On 01/26/06 11:14, Dave Butler wrote:
wrote:
Hello,

Yesterday I was out getting an IPC. We were doing the Stockton, CA
ILS. ATC
had us intercepting the localizer at 2000 feet. The altitude for
glideslope
interception is 1800 ( underlined ).

My old CFII taught me that the glideslope interception altitude on
the chart is a minimum altitude, and that it was fine to intercept it
higher. So I just tootled along
at 2000 - figuring it was simpler to do one configuration change at GS
interception
rather than three changes - one to descend the 200 feet, another to
level off, and
a third to intercept the glideslope.

The new CFII criticized this procedure and told me that the plate
specified 1800,
and it was wrong to intercept at 2000. Which one was right?

My first thought was, "your old CFII" was right.

I certainly would have done exactly what you did, and had no heartburn over it.

OTOH, that got me wondering how much above the published glide slope intercept
altitude I would accept. To take an extreme example to illustrate the question
(not a realistic example, of course) suppose ATC had you intercepting the
localizer at 10000 feet.

For the purposes of the thought experiment, assume this still allows you to
intercept the glide slope from below. Could you be confident that the glide
slope had been flight-checked up to 10000 feet? No. You also don't know that
it's been flight checked to 2000 feet. Where do you draw the line?

Dave

The other thing to remember is that when you are backed-up from the
Final Approach Point, you know you will intercept the GS at a higher
altitude, but where exactly? After all, if you are too high, you
could be picking up an erroneous echo of the GS signal.

This is part of the risk (minor that it is) in doing this - because
if you follow the signal down to the outer marker (in the OP's case)
and are not at the correct GS altitude, you probably should go missed.

However, in the real world, ATC isn't going to vector you in this way
if the altitude wouldn't intercept the actual GS signal, so although
the pilot should remain vigilant and watch for things to go south, it will
generally work out.

--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA