I should think centerline intercept at 45 degrees or less well outside the
traffic pattern radius qualifies,
but otherwise "roll your own" about covers it.
Ask the controller to be more specific if you're unsure;
It's your ass up in the air, not his.
Hmm, let's do the trig:
Initial distance 10 mi.
Say "well outside pattern" = 3 miles from the center of the airport.
Two legs of the triangle are the 10 mile line to the airport center and the
three mile line along the extended runway 20 centerline.
The turn to centerline is 20 right if the bearing to the airport is 180 so
the included angle is 20 degrees.
The left correction is then arctan ((3*sin(20))/(10-3cos(20))) = 6.3 or so
degrees.
Make a 6.3 degree left turn and you'll intercept the centerline three miles
out.
Realistically what are you gong to do? Nudge it 5 left and see what happens.
H.
N502TB

"Ron Natalie" wrote in message
m...

"HankC" wrote in message
om...
I'm 10 miles N of the field and the tower calls for a straight-in on
runway 20.

What's the best way intercept the runway centerline?

In good VFR conditions, I'd just head straight for a point on the
extended centerline about a 1/4 mile out from the runway (i.e., a
base leg at a very obtuse angle).

In other cases, I might boogie over to the centerline and a decent
angle to pick up the localizer (if available).