On Tuesday, September 29, 2015 at 12:15:04 AM UTC-4, wrote:
I used an Lnav many moons ago (1990) and although a good unit at the time a little antiquated.

I'll echo JJ's comments about the LNAV. I bought mine in 1992 and it's worked great ever since, for most of that time coupled with an "antique" Compaq 1550 running Glide Navigator II. I'm currently exploring a flight computer upgrade using open source software (e.g, TopHat) and a cheap tablet. But based on input from several pilots whose opinions I trust, including several national champions, I've been reassured that any improvement in the new varios vis-a-vis the LNAV is modest, at best, and doesn't justify my investing the required price. I'll revisit if it looks like I need more of a data stream than can be provided by my current hardware (or if my fellow pilots are lying to me in order to hobble my performance!) but in the meantime, I'll continue to rely on the LNAV.

Chip Bearden
ASW 24 "JB"
U.S.A.

It's very easy to install a top quality vario and drag it down to below LNav performance. Sharing a TE source with a mechanical vario (think of it as a big leak) is the most common problem I see. How much havoc this causes depends upon things we don't have good ways to measure (e.g. the impedance of the TE system).

Evan Ludeman (ClearNav guy)