Flying a non-GPS approach with GPS guidance

MikePapa

MikePapa

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MikePapa
The instructor for my instrument rating told me that when flying a non-GPS approach, you must be on the green needles(G1000 HSI) for anything past the IAF. I'm pretty sure this is incorrect, and in Max Trescott's GPS and WAAS book, he mentions that the green needles are only required for intercepting and flying the final approach course, which is what I have always heard.

What I'd like to know is where this requirement is officially specified.
 
I believe in the AIM, where they talk about where GPS can be substituted, the essential skinny is some language about guidance on the final approach course is where GPS can NOT be substituted. Because guidance from point-to-point (or along an arc) is a permitted use of an IFR GPS, and that's all the path from the IAF to the FAF is, it's fine to use an IFR GPS for that segment. But there's explicit language in the AIM that says you CAN'T use IFR GPS to provide course guidance along the final approach course if the approach isn't one with a GPS overlay in the database.

Ron or other active instrument instructors will know this off the top of their heads and can probably quote the AIM language, and can correct me if I'm wrong. But that's where you should look for the guidance.

Later today when I'm officially an IGI, I'll look it up if nobody's provided it. But you really can trust Max on this one.
 
MikePapa said:
The instructor for my instrument rating told me that when flying a non-GPS approach, you must be on the green needles(G1000 HSI) for anything past the IAF. I'm pretty sure this is incorrect, and in Max Trescott's GPS and WAAS book, he mentions that the green needles are only required for intercepting and flying the final approach course, which is what I have always heard.

What I'd like to know is where this requirement is officially specified.
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I believe that the requirement is stated either in the Pilot Guide or AFMS for the particular system.

For the G1000, the Pilot guide states:

The system automatically switches from GPS to LOC navigation source and changes the CDI scaling accordingly when all of the following occur:
• A localizer or ILS approach has been loaded into the active flight plan
• The final approach fix (FAF) is the active waypoint, the FAF is less than 15 nm away, and the aircraft is moving toward the FAF
• A valid localizer frequency has been tuned
• The GPS CDI deviation is less than 1.2 times full-scale deflection GPS steering guidance is still provided after the CDI automatically switches to LOC until LOC capture, up to the Final Approach Fix (FAF) for an ILS approach, or until GPS information becomes invalid. Activating a Vector-to-Final (VTF; see the Flight Management Section) also causes the CDI to switch to LOC navigation source; GPS steering guidance is not provided after this switch.

In the AFMS for other GPS Navigators such as the GNS530W, it states that if the approach is not approved for GPS such as an ILS, the CDI must have the ILS displayed on it and the GPS cannot be used for navigation.​
 
Here you go - AIM Section 2:
1-2-3. Use of Suitable Area Navigation (RNAV) Systems on Conventional Procedures and Routes
a. Discussion. This paragraph sets forth policy concerning the operational use of RNAV systems for the following applications within the U.S. National Airspace System (NAS):
1. When a very-high frequency omni-directional range (VOR), DME, tactical air navigation (TACAN), VORTAC, VOR/DME, nondirectional beacon (NDB ), or compass locator facility including locator outer marker and locator middle marker is out-of-service (that is, the navigation aid (navaid) information is not available); an aircraft is not equipped with an ADF or DME; or the installed ADF or DME on an aircraft is not operational. For example, if equipped with a suitable RNAV system, a pilot may hold over an out-of-service NDB. This category of use is referred to as “substitute means of navigation.”
2. When a VOR, DME, VORTAC, VOR/DME, TACAN, NDB, or compass locator facility including locator outer marker and locator middle marker is operational and the respective aircraft is equipped with operational navigation equipment that is compatible with conventional navaids. For example, if equipped with a suitable RNAV system, a pilot may fly a procedure or route based on operational VOR using RNAV equipment but not monitor the VOR. This category of use is referred to as “alternate means of navigation.”
NOTE-
1. Additional information and associated requirements are available via a 90-series Advisory Circular titled “Use of Suitable RNAV Systems on Conventional Routes and Procedures.”
2. Good planning and knowledge of your RNAV system are critical for safe and successful operations.
3. Pilots planning to use their RNAV system as a substitute means of navigation guidance in lieu of an out-of-service navaid may need to advise ATC of this intent and capability.
b. Types of RNAV Systems that Qualify as a Suitable RNAV System. When installed in accordance with appropriate airworthiness installation requirements and operated in accordance with applicable operational guidance (e.g., aircraft flight manual and Advisory Circular material), the following systems qualify as a suitable RNAV system:
1. An RNAV system with TSO-C129/-C145/-C146 (including all revisions (AR)) equipment, installed in accordance with AC 20-138 (including AR) or AC 20-130A, and authorized for instrument flight rules (IFR) en route and terminal operations (including those systems previously qualified for “GPS in lieu of ADF or DME” operations), or
2. An RNAV system with DME/DME/IRU inputs that is compliant with the equipment provisions of AC 90-100A, U.S. Terminal and En Route Area Navigation (RNAV) Operations, for RNAV routes.
NOTE-
RNAV systems using DME/DME/IRU, without GPS/WAAS position input, may only be used as a substitute means of navigation when specifically authorized by a Notice to Airmen (NOTAM) or other FAA guidance for a specific procedure, NAVAID, or fix. The NOTAM or other FAA guidance authorizing the use of DME/DME/IRU systems will also identify any required DME facilities based on an FAA assessment of the DME navigation infrastructure.
c. Allowable Operations. Operators may use a suitable RNAV system in the following ways.
1. Determine aircraft position over or distance from a VOR (see NOTE 4 below), TACAN, NDB, compass locator, DME fix; or a named fix defined by a VOR radial, TACAN course, NDB bearing, or compass locator bearing intersecting a VOR or localizer course.
2. Navigate to or from a VOR, TACAN, NDB, or compass locator.
3. Hold over a VOR, TACAN, NDB, compass locator, or DME fix.
4. Fly an arc based upon DME.
These operations are allowable even when a facility is explicitly identified as required on a procedure (e.g., “Note ADF required”).
These operations do not include navigation on localizer-based courses (including localizer back-course guidance).
Click to expand...

Sooo, you can certainly use your IFR GPS for lateral guidance right up until you're using the localizer for lateral guidance.

From your newly-minted IGI,
 
As Tim said, you are not permitted to use GPS as your primary guidance inside the FAF for a non-GPS approach. You must use the published system (e.g., ADF for an NDB approach not overlaid as "NDB or GPS"). Of course, that's not to say that you can't use the GPS to aid your situational awareness, especially when the non-GPS needles are wandering a bit (as often happens). But you are not permitted to deliberately deviate from the published system steering to center the GPS needles. In addition, unless your GPS has stepped into approach mode, the GPS needles may be far less sensitive to deviations than the published system steering.

All that said, the tracking tolerance inside the FAF is half-scale (or 5 degrees for ADF/RMI), so no matter what system you're flying, you aren't required to have the needle dead center all the way down the approach. In many cases, having the needle steady but a little off is better than chasing it back and forth across the final approach course in a futile effort to nail it in the center.
 
Ron Levy said:
As Tim said, you are not permitted to use GPS as your primary guidance inside the FAF for a non-GPS approach. You must use the published system (e.g., ADF for an NDB approach not overlaid as "NDB or GPS"). Of course, that's not to say that you can't use the GPS to aid your situational awareness, especially when the non-GPS needles are wandering a bit (as often happens). But you are not permitted to deliberately deviate from the published system steering to center the GPS needles. In addition, unless your GPS has stepped into approach mode, the GPS needles may be far less sensitive to deviations than the published system steering.

All that said, the tracking tolerance inside the FAF is half-scale (or 5 degrees for ADF/RMI), so no matter what system you're flying, you aren't required to have the needle dead center all the way down the approach. In many cases, having the needle steady but a little off is better than chasing it back and forth across the final approach course in a futile effort to nail it in the center.
Click to expand...

Hey, Ron,

The guidance seems to have changed. I don't see the AIM language (and the table) that used to be there about primary guidance inside the FAF anymore, and substituting for DME except when used for navigation on the final approach course - all I found was what I quoted above, which now seems to say that unless it's a localizer, your IFR RNAV system is good.

From what I found, if your GPS has the approach in the database, you can fly it, and use the GPS sensor as your means of lateral guidance UNTIL/UNLESS you are flying inside the FAF on a localizer based approach. Every IFR GPS I've worked with lately either switches from GPS to LOC automatically (if it's integrated like the G1000/430/530), pops up a message telling you you must use the loc (if it's not integrated), or won't have the LOC procedures in it's database.

I'm going to have to see if I can fly the KMTN (VOR/DME 33 I think) approach in the G1000 and see what the unit does.
 
John Collins said:
I believe that the requirement is stated either in the Pilot Guide or AFMS for the particular system.

For the G1000, the Pilot guide states:

The system automatically switches from GPS to LOC navigation source and changes the CDI scaling accordingly when all of the following occur:
• A localizer or ILS approach has been loaded into the active flight plan
• The final approach fix (FAF) is the active waypoint, the FAF is less than 15 nm away, and the aircraft is moving toward the FAF
• A valid localizer frequency has been tuned
• The GPS CDI deviation is less than 1.2 times full-scale deflection GPS steering guidance is still provided after the CDI automatically switches to LOC until LOC capture, up to the Final Approach Fix (FAF) for an ILS approach, or until GPS information becomes invalid. Activating a Vector-to-Final (VTF; see the Flight Management Section) also causes the CDI to switch to LOC navigation source; GPS steering guidance is not provided after this switch.

In the AFMS for other GPS Navigators such as the GNS530W, it states that if the approach is not approved for GPS such as an ILS, the CDI must have the ILS displayed on it and the GPS cannot be used for navigation.​
Click to expand...

John, I don't think that it's required that you switch the CDI to VOR/LOC at the point where the 430(W) does it automatically, AFaIK this is only required before or at the point where you pass the FAF. Also FWIW, I believe it's perfectly legal to let the 430(W)'s CDI remain on GPS guidance if you have a second CDI in the pilot's view showing the appropriate ground based guidance.
 
Lance,

I agree with your interpretation. As a side note, automatic switching of the CDI is a pilot selectable option for most installations, with the exception being installations with a KFC225 or KAP 140. For installations with these autopilots, automatic switching of the CDI is disabled and the pilot can not override it.
 
gismo said:
Also FWIW, I believe it's perfectly legal to let the 430(W)'s CDI remain on GPS guidance if you have a second CDI in the pilot's view showing the appropriate ground based guidance.
Click to expand...
I think so too. I remember learning about it in school so I looked it up. This comes from a Honeywell FMS supplement listing operating limitations, but I don't they would have written it this way if it was not legal according to the FARs.

7. When using FMS guidance for conducting instrument approach procedures that do not include "or GPS" in the title of the publilshed approach procedure, the flight crew must verify that the procedure specified navaid and associated avionics are operational. The primary navigation source (other than the FMS) must be displayed to the flight crew during the approach.

10. ILS, LOC-BC, LDA, SDF, and MLS approaches using the FMS for final approach guidance are prohibited.
Click to expand...
 
TMetzinger said:
Here you go - AIM Section 2:


Sooo, you can certainly use your IFR GPS for lateral guidance right up until you're using the localizer for lateral guidance.

From your newly-minted IGI,
Click to expand...

Tim,

Although I agree with your conclusion, I can't find any mention of your conclusion in the text you cited, there is no mention of tracking a localizer, or of using a GPS for navigating on the final approach leg when GPS is not in the title of the approach. If there is, can you point it out?
 
TMetzinger said:
The guidance seems to have changed. I don't see the AIM language (and the table) that used to be there about primary guidance inside the FAF anymore, and substituting for DME except when used for navigation on the final approach course - all I found was what I quoted above, which now seems to say that unless it's a localizer, your IFR RNAV system is good.

From what I found, if your GPS has the approach in the database, you can fly it, and use the GPS sensor as your means of lateral guidance UNTIL/UNLESS you are flying inside the FAF on a localizer based approach. Every IFR GPS I've worked with lately either switches from GPS to LOC automatically (if it's integrated like the G1000/430/530), pops up a message telling you you must use the loc (if it's not integrated), or won't have the LOC procedures in it's database.

I'm going to have to see if I can fly the KMTN (VOR/DME 33 I think) approach in the G1000 and see what the unit does.
Click to expand...

There was a thread about this on the Red Board, and Ron found out that it was a case of the left hand not having caught up with what the right hand was doing:

Spoke to AFS-470 today. Apparently, the cart showed up on the street before the horse left the stable. They did not intend to allow the use of GPS for lateral course guidance on approaches without "GPS" in the title when they made the changes to 1-2-3c. They are simply moving the prohibition on the use of GPS for lateral course guidance from the AIM to AC 90-94, which deals specifically with what you can/can't do with GPS. However, the new version of AC 90-94 with that change is still in work. They didn't realize that folks would read the new 1-2-3c language and get the idea that it was suddenly OK to do what wasn't OK before. They are now trying to figure out how to deal with the situation.

Your tax dollars at work. [sigh]
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http://forums.aopa.org/showpost.php?p=822975&postcount=56
 
John Collins said:
Tim,

Although I agree with your conclusion, I can't find any mention of your conclusion in the text you cited, there is no mention of tracking a localizer, or of using a GPS for navigating on the final approach leg when GPS is not in the title of the approach. If there is, can you point it out?
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Sure.

Read it again, and see if you get what I'm paraphrasing here.

"With approved RNAV, you can:
Determine your position relative to any fix in the database
You can navigate to or from any fix in the database
You can track a DME arc
You can hold over any fix in the database or DME fix
But... you cannot navigate on localizer-based courses".

So, if you're flying an approach, the only thing you can't do is <drum roll> navigate on localizer-based courses! Doesn't matter where on the approach you are, blah blah blah, unless you're supposed to be tracking a localizer, you can use your approved RNAV.

Now, that's how it reads. As previously mentioned, that may not be what the FAA had in mind.
The way they should fix it is say what they mean in the AIM, because that's the pub they can reasonably expect most pilots will read. Saying one thing in the AIM and saying "but what we really meant is..." somewhere else that may be more obscure, like an AC, is practically entrapment, and if it's really a safety issue to navigate by RNAV inside the FAF then implying it in such a widely read pub like the AIM is in my opinion grossly negligent.
 
Tim,

Thanks.

I have reread the text several times, and one could conclude that you could fly an NDB approach or VOR approach (flying a course to or from a VOR or a bearing to or from an NDB if it was in the database even though GPS was not part of the approach title. Of course, my AFMS prohibits this, so it may be a moot point, but I don't think this was intended, or at least it is very unclear.
 
John Collins said:
Tim,

Thanks.

I have reread the text several times, and one could conclude that you could fly an NDB approach or VOR approach (flying a course to or from a VOR or a bearing to or from an NDB if it was in the database even though GPS was not part of the approach title. Of course, my AFMS prohibits this, so it may be a moot point, but I don't think this was intended, or at least it is very unclear.
Click to expand...

That's exactly the conclusion the AIM leads a person to, at least for the terminal part of the procedure (IAF to the FAF), and I think that it's accurate. And your AFMS brings up a good point. Over time, the real-world performance of GPS has been sufficiently demonstrated to the point that limitations placed on it's usage in the early days may not make sense any more.

But, (and here's the really important part), IF THE APPROACH IS IN THE DATABASE, then it's either an overlay (in which case you can fly it using just the GPS), or it's likely to be a localizer based approach, in which case the unit will either prompt you or automatically switch the CDI source.

So unless there's a specific NOTAM making a procedure NA, I am pretty confident that if you can load the approach from the database, it's ok to fly it. The old language used to make it VERY clear that you had to load any approach procedures from the database, and you could not just "program" the approach into a flight plan. I'm pretty sure that ALL AFM supplements require you to load the approach from the database, so the issue with the AIM may be mostly moot if folks follow the supplement. I'd really like to see:
  • The AIM say "if you can load it, you can fly it".
  • The AFM supplement say "if you can load it, you can fly it"
  • An AC or TSO or installation guidance directed at the manufacturers/database guys specifying what procedures, and portions of procedures, can be flown with GPS guidance based on the type of unit.
Then the burden goes on the Suppliers to make the procedure database match the capabilities of the unit and the current FAA guidance.

Of course, you'll have approaches NA because they haven't been flight checked, or for other reasons, so you'll still have to check NOTAMs to make sure the approach itself is legit, but you shouldn't have to be looking in three different pubs to determine if this unit can fly this approach on this day.
 
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TMetzinger said:
So unless there's a specific NOTAM making a procedure NA, I am pretty confident that if you can load the approach from the database, it's ok to fly it.
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On the red board this screenshot for a VOR-A approach was posted from 530W trainer software, warning that although you can load the approach, it is for monitoring only. If this accurately represents the behavior of the actual GPS receiver, then that would seem to be definitive for that model:

KCON.jpg



http://forums.aopa.org/showpost.php?p=810625&postcount=34

The old language used to make it VERY clear that you had to load any approach procedures from the database, and you could not just "program" the approach into a flight plan.
Click to expand...

The AIM still says that, in 1-1-19f1(b):

All approach procedures to be flown must be retrievable from the current airborne navigation database supplied by the TSO-C129 equipment manufacturer or other FAA approved source.
Click to expand...
 
Tim,

There are fewer and fewer overlay approaches available today, many of which used to be overlay approaches. There are many examples of NDB or VOR approaches that are not overlay approaches, but are in the database, often with no other GPS approach available. My AFMS, which is the STC AFMS for the 530W, has the limitation, so IMHO it is controlling. One would need a field approval to obtain a modification to the STC AFMS and I seriously doubt it would be granted.
 
John, are you sure that the overlay has gone away, or has the chart title changed? If it's not an overlay, your 530 should give you the warning message. Regardless, you can still use the GPS to navigate to the FAF.
 
To make it even stranger, here's what the FAA said in 1993: (AC 97-2, not superseded)

GPS accuracies have been evaluated to ensure that aircraft remain within the protected airspace of all currently published nonprecision approach procedures, excluding localizer-based procedures. These include the following:
a. Very high frequency omnidirectional range (VOR).
b. VOR/distance measuring equipment (DME).
c. Nondirectional beacon (NDB).
d. NDB/DME.
e. Tactical air navigation (TACAN).
f. Area navigation (RNAV).
(1) Long-range navigation (LORAN-C). ’
(2) VOR/DME.

Sooo... why wouldn't you be able to fly from the FAF to the MAP with a GPS in approach sensitivity? Note - I'm not saying you CAN, I'm just wondering why not, if the FAA found that you'd stay within the protected airspace?
 
TMetzinger said:
The guidance seems to have changed. I don't see the AIM language (and the table) that used to be there about primary guidance inside the FAF anymore, and substituting for DME except when used for navigation on the final approach course - all I found was what I quoted above, which now seems to say that unless it's a localizer, your IFR RNAV system is good.
Click to expand...
No change to the rules, just where they're written. They deleted them from the AIM in anticipation of publishing them in a revision to an AC, but the AC didn't come out before the revised AIM -- your tax dollars at work.:rolleyes: In any event, you still must use the named system for primary lateral guidance inside the FAF. This info from AFS-400.
 
Ron Levy said:
No change to the rules, just where they're written. They deleted them from the AIM in anticipation of publishing them in a revision to an AC, but the AC didn't come out before the revised AIM -- your tax dollars at work.:rolleyes: In any event, you still must use the named system for primary lateral guidance inside the FAF. This info from AFS-400.
Click to expand...

See my earlier comments. BEEEE ESSS. If they pulled them from where they were written, but didn't publish them elsewhere, then they CHANGED it. Maybe they didn't mean to, but they did.

Or is the new AC actually out yet? Nope, but let's look at what the current 90-94 actually says:
5 OVERLAY APPROACH. In order to accelerate the availability of nonprecision instrument
approach procedures that can be flown using certified GPS equipment, the FAA has authorized the GPS
Approach Overlay Program. This program allows pilots to use GPS equipment to fly existing VOR,
VOR/DME, NDB, NDB/DME, and RNAV nonprecision instrument approach procedures. The purpose
of this program is to permit pilots to transition from ground-based to satellite-based navigation
technology for instrument approaches. Approach operations are defined as that phase of flight from the
Initial Approach Fix (IAF) to the Missed Approach Point (MAP) when flying an established
nonprecision procedure. The approaches to be flown with GPS must be retrieved from the avionics
database. (Refer to Section 2, “Airborne Navigation Databases” for a more detailed description of the
required database.) GPS equipment may be used to fly all codable nonprecision instrument approach
procedures, except localizer (LOC), localizer directional aid (LDA), and simplified directional facility
(SDF) approach procedures. Any required alternate airport should have an approved instrument
approach procedure (other than GPS or LORAN-C) which is anticipated to be operational at the
estimated time of arrival. The program has progressed through three phases. Each phase has specific
provisions and limitations.
a. Phase I. This phase ended in February 1994 when the FAA declared GPS operational for
civil operations.
b . Phase II. This phase began on February 17, 1994 when the FAA declared the system
suitable for civil IFR operations. GPS equipment can be used as the primary IFR flight guidance during
a nonprecision approach without actively monitoring the applicable navaid(s) which define the approach
being used. However, the traditional ground-based navaid(s) required for the published approach and
alternate should be operational and the associated avionics should be installed and operational. The
avionics need not be operating during the approach if RAIM provides integrity for the approach. Equipment that does not use RAIM for approach integrity are required to use ground-based navaids and
operational airborne avionics. The approach should be requested and approved by its published name,
such as “NDB Runway 24,” “VOR Runway 24.” Modification of the published instrument approach
name is not required for Phase II.
c. Phase III (After Name Modification). Phase III requires modification of the instrument
approach procedure name to include “or GPS” in the title of the published approach procedure. Neither
the aircraft traditional avionics nor the ground station navaid(s) need be operational or monitored to fly
nonprecision approaches at the destination airport if RAIM is providing integrity for the approach. For
systems that do not use RAIM for approach integrity the ground-based navaids and operational airborne
avionics needed to provide RAIM equivalency should be installed and operational. For any required
alternate airport, the ground-based and airborne navigational equipment that defines the instrument
approach procedure and route to the alternate should be installed and operational. The Phase III
published approach will include the underlying navaid and GPS in the title; however, the type of
approach must be specifically requested and approved. For example, when electing to use GPS for the
“VOR or GPS RWY 24” approach, the approach should be requested and approved as “GPS RWY 24”.
When electing to use the VOR for the approach, the approach should be requested and approved as
“VOR RWY 24”.
d . Additional criteria for all Phases. For all phases of the Approach Overlay Program, civil
aircraft are not authorized to use GPS to fly any segment of any instrument approach under IFR weather
conditions unless the following criteria are met:
(1) The GPS avionics used to fly any nonprecision instrument approach must be
certified to TSO C 129 or equivalent criteria. The installation in the aircraft should be in accordance with
AC 20- 138 and the provisions of the applicable Approved Flight Manual (AFM) or Flight Manual
supplement should be met.
(2) The airborne navigation database should contain all waypoints for the published
nonprecision approaches to be flown. The use of non-differential GPS equipment is not authorized for
LOC, LDA, and SDF approaches.
(3) The approach cannot be flown unless that instrument approach is retrievable
from the avionics database. Some approach procedures are not included in the database due to safety
reasons or non-codability. It is the responsibility of the pilot to determine if the intended approach
procedure is in the database.
(4) The GPS avionics should store all waypoints depicted in the approach to be
flown, and present them in the same as the published nonprecision instrument approach procedure chart.
(5) Approaches must be flown in accordance with the FAA AFM or Flight Manual
Supplement and the procedure depicted on the appropriate instrument approach chart.
(6) Any required alternate airport should have an approved instrument approach
procedure, other than GPS or LORAN-C, which is anticipated to be operational at the estimated arrival
time. The aircraft should have the appropriate avionics installed and operational to receive the
navigational aids. The pilot is responsible for checking NOTAMs to determine the operational status of
the alternate airport navigational aids.
Para 3.5 15
AC 900 94 12/14/94
(7) The general approval to use GPS to fly overlay instrument approaches is initially
limited to the U.S. National Airspace System (NAS). GPS instrument approach operations outside the
United States also should be authorized by the appropriate sovereign authority.
(8) Procedures should be established by the pilot in the event that GPS outages
occur. In these situations, the pilot should rely on other approved equipment, delay departure, or
discontinue IFR operations.
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From reading this, I conclude (and please point out my errors) that we are operating in Phase II, with Phase III underway.

Phase II says that you can use GPS for approaches even if the approach doesn't have "or GPS" in the title. Phase III is an effort to add "or GPS" to the title, but essentially, as I read this, when Phase I was complete ALL non-localizer based approaches were good to fly using GPS under Phase II. You must have the equipment, but if you've got RAIM (or SBAS) you don't even need to turn on the equipment.

Phase III appears to be an administrative clean up of renaming the approaches to make it explicit that they are overlays, but phase II guidance clearly says that modification of the approach name isn't required.

So, as I read this, if the approach procedure for a non-precision approach is in the navigator, I CAN FLY IT using the navigator, and if the navigator has RAIM, I don't have to monitor the underlying navaid.

Please PLEASE point me to currently published guidance (AC, NOTAM, FAR, AIM) that says something different.

'Cause otherwise, how the hell am I supposed to tell an instrument student "you can't use the GPS for guidance inside the FAF, because a guy I know (Ron) says a guy he knows (in AFS-400) says you can't" with a straight face?:incazzato:

ps - thanks for the smiley!
 
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Tim,

This AC is way out of date. I believe that we are in phase III+ with the possibility of TSO C145a/146a GPS navigators. Phase II had (GPS) in the title if it was an overlay approach. Phase III has "or GPS" in the title if the approach could use GPS and a ground based navigation aid.

This approach is not an overlay:
http://204.108.4.16/d-tpp/0909/09530N5.PDF

This one is:
http://204.108.4.16/d-tpp/0909/06957VDRG17.PDF

I can't find any of the old style overlay approaches that were titled with the (GPS) such as VOR (GPS) RWY 5. They may no longer exist.
 
Tim, you can claim "BS" all you want, but I'm giving you the FAA's position on the matter. If you don't like it, take it up with them (AFS-400, to be specific). Until then, do otherwise at the risk of your ticket if they catch you doing it. Caveat aviator.
 
John Collins said:
Tim,

This AC is way out of date. I believe that we are in phase III+ with the possibility of TSO C145a/146a GPS navigators. Phase II had (GPS) in the title if it was an overlay approach. Phase III has "or GPS" in the title if the approach could use GPS and a ground based navigation aid.

This approach is not an overlay:
http://204.108.4.16/d-tpp/0909/09530N5.PDF

This one is:
http://204.108.4.16/d-tpp/0909/06957VDRG17.PDF

I can't find any of the old style overlay approaches that were titled with the (GPS) such as VOR (GPS) RWY 5. They may no longer exist.
Click to expand...

Unfortunately, the AC is still the most current one published - though I agree it's way out of date. But it specifically said that in phase II the approach title may not have changed at all!

As it stands, if it says "or gps" you know it's an overlay, but if it doesn't, how can you be SURE it's not an overlay?

Ron, I remember the AIM language, but even that language appears to have been in conflict with 90-94 as currently published.
As I see it, we're all in agreement that:
  • You can use your IFR GPS to navigate TO the FAF. (even though that's not explicitly said anywhere)
  • For Localizer based courses(ILS/LOC/LDA/SDF), you MUST use the underlying navaid for the final approach segment, not the GPS.
  • You must load any approach from the database.
  • Any GPS overlay approach can be flown with GPS guidance only.
  • Any nonprecision approach that says "RNAV" or "or GPS" in the title it's an overlay and thus can be flown with GPS guidance only.
  • There used to be AIM language that specifically forbade using IFR GPS for lateral navigation along the final approach course of non-overlay approaches.
We disagree on:
  • If the nonprecision approach doesn't say "RNAV" or "or GPS" in the title, it's not an overlay. I say it might be an overlay according to AC90-94, John seems to say that Phase II is over and all the overlay approaches should be properly titled by now.
Am I accurate?
Ron, can you give me (via PM please) the name of your contact in AFS-400? I'd like to reach out to him - because this topic would be a very good one for the CFI workshops. I asked four different experienced CFII's today "If you can load a non-precision approach on the G1000, can you fly it without switching to the underlying VOR or NDB?" and got three answers:
  • If it's in the database and the unit doesn't alert you to use the underlying navaid, you can fly it with just GPS.
  • You can't use GPS for guidance on the final approach course unless the title of the approach has RNAV or GPS in it, even if it's in the database and doesn't warn you.
  • I don't know - I'd think you can trust the database but I can't find language in the FAR or AIM that addresses this (to me this was the most honest answer in the bunch).
And John, your first approach does trigger a warning in the G1000 that it's not approved for GPS, supporting your contention that it's not an overlay. I just wish I was confident that a KLN-94 would spawn the same warning, because otherwise, a pilot who reads the current pubs is gonna come up with the wrong answer. I appreciate Ron asking the question and getting an answer, and my BS comment isn't saying that he's wrong, it's just saying that I can't see how the FAA can be so fugging dense as to not make something that affects a critical phase of flight both clear and consistent. They could have put out a NOTAM, for pity's sake.

I'd really like to see things set up so that the first bullet (if it's in the database and the unit doesn't tell you otherwise, you don't need the underlying navaid or receiver).
 
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Tim,

This is from the most current update to the AIM, dated 8/27/2009, section 1-1-19, pay particular attention the the sentences that I highlighted with a bold font:

g. GPS Approach Procedures​


As the production of stand −alone GPS approaches has progressed, many of the original overlay approaches have been replaced with stand−alone procedures specifically designed for use by GPS systems. The title of the remaining GPS overlay procedures has been revised on the approach chart to “or GPS” (e.g., VOR or GPS RWY 24). Therefore, all the approaches that can be used by GPS now contain “GPS” in the title (e.g., “VOR or GPS RWY 24,” “GPS RWY 24,” or “RNAV (GPS) RWY 24”). During these GPS approaches, underlying ground−based NAVAIDs are not required to be perational and associated aircraft avionics need not be installed, operational, turned on or monitored (monitoring of the underlying approach is suggested when equipment is available and functional). Existing overlay approaches may be requested using the GPS title, such as “GPS RWY 24” for the VOR or GPS RWY 24.



So, any approach that doesn't have GPS in the title is not authorized to be conducted with a GPS navigator.​

 
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Tim,

I think we are getting close, but I have a few minor nits to pick.

You listed:

"Any nonprecision approach that says "RNAV" or "or GPS" in the title it's an overlay and thus can be flown with GPS guidance only."

It can be RNAV and not be a GPS approach, example RNAV (RNP). It must have (GPS) in the title, even if it is RNAV as in RNAV (GPS). An overlay means that other ground based navaids are used to define the approach and to meet the TERPS criteria, so by definition an approach with the title RNAV (GPS) is not an overlay and neither is a standalone GPS approach that only has GPS in the title and no ground based navigation system is included.

So if you re-stated your listed text to as follows, I would agree:

Any non-precision approach that includes GPS in the title can be flown with GPS guidance only.
 
Tim,

This is helpful from the same AIM update, section 1-1-19 e. 3.

​
​
​
​
​
The GPS Approach Overlay Program is an authorization for pilots to use GPS avionics under IFR for flying designated nonprecision instrument approach procedures, except LOC, LDA, and simplified directional facility (SDF) procedures. These procedures are now identified by the name of the procedure and “or GPS” (e.g., VOR/DME or GPS RWY 15). Other previous types of overlays have either been converted to this format or replaced with stand−alone procedures. Only approaches contained in the current onboard navigation database are authorized. The navigation database may contain information about nonoverlay approach procedures that is intended to be used to enhance position orientation, generally by providing a map, while flying these approaches using conventional
NAVAIDs. This approach information should not be confused with a GPS overlay approach (see the receiver operating manual, AFM, or AFM Supplement for details on how to identify these approaches in the navigation database).

I may be wrong, but I don't think that the KLN94 contains any of the approaches that are just there to enhance positional awareness, but the 430/530/G1000 has them in the database and they generate the lawyer message.​

 
John Collins said:
Tim,

This is from the most current update to the AIM, dated 8/27/2009, section 1-1-19, pay particular attention the the sentences that I highlighted with a bold font:

g. GPS Approach Procedures​

As the production of stand −alone GPS approaches has progressed, many of the original overlay approaches have been replaced with stand−alone procedures specifically designed for use by GPS systems. The title of the remaining GPS overlay procedures has been revised on the approach chart to “or GPS” (e.g., VOR or GPS RWY 24). Therefore, all the approaches that can be used by GPS now contain “GPS” in the title (e.g., “VOR or GPS RWY 24,” “GPS RWY 24,” or “RNAV (GPS) RWY 24”). During these GPS approaches, underlying ground−based NAVAIDs are not required to be perational and associated aircraft avionics need not be installed, operational, turned on or monitored (monitoring of the underlying approach is suggested when equipment is available and functional). Existing overlay approaches may be requested using the GPS title, such as “GPS RWY 24” for the VOR or GPS RWY 24.



So, any approach that doesn't have GPS in the title is not authorized to be conducted with a GPS navigator.​
Click to expand...
Agreed! That's clear.
 
Ron Levy said:
...for lateral guidance on the final segment. You can still use the GPS up to that point, and once you pass the MAP.
Click to expand...

Ron, I agree. But I wish I could find something that SAYS so in currently published guidance. It still strikes me as a potential point of confusion - exactly what is an "approach"? Is it only the final approach segment? If it's not (and I don't think it is), then why can I use GPS to navigate from an IAF to the FAF?
 
John Collins said:

I may be wrong, but I don't think that the KLN94 contains any of the approaches that are just there to enhance positional awareness, but the 430/530/G1000 has them in the database and they generate the lawyer message.​
Click to expand...

That's what I'm hoping for, and maybe tomorrow I can confirm it. It would be so much easier (and render all of this moot) if the unit enforced the rules, either by:
  • Not having the procedures in the database (hey, if you can't load it, you can't fly it!).
  • Having the warning message.
That renders the topic an academic exercise (because we're back to "if you can load it, you can fly it"), and perhaps that's the case (and would explain why there's no panic at the FAA to get the new 90-94 out the door. I'm pretty sure it's true for the 89B as it's memory is pitiful and there wouldn't be room for all the non-flyable procedures. We know the 430/530/G1000 contain warnings. I'll see if I can get at a KLN-94 tomorrow after my lesson. Anybody else who hasn't MEGO'ed on this thread who can provide other data for the 480 or other IFR GPS (KLN90?) would be appreciated.
 
TMetzinger said:
Or is the new AC actually out yet? Nope, but let's look at what the current 90-94 actually says:
Click to expand...
Tim,
Just wanted to pass this along for your info. As John mentioned AC 90-94 is not just just out of date, it has been cancelled by the FAA.

gary
 

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  • 90-94 Cancellation.jpg
    90-94 Cancellation.jpg
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gprellwitz said:
And that comes up when you explicitly search for status = "current" (vs. "cancelled" or "all").
Click to expand...
Yep. So the left web site doesn't know what the right web site is doing, either.

Delving too deep into regs always ends up feeling like a trip to the slaughterhouse, or congress. Do I really want to know how messed up the system is?:loco:
 
TMetzinger said:
That's what I'm hoping for, and maybe tomorrow I can confirm it. It would be so much easier (and render all of this moot) if the unit enforced the rules, either by:
  • Not having the procedures in the database (hey, if you can't load it, you can't fly it!).
  • Having the warning message.
That renders the topic an academic exercise (because we're back to "if you can load it, you can fly it"), and perhaps that's the case (and would explain why there's no panic at the FAA to get the new 90-94 out the door. I'm pretty sure it's true for the 89B as it's memory is pitiful and there wouldn't be room for all the non-flyable procedures. We know the 430/530/G1000 contain warnings. I'll see if I can get at a KLN-94 tomorrow after my lesson. Anybody else who hasn't MEGO'ed on this thread who can provide other data for the 480 or other IFR GPS (KLN90?) would be appreciated.
Click to expand...

The GNS480 has non-GPS approaches in the DB and pops up a warning when you load a non-GPS approach.

The KLN-94 works that way as well.
 
OK, then so far we're at:

If it's in the database, and it doesn't tell you otherwise, you can fly it using the GPS.
 
TMetzinger said:
OK, then so far we're at:

If it's in the database, and it doesn't tell you otherwise, you can fly it using the GPS.
Click to expand...

You might be there, but I'm not. Regardless of what the AIM no longer says, until I see something that positively states you can do otherwise, I don't plan to fly any approaches without GPS in the title using GPS for primary guidance.
 
gismo said:
You might be there, but I'm not. Regardless of what the AIM no longer says, until I see something that positively states you can do otherwise, I don't plan to fly any approaches without GPS in the title using GPS for primary guidance.
Click to expand...

I suppose that's the reason the 430 fairly screams that it "CAN ONLY BE USED FOR APPROACH MONITORING!!"
 
TMetzinger said:
How interesting! Here's what I find this morning... no mention of cancellation. Where did you find your info? Mine's at
http://www.faa.gov/regulations_poli....cfm/go/document.information/documentID/74460
Click to expand...
Tim,
I used this site http://www.airweb.faa.gov/Regulator...rgAdvisoryCircular.nsf/MainFrame?OpenFrameSet and looked under the section called "Current AC's" and it is not in the list. I typed "90-94" in the search function on that page and got the info I posted earlier.
 
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