Sign in to follow this  
Guest

Opinions on LNAV/VNAV approaches

Recommended Posts

Hey guys, got a question to propose to you all. The way we have been training and executing LNAV/VNAV approaches such as RNAV(GPS), VOR overlays and NDB overlays, is the use of VNAV as well as use of GPS/FMS LNAV. The concern is lately and with the addition of WAAS coming online quickly is that we are going to start to see lower and lower GPS approach minimums. Already there are some that are going to minimums of 300agl and 3/4 or even 1/2 miles in some instances at places like KMEM and KDEN. It is proposed and some are even in Beta testing that approach mins of those of a CAT 1 ILS. The operational experience of both airlines and corporate operators with GPS has been phenominal and WAAS and LAAS are only going to give us more leway. Now my question to you is how are we going to execute these approaches. There have been conflicting techniques and i understand that some of these may be aircraft specific but, in some groups the preferred method is to set the altitude selector to MDA. However i have a different opinion of that. The way the VNAV works is that you are designed to be at the VDP on most of these approaches and with an altitude selector set at MDA it is the hard altitude that the aircraft will not violate and therefore have a tendency to capture and level off at the MDA not giving you the ability to see the runway on a minimums approach due to the nose coming up and not giving you a downward view such as on an ILS. This works fine if you break out before mins and capture your current vertical speed to stay with VPATH, then set the missed approach altitude. I have also been seeing certain crewmembers setting the actual runway TDZE in the altitiude selector to keep the VPATH all the way to the runway, again nothing wrong with this technique, however on a missed approach it becomes critical to set the missed approach alt in a extremely loaded work enviroment. Now what is everyones opinion on this? I understand that on certain approaches that it denotes that "only approved operators may use LNAV VNAV DH in lieu of MDA", and you wont get the extra 100 ft below the MDA like on the others unless the POI has approved it. Now does anyone have an opinion on how to execute that approach procedure? Thank you for your time in reading and responding, im sure i have left something out due to being tired, but will update any omitted comments. MaxGulfstream 1159, IV, V

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this