VNAV only approach
 

hello
Could someone help answer this question please. Can you fly a VNAV only approach? I know you can do LNAV and LNAV/VNAV, but never heard of VNAV only, is this something you can do?

yes...i have seen on some state charts that they publish VNAV minima approach only is this possible?? the minima is lower than a LNAV why is that

There has to be some lateral guidance. Any chart references

• Non-precision Approach:

– Lateral Navigation (LNAV):

– Localiser Performance (LP) minima line

• APV BARO:

– LNAV/VNAV (vertical navigation);

– SBAS:

And finally - RNP AR APCH

As has been said there must be some lateral guidance... We need an example of what you are looking at but I'll offer up an example such as:

"JFK RNAV (GPS) Y 31 R"...

I'll have a stab at this but more than willing to be corrected.

1. Looking at the JFK plate (which you could do if I could paste it here) it's implicit right from the start that you are going to use ( in our case), LNAV "coupled" to GPS for the lateral mode, to comply with the RNAV (GPS) bit that is at the top of the plate and above all the minima.

2. The specific minima labelled RNAV GPS VNAV" minima (370 feet,) makes no mention of LNAV but the assumption has to be that the modes to be used are LNAV (lateral) / VNAV.

3. The " RNAV GPS LNAV" minima (460) is for LNAV plus some vertical mode other than VNAV (e.g; V/S) and is for use e..g; when cold weather takes you below the minimum uncompensatedd BARO VNAV temperature.

To cite such a concern without providing the specific approach procedure is a bit suspect.

Surely, aterpster, this isn't the first suspect thing you've seen around here...

Just one of many. Seems to have gotten worse though over the years.

I'm thinking pure technical; not legal nor minima, and B737NG. Could the a/c operate in VNAV & VOR/LOC or HDGSEL for either a LOC ONLY or NDB? I've never tried and not be allowed to, but they are separate channels?? Maybe next time in the sim?

Certainly looks like my poorly worded effort was a waste of time - should have known better.

Somebody looking at Flt sim "plates"?

Ah, Rat5, the old NDB/GS approach, remember well from the days of carting checks around in a Baron with questionable radios.

IF the question is can you use VNAV on a non precision approach whilst using VOR/LOC then the answer is yes. YOu don't need to use LNAV for it to work. This is true for a 737NG.

VORLOC & VNAV is SOP for many for LOC Only approaches.

Our SOP is V/S for vertical path if HDG SEL has to be used for an approach (e.g. FMC error, bad coding, etc) however the aircraft will quite happily follow a VNAV path if its coded in the FMC if you use VNAV.

That is what I would have expected, but previous company SOP's were LNAV/VNAV or HDGSEL + V/S. I wondered why we couldn't do use VNAV for vertical. Never did get a reply. I wonder if the questioner had forgotten to include a roll mode in the question?

Even IAN uses something similar to LOC/VNAV, it uses LOC and GP, which is the FMC computed glide path.

thanks all for the replies,
I can't think off the top of my head the exact airport (s) that i'm talking about but I can say one is Indonesia and the other is Denmark. I will get the exact ICAO code and procedure when i get to work tomorrow. What i can say is that i know it is an RNAV (GNSS) chart and the minima that the state is already showng is an LNAV and also VNAV only, with the minima being lower than the LNAV....

i will get the exact airport for you

the airports in question are Denmark EKSB RNAV (GNSS) RWY 14 and the other airport is WITK in Indonesia. Both of these show VNAV only minima..

Hello ASHTAM

Yes you are correct. It seems different countries around the world have not standardised the way they name procedure minima on their charts. I think you can assume that VNAV minima are the same thing as LNAV/VNAV minima and apply to an APV approach using either WAAS or baro-VNAV for vertical guidance.

thanks oggers.

Here are the IAPs in question: