Why do some approaches only have VNAV minima?
Thread Starter
Joined: Mar 2017
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From: London
Why do some approaches only have LNAV minima?
Some approaches only show an LNAV minima and not a VNAV/LNAV minima as well?
Thank you in advance
Thank you in advance
Last edited by applecrumble; 26th September 2017 at 09:47.
Joined: Dec 2002
Aviation Qualifications: ATP+Mil
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From: Where the Quaboag River flows, USA
Use the search function, this subject was done and dusted about a year ago.
Post the approach because there cannot be an approach w/o lateral navigation.
Post the approach because there cannot be an approach w/o lateral navigation.
Joined: Aug 2013
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From: PA
Post the approach because there cannot be an approach w/o lateral navigation.
Apple, yes, please provide the approach plate. One can get creative and use a VNAV SPD and VNAV PTH from TOD, but I would have to really understand why there would be minima.
Last edited by underfire; 26th September 2017 at 00:53.
Thread Starter
Joined: Mar 2017
Posts: 177
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From: London
I see what guys are saying and you are all of course correct you require a lateral course to have any form of Rnav app.
What I am actually referring to is where you only have an LNAV minima displayed on the plate. Usually you have an LNAV/VNAV minima as well which has lower minimums (typically).
http://vau.aero/navdb/chart/LTBS.pdf
Have a look at Dalaman GNSS 19. Only an LNAV minima is given.
My thoughts are that because of the terrain the approach designer couldn't come up with an LNAV/VNAV minima that was lower than the LNAV only minima so they just didn't publish one?
What I am actually referring to is where you only have an LNAV minima displayed on the plate. Usually you have an LNAV/VNAV minima as well which has lower minimums (typically).
http://vau.aero/navdb/chart/LTBS.pdf
Have a look at Dalaman GNSS 19. Only an LNAV minima is given.
My thoughts are that because of the terrain the approach designer couldn't come up with an LNAV/VNAV minima that was lower than the LNAV only minima so they just didn't publish one?
Joined: Jun 2005
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From: USA
A fair number of RNAV/GPS approaches here in the US have LNAV mins that are lower than the LNAV/VNAV mins. I've speculated as to why that is, but haven't seen a reference that either confirms or refutes my theory as to why that is. Anyone else believe it has to do with the obstacle clearance plane between the "on glidepath" at DA and the runway versus that of the "at the MAP at MDA?"
Joined: Aug 2007
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From: The Netherlands
Temperature Correction
When LNAV minimum is lower than LNAV/VNAV minimum, that could be because of temperature considerations:
The LNAV/VNAV minimum is valid down to the published minimum temperature stated on the chart.
The stated minimum temperature is not valid for the LNAV minimum - that minimum has to be corrected in case of temperatures below ISA and the result of a comparison near the charted minimum temperature could well be that the LNAV only minimum is then higher than the LNAV/VNAV minimum.
The LNAV/VNAV minimum is valid down to the published minimum temperature stated on the chart.
The stated minimum temperature is not valid for the LNAV minimum - that minimum has to be corrected in case of temperatures below ISA and the result of a comparison near the charted minimum temperature could well be that the LNAV only minimum is then higher than the LNAV/VNAV minimum.
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From: Just Around The Corner
