Reserve altitude

I prefer setting an appropriate pattern entry altitude for the simple reason that many places I fly have a ridge or other high obstacle to clear before I get home. The LX9000 software will show if my current final glide will clear the offending obstacle. Granted, it isn't full proof, but it gives a general idea. Setting the reserve to zero negates this feature.
Craig

On Saturday, May 27, 2017 at 5:18:24 PM UTC-7, Craig Reinholt wrote:
I prefer setting an appropriate pattern entry altitude for the simple reason that many places I fly have a ridge or other high obstacle to clear before I get home. The LX9000 software will show if my current final glide will clear the offending obstacle. Granted, it isn't full proof, but it gives a general idea. Setting the reserve to zero negates this feature.
Craig

I agree with Craig and John.

1) I don't like the idea of setting up a final glide where I get no indication if the calculation works out that I will clear a ridge by 1 foot. I'd like to know if it's going to be close.

2) Most contest finish cylinders are 1000' - the scoring equivalent of ground level (sort of).

Therefore 1000' reserve is what I use. If I have a half-decent climb I will go to at least Mc=4 plus an additional 500-1000'.

Andy Blackburn
9B

On Sunday, May 28, 2017 at 9:17:29 AM UTC+3, Andy Blackburn wrote:
On Saturday, May 27, 2017 at 5:18:24 PM UTC-7, Craig Reinholt wrote:
I prefer setting an appropriate pattern entry altitude for the simple reason that many places I fly have a ridge or other high obstacle to clear before I get home. The LX9000 software will show if my current final glide will clear the offending obstacle. Granted, it isn't full proof, but it gives a general idea. Setting the reserve to zero negates this feature.
Craig

I agree with Craig and John.

1) I don't like the idea of setting up a final glide where I get no indication if the calculation works out that I will clear a ridge by 1 foot. I'd like to know if it's going to be close.

2) Most contest finish cylinders are 1000' - the scoring equivalent of ground level (sort of).

Therefore 1000' reserve is what I use. If I have a half-decent climb I will go to at least Mc=4 plus an additional 500-1000'.

Not having used one of these devices: if you set 1000' reserve and Mc=10, will you be at 1000 ft when you arrive, or after you pull up?

On Sunday, May 28, 2017 at 2:17:08 AM UTC-7, Bruce Hoult wrote:
On Sunday, May 28, 2017 at 9:17:29 AM UTC+3, Andy Blackburn wrote:
On Saturday, May 27, 2017 at 5:18:24 PM UTC-7, Craig Reinholt wrote:
I prefer setting an appropriate pattern entry altitude for the simple reason that many places I fly have a ridge or other high obstacle to clear before I get home. The LX9000 software will show if my current final glide will clear the offending obstacle. Granted, it isn't full proof, but it gives a general idea. Setting the reserve to zero negates this feature.
Craig

Not having used one of these devices: if you set 1000' reserve and Mc=10, will you be at 1000 ft when you arrive, or after you pull up?

My understanding is they have total energy in the calculation, but I believe they calculate finish height assuming you are still going at the STF for the McCready setting, so the total energy altitude adjustment is for deviations away from the Mc setting. Pushing and pulling on final glide ought not generate changes in estimated arrival altitude, unless you fly off-STF for a long time.

It's hardly ever well documented, so YMMV.

Andy Blackburn
9B

I use a circuit height reserve altitude (and 500 foot clearance for obstructions). The benefit for me is that alternates show up green on the map. If you don't set a reserve then green on the map does not tell you whether an alternate is reachable. I watch how the arrival height changes to see how I am doing against polar (and the number of up arrows tells you your % over glide). I don't use the glide amoeba.

With ClearNav you can use the Amoebas as a good way of verifying ridge clearance. Set one amoeba to zero and the other to 1000 ft. Using the Amoebas for the ridge problem, allows the more sensible: reserve = 0 setting. Using the amoeba this way gives a visual / analog sense of clearance that is really better than a go/ no go. The width of the amoeba clearance through the pass or over the ridge provides a great indication of margin.