Commencing a GPS approach from a fix other than the FAF

Dave Butler wrote:
There's no need to clear the discontinuity. Just select EWTOF from the
flight plan and go direct.
snip

Ok, again after more fiddling, you are correct. I was able to do that
just now, although I swear I couldn't make it happen a couple of hours
ago. It doesn't get rid of the discontinuity that is automatically
inserted, but it does bypass it! Interestingly enough, I checked out
the 530 behavior and it doesn't add the discontinuity.

Problem solved. I guess.

To echo comments that Dave J. made, I think the interfaces to these
things suck! I'm also in my early 30's, used to make my living in high
tech, and am fairly computer savvy. I am amazed at how poor the
interface design is. I'm just happy that I grew up (not matured!) with
exposure to computers. Trying to help my sexagenarian uncle wrap his
brain around the 530/STEC/GPSS system in his Twin Commanche seems like
a large task! He's back to flying from taking a 20 year layoff and the
flying is the easy part. The automation/avionics are more difficult by
a long shot, but he's doing pretty good thus far.

Cheers,
--Chris

Peter wrote:

"Dave J" wrote


Aviation used to represent the cutting edge in human factors research.
What happened?


I think that anybody with more than half a brain departed the GA
avionics business at least 20 years ago.

If you were seriously smart, would you work for a company that makes
stuff using 1980s technology (colour LCDs aside) and brings out a new
product once every 10 years? No company that does that will retain
good people. To top it, they blame it on certification; it doesn't
take 10 years to certify a product... especially if the company is
already loaded with competent paper-pushers.

The manner in which a GPS approach is flown with an IFR GPS should be
far simpler.


Avionics for GA is a tough business to begin with. You've got a very
limited market to begin with: only a few thousand new planes per year on
a good year, with only a chance that the manufacturer will select your
gear, and a retrofit market that isn't all that much bigger. What is it
about 200,000 aircraft total. Of those, a few percent will upgrade
their avionics in a given year. Say by some miracle, you catch 20% of
the market, that's still only 40000 units and once you sell those units,
those aircraft won't be upgrading again for probably at least 10 years.
that means, only a couple thousand units per year sales. It is hard
to spread out the production and design costs enough to make the unit
affordable enough for folks to buy it and yet profitable enough for the
business to break even or (gasp) make a profit. That, folks is the real
problem. Fixing it requires either a lot more people buying airplanes
(don't hold your breath for that), or having the avionics boxes have
some other higher volume market that can share much of the development
(eg. boating and automotive GPS supports our aviation GPS by using a
common platform).

-----Original Message-----
From: Ray Andraka ]
Posted At: Saturday, January 20, 2007 10:47 PM
Posted To: rec.aviation.ifr
Conversation: Commencing a GPS approach from a fix other than the FAF
Subject: Commencing a GPS approach from a fix other than the FAF

....

Avionics for GA is a tough business to begin with. You've got a very
limited market to begin with: only a few thousand new planes per year
on
a good year, with only a chance that the manufacturer will select your
gear, and a retrofit market that isn't all that much bigger. What is
it
about 200,000 aircraft total. Of those, a few percent will upgrade
their avionics in a given year. Say by some miracle, you catch 20% of
the market, that's still only 40000 units and once you sell those
units,
those aircraft won't be upgrading again for probably at least 10
years.
that means, only a couple thousand units per year sales. It is hard
to spread out the production and design costs enough to make the unit
affordable enough for folks to buy it and yet profitable enough for
the
business to break even or (gasp) make a profit. That, folks is the
real
problem. Fixing it requires either a lot more people buying airplanes
(don't hold your breath for that), or having the avionics boxes have
some other higher volume market that can share much of the development
(eg. boating and automotive GPS supports our aviation GPS by using a
common platform).

Maybe the solution would be to design a system that meets not only GA
purposes but also 121 needs. I'm willing to be the increase in volume
could more than offset the delta in engineering costs. After all, we
work in the same system with usually the same minimums. If the
supporting infrastructure (electric bus, rack space, etc) could be made
similar there should be an economy of scale.

Even if Garmin was to make remote control/display an option so the
equipment could be mounted in an avionics bay, that additional
engineering would probably be justified by the increased volume for a
single design.

I hear all this about how avionics is a tough business, and I get it --
and yet that explanation is not completely satisfying. As others have
pointed out, there are business with lower margins and smaller markets
that seem to get by.

The reason I think about certification is that the non-certified area
of avionics seems to be quite healthy (or is at least not completely
moribund.) Look at the handheld GPS market, the for-kit primary nav
stuff (blue mountain, dynan, etc), EFBs, TCAS-like devices, headsets,
etc.) There is some real competition going on here and some of these
markets are way smaller than that for panel-mount GPS units.

-- dave j

Roy Smith wrote:


It ATC is allowed to send you direct to an IF, then the distinction between
IF and IAF has, for all practical matters, been eliminated. If that's the
case, then the databases and/or software needs to be updated to have the
IFs show up in the menu.

It will take quite a few years for the FAA to identify all the IFs.
Direct-to-the IF is not an "if" for RNAV IAPs. ;-)

It's been in the AIM and 7110.65 for about a year now.

Peter wrote:

If you were seriously smart, would you work for a company that makes
stuff using 1980s technology (colour LCDs aside) and brings out a new
product once every 10 years? No company that does that will retain
good people. To top it, they blame it on certification; it doesn't
take 10 years to certify a product... especially if the company is
already loaded with competent paper-pushers.


In this case certification standards and obstacle clearance protected
airspace are pretty much married to each other.

"Sam Spade" wrote in message
...
Roy Smith wrote:


It ATC is allowed to send you direct to an IF, then the distinction
between IF and IAF has, for all practical matters, been eliminated. If
that's the case, then the databases and/or software needs to be updated
to have the IFs show up in the menu.

It will take quite a few years for the FAA to identify all the IFs.
Direct-to-the IF is not an "if" for RNAV IAPs. ;-)

It's been in the AIM and 7110.65 for about a year now.

What's to identify? If it is not an IAF, and not the FAF, and is on an
intermediate segment, it is an IF. Why does it need to be "identified"?

PCG:

INTERMEDIATE FIX- The fix that identifies the beginning of the intermediate
approach segment of an instrument approach procedure. The fix is not
normally identified on the instrument approach chart as an intermediate fix
(IF).

Intermediate Approach- The segment between the intermediate fix or point and
the final approach fix.

(Is that circular, or what?)

Stan Prevost wrote:
"Sam Spade" wrote in message
...

Roy Smith wrote:


It ATC is allowed to send you direct to an IF, then the distinction
between IF and IAF has, for all practical matters, been eliminated. If
that's the case, then the databases and/or software needs to be updated
to have the IFs show up in the menu.

It will take quite a few years for the FAA to identify all the IFs.
Direct-to-the IF is not an "if" for RNAV IAPs. ;-)

It's been in the AIM and 7110.65 for about a year now.


What's to identify? If it is not an IAF, and not the FAF, and is on an
intermediate segment, it is an IF. Why does it need to be "identified"?

Because sometimes there is a stepdown fix, or two, in the initial
segment, and sometimes there is a stepdown fix, or two, in the
intermediate segment. In that event you do not know which fix is the
intermediate fix (well, we're really speaking of waypoints since this is
an RNAV-only procedure).

If there is only one fix between the IAF and the FAF that, indeed, is
the IF. You are free to determine that on a ad hoc basis as are
controllers.

Jeppesen and NACO, are not. They will not designate the IF until it
appears on the official source. The database vendors, if they chose to
designate IFs in the database, would also not do it on an ad hoc basis.

That's the way the procedures and charting systems work.

"Sam Spade" wrote in message
...
Stan Prevost wrote:
"Sam Spade" wrote in message
...



What's to identify? If it is not an IAF, and not the FAF, and is on an
intermediate segment, it is an IF. Why does it need to be "identified"?

Because sometimes there is a stepdown fix, or two, in the initial segment,
and sometimes there is a stepdown fix, or two, in the intermediate
segment. In that event you do not know which fix is the intermediate fix
(well, we're really speaking of waypoints since this is an RNAV-only
procedure).


OK, that helps. Although, as Roy said, it doesn't seem to matter much, the
distinction has become blurred. The controller is supposed to issue an
altitude restriction for the vector that is consistent with the MVA/MIA,
thus insuring obstacle clearance, so it is not obvious why IAF vs IF vs
stepdown fix really matters. But, the rule ought to be clear.

I had thought that all the fixes between an IAF (or the beginning of the
procedure) and the FAF are IFs (disregarding fix vs waypoint). Apparently
that is not true, given stepdown fixes on the initial segment. Don't think
I have seen one of those, but they seem to be allowed by TERPS. But I also
thought that all fixes on the intermediate segment were IFs. But that does
not seem to meet the definition of IF in the P/CG.

The altitude issue is a big problem with this business of vectoring to the
IF on RNAV approaches. If the IF altitude is not at or above MVA/MIA, the
approach may not be flyable with vectors to IF. 7110.65 does not give
guidance to controllers on that issue, that I can find.

Stan Prevost wrote:

"Sam Spade" wrote in message
...

Stan Prevost wrote:

"Sam Spade" wrote in message
...



What's to identify? If it is not an IAF, and not the FAF, and is on an
intermediate segment, it is an IF. Why does it need to be "identified"?

Because sometimes there is a stepdown fix, or two, in the initial segment,
and sometimes there is a stepdown fix, or two, in the intermediate
segment. In that event you do not know which fix is the intermediate fix
(well, we're really speaking of waypoints since this is an RNAV-only
procedure).



OK, that helps. Although, as Roy said, it doesn't seem to matter much, the
distinction has become blurred. The controller is supposed to issue an
altitude restriction for the vector that is consistent with the MVA/MIA,
thus insuring obstacle clearance, so it is not obvious why IAF vs IF vs
stepdown fix really matters. But, the rule ought to be clear.

Look at KSEA RNAV 16L. That was recently revised to designate the IF.
Prior to January 18 you had several fixes between the IF and the FAF and
you didn't know which one was the IF. I could search all night and find
some like this without IF designated. It was decided that sending an
aircraft to a fix within the IF is into a narrow area that is more
properly handled with vectors to final. But, where there are multiple
stepdown fixes in the intermediate odds are the MVA would be too high to
be compatible with descent requirements.

I had thought that all the fixes between an IAF (or the beginning of the
procedure) and the FAF are IFs (disregarding fix vs waypoint). Apparently
that is not true, given stepdown fixes on the initial segment. Don't think
I have seen one of those, but they seem to be allowed by TERPS. But I also
thought that all fixes on the intermediate segment were IFs. But that does
not seem to meet the definition of IF in the P/CG.

No, The IF is where the rampdown from initial widths to final segment
width begins and were 500 feet of obstacle clearance comes into play.
The fixes between the IF and FAF are just step-down fixes.

The altitude issue is a big problem with this business of vectoring to the
IF on RNAV approaches. If the IF altitude is not at or above MVA/MIA, the
approach may not be flyable with vectors to IF. 7110.65 does not give
guidance to controllers on that issue, that I can find.

Yes, it is there and clearly stated. In 4 (f) of 4-8-1 it states "at an
altitude that will permit normal descent..." Then the note defines that
as 300 feet per mile

(f)The aircraft is on a course that will intercept the intermediate
segment at an angle not greater than 90 degrees and is at an altitude
that will permit normal descent from the Intermediate Fix to the Final
Approach Fix.

NOTE−Controllers should expect aircraft to descend atapproximately 300
feet per NM when applying guidance insubpara 4(f) above