430 LNAV approach question

[Browncbr1]

For non-precision GPS approaches (non-waas) with the 430, does a reference glideslope appear?  Just wondering, as all approaches I would fly have LPV, LNAV/VNAV, and LNAV minmums...  

So, are you able to follow a glide slope on the CDI, so long as you adhere to the published LNAV minimums for each fix?    just want to know if the glide slope comes alive on the cdi/hsi or not with the non waas 430.  I've searched, but couldn't find something that clearly says so..  thanks!

[midlifeflyer]

1 hour ago, Browncbr1 said:

For non-precision GPS approaches (non-waas) with the 430, does a reference glideslope appear?  Just wondering, as all approaches I would fly have LPV, LNAV/VNAV, and LNAV minmums...  

So, are you able to follow a glide slope on the CDI, so long as you adhere to the published LNAV minimums for each fix?    just want to know if the glide slope comes alive on the cdi/hsi or not with the non waas 430.  I've searched, but couldn't find something that clearly says so..  thanks!

Look at your Pilot's Guide. The 430W one has a whole section dedicated to LNAV+V advisory glideslopes; The non-WAAS 430 manual  doesn't even mention it. Even the calculated advisory glidepath (that does not guaranty terrain separataion) depends on the enhanced accuracy of WAAS

[Browncbr1]

3 minutes ago, midlifeflyer said:

Look at your Pilot's Guide. The 430W one has a whole section dedicated to LNAV+V advisory glideslopes; The non-WAAS 430 manual  doesn't even mention it. Even the calculated advisory glidepath (that does not guaranty terrain separataion) depends on the enhanced accuracy of WAAS

I don't have one.. considering purchase of gps and just wanted to properly understand the differences in operation between Waas and Non waas, apart from DA/MDA...   for all the approaches I'm looking at, the difference is only 100ft

[Brian Scranton]

I have a non WAAS 430...the glide slope does NOT come alive for LNAV approaches. 

[Browncbr1]

1 minute ago, Brian Scranton said:

I have a non WAAS 430...the glide slope does NOT come alive for LNAV approaches. 

Is that just for IAPs which ONLY include LNAV minima or does this also apply to IAPs that  ALSO publish LPV minima?   

[glafaille]

That is correct.  WAAS enables you to go a little lower on an approach by providing a glide path reference, and can provide a position source for an ADS-B out solution.

[Browncbr1]

I understand the difference between what waas and non waas allows.. i'm just trying to discern if a non waas box provides a glideslope just for reference...   similar to how a glideslope will come alive if you are flying a LOC approach if there is also an ILS.    

Brian has confirmed that the GS does NOT come alive on LNAV approaches, but I am unclear if he is saying the GS does not come alive universally, or if it just for LNAV approaches.    

For example, I understand that the GS does not come alive for RNAV RWY 10 below, but does it come alive on the RNAV RAY 28 below?  (understanding that you still must fly the LNAV minima)

 

[carusoam]

A portable Garmin 196(?) from back in the y2k era had WAAS and gave a glide slope indication.  A nice tool for planning VFR descents as it visually gave a TOD indication.  It could be programmed for  desired descent rate and how far away from the target airport the descent should end, giving a programmed distance to slow before entering the traffic pattern...

One of the challenges with the older equipment is the update rate is measured in seconds.  Non-WAAS equipment has a significant error in accuracy...

Near the ground two things you want to avoid... crummy accuracy that gets delivered slowly.

I would expect that if big G gave a glide slope where and when it doesn't belong... Some pilot would use it at the wrong time and place.... possibly believing it was the same as a certified unit...

I would not expect to find any vertical guidance from a unit that is not capable of giving proper guidance.  WAAS is required for proper vertical guidance.  And of course using a portable device isn't a good idea for primary nav either...

PP ideas only, not a CFI...

Best regards,

-a-

[Marauder]

I understand the difference between what waas and non waas allows.. i'm just trying to discern if a non waas box provides a glideslope just for reference...   similar to how a glideslope will come alive if you are flying a LOC approach if there is also an ILS.    

Brian has confirmed that the GS does NOT come alive on LNAV approaches, but I am unclear if he is saying the GS does not come alive universally, or if it just for LNAV approaches.    

For example, I understand that the GS does not come alive for RNAV RWY 10 below, but does it come alive on the RNAV RAY 28 below?  (understanding that you still must fly the LNAV minima)

 

I don't know how much difference there is between a 430 and my 650, but if my 650 is setup for an RNAV, the "brain" in the box will do the selection of the approach (LPV, LNAV, etc.) based on the required criteria needed for that particular approach. If it selects a non-precision approach, I will not see the glideslope even for reference.

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[N6758N]

My understanding is that the Non-WAAS 430 will not provide any vertical guidance on a LNAV only approach, where as the WASS 430 will provide an advisory glideslope on that same approach. 

[Browncbr1]

1 minute ago, N6758N said:

My understanding is that the Non-WAAS 430 will not provide any vertical guidance on a LNAV only approach, where as the WASS 430 will provide an advisory glideslope on that same approach. 

ok, yea, someone on another forum said that the advisory GS comes alive for non waas 430 that is on an approach that also has VNAV and/or LPV minima...   in any case, i think i've got my question answered.. thanks guys.

[Piloto]

I have a G530W and the GS only comes alive for LPV, LNAV+V and ILS approaches. However for non approaches direct to the airport the G530W provides a VSR vertical speed required to the airport with similar characteristics as a glide slope. If you set the OBS to the runway heading and using VSR you get similar ILS guidance to a non approach runway. I found this feature to be accurate and useful. 

 

[Brian Scranton]

1 hour ago, Browncbr1 said:

Is that just for IAPs which ONLY include LNAV minima or does this also apply to IAPs that  ALSO publish LPV minima?   

Yeah--the only time the GS comes alive is when the 430 is on an ILS...no GPS-based vertical nav at all. 

 

[Robert C.]

I thought you couldn't even load a WAAS approach on the 430 (non-WAAS) so any LPV or LNAV/VNAV won't show up when you press "APR" and hence you can't get symbology either.

[bradp]

Everyone is on the same page. The only time the 430-no-WAAS gives any GS information displayed on an CDI or HSI is when flying an ILS in LOC mode. The GS is flagged for all GPS approaches.


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[midlifeflyer]

2 hours ago, Robert C. said:

I thought you couldn't even load a WAAS approach on the 430 (non-WAAS) so any LPV or LNAV/VNAV won't show up when you press "APR" and hence you can't get symbology either.

Well, most if not all LPV approaches also have VNAV minimums (pull up any GPS approach with LOV minims at random), so you can load the approach, but you won't see LPV annunciated and you won't have a glideslope.

[Browncbr1]

4 hours ago, Piloto said:

I have a G530W and the GS only comes alive for LPV, LNAV+V and ILS approaches. However for non approaches direct to the airport the G530W provides a VSR vertical speed required to the airport with similar characteristics as a glide slope. If you set the OBS to the runway heading and using VSR you get similar ILS guidance to a non approach runway. I found this feature to be accurate and useful. 

 

This feature is also on the aera510 and other handhelds... There is a panel page that will actually show a GS on A CDI on screen. Never used it though.  I usually plan vfr descents to start when I see about 400 rpm in cruise. 

[kortopates]

On 1/12/2017 at 10:35 AM, Browncbr1 said:

For example, I understand that the GS does not come alive for RNAV RWY 10 below, but does it come alive on the RNAV RAY 28 below?  (understanding that you still must fly the LNAV minima)

 

The chosen plates are actually a really good example of different GPS glideslopes and you should see a GPS glideslope on both of these approaches (with a WAAS GPS). Its very important to understand the differences between them because you could be seeing true VNAV in the case of the R28 or just +V in the case of R10 as well as possibly just +V on R28 also.  If that is clear, feel free to skip the rest of this post. But given the confusion I thought I'd elaborate beyond the basic that you need WAAS to get any GPS glideslope.

First note that the RWY10 approach depicts a calculated GS taking you from TONSR at 2800 to the threshold at 40' of 3.04 degrees - this is what the box uses to provide you +V or advisory GS, or otherwise referred too as LNAV+V. This dosen't change the minimums, depicted as LNAV nor your need to level off by the MDA until you have the criteria prescribed in 91.175. The WAAS box simply gives you the 3.04 degree glideslope as advisory information only - which is very valuable since it gives you guidance to fly a constant descent rather than the dive and drive method.

On the R28 you could see either of the three possible GPS glideslopes (LPV, LNAV/VNAV, or LNAV+V). The GPS is going to always give you LPV if its circular position error is within tolerance or requirements for LPV, but if not, it will degrade to LNAV/VNAV, and if its really bad, such as a WAAS outage which isn't that uncommon operating on the fringe of WAAS at a coastal airport, you may not get any. Therefore we need to verify the mode the box is enunciating for which minimums. For Example, it went from Enroute to Terminal mode as you got close to your destination and we saw a tightning of lateral limits of the CDI. Before you pass the FAF you'll see it change from Terminal to LPV to indicate you are good for LPV minimums. But it may only enunciate LNAV/VNAV indicating those higher minimums, or even just LNAV in which case GS displayed will only be advisory +V (if it can even display +V). So much like the need to identify the proper frequency and GS intercept at the FAF on an ILS, with the WAAS GPS its very important to verify what minimums the box is giving you (as well as the GS intercept).

Edited January 13, 2017 by kortopates

[midlifeflyer]

1 hour ago, kortopates said:

For Example, it went from Enroute to Terminal mode as you got close to your destination and we saw a tighting of lateral limits of the CDI. Before you pass the FAF you'll see it change from Terminal to LPV to indicate you are good for LPV minimums. But it may only enunciate LNAV/VNAV indicating those higher minimums, or even just LNAV in which case GS displayed will only be advisory +V (if it can even display +V). So much like the need to identify the proper frequency and GS intercept at the FAF on an ILS, with the WAAS GPS its very important to verify what minimums the box is giving you (as well as the GS intercept).

No disagreement with the post but it reminded me one of our favorite local  instrument training questions  is what the minimums are for a WAAS-enabled GPS annunciating LPV on the KTTA RNAV/GPS 21 approach. http://155.178.201.160/d-tpp/1701/09472R21.PDF

[cliffy]

So what's wrong with a plain ol' simple ILS?   :-)

[kortopates]

57 minutes ago, cliffy said:

So what's wrong with a plain ol' simple ILS?   :-)

Nothing except that as of February 6, 2014, there are 13,134 RNAV (GPS) approaches available for general use in the U.S. National Airspace System. In contrast to 1285 ILS approaches. Roughly 2/3's of those offer VNAV of some form. Of course GPS approaches have been growing the last 3 years while ILS have not. GPS with VNAV beats ILS by nearly a 10 to 1. 

[kortopates]

2 hours ago, midlifeflyer said:

No disagreement with the post but it reminded me one of our favorite local  instrument training questions  is what the minimums are for a WAAS-enabled GPS annunciating LPV on the KTTA RNAV/GPS 21 approach. http://155.178.201.160/d-tpp/1701/09472R21.PDF

I'll bite - Is that for the higher minimums when using the Raleigh/Durham altimeter adding 81' and 1 1/4mi vis? Or is there more?

Edited January 13, 2017 by kortopates

[midlifeflyer]

3 hours ago, kortopates said:

I'll bite - Is that for the higher minimums when using the Raleigh/Durham altimeter adding 81' and 1 1/4mi vis? Or is there more?

I thought I gave the clue with my highlight in your post. Notice that on this approach, the LNAV/VNAV minimums are lower than the LPV minimums (don't ask me why, beats me). But since LNAV/VNAV is a "lower form" of precision those lower minimums can be used. Many pilots don't even look past the LPV line to even see the lower available minimums.

[carusoam]

You guys are good!

There must be a certain amount of weirdness that creeps into old systems that evolve slowly over time.

The Wall Street guys seem to take this type of knowledge and profit from it.

You guys would be Billionaires.  

Thanks for sharing your knowledge.

Best regards,

-a-

[Browncbr1]

7 hours ago, cliffy said:

So what's wrong with a plain ol' simple ILS?   :-)

Nothing, if it is available.    Here, if there is a west wind all is good. If there is an east wind, all I could do is ask for is a contact or PAR approach.   My mission airports only have VOR/DME  approaches apart from GPS.  One field uses an unmonitored vortac DME, which you don't know if it works until you get there.