Turning on a VOR

[Pass your message]

What technique do you recommend I use for turning over a VOR onto a new outbound radial. Eg say you are at 2000ft (I know height matters) and are tracking to DET inbound on 120 degrees. Then you want to track DET outbound on say 220 degrees. Do you go past DET for a couple of miles on the track to maintain 120 on the DME then turn at an intercept angle to bring in 220. Or, do you turn before it changes from "To", if so by how much on the DME and then on to 220 or an intercept from that point. Or do you turn at the actual point where To becomes From? On any situation it seems picking up the outbound radial is not easy to do in a quick manner and if you are close to CAS this might matter.

[ChickenHouse]

Don't know of a setting or rule for this, but I usually turn at entering the cone of silence, but I am flying slow.

[7of9]

Rate one turn on entering cone of silence is method I use.

[BackPacker]

If the VOR is an "overfly" fix, for instance as part of an approach procedure, you should not anticipate the turn, but rather initiate the turn right after passing the turn. Obviously you've now overshot the new radial, so you need to turn a bit more to setup an interception course - typically 30 degrees or so.

If you are allowed to anticipate the turn, here's what I do. You calculate the heading change, and calculate how much time such a heading change is going to take, assuming a rate 1 turn. So if I need to turn by 100 degrees (per your example), it will take 33 seconds (3 degrees per second). I then anticipate the turning point by starting my turn half of this number of seconds early. In this example, 16 seconds before I overfly the VOR. If necessary, you can convert this into a distance if you know the groundspeed, but most DMEs will actually do this for you already.

For relatively shallow turns, up to approximately 90 degrees, this works a treat. For turns significantly more than 90 degrees you've got to start the turn a lot earlier in order to end up on the proper outbound radial. There are better methods for calculating that, but they're more complex and not as easy to remember.

And in any case you have to take slant distance into account. If you're at about 3000', directly over the VOR/DME, the DME will show 0.5 nm, not zero. A GPS makes this a lot easier, and a moving map GPS even more so.

[Jan Olieslagers]

"cone of silence" is a term I never heard - but then there's no nav-receiver in my plane so I never studied VOR's in depth. I reckon it means one is so close to the VOR that its information is either unavailable or unreliable? what is its typical size, at some typical altitudes?

[S-Works]

You turn onto the new heading the moment the VOR indicates station passage. Then dead reckon until it comes alive again then carry out any correction as needed.

No fancy rules or algorithms needed. It's been done for decades successfully.

[Johnm]

Just use it as a waypoint in the GPS and turn when the GPS tells you to :E

Edited to add: It's unwise to get too close in any event as they can be honeypots for VERY accurate GPS nav. I normally avoid them by a couple of miles or more and keep a good look out if in VFR/VMC conditions.

[thing]

I usually start a ten degree or so bank turn with about 4 miles to run onto a 30 degree intercept with the new radial. By the time you have reached intercept the needle is steady and not faffing around all over the shop. Obviously this is for a large change of track from the VOR. If you are more or less going straight on and just using it as a nav point then ignore everything from 4 miles inbound to 4 miles outbound and just fly dead reckoning. Unless you are dodging airspace there's no need to bust a gut flying straight over the top. As someone has said, VOR's tend to be honeypots anyway, best to stay on the outskirts IMO.

There's no need to split hairs doing this stuff, don't over complicate it.

[Talkdownman]

I thought one simply plugged it into a 240v supply and pulled a massive knife-switch...

[Flyingmac]

I thought you licked its ear.

[evansb]

The "Cone of Silence" is generally a 60 degree splay from overhead the transmitting antenna. So, at 6,000 ft. above the transmitter, it is about a mile in diameter.

[glendalegoon]

isn't the cone of silence a term most properly used with the aural range? or Maxwell smart?

zone of confusion or ambiguity might be the better term.

In the AIM of the USA there is quite a nice page or two on the subject. I can't imagine that you haven't read the aim or similar of your own country.


station passage of the VOR is noted by the first positive change of the ambiguity detector from to to from or vice versa.

[RatherBeFlying]

If you are flying an IFR clearance, the change in course enroute will be minimal -- wait until you see from, turn to new course, set the dial and correct as needed. In a non radar environment, you have to report crossing time to ATC.

In the terminal environment, there will be a procedure turn where a large course change is required -- or you just follow the active STAR. ATC expects you to fly to the fix, then turn. Cutting corners gets you too close behind the guy ahead.

[glendalegoon]

https://www.faa.gov/air_traffic/publications/atpubs/aim/aim0503.html


here is what the FAA says about leading a turn on an airway with vor nav...really not for slow planes...they say 290knots true airspeed or better...but have a look.

fig 5-3-1 and section 5-3-5...closer to the bottom.

[ChickenHouse]

"cone of silence" is a term I never heard

Did you ever pass an exam for electronic navigation, are you still on ICAO PPL without CVFR? It should have been in your theory training syllabus ... and your navigational aid training practice ...

[Mach Jump]

As Glendale said, the 'cone of silence' was a term associated with the old radio ranges, where being left or right of track was indicated by audio 'dots' and 'dashes' rather than a visual display. It's modern equivalent is the 'cone(or area) of confusion' This is found in the area above a VOR, where the receiver cannot differentiate the signals from the transmitters to the extent required to determine the bearing.(Indicated by the 'OFF' flag showing on the indicator.)

If you are using the VOR on it's own,(without DME) then you must fly across the cone of confusion until you get a positive indication of station passage on the TO/FROM flag. Inevitably, this will mean that you will have to fly past the VOR, and then re-intercept the new track.

If you also have DME, you can use this to confirm that you are overhead the VOR, so long as you take into account the 'slant range' effect, in that when overhead, the DME will indicate the vertical distance from the beacon.(and will stop decreasing) You can also use the DME to anticipate the turn a little so that you roll out on the new track. This obviously, requires a reasonable estimate of the radius of turn.


MJ:ok:

[piperboy84]

Its amazing how technology has changed the game for navigating, with essentially free apps running on phones and inexpensive portable units that provide such an accurate backup source of situational awareness. I fly with a rock solid panel mounted VFR Garmin 496 and no matter how hard I try to fly with reference to the CDI only, a 2 second scan of the moving map puts it all in perspective. Old school flying? Probably not, but simple and efficient. Young pilots in the future will laugh at concepts such as slant range and zone of confusion.

[ChickenHouse]

@MachJump: Almost, the VOR emits radio waves from an electrical dipole. There is no e-m radiation going to the cone of silence due to the directional character of the antenna based radiation and this is valid for the radiation itself as well as the modulated sidetones used for identification.

http://content.answcdn.com/main/content/img/McGrawHill/Aviation/f0169-03.gif

[ETOPS]

Cone of confusion = the area between my ears that expands with increasing altitude :confused:

[ChickenHouse]

@ETOPS: I hope it is "volume" instead of "area" :confused: , otherwise I would ask for a photo of your flathead ...

[Jan Olieslagers]

Have you read what I wrote? Or only the part you wanted to read?

[BEagle]

bose-x wrote:

You turn onto the new heading the moment the VOR indicates station passage. Then dead reckon until it comes alive again then carry out any correction as needed.

No fancy rules or algorithms needed. It's been done for decades successfully.

Absolutely spot on - at least for light a/c. These days though, very few faster / larger aircraft will do anything except to lead the turn as required by on-board automatic computation systems such as FMS unless the VOR has been tagged as a 'fly-over' waypoint (such as when it forms part of the SID routing). After overflying a 'fly over' waypoint, the track intercept angle should be at 30° to the course between the VOR and the subsequent waypoint (aircraft is flying from the south to WYP, thence joining UZ28 at BAMVI):

http://i14.photobucket.com/albums/a341/nw969/FLYOVER_zpsfcbc68ec.png (http://s14.photobucket.com/user/nw969/media/FLYOVER_zpsfcbc68ec.png.html)

However, if the ATCC had cleared a direct route from WYP to BAMVI, the turn at WYP would not require this 30° intercept, but would be direct to BAMVI.