LPV Approaches - 2 Instructors - 2 viewpoints

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ruthsindelar

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Ruth
One of my IFR students was chatting with her buddy who is also getting their instrument rating. My student shared that his CFII's view on LPV approaches is different than mine. Here is the question:

Non WAAS Garmin 430

- KOGD RNAV Z Approach:
* We both agree, cannot shoot the approach since the plate specifically states "LNAV: NA" (Not Authorized)

- KLWS, RNAV Runway 12:
* I say we cannot shoot the approach since my GPS is not capable of supplying the VPL/HPL required for LPV approaches
* Other instructor says you can shoot the approach but just down to circling minimums

I'd love to be wrong on this as it would open up some new approaches to me and my students. But, I'm fairly confident that I am correct. I respect the groups knowledge and would appreciate your thoughts.

Thanks
 
Good question Ruth. I agree with you. The fact that there is not an LNAV MDA says to me that WAAS is required. An approach like RNAV RWY 8 at KLWS can use either.

Now if I could just find a reference to prove us right. I'll look.

Joe
 
Ruth,

I come to the same conclusion you do, but for a different reason. Because the approach has LPV minimums and no LNAV minimums, the approach was never surveyed to meet the wider LNAV lateral ROC (required obstacle protection) safe areas. The non WAAS GPS uses guidance for full scale CDI of +/- .3 NM, whereas the WAAS full scale is angular at +/- 2 degrees and narrows down to +/- 350 feet at the threshold. The circling minimums assume flying the GP of the LPV down to circling minimums and must be visual from that point.
 
Thanks All,

Cap'n Ron.... good point on providing the link to the approaches. I'll do so next time. I'm still working on understanding the norms of this board.

I've posted several questions this past month and it has been nice to hear everyone's perspectives. Thank you.
 
Just curious does your 430 allow you to load the approach?...I never seen (or noticed) an RNAV sans LNAV mins before...interesting.
 
Last edited:
Ron Levy said:
Sure would save aggro if folks posted links to the approaches they ask about...

...in any event...

On the LWS RNAV(GPS) 12 approach (http://204.108.4.16/d-tpp/1004/00515R12.PDF), the lack of any non-LPV minima in conjunction with the note Harry mentioned makes non-WAAS use prohibited.
Click to expand...
Just a quick comment. Links like that will expire in 56 days at most, whenever the next cycle becomes effective.

IMHO it's better to attach the pdf. I did that to this post with Ron's link.

Joe
 

Attachments

  • 00515R12.PDF
    215.4 KB · Views: 19
The only approaches at LWS you could use with a non-WAAS GPS are the RNAV Y RWY 8 and the RNAV Y RWY 26. If you wanted to land specifically on RWY 12, your only option would be to circle-to-land from either of these approaches.
 
Areeda said:
Just a quick comment. Links like that will expire in 56 days at most, whenever the next cycle becomes effective.

IMHO it's better to attach the pdf. I did that to this post with Ron's link.

Joe
Click to expand...
Actually, while it's nice either way, I have no problem spending 10 seconds of my incredibly valuable time getting the current chart as long as someone says which airport and approach it is.
 
SbestCFII said:
The only approaches at LWS you could use with a non-WAAS GPS are the RNAV Y RWY 8 and the RNAV Y RWY 26. If you wanted to land specifically on RWY 12, your only option would be to circle-to-land from either of these approaches.
Click to expand...

FOLKS FYI before you reply to OP- this was a resurrection of a 5 year old thread. The procedure has changed. There is now no circling minima so the question is OBE.
 
midlifeflyer said:
Actually, while it's nice either way, I have no problem spending 10 seconds of my incredibly valuable time getting the current chart as long as someone says which airport and approach it is.
Click to expand...

In this case, it's nice that it was attached as it has since changed in 5 years.
 
How about that!
 
Brad Z said:
FOLKS FYI before you reply to OP- this was a resurrection of a 5 year old thread. The procedure has changed. There is now no circling minima so the question is OBE.
Click to expand...

Sometime after Amendment 1 was published (perhaps 3 years ago) the FAA changed its policy on CTL minimums on APVs.
 
aterpster said:
Sometime after Amendment 1 was published (perhaps 3 years ago) the FAA changed its policy on CTL minimums on APVs.
Click to expand...

And probably for the better if the prior debate cited in this thread is any indication.
 
John Collins said:
Ruth,

I come to the same conclusion you do, but for a different reason. Because the approach has LPV minimums and no LNAV minimums, the approach was never surveyed to meet the wider LNAV lateral ROC (required obstacle protection) safe areas. The non WAAS GPS uses guidance for full scale CDI of +/- .3 NM, whereas the WAAS full scale is angular at +/- 2 degrees and narrows down to +/- 350 feet at the threshold. The circling minimums assume flying the GP of the LPV down to circling minimums and must be visual from that point.
Click to expand...

My hunch is that the terrain was evaluated for LNAV/VNAV but that the obstacle environment to the left side of course is too onerous for the LNAV trapezoids. As it is the terrain is sufficiently onerous to cause the LPV trapezoids to be cleared by raising the GS angle to 3.87 degrees. That is why there are no Approach Category C and D minimums.

Worth noting: The RNP AR approach to Runway 12 has a 3.1 degree GS, thus all four approach categories are permitted. This is because the flexibility of RF legs permitted the terrain issue to be avoided, even at what I call "entry level" RNP (0.30).

Attached are both the FAA and Jepp charts. The Jepp chart show the terrain so the concept is a bit clearer.
 

Attachments

  • FAA RNP 12.pdf
    262.1 KB · Views: 9
  • Jepp RNP 12.pdf
    82 KB · Views: 22
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