VOR Range
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VOR Range
No doubt, the effective range of a VOR beacon will depend on your altitude, but is there a rule of thumb, or indeed, somewhere that officially has the info.
Regards,
C23
Regards,
C23
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DOC only works if you have line of sight with the station.
Rule of thumb for line of sight (in NM) = sqrt(height in feet)
Assuming no big hills in the way etc.
e.g 2500' - 50NM
5000' - 70NM
Rule of thumb for line of sight (in NM) = sqrt(height in feet)
Assuming no big hills in the way etc.
e.g 2500' - 50NM
5000' - 70NM
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The exact solution for length of tangent (assuming station at GL) is:
sqrt(2rh+h^2)
where r is the radius of the earth
and h is the height of the observer.
To a first order the h^2 term is negligible.
So length of tangent = sqrt(2r) * sqrt(height)
In nautical miles the coefficient works out at 1.0634
In statute miles it is 1.2245
So 1 is an easy conservative value for a rule of thumb.
sqrt(2rh+h^2)
where r is the radius of the earth
and h is the height of the observer.
To a first order the h^2 term is negligible.
So length of tangent = sqrt(2r) * sqrt(height)
In nautical miles the coefficient works out at 1.0634
In statute miles it is 1.2245
So 1 is an easy conservative value for a rule of thumb.
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Originally Posted by Mark 1
The exact solution for length of tangent (assuming station at GL)...
In nautical miles the coefficient works out at 1.0634
In nautical miles the coefficient works out at 1.0634
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The exact solution for length of tangent (assuming station at GL) is:
sqrt(2rh+h^2)
sqrt(2rh+h^2)
I'm sure for the ATPLs it was something like height of Tx + height of Rx (feet), square rooted, x 1.25. Anyone more current?
Bookworm,
The ATPL assumes line of sight.
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Back to the original question....
For a rule of thumb, I prefer 1 as its easy to remember and slightly conservative.
I remember seeing 1.25 in one of the CPL text books, but this may be for a distance in stat. miles.
If the VOR is positioned significantly higher than the surrounding land then you can add a bit for this, as bookworm says.
Given the variability with local geography, I'd go for the conservative factor.
This is only for planning anyway. If you have a flag and ident, and are less than DOC distance, then it's OK to use it.
For a rule of thumb, I prefer 1 as its easy to remember and slightly conservative.
I remember seeing 1.25 in one of the CPL text books, but this may be for a distance in stat. miles.
If the VOR is positioned significantly higher than the surrounding land then you can add a bit for this, as bookworm says.
Given the variability with local geography, I'd go for the conservative factor.
This is only for planning anyway. If you have a flag and ident, and are less than DOC distance, then it's OK to use it.
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Straight Line Propagation Paths - Direct or Space Wave
D (NM)=1.25(sqrt HTTX Station + 1.2 sqrt HTRX Station)
Example.
VOR 400ftamsl
Aircraft 5000ft amsl
D= 1.25 x (sqrt400 + sqrt5000) = 113.38NM
D (NM)=1.25(sqrt HTTX Station + 1.2 sqrt HTRX Station)
Example.
VOR 400ftamsl
Aircraft 5000ft amsl
D= 1.25 x (sqrt400 + sqrt5000) = 113.38NM
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None of this ATPL ground school stuff is very relevant in practice, because if you potter about the UK at low levels you won't be receiving anything a lot of the time (except GPS) and if flying UK/European airways then ATC will send you all over the place and quite happily DCT some VOR which is way outside the DOC - they simply assume you have BRNAV which means a GPS.
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It's the damned exams one has to get through
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And to help complicate things a bit more:-
We ancient master mariners were taught:-
Distance of the horizon = (1.15 x sqrt H) + (1.15 x sqrt h)
Were H = Your height of eye and
h = Height of object (normally a ruddy lighthouse)
Although they did make a consession that a constant of 1.17 a better value for average conditions.
Just thought you ought to know.
We ancient master mariners were taught:-
Distance of the horizon = (1.15 x sqrt H) + (1.15 x sqrt h)
Were H = Your height of eye and
h = Height of object (normally a ruddy lighthouse)
Although they did make a consession that a constant of 1.17 a better value for average conditions.
Just thought you ought to know.
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Given the variability with local geography, I'd go for the conservative factor...This is only for planning anyway. If you have a flag and ident, and are less than DOC distance, then it's OK to use it.
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