Reserve altitude

Reserve alt. is less and less helpful the farther out you are. Glide ratio will become the dominant factor when you are 25 miles out.

With Oudie, I tend to do the following:

First, make sure your ship's actual performance comes close to what the polar says. You can adjust (degrade) it by flying a final glide on a still air day and using the "bugs" setting. Fly the correct STF and watch your arrival altitude. if it starts to drop, your glide ratio is worse than the Oudie thinks- add in a few points of bugs and continue doing this until arrival altitude remains more or less constant over 5 minutes. As an example, I always set "bugs" to 6% in my ship.

I set my safety height to 1500'. Your milage may vary, but I like flying the pattern a bit higher/faster anyway. You can use the arrival alt. to plan your exit from your final climb. Once you have climbed 0-500' above final glide, leave the thermal (YMMV) and head home. Make sure your MCCready is set to what you want FIRST though, as it will effect your glide slope.

Set up the Oudie to display both your current L/D and required L/D to your target. No matter how far out you are, this will tell you if you are going to make it home, IF conditions remain constant (current L/D required L/D)

I also like to set the Oudie to display required L/D to each airport on the map. That way I can tell at a glance what is reachable and how challenging it might be to get there, based on my current L/D.

Everyone has a different way of thinking about all this. I am just sharing what works for me.

Matt H

On Friday, May 26, 2017 at 8:46:28 AM UTC-4, MNLou wrote:
Hi Evan -

Would you please expand a bit on why you think it is better to set reserve altitude to zero?

Thanks!

Lou

I think the idea behind reserve altitude is somehow simplify thinking about getting home. Unless you have a positive number for your arrival, don't start your final glide. However, I think it does the opposite. Every pilot I know (and me when I used a reserve) would be thinking " I have a thousand feet over a thousand feet (reserve)". So when it was supposed save math, it really complicates it. No big deal on a fat glide, but the real problem is when it is not working out on final.

So you are on final glide, things go south, and now you are "under glide". You could be in a reasonable position, but you are seeing a very worrying -270 ft on the display. Is it safe to stay on glide, or do you need to really worry. Much better to have set your "goal" to arrive at 1000 ft, have no reserve, and then when it does not work out, you are seeing exactly what you want (or don't want) to know, you are 730' over. If your panties are in a bunch, and you are trying to add a reserve (was it 1000, or 800ft) to your negative glide number, it is just the distraction you don't want.

Set the reserve to 0, and head home at your comfort level + the amount you used to have in your reserve. It will be a much better display if you end up with a squeaker...

Rick

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?

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.

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.