The lateral path is the same as LNAV
A tiny bit of extra detail. The way an LNAV CDI displays is not the same on a WAAS and non-WAAS box.
On an earlier GNS, it is a .3 nm FSD pair of tramlines, on a GNSW or GTN it has increasing sensitivity, like all other approach technologies.
This makes a big difference at DA, where a small deviation on the CDI can be a big displacement on the ground with a non-WAAS box.
What is the difference between LPV and LNAV/VNAV flown with WAAS (instead of BARO-alt) ?(sorry if naive)
@JasonC
Are you equipped with both WAAS and BARO VNAV ?
For one LNAV/VNAV procedure, are you able to choose between the altitude sources ?
PetitCessnaVoyageur wrote:
@JasonC
Are you equipped with both WAAS and BARO VNAV ?
For one LNAV/VNAV procedure, are you able to choose between the altitude sources ?
Yes. You could deselect SBAS but I don’t know why you would ever do that. Baro-VNAV is helpful for when you are outside SBAS coverage.
What is the difference between LPV and LNAV/VNAV flown with WAAS (instead of BARO-alt) ?(sorry if naive)
The practical difference is that LNAV/VNAV minima are normally (but not always) higher.
The technical differences are that the LPV approach has in the database a detailed description of the leg between FAF and MAP, called the FAS Data Block, and more sensitive FSD in the missed approach, both of which provide greater precision and dependability, which is what permits the lower minima.
Timothy wrote:
The practical difference is that LNAV/VNAV minima are normally (but not always) higher.The technical differences are that the LPV approach has in the database a detailed description of the leg between FAF and MAP, called the FAS Data Block, and more sensitive FSD in the missed approach, both of which provide greater precision and dependability, which is what permits the lower minima.
All absolutely correct however, other than a difference in the annunciation or possibly how the vertical GP is shown (eg in G1000 it uses a different colour caret), they are indistinguishable in flight.
Thank you both, that’s enlightening.
Just to sum up, can you confirm that:
Different topic: @JasonC, you said earlier that intermediate approach segments should have their altitude corrected for temperature.
Do you actually do that ?
Or is there an automated temperature compensation in your aircraft, including at this stage of the approach ?
PetitCessnaVoyageur wrote:
Just to sum up, can you confirm that:LNAV+V is 2D approach with a purely extrapolated glide path between FAF and MAP.
It draws a 3 degree GPS line throught the threshold crossing height to the touchdown point. It doesn’t stop at the MAP, although of course a pilot should if not visual.
LPV and LNAV/ VNAV are 3D approaches, where the trajectory between FAF and MAP, is made by a great deal of points (known in space by the 3 dimensions), actually coded in the database procedure ?
The difference really is that the line is surveyed. And depending on the type of approach the CDI Full scale deflection is different.
Different topic: @JasonC, you said earlier that intermediate approach segments should have their altitude corrected for temperature. Do you actually do that ?
Only in places such as Greenland where terrain is high and it can get very cold. The FMS will do the calculation if you input the temperature.
Reading again NCY, I also understand that LNAV/VNAV uses nonWAAS precision for lateral guidance, while LPV has the superiority in that regards.
@NCYankee
Do you have an example of approach where LNAV/VNAV has lower minima that LPV, according to the differences you explained in obstacle clearance computation ?
PetitCessnaVoyageur wrote:
Do you have an example of approach where LNAV/VNAV has lower minima that LPV, according to the differences you explained in obstacle clearance computation ?
Straubing EDMS.
And that’s significant !
I’ve learned a lot through this thread. Thank you all.
