captainflyguy
New Member
according to a KLM captain, he tells me that he disconnects VNAV below 10,000 ft is this the norm? I know some captains that disable it altogether. Can someone give some more insight on this please?
use of VNAV.......
- Thread starter captainflyguy
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DE727UPS
Well-Known Member
VNAV does some weird stuff, sometimes. The best way to describe it is to say sometimes it just doesn't do what I would do, or what I think it should do. It's really great for meeting a crossing restriction on an arrival. You gotta watch it, cause if there is a tailwind, it might be a bit behind, but for the most part, I'm amazed on how efficiently it meets a restriction. Much better than I could do hand flying a 727.
It's pretty standard to NOT use VNAV below 10K. It was even mentioned to me in F/O IOE. In an active ATC vectoring environment, you can't really use it cause ATC doesn't want you "on path" like VNAV wants. I think that's the main reason guys don't mess with it. It does work pretty well for non-precision approaches, though. Makes it a lot like an ILS, just a lot more setup and button pushing.
It's pretty standard to NOT use VNAV below 10K. It was even mentioned to me in F/O IOE. In an active ATC vectoring environment, you can't really use it cause ATC doesn't want you "on path" like VNAV wants. I think that's the main reason guys don't mess with it. It does work pretty well for non-precision approaches, though. Makes it a lot like an ILS, just a lot more setup and button pushing.
captainflyguy
New Member
O:K..... thats kind of what I was thinking; just wanted to make sure that I had a clarified view of its proper use.
seagull
Well-Known Member
However, disconnecting it also means you lose many of the protections that it can add. If the routing is pretty close to what the actual will probably be, the FMS on the later aircraft (4th generation onward, for sure) can do a pretty decent job of keeping you from descending too early, or too late.
The two reasons not to use it would be:
1. You have no idea what the actual "miles to run" are, and/or, ATC needs to you at an altitude immediately;
2. More commonly, the crew does not understand the FMS well enough to program it such that it will provide useful information, possibly procedures that lead to not having a useful routing in the system before arriving in the critical phase of flight (I am NOT advocating mucking with it below 10k!), or, too often, not understanding what the system is doing well enough to know that it was going to do a fine job if you just left it alone! All are really training issues.
The two reasons not to use it would be:
1. You have no idea what the actual "miles to run" are, and/or, ATC needs to you at an altitude immediately;
2. More commonly, the crew does not understand the FMS well enough to program it such that it will provide useful information, possibly procedures that lead to not having a useful routing in the system before arriving in the critical phase of flight (I am NOT advocating mucking with it below 10k!), or, too often, not understanding what the system is doing well enough to know that it was going to do a fine job if you just left it alone! All are really training issues.
Velocipede
New Member
If I'm getting vectors to an ILS, then the VNAV is off below 10K. If I'm doing RNAV RNP or any non-precision approach (VOR, NDB) then LNAV/VNAV path works pretty slick.
Cptnchia
Dissatisfied Customer
So is doing the Kermit One CDA approach into ATL. Although, only those lucky enough to fly redeyes domestically get to do it. It will take you from MEM all the way to the outer marker at close to idle thrust in VNAV/LNAV. All you have to do is configure at the speed changes and depending on the wind, maybe crack the boards a little bit to help out. It's funny watching the captains who don't trust the system having to refrain themselves from switching over to V/S or FLCH.
seagull
Well-Known Member
It can work fine with vectors to an ILS, really just depends on what you have in the box and how you edit. I would say it's about 50/50, as ATC sometimes does things that you really can't predict.
NOO!
Cptnchia
Dissatisfied Customer
Sorry, I guess I should clarify. The CDA starts at MEM, not the descent portion. But as was posted by someone else, once you start down, the power is way back.
Mr.Maximus
New Member
Personally, I love VNAV - most of the time. I'll use it alot on arrivals and then on most non-precisions including visuals. Pre-programming crossing restrictions / speeds for arrivals and sit back and enjoy. Once in the terminal environment though, I a strictly VS guy until on an approach. Not real big on FLC though, although some guys swear by it. Gotta love the snowflake.
Max
Max
my_controls
Well-Known Member
Don't know, I think with VNAV you get what you put in. If you program it well and give it the proper data with temps winds and so on it's pretty slick. I've found myself going "what's it doing?" myself but mostly it's my lack of understanding the system (737-800).
Once programmed it can take you nicely from cruise all the way down to being established on an ILS for example. (Assuming of course you set everything else up). I'm doing my sim training for VNAV non-precision approaches soon and it looks pretty cool compared to the way we do it now.
However for the other types of approaches it's still company policy to use something other than vnav below fl100. It's also not suitable of course for radar control and vectoring because you don't know what you're going to get next. The VNAV mode in my mind was meant to be used with LNAV as a pre-programmed route ending in an approach. Left alone with the correct parameters it will do that nicely.
Once programmed it can take you nicely from cruise all the way down to being established on an ILS for example. (Assuming of course you set everything else up). I'm doing my sim training for VNAV non-precision approaches soon and it looks pretty cool compared to the way we do it now.
However for the other types of approaches it's still company policy to use something other than vnav below fl100. It's also not suitable of course for radar control and vectoring because you don't know what you're going to get next. The VNAV mode in my mind was meant to be used with LNAV as a pre-programmed route ending in an approach. Left alone with the correct parameters it will do that nicely.