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LNAV/[email protected] minima difference

Old 6th Apr 2020, 14:40
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LNAV/[email protected] minima difference

What the difference between these minimums? Thanks
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Old 6th Apr 2020, 14:51
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The TEMPO one has a 3.2deg glidepath, which probably clears more obstacles than the 3deg one, hence lower OCA/DA?
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Old 6th Apr 2020, 15:01
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Itís the difference between a 3D (LNAV + VNAV) and 2D (LNAV + V/S, FPA, etc.) approach. With LNAV/VNAV you have lateral and vertical path guidance but with LNAV you are only getting a lateral path, hence separate minima.

There is also the steeper approach on the noise abatement trial procedure, which will have a different obstacle profile, as FlyingStone points out. The LNAV minima are the same as you are not using vertical guidance.
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Old 6th Apr 2020, 19:28
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Originally Posted by Boroda View Post
What the difference between these minimums? Thanks
I mean the same type of minima is called on on chart VNAV and on another one LNAV/VNAV. Why?
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Old 6th Apr 2020, 19:49
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There is no difference. It may be typographical error or a naming convention change. On the equivalent Jeppesen plates they are both referred to as LNAV/VNAV.
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Old 6th Apr 2020, 20:33
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Look at the change in Circling minima, there’s a close in obstruction. LNAV minima will assume a dive and drive type approach where as the LNAV/VNAV will give a glide path with a corresponding obstruction clearance surface which may clear obstructions in the LNAV only area.

LNAV+V and LNAV/V (depending on brand of electronic wizardry) is the difference between advisory and mandatory guidance.
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Old 6th Apr 2020, 21:19
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The newer, TEMPO chart, refers you to AIP SUP 40/2019 - https://www.aurora.nats.co.uk/htmlAI...040-en-GB.html
The SUP actually includes the charts and there it says, from the CAA mouth direct OCA(H) for LNAV/VNAV.

But already you knew that.

Neither of which explains what was the reason for VNAV label on the previous version RNAV (GNSS) Z. Checking with the AIP again, https://www.aurora.nats.co.uk/htmlAI...ics/124009.pdf the CAA called it LNAV/VNAV already there.

Apparently the nice LSY people for some reason changed the labelling on the original chart, but not on the TEMPO one.



Voila. In LSY graphical language There are 3 different methods how they depict the same minima (my screen is from the LAT chapter, also available to you in FIV under the "Manuals" link from the top-level menu).




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Old 6th Apr 2020, 22:12
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Originally Posted by snips View Post
Look at the change in Circling minima, thereís a close in obstruction. LNAV minima will assume a dive and drive type approach where as the LNAV/VNAV will give a glide path with a corresponding obstruction clearance surface which may clear obstructions in the LNAV only area.

LNAV+V and LNAV/V (depending on brand of electronic wizardry) is the difference between advisory and mandatory guidance.
Heís not asking about LNAV vs LNAV/VNAV, heís asking why on one plate the LNAV/VNAV minima is referred to as just VNAV.
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Old 7th Apr 2020, 03:28
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Originally Posted by AerocatS2A View Post
Heís not asking about LNAV vs LNAV/VNAV, heís asking why on one plate the LNAV/VNAV minima is referred to as just VNAV.
That is true. Thanks
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Old 7th Apr 2020, 10:25
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My idea is that an LNAV/VNAV minima , is a procedure based on GPS signal not corrected by ground station,
VNAV ( or Baro-VNAV ) is an APV procedure ( Approach with Vertical Guidance ) flown with reference to baro altitude , hence the need
for higher minima.
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Old 7th Apr 2020, 10:40
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That seems at odds with the reason for UK AIP SUP 40/2019 as well as the chart producer's explanatory guide on minima box labelling.

Both charts in the AIP have LNAV/VNAV designation on them. Only the LIDO re-draw of those has the sleek looking (and confusing) version on the older chart.

Last edited by FlightDetent; 7th Apr 2020 at 12:52.
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Old 7th Apr 2020, 10:46
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Unusually, I find myself in agreement with Flight Detent. The LIDO legends and tables section will tell you the LNAV/VNAV and VNAV are the same type of approach - RNP approach based on LNAV and VNAV guidance.

rgds
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Old 7th Apr 2020, 12:37
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The temporary chart is to be used when issued by ATC. My guess is a crane that is not always extended.
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Old 7th Apr 2020, 12:55
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In this particular case, it is a live operational trial of a steeper angle procedure, while the old RNAV-Z use is suspended.

Not sure if anyone's mentioned it here yet, the details are available from the full AIP SUP for this [UK 40/2019]
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Old 15th Aug 2020, 11:27
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Do you use Vert RNP 125 when flying LNAV minima, using LNAV/VNAV minima the aircraft is to be within +/- 75' of profile in the final approach segment, the UK (Standard Doc 24) says this applies to both 2D & 3D approaches EASA doc's are clear on this when flying LNAV/VNAV minima but I can't see/find clarity on the required tolerance on 2D and I know some 737 European operators don't use 125 for RNP flown to LNAV minima (CDFA) using either VNAV or V/S
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Old 15th Aug 2020, 13:57
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Originally Posted by Nick 1 View Post
My idea is that an LNAV/VNAV minima , is a procedure based on GPS signal not corrected by ground station,
VNAV ( or Baro-VNAV ) is an APV procedure ( Approach with Vertical Guidance ) flown with reference to baro altitude , hence the need
for higher minima.
They're the same
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Old 26th Aug 2020, 08:02
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ICAO has now standardised the naming of RNAV approaches to stop the confusion. LNAV/VNAV won't be a term used, but instead just VNAV.
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