Glider computers - what's important?

"ContestID67" wrote:

I think that everyone understands that the free programs do not give
you the features or support of the for-pay programs.

Well,... Speak for yourself. It is exactly this kind of attitude that
gives free programs a "bad name".

Personally I always hear how awfull the support for paid for programs
is .

Cheers,
Henryk Birecki

Henryk Birecki wrote:


Plase confirm this function uses current MC. I browsed the on-line
manual and I thought it said ZERO MC which is not the implementation I
would want.

You are right about documentation. I will need to check in the code.
It may well be ZERO MC as it is a "safety" feature. If you are looking
for a safe place to land you want to fly at best glide angle, not best
time. Anyone would like to comment?

A MC = 0 glide path is very shallow, making it sensitive to small errors
in the assumptions - headwind, bugs, sink, polar. It is very likely to
go wrong. A MC = 4 glide path is much steeper, and by flying it at a MC
= 1 (for example), you have a lot of extra altitude to handle the same
problems. As you point out, if you are trying to get to some place
safely, there's no need to rush!

I would never trust my safety to a MC = 0 glide path, instead, I
routinely use MC = 4. This has proven reliable (but not 100%) over 30
years of soaring in several different gliders.

On days with wave, in the mountains, or gliding over poor landing areas,
I'll use MC = 5, possibly higher, or raise my arrival altitude setting.

It is possible to use an MC = 0 safely if you set a very high "arrival
altitude". To have the same margins I get with MC = 4 and a 1000' AGL
arrival, I estimate it would have to be at least 2000' AGL. Perhaps
someone can comment on the relative merits of a higher MC with a lower
arrival altitude, versus doing the reverse.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Thanks Eric,

The way I read your post is that you are using MC setting as a safety
margin thing to avoid false hopes. GPS_LOG uses pattern altitude to
accomplish that. On the other hand it just says that different people
have different preferences. Since philosophy behind GPS_LOG is to
allow users to configure it as much as possible to their preferences
rather than me telling them what they should use, I will add a YABO
(Yet Another Bloody Option) in next release of the program.

And yes, code says program is currently using zero MC.

Henryk Birecki

Eric Greenwell wrote:

Henryk Birecki wrote:


Plase confirm this function uses current MC. I browsed the on-line
manual and I thought it said ZERO MC which is not the implementation I
would want.

You are right about documentation. I will need to check in the code.
It may well be ZERO MC as it is a "safety" feature. If you are looking
for a safe place to land you want to fly at best glide angle, not best
time. Anyone would like to comment?

A MC = 0 glide path is very shallow, making it sensitive to small errors
in the assumptions - headwind, bugs, sink, polar. It is very likely to
go wrong. A MC = 4 glide path is much steeper, and by flying it at a MC
= 1 (for example), you have a lot of extra altitude to handle the same
problems. As you point out, if you are trying to get to some place
safely, there's no need to rush!

I would never trust my safety to a MC = 0 glide path, instead, I
routinely use MC = 4. This has proven reliable (but not 100%) over 30
years of soaring in several different gliders.

On days with wave, in the mountains, or gliding over poor landing areas,
I'll use MC = 5, possibly higher, or raise my arrival altitude setting.

It is possible to use an MC = 0 safely if you set a very high "arrival
altitude". To have the same margins I get with MC = 4 and a 1000' AGL
arrival, I estimate it would have to be at least 2000' AGL. Perhaps
someone can comment on the relative merits of a higher MC with a lower
arrival altitude, versus doing the reverse.

Hi Eric,

I agree that higher MacCready settings are safer. I have found that many
glider pilot find that point difficult to get their heads around - probably
because using a higher MC causes your glide computer to show that you need
more altitude, and because you will be flying faster (which seems less
conservative) if you follow the speed director.

But you are correct that it gives you a less shallow glide with more
options. Also, if you slow down and fly at best L/D you should do much
better than the glider computer thinks you can do.

I never fly with my MacCready ring or speed director set to zero. I think
that is unsafe.

Here in Minnesota I don't use a MacCready of 4 though. I use about 1/2 to
3/4 of the value of my actual measure climb rates in thermals.

I suppose that higher arrival altitudes can be used to do the same thing -
increase safety.

Good Soaring,

Paul Remde

"Eric Greenwell" wrote in message
news:sYoJh.9072$S06.356@trndny08...
Henryk Birecki wrote:


Plase confirm this function uses current MC. I browsed the on-line
manual and I thought it said ZERO MC which is not the implementation I
would want.

You are right about documentation. I will need to check in the code.
It may well be ZERO MC as it is a "safety" feature. If you are looking
for a safe place to land you want to fly at best glide angle, not best
time. Anyone would like to comment?

A MC = 0 glide path is very shallow, making it sensitive to small errors
in the assumptions - headwind, bugs, sink, polar. It is very likely to go
wrong. A MC = 4 glide path is much steeper, and by flying it at a MC = 1
(for example), you have a lot of extra altitude to handle the same
problems. As you point out, if you are trying to get to some place safely,
there's no need to rush!

I would never trust my safety to a MC = 0 glide path, instead, I routinely
use MC = 4. This has proven reliable (but not 100%) over 30 years of
soaring in several different gliders.

On days with wave, in the mountains, or gliding over poor landing areas,
I'll use MC = 5, possibly higher, or raise my arrival altitude setting.

It is possible to use an MC = 0 safely if you set a very high "arrival
altitude". To have the same margins I get with MC = 4 and a 1000' AGL
arrival, I estimate it would have to be at least 2000' AGL. Perhaps
someone can comment on the relative merits of a higher MC with a lower
arrival altitude, versus doing the reverse.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Henryk Birecki wrote:
Thanks Eric,

The way I read your post is that you are using MC setting as a safety
margin thing to avoid false hopes.

Yes, the flight computer MC setting is based on safety, usually with a
MC=4 setting to give me a conservative glide to airports and landing
areas. The MC setting on my 302 vario set to the speed-to-fly I am
using; typically, that's 1 or 2 knots, except in very good conditions.

So, two MC settings, two different purposes: safety and speed.

GPS_LOG uses pattern altitude to
accomplish that.

I also use an "arrival altitude" of 1000'. My experience is a 1000'
arrival altitude and an MC=0 glide is very risky business.

On the other hand it just says that different people
have different preferences. Since philosophy behind GPS_LOG is to
allow users to configure it as much as possible to their preferences
rather than me telling them what they should use, I will add a YABO
(Yet Another Bloody Option) in next release of the program.

For people like me, using the same MC setting the flight computer is
using would be ideal. It would be interesting to hear how other pilots
use the MC settings in their flight computer and vario, and now a third
choice: the glide footprint setting.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

I agree that higher MacCready settings are safer. I have found that many
glider pilot find that point difficult to get their heads around - probably
because using a higher MC causes your glide computer to show that you need
more altitude, and because you will be flying faster (which seems less
conservative) if you follow the speed director.

I was flying a contest last year and made the bone-headed error of
increasing my MC when I hit bad sink on final glide. I don't recall if
it was nerves, fatigue, or what, but during the last 12-15 miles
across the tiger terrain west of Turf, the sink got worse and worse,
and instead of reducing my MC, I increased it.

Of course, that would have been the proper action during my last
climb, but I got my wires crossed when the vario turned into a
divining rod after I passed up the last landing option. I ended up
doing a rolling finish, and being most thankful that the mistake did
not damage anything beyond my ego!

~ted/2NO

XCSoar has all that, and more.
You can preset a safety MC setting for final glide, you get a glide range footprint, all the bells and whistles.
The support is really good in that the open source base is available for anyone to change. If a user comes up with a worthwhile suggestion for another option, it is added to the program!
A dedicated nabble group assists in anyones problems, not just the programmers. Its free, what more do you need?

did I mention free?
FREE


bagger

On Mar 13, 8:32 am, "Paul Remde" wrote:
Hi Eric,

I agree that higher MacCready settings are safer. I have found that many
glider pilot find that point difficult to get their heads around

I never fly with my MacCready ring or speed director set to zero. I think
that is unsafe.

Paul you may need to be more flexible with your use of the MC
setting. Using a hi setting to estimate glide margin does not
preclude using a low setting to drive the speed director. Using a
zero MC glide is not unsafe, it's the only sensible thing to do if the
glide is marginal, but planning a safe glide margin on MC 0 may well
be unsafe.

As an example if I see my MC4 glide margin eroding to mins I'll head
for the best landable at reduced MC, perhaps zero MC. My MC knob is
not a fixed setting but a variable input to several what if questions.
What is my glide margin, how high should I climb in this thermal, how
fast should I fly a safety glide, how fast should I fly final glide.

With the 302/GNII combination, glide margin and speed director can use
different MC setting and be completely independent. You can also keep
them linked and set the MC appropriate to the situation.

The other use for the MC setting is to make the speed director shut up
when you fly at the speed you want to.


Andy