Pirker Final Glide Theory

[jpg...@gmail.com]

Does anyone have a link to, or a copy of, an English language paper or explanation about Dr Herbert Pirker's final glide theory? I can't even locate one in German via Google.

I can find snippets about it relating to implementation on StrePla in 2006vand I understand that a couple of the NavBoxes on LX 8000/9000 relate to this.

http://www.strepla.de/StrePla4/english/News/News_in_pocket_Winter05.htm

Thanks,

John Galloway

[PapaFox]

Try this link
http://www.streckenflug.at/popup.php?xi=download/pirker_tacho.pdf&xy=J

the text is in German

PF

[pp2...@gmail.com]

I don't speak german, but that appears to be a paper about speed to fly.
try these?
http://libelle.bugwiper.com/ea_gr1000.ppt
http://www.streckenflug.at/download/reisegeschwindigkeit.pdf

from the xcsoar user archive

[jpg...@gmail.com]

Thanks to both responders but these articles refer to Herr Pirker's suggestions for estimating instantaneous cross country speed according to the calculated movement of the glider's shadow over the ground during climb and glide.

( See: http://www.glidingmagazine.com/FeatureArticle.asp?id=424 )

For the interest of LX 8/9000 users, the "Req.Mc" and "STFReq" navboxes are calculated according to Pirker's (other)glide theory.

John Galloway

[buc...@comcast.net]

AeroKurier had an article about eight years ago. I believe the title, translated in English, was something like: A New Computation for Final Glide. There is really nothing in English regarding Dr Pirker's theory, I know because I have exhausted every lead. Best get the AeroKurier article and have a friend translate it for you. Good luck,
John Iacobucci

[jpg...@gmail.com]

Thanks John I will try that.

LX NAV (who have a couple of Navboxes related to this on the LX 8000/9000) say that they do not know of an English article but they are in contact with Herr Pirker about the possibility of expanding the calculations to include glides around one or more way points.

I had wondered if John Cochrane might know something about it as Herr Pirker's calculations use MC settings as the primary glide slope consideration, similar to John's recent article - but with TAS factored into the calculations.

John Galloway

[buc...@comcast.net]

On Monday, January 14, 2013 10:19:27 AM UTC-5, jpg...@gmail.com wrote:

John: I've been looking through my stacks and finally found an english translation as well as the artilcle from aerokurier. I'll get around to scanning in PDF formats and email these articles to you.

[cernauta]

On Sat, 2 Feb 2013 13:45:12 -0800 (PST), buc...@comcast.net wrote:


>John: I've been looking through my stacks and finally found an english translation as well as the artilcle from aerokurier. I'll get around to scanning in PDF formats and email these articles to you.

If you don't mind, I'd also like to have it. Would it be possible?

Thank you!
best regards

aldo cernezzi

[jpg...@gmail.com]

Excellent. Many thanks. I appreciate your help.

John Galloway

[Paul Remde]

Hi,

I think we'd all love to have access to the document. I'd be glad to post
it on my web site if that would help.

Best Regards,

Paul Remde
Cumulus Soaring, Inc.
________________________

wrote in message
news:4b8c77f1-1a6e-489e...@googlegroups.com...

[pcool]

In short, the Pirker "theory" says that in a final glide to the determine
the best speed you do:
1) calculate the glide ratio needed to get over the final turnpoint
2) for that glide ratio you calculate the corrispondent MC value for your
polar
3) for that MC value you get the speed to fly

I did not know pirker wrote these things in 1999, for me they are just
obvious.

paolo


"Paul Remde" wrote in message news:kem6kc$pnl$1...@dont-email.me...

[Richard Brisbourne]

Isn't this the principle behind the Stocker final glide
calculator, as described in Reichmann's
"Streckensegelflug", mid 1970s?

>news:4b8c77f1-1a6e-489e-a98c-
650346...@googlegroups.com...

[pcool]

I remember I had implemente the Stocker final glide circles time ago in the
software, basically they represent glide ratio ranges.

Since these concept are just obvious nowadays, I assume that years ago -
before gps - everything had to be done using approximated distances and
airspeed only, so the final glide was relative to the airmass, in principle,
and not to the ground.
Apart from that, if I am not wrong the Pirker analysis does not consider the
wind in final glide according to the document I read.
Nor does it consider total energy, apparently.

paolo


"Richard Brisbourne" wrote in message
news:5118fce7$2$4196$862e...@ngroups.net...

[Richard Brisbourne]

The Stocker calculator as described by Reichmann
(with instructions on how to make one) was
substantially more complex.

From memory you had a transparent disc with
altitude spirals in one hemisphere and in the other
hemisphere one set of curves corresponding to wind
components and an intersecting set of curves
corresponding to McReady readings. The latter set of
curves depended on the polar of the glider.

This disc was mounted on a map with the centre at
the goal point and it could be rotated about that point.
Above the disc was a linear cursor, also transparent
marked with distances, rotated about the disc centre.

To read the calculator, you rotated the disc so that
the spiral corresponding to your altitude lay over your
current position on the map. You then rotated the
cursor so that the line also lay over that point; the
other end of the cursor intersected the wind and
McReady spirals; the correct setting for the wind
could then be read off.

[Tobias Bieniek]

actually, as far as I remember, that is incomplete. it also said that once the calculated MC reaches the current average of your thermal it is time for starting the final glide. that way you will not waste time climbing any higher and you have the most efficient final glide compared to others who decided to stop climbing earlier but have to fly slower due to that.

this is pretty much also how the Final Glide AutoMC feature in XCSoar (and I think also LK8000?) works. I've used that feature for years now, and I think it is quite simple to use and understand, and also works quite well from my experience.

[Dave Nadler]

On Monday, February 11, 2013 12:56:53 PM UTC-5, Richard Brisbourne wrote:
> The Stocker calculator as described by Reichmann
> (with instructions on how to make one) was
> substantially more complex.
>
> From memory you had a transparent disc with
> altitude spirals in one hemisphere and in the other
> hemisphere one set of curves corresponding to wind
> components and an intersecting set of curves
> corresponding to McReady readings. The latter set of
> curves depended on the polar of the glider.
>
> This disc was mounted on a map with the centre at
> the goal point and it could be rotated about that point.
> Above the disc was a linear cursor, also transparent
> marked with distances, rotated about the disc centre.
>
> To read the calculator, you rotated the disc so that
> the spiral corresponding to your altitude lay over your
> current position on the map. You then rotated the
> cursor so that the line also lay over that point; the
> other end of the cursor intersected the wind and
> McReady spirals; the correct setting for the wind
> could then be read off.

Yep - First commercial gliding product I did was a
version of this calculator, sold by Cambridge Aero
in the early 80s (maybe late 70s). Still have a few
in the basement I think ! Worked well but it was too
large for USA sectionals and LDs of modern gliders.
Anybody out there still have one ?
I think Chip Bearden needs one.

See ya, Dave "YO electric"

[Naviter Info]

When you're doing Auto MC please mind the MC theory:

If you hit sink on the final glide the required MC value will go down. According to AutoMC you would be advised to fly slower. **Slower through sink**??

You should always fly your Speed to fly director from the Vario. Even if you fall below final that's the only way to get to the other side as high as possible. "Auto MC" is just a value which is "nice to know" but certainly not the optimal way to get home.

Having said that I too always make my final glides (since before GPS and SeeYou Mobile) comparing required L/D with Current L/D (which is just another way to represent the required MC value)

The original Pirker final glide calculator deals with wind and final glide around the corner iirc which is not as trivial as doing it in a straight line.

Regards,
Andrej Kolar
--
glider pilots use
http://www.Naviter.com

[Richard Brisbourne]

At 10:14 12 February 2013, Naviter Info wrote:
>When you're doing Auto MC please mind the MC
theory:
>
>If you hit sink on the final glide the required MC
value will go down.

>Acco=

>rding to AutoMC you would be advised to fly slower.
**Slower through

>sink**=
>??

I don't quite follow this.

Surely the required McCready (McReady?) setting is a
function of height, wind and distance to run.

So if you hit sink and lose altitude of course your
required McCready setting will go down. But your
speed at that setting will still be what is appropriate
for that setting in that amount of sink.

You could of course keep your nerve and leave the
McCready setting where it is- if you expect to go
through lift later this is usually OK- it's a judgement
call. If you do this and don't go through any lift later
you're in a field.

The only way to avoid having to slow down at all is
not to fly through sink.

[Roel Baardman]

> If you hit sink on the final glide the required MC value will go down. According to AutoMC you would be
advised to fly slower. **Slower through sink**??

Imagine flying "not slower" in the extreme case: flying at Vne through the sink.
The influence of the sink itself will be minimal, since the time you spend in the sink is minimal.
However, your glider's polar is also important, and it will probably not be enough to compensate. It is the sum
of these two that determines your total vertical speed (assuming linear flight).
Thus, you should minimize the sum of these two. You appear to want to minimize only the effect of the sink.

[Naviter Info]

True. But while you're in sink you need to speed up. At least until you are flying the optimal speed for MC=0 for that sink. The AutoMC suggests you to slow down which is not ok any way you look at it.

Andrej Kolar
--
glider pilots use
http://www.Naviter.com

[Peter Higgs]

If you have lost height in a sink zone, your speed will need to be Lower
AFTER the sink zone.

What you do in the sink is up to you (I suppose speed up.)

[jpg...@gmail.com]

On Tuesday, February 12, 2013 12:09:20 PM UTC, Naviter Info wrote:
> True. But while you're in sink you need to speed up. At least until you are flying the optimal speed for MC=0 for that sink. The AutoMC suggests you to slow down which is not ok any way you look at it.
>
>
>
> Andrej Kolar
>
> --
>
> glider pilots use
>
> http://www.Naviter.com

I have been looking at it differently. For an area of strong sink the appropriate airspeed at the optimum MC0 setting for prioritising getting through sink with minimum height loss (rather than maximising XC speed) may well be higher than the optimum speed for cruising in still air at a positive MC setting. For example if, when cruising at MC3kts in still air, one encounters sink of anything greater than 3kts then MC0 will command a higher speed.

So, if I encounter strong sink at an altitude low enough that I am concerned about dropping below a sensible operating band, I wind the MC back to zero (or small positive if final gliding into a headwind) temporarily. That is the one situation that I actually pay close attention to the speed command which will be telling me to speed up rather than slow down.

In the case of a Required MC advisory reading, the calculation will presumably be related to optimising a final glide and it would be dropping the advised MC gradually as the reserve is eaten up, rather than winding straight back to zero as I do, so it is even more likely that the speed command would call for an increase in airspeed in strong sink rather than a decrease.

John Galloway

[Richard Brisbourne]

At 14:25 12 February 2013, Peter Higgs wrote:
>If you have lost height in a sink zone, your speed
will need to be Lowe

>AFTER the sink zone.
>
>What you do in the sink is up to you (I suppose
speed up.)
>
>
>At 12:09 12 February 2013, Naviter Info wrote:
>>True. But while you're in sink you need to speed
up. At least until yo

>are
>>flying the optimal speed for MC=0 for that sink.
The AutoMC suggests yo

>to
>>slow down which is not ok any way you look at it.
>>
>>Andrej Kolar
>>--
>>glider pilots use
>>http://www.Naviter.com
>>

Either you're wrong or we have a different
interpretation of what we mean by auto MC.

The theory we are talking about (be it Pirker, Stocker
or whoever), calculates a McCready setting that will
give you the optimum glide path to get in, given
either "dead air" or an averaged amount of lift and
sink to fly through.

Auto MC as I understand the term simply calculates
that notional MC setting for you- it doesn't substitute
for the MC ring, flight director, whatever you use, just
tells you where to set it (or possibly effectively sets it
for you).

If you hit sink, the Auto MC value will go down, as
you've dropped below the predicted glide path.

If you aren't expecting to go through any further lift
to put you back up again, then the correct speed to
fly will be the speed commanded _for the sink rate
you are in_, at the new McCready setting. This may
or may not be faster than you were going before you
hit the sink- either way it's the optimum speed.

The only time you will fly at the MC=0 speed
through the sink will be if the calculation, based on
height and distance, says you can just reach your
goal at MC=0; I'd suggest if that is the case then zero
is indeed the best setting unless you are confident of
finding another thermal and therefore aren't on final
glide any more. It's still the MC speed for the sink
you are in, so may still be fast.

In the extreme case, if the auto MC reading winds
down to zero, but you ignore it and continue to fly on
a high MC setting you will definitely put yourself
below glide path.

Of course if you are still confident of flying through lift
before reaching the goal, by all means keep the
speed on. As I said, it's a judgement call.

[pcool]

My point of view on how AutoMC is actually working on LK.
1. Computer tell you that you can make it to the finish from the current
position and altitude, wind considered, eventually considering also your
current IAS, as an extra altitude if you pull up. This last extra altitude
is optional and by default disabled, to leave some margins.
2. Computer tell you that you shall arrive 0 meters (at worst) over the
desired destination's altitude with a certain MC setting, say 1.2 (I use
m/s).
It considers ballast. And if you dump ballast and it takes 3 minutes to
do it, during those 3 minutes it will shift the polar for wing loading,
adjusting all parameters.
This is the same as in xcsoar .
3. You set the desired MC on your speed to fly instrument, or this value is
sent automatically to it eventually, and you start following the
pullup-pushdown commands seconding the airmass you travel in.
4. If the airmass is equally distributed in sinks and lift, you will be more
or less flying at the desired MC.
5. If unfortunately you meet a large sink area, you will be commanded to
speed up of course, following the STF indicator on the vario, which is still
relative to the desired MC.
6. After some time, your average airspeed will not be anymore the one
relative to the original MC, and of course the glidepath and the arrival
altitude will change, even drastically, to a worst prediction.
7. In LK we use eMC, Equivalent MC , telling you what is the real MC you are
flying it, no matter what you think you are doing.
This eMC (widely used by paragliders, who cannot play with their
instruments too much, not to mention hangglider pilots) can also be assigned
automatically to MC, thus resulting in an accurate prediction based on what
you are actually doing, concentrated on the airmass and not on the
instrument.
In still air, if you fly at MC 2 following the speed to fly indicator on
your vario, the eMC will read 2, precisely.
In sink air, if you try to fly at MC 1.2 but it has been some time since
you have been speeding up to pass a neverending sink area, you may read eMC
3 !

8. You decide what to do. Computer tell you what happen if you start flying
again at the proper STF relative to desired MC 1.2, what happen if you keep
flying like you do, at a real MC 3, and what if you slow down to MC 0.
You want to make it over the finish, not below. Pilot can judge if he can
speed up, slow down, or stop circling as soon as possible.
No computer can estimate an airmass 2 km away, guessing if it is sinking or
raising air.
What we can do, is give clear informations about different scenarios, and
the Equivalent MC helps a lot on this, because otherwise - like it currently
happen on most flight computers, you still keep reading MC set to 1.2, while
your arrival altitude gets lower and lower, and you have no clue on what you
are actually doing.
If you fly using MC, you ought to know what MC you are really flying with,
no matter what you hope to have been using so far.

EqMC stand to MC like CurrentGlide Ratio stand to Required Glide Ratio to
get to a destination.
The difference is that the latter does not consider wind, ballast, extra
speed.

paolo






"Richard Brisbourne" wrote in message

news:511a6e0a$1$4227$862e...@ngroups.net...

[buc...@comcast.net]

On Monday, January 14, 2013 10:19:27 AM UTC-5, jpg...@gmail.com wrote:

John: send me your email by responding to buc...@comcast.net

[buc...@comcast.net]

Agree 100%. You can fly yourself into the ground before reaching your goal. If you are really on final glide, you, by definition, are not going to stop and thermal. That, is final glide, by definition. If you are flying a MC value of four and fall below glide path, auto MC may tell you to slow down just enough to make your goal, at a lesser MC value. Auto MC continues to give you the speed to fly in sink. Auto MC really just resets the equation such that you can make it to goal without stopping to thermal.
To make a point in argument, it is often helpful to push the situation to extremes to test the validity of arguments.
If, for example, you are flying a MC value of 10 and you hit sink, your computer will tell you to speed up. Better judgement would be to reset MC value to a value of 3. Doing so gives you the added altitude for computations for making the final glide home. The computer will still give you speed to fly signals while flying through sink as well as through lift. If you are already flying a McCready of 0, then you are no longer on final glide if you hit sink and fall below glide path to make the goal home.

[SoaringXCellence]

I have one for a Libelle H-301