LNAV and VNAV

[kantk2008 2]

Hi,I'm just used to using one NAV, and I would like more insight on how to use 2. Thanks!

[Guest]

Er...? What exactly do you mean? LNAV is lateral navigation (direction) and VNAV is vertical navigation (altitude). You need both to get somewhere... ;) Maybe you are confusing LNAV and VNAV with NAV radio's...?

[kantk2008 2]

ahhh....I think you are right. I was referring to NAV radio and VORs, but Now I see what you mean...but I would greatly appreciate it if you can tell me what they do. Thanks!

[aentwis 61]

They don't "do" anything specifically, as they are not devices...It would be helpful if you stated for which aircraft you need help on this subject. Although the basic concepts are generally the same, the implementation of LNAV and VNAV (which is known as PROF (profile) in the MD-11 world) is aircraft specific.LNAV means lateral navigation, ie the course, track, or heading of the aircraft and it following a specified route, normally entered into the FMS on the ground. It is armed by pressing the (L)NAV button on the MCP or FCP. Once armed, the aircraft will then follow the predefined route laterally (ie in 2D as viewed from above...)VNAV is concept relating to the vertical plane path of the aircraft, its ascent and descent, and the speeds at which these occur. The vertical profile is calculated by the FMS using parameters such as cruise altitude, cost index, altitude and speed constraints at various waypoints en route, aircraft weights, distance, and so on... It is armed by pressing the VNAV or PROF buttons on Boeings or MD11...I would strongly recommend you read up on things in the manuals or on the Internet...Andrew