Reserve altitude

[[email protected]]

Just double checking my understanding of the see you mobile, (Oudie) reserve altitude correction.

If I set my reserve at 1000' and my target field is at 700' and my "Arrival Altitude" says 2700' ... does that mean I will arrive at 3700' essentially 2000 above the ground?

Dennis DC

[Richard Pfiffner[_2_]]

On Thursday, May 25, 2017 at 4:00:44 PM UTC-7, wrote:
> Just double checking my understanding of the see you mobile, (Oudie) reserve altitude correction.
>
> If I set my reserve at 1000' and my target field is at 700' and my "Arrival Altitude" says 2700' ... does that mean I will arrive at 3700' essentially 2000 above the ground?
>
> Dennis DC

Dennis

If you set your Alt Res [ft] at 1000'. The Arrival will say 0' when you have final glide to the target selected. You will arrive at 1000' above the target point selected assuming nothing changes on the glide.

If arrival says 1000' you will arrive 2000' above the target point. The Alt Res + 1000'.

Richard
www.craggyaero.com

[6PK]

On Thursday, May 25, 2017 at 4:44:36 PM UTC-7, Richard Pfiffner wrote:
> On Thursday, May 25, 2017 at 4:00:44 PM UTC-7, wrote:
> > Just double checking my understanding of the see you mobile, (Oudie) reserve altitude correction.
> >
> > If I set my reserve at 1000' and my target field is at 700' and my "Arrival Altitude" says 2700' ... does that mean I will arrive at 3700' essentially 2000 above the ground?
> >
> > Dennis DC
>
> Dennis
>
> If you set your Alt Res [ft] at 1000'. The Arrival will say 0' when you have final glide to the target selected. You will arrive at 1000' above the target point selected assuming nothing changes on the glide.
>
> If arrival says 1000' you will arrive 2000' above the target point. The Alt Res + 1000'.
>
> Richard
> www.craggyaero.com

Richard
With all due respect,just maybe my ignorance, the Oudie 2 manual says quote; "All final glide calculations are subject to correction of the altitude reserve. If this value is greater than 0,
then your arrival altitude to the waypoint will be this much above the altitude of the waypoint elevation
from the waypoint database (this may not be its actual altitude, so use at own risk, needless to say)."
So.... soI'm confused ?

[Richard Pfiffner[_2_]]

On Thursday, May 25, 2017 at 6:15:58 PM UTC-7, 6PK wrote:
> On Thursday, May 25, 2017 at 4:44:36 PM UTC-7, Richard Pfiffner wrote:
> > On Thursday, May 25, 2017 at 4:00:44 PM UTC-7, wrote:
> > > Just double checking my understanding of the see you mobile, (Oudie) reserve altitude correction.
> > >
> > > If I set my reserve at 1000' and my target field is at 700' and my "Arrival Altitude" says 2700' ... does that mean I will arrive at 3700' essentially 2000 above the ground?
> > >
> > > Dennis DC
> >
> > Dennis
> >
> > If you set your Alt Res [ft] at 1000'. The Arrival will say 0' when you have final glide to the target selected. You will arrive at 1000' above the target point selected assuming nothing changes on the glide.
> >
> > If arrival says 1000' you will arrive 2000' above the target point. The Alt Res + 1000'.
> >
> > Richard
> > www.craggyaero.com
>
> Richard
> With all due respect,just maybe my ignorance, the Oudie 2 manual says quote; "All final glide calculations are subject to correction of the altitude reserve. If this value is greater than 0,
> then your arrival altitude to the waypoint will be this much above the altitude of the waypoint elevation
> from the waypoint database (this may not be its actual altitude, so use at own risk, needless to say)."
> So.... soI'm confused ?


Then you should check every waypoint in the data base you use. It is contingent on the pilot to use a correct waypoint database. In my experience airports altitudes on the worldwide turnpoint exchange in the USA are correct.

If arrival is 0 and your Alt Res is 1000 then you will arrive 1000 above your target if the altitude of the target is correct.

I was relating how the program works not if the database you use is correct.


Richard

[Tango Eight]

On Thursday, May 25, 2017 at 7:00:44 PM UTC-4, wrote:
> Just double checking my understanding of the see you mobile, (Oudie) reserve altitude correction.
>
> If I set my reserve at 1000' and my target field is at 700' and my "Arrival Altitude" says 2700' ... does that mean I will arrive at 3700' essentially 2000 above the ground?
>
> Dennis DC

Hi Dennis,

The better way to do this is set the reserve altitude to zero and let the device report estimated arrival height. Then do that PIC thing and make appropriate decisions. Targeting an arrival at Post Mills (and many other places) at an arbitrary 1000 agl from 20 miles out is going to lead to problems.

best,
Evan / T8

[[email protected]]

On Thursday, May 25, 2017 at 7:00:44 PM UTC-4, wrote:
> Just double checking my understanding of the see you mobile, (Oudie) reserve altitude correction.
>
> If I set my reserve at 1000' and my target field is at 700' and my "Arrival Altitude" says 2700' ... does that mean I will arrive at 3700' essentially 2000 above the ground?
>
> Dennis DC

Thank you all. I just wanted to double check the logic. Yes Evan I think you are right in keeping the information unfiltered is ultimately the way to go.

Dennis DC

[MNLou]

Hi Evan -

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

Thanks!

Lou

[Tango Eight]

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

Uh, sure. This is a semi-religious issue, so opinions will vary. Here's my $0.02 on a rainy day:

Conditions vary. Airport environments vary. I happen to fly in a region of the world (Northern New England) that features a lot of terrain that runs between poorly landable and completely unlandable, and weather than runs from benign to a crash-waiting-to-happen. While my environment is more challenging than many, yours isn't uniform, either.

So, the basic point is: there is no one standard reserve height that is appropriate in all situations. You as PIC need to be making decisions based on environment, current conditions & anything else that affects safety of flight. The computer is your assistant, not your decision maker.

For example: At my home airport (also DC's home airport) our traffic pattern is high due to surrounding terrain and your final glide ought to be padded well beyond this because there is simply no safe place to land other than the airport for a radius of about 5 miles (and then only one or two places, not necessarily where you want them!). Furthermore, the "safe" (that is, landable) route into my home airport follows a river valley which often features a) valley winds and b) subsiding air. I'm usually looking for 1500' over an MC 2.0 (kts) final glide from 25 out, based on the airport elevation. When I was learning to fly XC here, it was more like 2000 over.

This is total overkill at a million flat lands airports.

The obvious, simple solution is to set your flight computer to report estimated arrival height at any destination without any reserve, then do the PIC decision making thing. For old Cambridge gear, that's trivial. For ClearNav, there's one gotcha involved (easily handled, set the purple amoeba to zero and the red one to 1000 agl), for SN-10, you have to build yourself a whole new database with fake-news airport elevations (yes, people really do this, I've watched).

Go fast, make good decisions, land safe!

best,
Evan Ludeman / T8

[Steve Thompson[_2_]]

I agree with Evan.

But why not get the guys at LXNav, Naviter,
LXNavigation, to call it arrival "height" and reserve
"height" if you must have it? Which imho is what it is
displayed, and this more precise terminology might
remove at least one source of confusion.

While you're at it, Waypoints have Elevation, perhaps.



At 14:08 26 May 2017, Tango Eight wrote:
>On Friday, May 26, 2017 at 8:46:28 AM UTC-4, MNLou
wrote:
>> Hi Evan -=20
>>=20
>> Would you please expand a bit on why you think it is
better to set
>reserv=
>e altitude to zero?
>>=20
>> Thanks!
>>=20
>> Lou
>
>Uh, sure. This is a semi-religious issue, so opinions will
vary. Here's
>m=
>y $0.02 on a rainy day:
>
>Conditions vary. Airport environments vary. I happen
to fly in a region
>o=
>f the world (Northern New England) that features a lot
of terrain that
>runs=
> between poorly landable and completely unlandable,
and weather than runs
>f=
>rom benign to a crash-waiting-to-happen. While my
environment is more
>chal=
>lenging than many, yours isn't uniform, either.
>
>So, the basic point is: there is no one standard reserve
height that is
>app=
>ropriate in all situations. You as PIC need to be making
decisions based
>o=
>n environment, current conditions & anything else that
affects safety of
>fl=
>ight. The computer is your assistant, not your decision
maker.
>
>For example: At my home airport (also DC's home
airport) our traffic
>patter=
>n is high due to surrounding terrain and your final glide
ought to be
>padde=
>d well beyond this because there is simply no safe
place to land other
>than=
> the airport for a radius of about 5 miles (and then only
one or two
>places=
>, not necessarily where you want them!). Furthermore,
the "safe" (that
>is,=
> landable) route into my home airport follows a river
valley which often
>fe=
>atures a) valley winds and b) subsiding air. I'm usually
looking for
>1500'=
> over an MC 2.0 (kts) final glide from 25 out, based on
the airport
>elevati=
>on. When I was learning to fly XC here, it was more
like 2000 over.=20
>
>This is total overkill at a million flat lands airports.=20
>
>The obvious, simple solution is to set your flight
computer to report
>estim=
>ated arrival height at any destination without any
reserve, then do the
>PIC=
> decision making thing. For old Cambridge gear, that's
trivial. For
>Clear=
>Nav, there's one gotcha involved (easily handled, set
the purple amoeba to
>=
>zero and the red one to 1000 agl), for SN-10, you have
to build yourself a
>=
>whole new database with fake-news airport elevations
(yes, people really
>do=
> this, I've watched).
>
>Go fast, make good decisions, land safe!
>
>best,
>Evan Ludeman / T8
>
>
>
>

[John Cochrane[_3_]]

I also set reserve to zero. Remembering which reserve altitude is set for the glide to turnpoint, glide to alternates, glide to finish, and the two amoebas (clearnav) is too much for me. So I set them all to zero. If I want to arrive at 1000', I don't proceed unless it says 1000' (plus a decent macCready). The one exception is the finish -- if it's a contest finish and the arrival height is 1000' MSL, then I set that to 1000' MSL, which is the logical equivalent of zero.

John Cochrane BB

[Matt Herron Jr.]

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

[[email protected]]

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

[Craig Reinholt]

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

[Andy Blackburn[_3_]]

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

[Bruce Hoult]

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?

[Steve Koerner]

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.

[Andy Blackburn[_3_]]

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

[waremark]

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.