Garmin 430W Questions. Experts?

[C. Brenden]

I'm getting close to my CFII checkride and have been learning the 430W as we go along. Today I was flying the GPS RWY 2 approach at SAF and was surprised to see LNAV+V illuminate as I got to the FAF. This approach has LNAV min's only.
question 1) Do all approaches like this one have v (vertical) ? if not, can I determine ahead of time if this is available?

i preface this with the fact that I have not yet flown a LPV approach,

question 2) Why is the WAAS Channel listed in the pilot briefing section of the approach plate on a LPV approach?

Thanks for all your help,

[MarkW]

The +V is for vertical guidance.
From the FAA
Advisory Vertical Guidance
Depending on the manufacturer, a few WAAS-enabled GPS units provide advisory
vertical guidance in association with LP or LNAV approaches. Typically, the
manufacturer will use the notation of LNAV+V. The system includes an artificially
created advisory glide path from the final approach fix to the touchdown point
on the runway. This may aid the pilot in flying constant descent to the MDA.
LNAV+V is not the same as LNAV/VNAV or LPV. Pilots must use the barometric
altimeter as the primary altitude reference to meet all altitude restrictions.
Advisory vertical guidance is not required and is an optional capability.
See AC 90-107.

I don't remember why they list the WAAS freq. We don't use it.

[C. Brenden]

Will +V be available whenever I do a similar approach with this unit?

[BobTurner]

Originally Posted by C. Brenden

Will +V be available whenever I do a similar approach with this unit?

NO, not always. The box will say "LNAV" or "LNAV+V" in the lower left corner.

Mark explained this well. "LNAV+V" is an LNAV approach. Period. A glide slope is generated which you may use if you like, but you must adhere to LNAV minimums. The missed approach point is NOT a particular altitude when on GS (not a DA). On many of these approaches you will reach the MDA prior to the missed approach point. If the airport environment is not in sight, you may either (1) begin the missed approach climb (early), or (2) level off at the MDA and continue to the MAP. There may be times where the visibility is such that the airport is not in sight where the GS intersects the MDA, but following option (2) it does come into sight, with the required visibility, in time to land.

As Mark said, these are not to be confused with LNAV/VNAV.

[Dan B]

"question 2) Why is the WAAS Channel listed in the pilot briefing section of the approach plate on a LPV approach?"

From being involved in the WAAS development, it was briefed that the channel number was a capability for WAAS avionics to select an approach solely by the channel number. Some avionics can use either the approach name or the channel number to select the approach. I have not seen any WAAS avionics that only used the channel number.

The source would be RTCA DO-229,C. This document contains Minimum Operational Performance Standards (MOPS) for airborne navigation equipment (2D and 3D) using the Global Positioning System (GPS) augmented by the Wide Area Augmentation System (WAAS).
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For Ground Based Augmentation System (GLS) approaches, we use a tuner that only uses the channel number on the GLS approach chart. You can look at Newark (KEWR) or Houston (KIAH) GLS approaches as examples.

[C. Brenden]

Thanks for that. I feel like if the information is in the pilot briefing area for an approach that I better know why its there.

I didn't ever get an answer to my first question though. Any more ideas?

When I conduct a GPS LNAV approach can I tell ahead of time with the 430W if I will have LNAV or LNAV+V ?

[g3xpert]

Hello Craig,

Please see the GNS 430W Pilot's Guide for a full description of LNAV+V approaches. As stated above, these are non-precision LNAV approaches with an additional advisory glidepath indication. More information is available on page 113.

Many LNAV approaches have "+V", but not all. You can determine ahead of time which service level applies to an approach by using the WPT page. More information is available on page 124.

- Matt

[Dan B]

"When I conduct a GPS LNAV approach can I tell ahead of time with the 430W if I will have LNAV or LNAV+V ?"

Bob T answered your question in post #4.

Some additional information:
Flight inspection may have had the vertical guidance data removed from the ARINC 424 code that provides the approach guidance in your avionics navigation database. The vertical guidance is removed when it would provide centered needle flight guidance into (or dangerously close to)obstructions, below MDA, prior to the runway threshold. This happens on approaches designed into runway ends that the obstruction environment will not allow an LPV approach to be developed.

[C. Brenden]

Thank you for posting the link to the Garmin manual. I will be reading that this weekend.
I understand that I can tell in the lower left corner of the GPS whether or not there is "+V", I would like to know BEFORE I load the approach in the GPS if this is to be expected.
Can I tell from the plate or type of approach or do I ONLY get that info after loading the approach into the GPS and seeing what is in the lower left box.
I apologize but I'm trying to learn this as best I can so I can teach others this information.

[dougweil]

When making an LNAV approach using the 430W, my understanding is that whenever an approach slope angle is shown on the plan view, the 430W will display LNAV+V on the instrument and generate an advisory glide path. See the 3.0 designation here on this approach between ROTIE and RWY 32 to my home airport: