On 10/6/2005 10:42, Greg Farris wrote:

The title just about says it - I've always wondered WHY many
non-precision approaches (not talking about LOC only here, but VOR,
VOR/DME, NDB etc) are not lined up with the runway heading. Sometimes it
looks as though the approach desginers have gone out of their way to
make sure the non-precision approach is just a few degrees off - as if
to say - "look stupid - this is not a precision approach . . ." But if
this were so, then we would have to wonder why SOME of these approaches
ARE lined up and straight-in. I'm surev there's a simple explanation
that will be pointed out here.

thanks,
G Faris


I can think of a couple reasons. First, as other have said, the VOR
will not always be lined-up with the runway.

Secondly, it may be that the approach path has to come in at an
angle to avoid something, like high terrain, housing communities,
etc. (so they may have placed the VOR off center to facilitate
that).

Also, you shouldn't think of the difference between precision and
non-precision approaches as being lined-up or not with the runway.

Precision approaches are those that provide vertical guidance. Non-
precision approaches do not. That's the difference.

The fact that the typical precision approach uses a localizer which
is lined up with the runway (because the antenna is situated at the
field) does not make the approach 'precision' - the fact that it
provides vertical guidance does.


--
Mark Hansen, PP-ASEL, Instrument Airplane
Sacramento, CA