I'm looking for an approach which has LNAV/VNAV minimums but no published LPV minimums.
It's for an experiment to satisfy my curiosity.
It's for an experiment to satisfy my curiosity.
LNAV/VNAV Only
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Chip Sylverne
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Quit with the negative waves, man.
RNAV 35 at THV, York PA.
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Low Level Flyer
RNAV 22 at 0J4, Florala AL
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So...what is the experiment? Inquiring minds and all!
Oops. Just realized you asked for LNAV/VNAV. Not LNAV only. Thought it was an odd request.
Oops. Just realized you asked for LNAV/VNAV. Not LNAV only. Thought it was an odd request.
I'll report when I have a chance to test it,
Clip4
Touchdown! Greaser!
Just don’t mix ammonia and bleach.
MauleSkinner
Touchdown! Greaser!
It’s a free country...he can mix ammonia and bleach if he wants to.
He can also identify as an ammonia and bleach mixer, regardless of whether or not he is one.
RussR
En-Route
Still need more?
2O8 (either runway)
SPS (15R and 33L)
MKO (rwy 4)
2O8 (either runway)
SPS (15R and 33L)
MKO (rwy 4)
Thanks @RussR
I'm wondering whether anyone here is near any of these and can check it out in flight. I've done it in the GTN simulator.
I know from the manual and FAA guidance material that our GPS boxes are authorized to use LAV/VNAV minimums. In a (very) few cases, the LNAV/VNAV minimums are lower than the LPV. In one I am familiar with, the unit selects and annunciates LPV. There is a decent argument either way for whether one can use the lower minimum. To briefly summarize, the "yes" looks to the AIM and the certification of the equipment. The "no" argues you are limited to the lowest minimums actually annunciated by the equipment.
I'm not about to settle that argument. But I was curious what the unit does when there are LNAV/VNAV minimums and no LPV minimums. I got my answer with the most current GTN simulator. The LNAV/VNAV approach is selectable - with no warning messages - and LNAV/VNAV annunciates.
I'm wondering whether anyone here is near any of these and can check it out in flight. I've done it in the GTN simulator.
I know from the manual and FAA guidance material that our GPS boxes are authorized to use LAV/VNAV minimums. In a (very) few cases, the LNAV/VNAV minimums are lower than the LPV. In one I am familiar with, the unit selects and annunciates LPV. There is a decent argument either way for whether one can use the lower minimum. To briefly summarize, the "yes" looks to the AIM and the certification of the equipment. The "no" argues you are limited to the lowest minimums actually annunciated by the equipment.
I'm not about to settle that argument. But I was curious what the unit does when there are LNAV/VNAV minimums and no LPV minimums. I got my answer with the most current GTN simulator. The LNAV/VNAV approach is selectable - with no warning messages - and LNAV/VNAV annunciates.
RussR
En-Route
I have flown the one at 2O8 numerous times, often during instrument training specifically because there is no LPV, only LNAV/VNAV (and LNAV). So it makes a good discussion point. I don't know that I've flown it with the 650/750, but I have definitely flown it with the 430W/530W, and the GPS will annunciate LNAV/VNAV.
Maybe this: The calculation of the LNAV/VNAV glidepath and minimums are not based on a WAAS-enabled GPS. They are based on a barometric system our airplanes don't have.I'm having trouble understanding the question or issue. I'm not sure why you would expect anything else to happen.
Let me see if I understand. You're on an approach with no LPV minimums but LNAV/VNAV minimums. The navigator annunciates LNAV/VNAV. The approach plate has a line for LNAV/VNAV.
What other minimum are you comparing it to if there is no published LPV? Why might you expect a warning?
I feel like I'm missing something fundamentally important here. I don't know what I don't know.
An approach plate has all the minimums available for an approach, whether you have the equipment to fly it or not. If you have a 430 (not WAAS) the approach plate will still have the LPV minimums.
My question was about the annunciation? Does the unit annunciate LNAV/VNAV? Not what to do if it does. I saw the simulator did, but that doesn't necessarily mean that's what happens in real life. @RussR answered that for me.
The disagreement I mentioned (and am not answering) is what happens if you have LNAV/VNAV minimums lower than LPV minimums and the system annunciates LPV. Can you fly to the lower LNAV/VNAV minimums?
chemgeek
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Although LNAV/VNAV mins were originally designed for baro-assisted systems, these minimums can now be flown with WAAS. (Source: FAA pubs.) The main difference between LPV and LNAV/VNAV is the configuration of protected areas around the approach path.
MauleSkinner
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I’m not going to engage in the argument, but what documentation is quoted by the proponents of the argument that you can’t fly the lower minimums?
Larry in TN
En-Route
We do LNAV/VNAV minimums, on some approaches, in airliners. Airliner's, at least none that I know of, do LPV. Instead of LPV, some airliners now do GLS approaches which is a form of what was once called LAAS and has ILS-like performance and minimums. GLS is eventually intended to support CAT II, CAT III, and autoland.
When using LNAV/VNAV minimums, we do not have baro-corrected VNAV. In cold weather the airplane flies below the desired glidepath and in hot weather it flies above it. That's why we must comply with the temperature restrictions in the notes. The same restrictions apply to RNP approaches which also use LNAV/VNAV but the minimums are not so labeled and special authorization is required.
When an LNAV/VNAV approach is flown to a published MDA, 50' is added to that otherwise applicable MDA to create a DDA (Derived Decision Altitude) so that the approach can be executed in the same was as an approach with a DA.
Have you reviewed the information on these approaches in the AIM? If not, it may help in answering your questions.
When using LNAV/VNAV minimums, we do not have baro-corrected VNAV. In cold weather the airplane flies below the desired glidepath and in hot weather it flies above it. That's why we must comply with the temperature restrictions in the notes. The same restrictions apply to RNP approaches which also use LNAV/VNAV but the minimums are not so labeled and special authorization is required.
When an LNAV/VNAV approach is flown to a published MDA, 50' is added to that otherwise applicable MDA to create a DDA (Derived Decision Altitude) so that the approach can be executed in the same was as an approach with a DA.
Have you reviewed the information on these approaches in the AIM? If not, it may help in answering your questions.
RussR
En-Route
Do you mean "LNAV" here? An LNAV/VNAV has a DA, not an MDA.
Larry in TN
En-Route
I see how that wasn't clear. I meant approaches flown in the LNAV and VNAV autoflight modes. Would also apply to an approach flown in LOC/VNAV.
Many (most?) of our Jepp plates are customized for our airline so we often don't know how the same information is presented on a NOS/NACA/whatever-they-call-it-now or standard Jepp plate.
Normal procedure is to fly all non-precision approaches in LOC or LNAV and VNAV. ILS and GLS approaches are flown in APR mode which includes both the lateral and vertical mode in one.
RussR
En-Route
Gotcha. Do you fly many GLS approaches? According to the FAA, there are only 11 in the U.S. HOU has 6, I don't know where the rest are.
https://www.faa.gov/air_traffic/flight_info/aeronav/procedures/ifp_inventory_summary/
Larry in TN
En-Route
I've flown them at IAH and EWR. Wasn't aware that HOU had them as well but we don't go there.
Roughly one-third of my fleet is equipped for GLS so I can only fly them when in one of those airplanes landing at EWR or IAH.
Clip4
Touchdown! Greaser!
Turn the WAAS off.
None I know of. I think it's a sense that the box is going to annunciate the best it can do.
Actually, we can't do that unless the ASD-B out GPS source is independent. We used to turn SBAS off to make an APV into a lateral only, but the reg says we can't turn off ADS-B out if we have it.
Clip4
Touchdown! Greaser!
Good point.
Funny. If I kept up with my reading, I would have had a good approach to play with. The Chartwise article in the February Flying Magazine talks about the RNAV (GPS) Y Rwy 21L approach into Atlanta's PDK airport.
But the article is wrong. It says because it does not have LPV minimums, you would not get a glideslope and goes through the whole nonprecsion step-down procedure.
But the article is wrong. It says because it does not have LPV minimums, you would not get a glideslope and goes through the whole nonprecsion step-down procedure.
MauleSkinner
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Ah...seems logical.
RussR
En-Route
Dang, I meant IAH has 6 of them. HOU doesn’t.
RussR
En-Route
I really have a problem reading those articles. There are so many errors. It’s really not well researched or proofread.
I more or less stopped reading them, except to quickly "brief" the approach for something interesting, a while back because of that. This one, of course, I noticed
.
It is. And there probably is written indirect support.Ah...seems logical.
I know that Garmin, for example, "downgrades" approach capability for various reasons not having anything to do with the general capability of the box. Consider a GPS approach with only LP and LNAV minimums. You are flying it with a WAAS box. When you load the approach it comes up "LNAV". As you approach the FAF the TERM annunciation changes to LNAV. Would you fly to LP minimums anyway?
(We have one of those around here. I've been using it on IPCs.)
When I said good arguments on both sides I meant it. There are people whose opinion I greatly respect, to whom I turn when I have a question, on both sides.
I just received an email from Flying acknowledging their error (I sent them a note, with that graphic, yesterday).
MauleSkinner
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As with anything, I’d need to see documentation that supports the argument directly rather than indirectly.
Same with the LP question...having never seen a box that can do LP approaches, I’d have to read the documentation to find out what needs to be annunciations.
aterpster
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aterpster
Another difference: Because LNAV/VNAV uses non-precision obstacle clearance, the DA can never be less than 250 HAT (height above touchdown) and usually higher. LPV can be, and often is, 200 HAT.
aterpster
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aterpster
I stopped reading that magazine several years ago for the same reason. One article was so bad I contacted them. They were obstinate in defense of their significant errors.
You have an issue with that one I don't. Sometimes we have to apply correlation, not simply rote. One of the basic limitations of the unit is that they may only fly an approach when the box is operating in the approach mode. I don't think it's even a half step to add that it has to be the mode for the minimums you want to fly to. But if you want something specific on that one:
I only have the magazine because it comes with my SAFE membership.
MauleSkinner
Touchdown! Greaser!
I guess that directly answers your LP question.
Keep in mind that LP is not a “downgrade” from LPV in the language of the TSO...it’s a separate certification. All of the SBAS boxes I’ve dealt with were certified before LP existed, and can fly LPV but not LP.
but again, it’s the documentation that provides the answer, not assumptions, no matter how logical they may be.
aterpster
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aterpster
I guess Rickard Collins is no longer writing for them.
aterpster
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aterpster
LPV downgrades to LNAV. In one of those SBAS boxes you mention, normally the hit from LP to LNAV isn't that great. Often only 20 feet.