required LD versus required MC to make it home ??

On Aug 23, 7:02*am, Andy wrote:
On Aug 23, 6:40*am, "kirk.stant" wrote:



Required L/D to target tells you what you need to achieve. It makes no
sense to fold wind into that, its just the distance divided by the
difference in height. Achieved L/D tells you what you are getting
obviously with wind affects as well, all without any assumptions about
polars, mass, bugs, or wind. That is the beauty of working with L/D
required and achieved.

But even better than asking on r.a.s. can you find a local
accomplished XC pilot(s) who can mentor you on all this stuff?

Darryl-

Darry is spot on. *I would go a little further and dispense with the
Achieved L/D - I just use L/D required and watch for the trend: if it
is getting better (lower L/D required) then you are gaining on the
glide and can either speed up or relax more. *If it's getting worse,
or not changing and looks a bit high (say more than half your
published L/D), then *you need to stop and get some altitude. *That
takes care of the wind, bugs, etc.

Totally agree with getting rid of all the navboxes that are "info
only" - unless your PDA is hooked up to a 302 and getting air data,
using GPS for fancy speed to fly info is a distraction. *Use it as a
digital sectional, with your task, airspace, and landable fields (with
L/D required) on it, and in most cases turn off the terrain (exception
is in ridge country where the terrain can be really useful). *Less is
more!

Cheers,

Kirk
66

I generally use arrival altitude for everything, especially final
glide. *That way I know how much I need to climb to get to my goal and
wind is accounted for automatically in the computer. I typically
program in 1,000' for arrival altitude and speed up/slow down
depending on whether the arrival height is building or declining.
Typically I dial in 4 knots for the computation because it corresponds
to a typical cruise speed. I try not to set below 3 knots unless it's
a last resort. Except on very long glides low Mc settings just don't
yield enough glide angle margin - a little sink and you're at best L/D
or can't make it at all.

9B

I do the same with arrival altitude, only am more conservative than
Andy. I increase or decrease MacCready accordingly. It seems the
only rational piece of data you need - arrival altitudes of less than
zero are likely to be less than useful.

Mike