KLN94 GPS and flying "overlay" GPS approaches

Peter wrote:



However, I've heard from an American pilot that all the overlay
approaches in the USA work just the same as the full GPS approaches,
in terms of GPS behaviour, auto sensitivity switching, etc.

Is this true?

Only where authorized by the FAA; i.e. "VOR or GPS Runway 36."

That translates to the approach being in the database with approach
sensitivity and RAIM available for the final approach segment.

If the approach doesn't have "or GPS" in the title; e.g, "VOR Runway 18"
the avionics vendor can still elect to have the approach in the database
but it cannot invoke approach senesitivity nor RAIM for the final
approach segment. In other words, it would be advisory only and only
"additional pilot information" to the VOR approach terminal routes and
final approach segment.


If so, it would indicate that Jepp have given non-US overlay
approaches a lower status as far as the GPS operation is concerned.

On 06/14/06 10:35, Peter wrote:
Sam Spade wrote

If the approach doesn't have "or GPS" in the title; e.g, "VOR Runway 18"
the avionics vendor can still elect to have the approach in the database
but it cannot invoke approach senesitivity nor RAIM for the final
approach segment. In other words, it would be advisory only and only
"additional pilot information" to the VOR approach terminal routes and
final approach segment.

That apears to be what's happened in Europe (Jepp database) but I will
have a look at some of these to see if the "GPS" flag shows. I've
never seen it showing before.

What does your KLN94 Pilot's Guide say in the section on selecting
approaches? Here is a note from the Pilot's Guide that I'm using:

NOTE: Those approaches not having the letters GPS to the right of the
approach name are not approved for GPS. Therefore, the KLN 94 may
ONLY be used to provide situational awareness and monitoring for these
approaches. When a non-approved approach is selected a page is displayed
for the pilot to acknowledge
by pressing the Fbutton (figure 6-
10). When a non-approved
approach is selected the unit will
remain in approach arm mode (or
terminal mode) and will not transition
to the approach active mode.

Now, if your unit follows the same rules, and none of your approaches have
"gps" next to them, then what good is the fact that the unit is certified
for IFR Approaches?

Something must be missing...


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

On 06/14/06 12:49, Peter wrote:
Mark Hansen wrote

Now, if your unit follows the same rules, and none of your approaches have
"gps" next to them, then what good is the fact that the unit is certified
for IFR Approaches?

Something must be missing...

The bit that's missing is that I am not in the USA

Well ... I wasn't missing that part ;-\


There are some proper GPS approaches in Europe that are fully active
now, e.g. LKPR

http://www.ead.eurocontrol.int/eadba...2006-04-13.pdf

but only a few of them. All the rest of the approaches in the European
GPS database are overlays, and I don't think they are authorised for
"GPS".

In the U.S., GPS Overlay approaches can be flown by an IFR-certified
GPS unit (TSO C-129 and the 146 whatever one).



My KLN94 manual is the same as yours - the GPS is identical too.

Good question about what is IFR certification good for over here. One
does need BRNAV capability at FL095+ in Europe and in the GA context
that means GPS, and it has to be a TSO-129 unit. But a lot of IFR GPS
installations have the GPS set to VFR only as a certification
requirement (mine was) and that works for en route nav.

Do you know whether or not you're allowed to use the GPS as primary
navigation to fly the GPS overlay approaches in your country?


What puzzles me is whether the KLN94 actually fails to do anything
with the HSI, when on a non-"GPS" approach. That sounds almost too
"vindictive"

Well, if the GPS cannot switch to Approach (Active) mode, then it
will still drive the CDI, but not at 0.3sm sensitivity. The manual
states that it will remain at the 1.0sm sensitivity.

I was taught that you cannot legally fly the approach with the GPS
unless it switches to Approach (Active) mode. Maybe that's a U.S.
only rule (I doubt it).



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

On 06/14/06 13:32, Peter wrote:
Mark Hansen wrote

Do you know whether or not you're allowed to use the GPS as primary
navigation to fly the GPS overlay approaches in your country?

Since the overlay approaches don't work properly within the GPS (no
automatic sequencing into APR mode, etc) I can't believe the answer is
Yes.

That's how it sounds, but I wonder if this is the case with all
GPS Overlay approaches, or just the ones you've noticed?


In practice, of course you can. You self-position a bit outside the
FAF (in fact you fly the proper procedure to get there) then track
across the FAF nicely established on the final approach track, check
the inbound on the navaid (VOR/ADF) just to make sure, and follow the
line on the GPS on the way down.

Well, if you're using the ground-based nav aid for primary navigation,
and just using the GPS for situational awareness, then sure. However,
when the approach is approved for GPS use and the GPS meets all of
its requirements for flying the approach, we can fly the approach
without the VOR being tuned in at all.




What puzzles me is whether the KLN94 actually fails to do anything
with the HSI, when on a non-"GPS" approach. That sounds almost too
"vindictive"

Well, if the GPS cannot switch to Approach (Active) mode, then it
will still drive the CDI, but not at 0.3sm sensitivity. The manual
states that it will remain at the 1.0sm sensitivity.

I didn't see that in the manual.

Yes.

Look in the sections on what is required to switch from Term (Arm) mode
to Approach (Active) mode. There is a list that includes RAIM, 2 miles
from the FAF inbound, etc.

It says what it will do if it can't switch.


I do see

"When a non-approved
approach is selected the unit will
remain in approach arm mode (or
terminal mode) and will not transition
to the approach active mode."

That's one of the things that will keep it from switching to Approach (Active)
mode.


but it also says, page 6-36, section 6.2.12,

"Since another navigation source is providing primary navigation
guidance, the KLN 94 may not be driving the CDI or HSI."

This assumes you've switched the GPS/VOR button to VOR (or whatever
it is that switches the CDI on the external VOR head from indicating
the GPS to indicating the VOR).

I think by "may not be driving", they are leaving open the possibility
that you haven't changed this switch as appropriate.


I was taught that you cannot legally fly the approach with the GPS
unless it switches to Approach (Active) mode. Maybe that's a U.S.
only rule (I doubt it).

That makes sense, though of course you can legally fly it using the
normal navaid equipment and use the GPS for monitoring only, and the
end result is about the same.

By "fly the approach with the GPS", I mean using the GPS as the
primary navigational source - where you could have your VOR/ILS/
NDB receivers switched off (not that you would do that).

If you still use the GPS to drive the CDI when it is not in Approach
(Active) mode, then you're not getting the sensitivity that is
required for this purpose. That is a difference, IMHO.

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

On 06/14/06 15:00, Peter wrote:
Mark Hansen wrote

This assumes you've switched the GPS/VOR button to VOR (or whatever
it is that switches the CDI on the external VOR head from indicating
the GPS to indicating the VOR).

That I can see; if the GPS/NAV switch is set to NAV then the GPS won't
be driving the HSI anyway.

This is a nice gotcha if you are flying an ILS, and the last leg of
the GPS track just happens to more or less line up with the runway
centreline, and you forget to change the switch to NAV In some odd
installations, if you set an ILS frequency in the radio, that switch
gets overriden by a relay, into the NAV position; not sure whether
that's a good solution.

I was taught to check the position of this switch as part of my
approach briefing. If I'm flying a GPS approach, make sure the
switch is in GPS, otherwise, make sure it is in NAV (or whatever).


By "fly the approach with the GPS", I mean using the GPS as the
primary navigational source - where you could have your VOR/ILS/
NDB receivers switched off (not that you would do that).

Indeed, but who knows what you have switched on or not.

The point is what is needed to fly the approach. If the GPS is
being used as primary (and you're ignoring the other nav receivers,
etc.) then the GPS must switch into Approach (Active) mode. If it
does not, you're not supposed to fly the approach.


If you still use the GPS to drive the CDI when it is not in Approach
(Active) mode, then you're not getting the sensitivity that is
required for this purpose. That is a difference, IMHO.

Yes, and that appears to be the only difference. However, you can
still set the 0.3nm sensitivity manually, as far as I can see.

The way I read the Pilot's Guide, I can't use the GPS for primary
navigation on the approach (with GPS selected on the GPS/Nav switch,
etc.) unless the GPS as switched into Approach (Active) mode.


Some of this stuff is wise, some isn't, but I still like to understand
how exactly it is supposed to work.

Always good to understand how it is supposed to work ;-)
The Pilot's Guide did a good job for me. Plus, I did an IPC using
this box, and so got lots of dual time using it for IR flight as
well.



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

Peter wrote:


Yes, and that appears to be the only difference. However, you can
still set the 0.3nm sensitivity manually, as far as I can see.

Forcing the scaling to 0.3 does not result in approach mode. Approach
mode includes approach RAIM and some additional accuracy that is not
apparent to the pilot.

So, if you fly an approach with 0.3 forced, and the approach
light/annunicator is not active, you are flying the approach effectively
in terminal mode.

Sam Spade wrote:
Peter wrote:


Yes, and that appears to be the only difference. However, you can
still set the 0.3nm sensitivity manually, as far as I can see.

Forcing the scaling to 0.3 does not result in approach mode. Approach
mode includes approach RAIM and some additional accuracy that is not
apparent to the pilot.

So, if you fly an approach with 0.3 forced, and the approach
light/annunicator is not active, you are flying the approach effectively
in terminal mode.

Approach mode may also make it go in and out of suspend mode at
appropriate times, and sequence to the missed at the MAP.

Roy Smith wrote:
Sam Spade wrote:


Approach mode may also make it go in and out of suspend mode at
appropriate times, and sequence to the missed at the MAP.


No doubt about it. And, suspend may occur more than once with a complex
missed approach procedure.

On 06/15/06 14:35, Peter wrote:
Sam Spade wrote

And, suspend may occur more than once with a complex
missed approach procedure.

What is "suspend"?

The Garmin series of GPS will move into SUSP mode when you turn
outbound for the procedure turn, or when you reach the MAP. Basically,
it stops the GPS from auto-sequencing to the next waypoint.

The KLN94 (and others?) goes into OBS mode when you get to the
MAP (which is essentially the same thing) but requires the pilot
to set OBS mode manually when approaching the procedure turn
fix (note that it reminds the pilot to do this when approaching
an IAF that is in the same location as a FAF, etc.)


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

In article ,
Peter wrote:

Sam Spade wrote

And, suspend may occur more than once with a complex
missed approach procedure.

What is "suspend"?

A flight plan consists of a sequence of waypoints. So, for example, let's
say I've got POU CMK HPN programmed in. As I depart POU, it makes CMK the
active waypoint and starts navigating to there. Once I reach CMK, it will
automatically sequence over to HPN being the active waypoint.

Now, before I get to CMK, the controller says, "hold at CMK, blah, blah,
blah". If I leave things as normal, once I reach CMK the first time, it'll
sequence over to HPN, which is a bad thing. I want it to stay on CMK as I
keep going round and round until the guy says, "proceed on course" and
*then* I want it to sequence over to HPN. So, what I do is put the GPS
into suspend mode (well, in reality, it goes into suspend mode
automatically when I program in the hold). When I'm done holding, I take
it out of suspend mode, and it sequences over to the next waypoint.