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gura75

RNAV 737 PMDG

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Hi

 

More and more major airports offer these days RNAV approach in thier instrumental approach charts. I think a RNAV approach is defined as an non precision instrumental approach based on inboard navigational systems. ENGM is one of these airports offering RNAV (GNSS) RWY for 19 R. According to an email I received from ENGM airport staff (Avinor) RNAV (GNSS) RWY 19 R is still without vertical guidance. The RNAV is certified for LNAV only. I know VNAV can work in PMDG product but I would love to perform a real life approach not using VNAV. Can this be done on PMDG 737 using LNAV/VNAV down to FAF and then (CDA) Continuous Descent Angle by V/S down to MAPt. And would this be a more real life approach using RNAV since VNAV is still NOT clarified.

 

I refer to following RNAV (GNSS) RWY 19 chart, ENGM:

 

https://www.ippc.no/...NGM_5-13_en.pdf

 

 

Sincerely

 

Geir


Geir Hansen

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Isn't it that RNAV approaches (throuhg fixes) are computed by FMC and guidance is performed by the currect position comapred to the computed one. The same goes for the vertical path, I would say. Because RNP is still relatively big on the approaches, those are categorised as non precision. But as you said and as the chart says, RNAV approach at ENGM for rwy 19 is GNSS based, which means that even planes like Cessna can fly it (assumed the proper GPS is on board + software like G1000 equipped cockpit).

 

I would say, but let someone correct me please if I'm wrong, that you can fly it down to minimums with VNAV but you might want to check the V/S to make sure it matches your calculated descend rate from the chart.

 

Note: Don't confuse GNSS with WAAS, a system that augments the on-board GPS position.


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Aljaz Prislan

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Why do you think you can't use VNAV? You would use the MDA of 1070' and add 50' for a "buffer" for the constant descent to create a DDA (Derived Decision Alt). Once you hit that DDA, you go missed - like an ILS.


Matt Cee

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Geir: You may use LNAV/VNAV as long as you stop descending and level off at the LNAV OCA(H).


Daniel Nilsson 

 

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I think what the airport people might really have meant, that the approach does not require VNAV vertical guidance, as in your aircraft does not need to be certified for VNAV guided approaches.

However seeing how the approach is structured, and considering there is no DME referencing, I say that VNAV is actually the best way to fly the approach (well unless you have IAN installed in your bird, which I am not sure now if it is option or standart on the NGX)


--Peter Fabian 
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From the FCTM, page 5.41

 

 

Approaches with a glide path (GP) angle displayed on the final approach segment of the LEGS page. The final approach segment is completely compatible with VNAV and complies with final approach step-down altitudes (minimum altitude constraints).

 

and

 

VNAV should be used only for approaches that have one of the following features:

 

- a published GP angle on the LEGS page for the final approach segment

- an RWxx waypoint coincident with the approach end of the runway

- a missed approach waypoint before the approach end of the runway, (e.g.,MXxx)


Daniel Nilsson 

 

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Geir: You may use LNAV/VNAV as long as you stop descending and level off at the LNAV OCA(H).

 

Thanks for good answers guys. I appreciate it. There is one more question, it goes to Vargveum. I think I can make it down to OCA(H). But then comes the interesting part. I will level off. I get you. Will I have to level off and follow the PAPI before making the final decent to the runway? (When runway in sight) What is the trick here?

 

Geir


Geir Hansen

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No you don't have to level off if you have visual you can proceed without the VNAV (and A/P). If you don't have visual or it isn't safe you will have to level off for a moment and/or go missed.


Jay Vorkapic

 

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The whole point of the CDA and VNAV is that it should remove the need for a level segment. It leads you down the GPA so you should be on PAPI if you beak out.


Matt Cee

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Like Jay says, you don't have to level off if you are visual and it's safe to continue the approach below minimums. Preferably, you would be visual some time before hitting the minima and can make the transition down to the runway nicely.


Daniel Nilsson 

 

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