In article ,
"C J Campbell" wrote:

"Greg Esres" wrote in message
...
| Can anyone suggest any reasons why you shouldn't use GPS or DME to
| lead your turns when approaching a fix, such as an IAF, on a non-GPS
| approach? (Meaning that you don't wait for complete reversal of the
| nav instrument.)
|
| The AIM has a couple of requirements for a "complete reversal" of the
| TO/FROM indicator, but they aren't instructions about how to fly an
| instrument approach. Regardless, those injunctions may be outdated in
| a GPS world.

I was taught as an Air Force navigator back in the 1970's to always begin my
turn before actually reaching the fix in order to avoid overshooting the
outbound (from the fix) course. I have never heard anything since then that
would suggest a better course of action.

What were you flying? In a spam can doing 120 kts (which is the
environment most civilian instrument is done in), the turn radius is
pretty small. If you're flying a jet, leading the turn may be the only
way to avoid blowing out the side of the airway on sharp turns.

Another factor is that up until a few years ago when GPS started to
become ubuiqitous, most instrument trainers had no DME so a full TO/FROM
reversal way the only way to be sure you had reached the fix. If you
have DME or GPS and thus accurately know your distance to the fix, I
don't see any reason not to lead the turn.