VOR approach- when to descend from the FAF

On Tue, 19 Feb 2008 05:22:18 -0800, Sam Spade
wrote:

Les Izmore wrote:
On Mon, 18 Feb 2008 07:24:39 -0800, Sam Spade
wrote:


Terence Wilson wrote:

On Sat, 16 Feb 2008 19:01:14 -0800, Sam Spade
wrote:



Terence Wilson wrote:


When flying a VOR approach in which the FAF is defined by the VOR, is
it appropriate to start the descent to the MAP, or next stepdown,
immediately after overflying the VOR or should I wait until I have
positive course guidance for the final approach segment?

I ask because it can sometimes take 1-2nm for the CDI to move, which
may require a rushed descent to the MAP on some approaches.

Are you a simulator only pilot?

I ask, because that is a question that would be answered during
instrument training.


Sam, I think you asked me that question before and I answered .

I'm a RW instrument student.

Forgive me my lousy memory. I figured your CFI-I would have covered
this by now.

When the two-from indicator indicated "from," you should turn to the
appropriate heading and begin descent at that time. You are effectively
on-course because you are over the station where the courses are very,
very small. Sort of like lines of longitude at the North Pole.



Now, the question is, when you are 2 miles from the VOR and the needle
still has not moved (because of bad navigation, winds, whatever),and
you have descended xhundred feet, what do you do?


Are you going back up? Probably not.

Starting down without at least some indication that the needle is
moving back towards center can very well be the beginning of the
pernicious and well-known accident chain.

Don't do it.



That would represent issues of lack of competency to be 2 miles from the
station and not have a needle moving back towards center. In fact the
needle should be moving back towards center far sooner than that.


Well, that is precisely the reason why it is bad advice to start down
with no indication of movement of the needle.

If it does indeed start moving far sooner than that, then there is
minimal if any penalty for waiting.

If it does not start moving sooner than that, there is good reason
(issues of incompetency being one) not to have already begun the
descent.

So I'll say it again for emphasis. Until there is some indication
that the needle is moving toward the center, indicating a return to
the desired course, don't descend below the FAF altitude.

(The 2 miles, incidentally, was what the poster used as a basis for
his question).