VOR Range
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From: East Midlands
Joined: Aug 2000
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From: S Warwickshire
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.
Joined: Aug 2000
Posts: 3,648
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From: UK
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
Guest
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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.
Joined: Aug 2000
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From: S Warwickshire
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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From: EuroGA.org
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.
It's the damned exams one has to get through
It's the damned exams one has to get through
Joined: Feb 2002
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From: Hampshire, UK
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.
Guest
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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.
