown in the Information dropdown section when moving the cursor. See manual for more instruction. 

 

This is one of my favorite NAV tutorials. It also never hurts to brush up on your compass basics first.

 

Online Speed and Distance calculator.

[UKJim 502]

Thanks for the help - I have been using Plan G since I started on FSX - so why change the habit of a life time Ill use that to plan a flight.

 

I think with the VOR - I get the concept, but I think I need to put it into practice to see what actually happens when I cross over the VOR.

 

My thoughts are that I set the OBI to the radial going away from the VOR which in affect should be my heading. The direction should say 'TO' until I pass over the VOR where it will now say 'FROM' but I will still be heading on that same radial hence the same heading. 

If I am not comfortable with the fact that it says 'FROM' and can get confusing - I can change the OBI to be the opposite side of the compass and it should say 'TO' - but I think I will just keep it tuned in on the radial I originally was flying to (keep it simple)

 

Great tutorial there Brett and the speed calculator is good too. I think that is another issue I have is knowing how far away I am from a VOR but I guess if I plan my flight I should know roughly how long I will be flying between VOR's.

 

Cheers guys

 

Jim 

[Andrew Godden 945]

 

What kind of range do VOR's transmit?

VORs come in three flavors - High, Low and Terminal. In FSX the ranges are, I think, 105, 60 and 38 NM, respectively. In the real world it's a little more iffy but as long as you're high enough they click right in at those exact distances in the sim.

You can find out what type a VOR in FSX is by bringing it up on the map view.

John

 

 

Jim,

 

It sounds like you are getting the hang of it and flying is all the practice you need.  When I first started with NDB / VOR navigation, I would create specific flight plans to practice with.  I would avoid use of the GPS unless I was totally lost, but when you learn to trust your own judgement and skills, it starts to come naturally.

 

Further to John's post on ranges, typical ranges for VORs in FSX are 195 nm (maximum), 75 nm, 60 nm, and 37.5 nm.

 

If the VOR is co-located with a DME, it is called a VOR-DME and is distinguishable by a square box around the VOR symbol on the map.  This type of VOR will provide a distance read out on the DME in the aircraft.

 

Cheers

Andrew

[UKJim 502]

Yeah the only problem I have with that is my aircraft does not have a distance read out - it only has the dial with the needle

 

I fly the jets a lot and have skimmed over the GA planes - with the jets you obviously programme the FMC and away you go - but I want to start looking more into the VOR navigation I think.

 

The plane I will be using is the new Alabeo Tomahawk - such a great plane but does not have a master avionics switch LOL. 

 

Cheers,

Jim

[jaydor 345]

Jim, the best plane for learning VOR is the RealAir Lancair Legacy.  You have to really learn to fly this aircraft as it is one of the few realistic models for FSX.  Read Andrews review in the reviews section..

 

You also get the full HSI gauge and the DME readout display, so you get a better understanding when learning..  

[UKJim 502]

OK so I jumped in the carenado Mooney as this has all the right gadgets for the show - took off from EGNX and went to head to TNT VOR. I could not pick up the signal for some reason - but after snaking a while I found the beeps and lined up - I got there eventually.

 

LOLOL

 

[brett 2,316]

A good exercise for navigation is the past MEBAR flights starting with the test flights for a visual idea of passing over a VOR (also Andrews GARR rallies). You would take off from an airport, circle around to pick up the radial, follow it back to overfly the airport and then follow the signal to another location.

 

You might want to stay away from some of the flights in this past years MEBAR as there were many, many, many, many VOR/NDB intersections to follow. This means you would fly along a VOR radial until you meet up with another signal from another NDB or VOR. 

 

These rally's are blast and I highly recommend them.

[brett 2,316]

I just saw your last post. If possible it is best to follow the out going radial from your departure airport or at least a predetermined heading and then, when closer, to pick up your destination airport. Surrounding mountains can also block signals so take that into account. The signal is a small line so you really have to watch the needle or you can pass it easily. It is best to approach them at around a 30deg angle vs a 90deg one for this reason. It causes the needle to move slower.  

[UKJim 502]

Yeah I think my second go will be better practice makes perfect I suppose

[allardjd 1,853]

If you're in range and tuned to the right frequency, you can just twirl the OBI knob until the needle comes alive if you don't know quite where the station is. Turn it until the needle centers with a TO indication and that's the bearing to the station.

 

Over a VOR there's a "cone of silence" where you lose the signal. The higher you are, the larger the dead zone. If you know the new heading outbound you can turn to the new heading while in the cone, reset the OBI and watch for the needle to come alive with a FROM flag as you exit the cone of silence. One technique is to turn a little too early and not quite to the new heading, guaranteeing you'll intercept the new radial at some point as you fly away from the station. When the needle centers up, turn to the desired heading, allowing for wind. It kind of amounts to cutting the corner.

 

When using the DME, remember that it's showing "slant distance" to the station. If you are 30,000' AGL the DME will not register much below 5 miles.

 

John

[UKJim 502]

Thanks John - I think I will try that method of tweaking the knob

[Andrew Godden 945]

A good exercise for navigation is the past MEBAR flights starting with the test flights for a visual idea of passing over a VOR (also Andrews GARR rallies). You would take off from an airport, circle around to pick up the radial, follow it back to overfly the airport and then follow the signal to another location.

You might want to stay away from some of the flights in this past years MEBAR as there were many, many, many, many VOR/NDB intersections to follow. This means you would fly along a VOR radial until you meet up with another signal from another NDB or VOR.

These rally's are blast and I highly recommend them.

Brett's suggestions of the GAAR and MEBAR routes as practice is a good one. You can either load them up with the existing weather files for an added challenge or change the weather to something more enjoyable.

My design of the GAAR and MEBAR routes follow different principles because the countries are so vastly different when it comes to NAVAID navigation, large and sparse versus small and compact. My design of the MEBAR routes is part cunning and dastardly plan - I just haven't worked out what it is at the moment.

Cheers

Andrew

[allardjd 1,853]

When practicing VOR work initially, avoid go-fast airplanes. Something eating up 6 NM/min and making 5 mile radius turns is not a great environment for figuring out the intricacies of VOR work.

 

Also, this...

 

http://www.visi.com/~mim/nav/

 

...is the best desktop nav trainer I've ever used. You don't have to worry about flying the plane, just twiddle the dials. Try it - you'll like it. Requires Java.

 

John

[Tim_A 997]

With apologies to Rudyard Kipling...

"There are nine and sixty ways of describing VOR's ways, and every single one of them is right!"

John

 

What you meant to say was

 

There are three hundred and sixty ways of describing VOR's ways, and every single one of them is a radial!

 

[UKJim 502]

Cool thanks John for that - I will have a looksy later when I get home from work

 

LOL Tim - Good stuff