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required LD versus required MC to make it home ??



 
 
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  #21  
Old August 24th 10, 02:54 AM posted to rec.aviation.soaring
akiley
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Posts: 114
Default required LD versus required MC to make it home ??

snip

For typical days where there is lift available and as you become more
comfortable with thermaling I would encourage you to try to start with
Mc near 1. Mc == 0 means you really are in desperation mode and don't
really plan to go anywhere. See the discussion in Reichman about this.
Mc=0 quickly becomes a kind of boat anchor dragging on you. If you are
dialing the Mc into a flight computer (or STF ring on a winter vario)
it also starts giving you a feel for how excess Mc helps you if you
run into worse conditions than you expect. You can increase the Mc
setting you fly at up from there as you gain confidence, but dont' go
crazy with it. A rule of thumb often used especially for new XC folks
it to set the Mc conservatively at 1/2 to 1/3 of what you think your
next average climb will be - and even then its just to give you an
idea of average speed to fly, don't go chasing it. Sounds like you
have a good approach as is. The last thermal average climb stats in
SeeYou Mobile can be interesting to check, it will often be much less
than you think, and even then it often misses time wasted mucking
around trying to find lift.


This brings up something I may have overlooked as I described how I
get home safely. I use MC more as a way to judge my wiggle room to my
home airport rather than STF. If my SeeYou is showing 10mc to get
home based on winds and safety altitude, I generally don't fly that MC
unless I'm very close and can see I have it made. Instead I fly
conservatively within 10kts of best L/D and use that high required MC
as my safety margin. Sort of like always being within half your best
L/D to your target airport. akiley

BTW details of wind effects and Mc may not be obvious, search for past
r.a.s. postings by John Cochrane and others on this.

[snip]

Darryl


Ads
  #22  
Old August 24th 10, 04:11 AM posted to rec.aviation.soaring
Andy[_1_]
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Posts: 1,565
Default required LD versus required MC to make it home ??

On Aug 23, 1:14*pm, johngalloway wrote:
All glide angles converge at
the destination so any glide angle that I can keep constant will
bring me to home at my arrival reserve altitude.


With the very, very, big caveat that there is no intervening terrain.

There is actually significant potential for advancement in gliding
computers. That is the display of a vertical profile view of the final
glide, complete with terrain. This display is known as the VSD
(Vertical Situation Display) in some non gliding display
applications. This type of display can clearly depict a multi-angle
final glide path when that is required to clear terrain and also make
the goal at the required finish altitude.

I suspect that this type of display would also be very useful for
understanding the effect on glide path and optimum MC when there is a
significant wind change when rounding the final turnpoint.

Andy (GY)
  #23  
Old August 24th 10, 05:08 AM posted to rec.aviation.soaring
Eric Greenwell
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Posts: 1,096
Default Getting rid of the bugs and gotchas!

On 8/23/2010 8:17 AM, akiley wrote:
Well, I've flown long enough to know not to trust electronics. I have
600 power hours using all sorts of navigators. Funny, when you use a
Garmin 396 on a computer, it sets magnetic variation to user set
instead of auto. SeeYou has quite a few bugs and gochas too. So my
primary is look at the down angle back to the airport.

I've used SeeYou Mobile for 1000+ hours all over the USA, and I'm not
aware of any bugs or gotchas. I would never go back to paper charts,
whiz wheels, or just looking out the window. For example, most of my
final glides begin 30 to 50 miles from the airport, where I can't even
see it, yet they work out well most of the time.

Your statement "So my primary is look at the down angle back to the
airport" suggests to me it's not SeeYou, but more likely your setup or
interpretation of what Mobile is telling you. If you are that close, the
computer should be working with no problems.

Flight computers can be a real aid to efficient, enjoyable soaring, so I
hate to see someone having problems with them. What version of mobile
are you using? Can you describe the two biggest bugs and gotchas?

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

  #24  
Old August 24th 10, 02:39 PM posted to rec.aviation.soaring
Westbender
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Posts: 154
Default Getting rid of the bugs and gotchas!

I'm with Mike. You can't get any simpler than using the "Arrival
Altitude" navbox. It takes into account all available parameters
(distance, Mc, bugs, ballast, wind), and is corrected for reserve
altitude. This requires you have reasonable polar info entered for the
ship you're flying. This feature is perfect for first forays into xc
flying. You can use this to "hop" from one airfield to the next. A
quick glance at the navbox will show whether you can make the current
waypoint from your current position. Negative value = climb, 0 or
higher = good to go.
  #25  
Old August 24th 10, 03:44 PM posted to rec.aviation.soaring
akiley
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Posts: 114
Default required LD versus required MC to make it home ??

On Aug 23, 11:11*pm, Andy wrote:
On Aug 23, 1:14*pm, johngalloway wrote:

All glide angles converge at
the destination *so any glide angle that I can keep constant will
bring me to home at my arrival reserve altitude.


With the very, very, big caveat that there is no intervening terrain.

There is actually significant potential for advancement in gliding
computers. That is the display of a vertical profile view of the final
glide, complete with terrain. *This display is known as the VSD
(Vertical Situation Display) in some non gliding display
applications. *This type of display can clearly depict a multi-angle
final glide path when that is required to clear terrain and also make
the goal at the required finish altitude.

I suspect that this type of display would also be very useful for
understanding the effect on glide path and optimum MC when there is a
significant wind change when rounding the final turnpoint.

Andy (GY)


I use Condor soaring simulator with my iPaq running from the serial
port. It's a great way to test if/then situations and to get familiar
with your navigator. One interesting way of looking at terrain is
also the program XC-Soar. It draws a dotted, terrain aware, wind
aware, polar aware circle around your current position that indicates
the terrain strike point at your current MC. For terrain, this dotted
line spills into other valley's through lower gaps and valleys. Also
SeeYou has a red box on the course line indicating any ridge you will
hit before reaching you destination. You can run somewhat parallel to
this ridge way before you get to it and if SeeYou finds a gap, the red
box disappears and you can proceed direct. akiley
  #26  
Old August 24th 10, 04:14 PM posted to rec.aviation.soaring
Andreas Maurer
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Posts: 345
Default required LD versus required MC to make it home ??

On Mon, 23 Aug 2010 11:56:48 -0700 (PDT), Joseph Kiley
wrote:


I don't think SeeYou does very well with winds. This is what I've
experienced and read in other posts. I get winds aloft from several
sources/stations during my home briefing. I enter those directly into
SeeYou and always check them before I do my MC required to target.


Well, actually SeeYou's wind calculations are actually very good, even
if its only data source is GPS. But you have to remember that the wind
is only calculated while you are circling, and that it might take a
couple of minutes to get accurate data.


My SeeYou is not plugged into anything so it's all GPS. To be honest,
I use it mostly to analyze me flight when I get home. I look at it in
flight to backup a possible creepy feeling because I look a bit low
for my liking. I fly MC zero generally because I'm flying local
working on my thermal technique. If I encounter sink I speed up maybe
10 or 15 knots depending on how large the sink area is. If I have a
headwind I'm trying to penetrate, I will speed up somewhat as well. I
guess what I really want to be sure of is NOT landing out.


Try this for your Cirrus:
- set MC on your PDA to 2 meters/second (do the maths for the units
you use)
- set bug factor to 30 percent
- set arrival altitude to a value of your liking, say, 600 to 900 ft

With these settings you can be nearly 100% sure that you are going to
reach the chosen airport with the desired arrival altitude.

If you know of any bugs in SeeYou Mobile, please report then to
Naviter.


Have done that.


Which bugs did you observe?
I've been flying with the relatively old SeeYou 2.71 for the last
15.000 kilometers and found no bugs worth mentioning.


Greetings from germany
Andreas
  #27  
Old August 24th 10, 04:24 PM posted to rec.aviation.soaring
mattm[_2_]
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Posts: 167
Default required LD versus required MC to make it home ??

On Aug 23, 11:11*pm, Andy wrote:
On Aug 23, 1:14*pm, johngalloway wrote:

All glide angles converge at
the destination *so any glide angle that I can keep constant will
bring me to home at my arrival reserve altitude.


With the very, very, big caveat that there is no intervening terrain.

There is actually significant potential for advancement in gliding
computers. That is the display of a vertical profile view of the final
glide, complete with terrain. *This display is known as the VSD
(Vertical Situation Display) in some non gliding display
applications. *This type of display can clearly depict a multi-angle
final glide path when that is required to clear terrain and also make
the goal at the required finish altitude.

I suspect that this type of display would also be very useful for
understanding the effect on glide path and optimum MC when there is a
significant wind change when rounding the final turnpoint.

Andy (GY)


Personally I love the SoarPilot final glide table. There's a picture
of it at
http://www.soaringpilot.org/dokuwiki...l_glide_screen
It displays a table of MC settings (values 0-5, or 0-10 by 2) along
with
the speed to fly and a choice of arrival altitude, required altitude,
or
difference from glide slope. I find it very easy to follow on final
glide --
if I'm picking up energy I can see how fast I can fly and still
arrive,
or if I'm losing energy I can see how much I need to slow up and still
make it back.

The only problem with SoarPilot is that it runs on PalmOS,
which goes on outdated hardware these days. There's a version of
StyleTap that runs on the iPhone, but there's no serial port or
bluetooth
to connect it to any other devices in your plane. I don't know if
anyone
has gotten it to work on the PNDs that are being used nowadays.

-- Matt
  #28  
Old August 24th 10, 07:09 PM posted to rec.aviation.soaring
Ramy
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Posts: 746
Default Getting rid of the bugs and gotchas!

On Aug 24, 6:39*am, Westbender wrote:
I'm with Mike. You can't get any simpler than using the "Arrival
Altitude" navbox. It takes into account all available parameters
(distance, Mc, bugs, ballast, wind), and is corrected for reserve
altitude. This requires you have reasonable polar info entered for the
ship you're flying. This feature is perfect for first forays into xc
flying. You can use this to "hop" from one airfield to the next. A
quick glance at the navbox will show whether you can make the current
waypoint from your current position. Negative value = climb, 0 or
higher = good to go.


Seems like many pilots are using multiple complicated methods to
determine their final glides. Most are using MC settings for that
purpose. Is it just me who never use MC setting to determine arrival,
but using bug factor instead? Following the KISS principal, this is
the simplest way. No need to compare L/D, guesstimate MC, disconnect
the vario or ignore the MC speed to fly, etc. Just set your bug factor
to degrade your polar to something you are comfortable with (I found
70-75% to work fine most of the time), set your MC to zero and watch
your arrival altitude. Once you are comfortable with the arrival
altitude just keep maintain the same number by either speeding up or
slowing down. Works perfect for me.

Ramy
  #29  
Old August 24th 10, 07:33 PM posted to rec.aviation.soaring
Andreas Maurer
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Posts: 345
Default Getting rid of the bugs and gotchas!

On Tue, 24 Aug 2010 11:09:01 -0700 (PDT), Ramy
wrote:


Seems like many pilots are using multiple complicated methods to
determine their final glides. Most are using MC settings for that
purpose. Is it just me who never use MC setting to determine arrival,
but using bug factor instead? Following the KISS principal, this is
the simplest way. No need to compare L/D, guesstimate MC, disconnect
the vario or ignore the MC speed to fly, etc. Just set your bug factor
to degrade your polar to something you are comfortable with (I found
70-75% to work fine most of the time), set your MC to zero and watch
your arrival altitude. Once you are comfortable with the arrival
altitude just keep maintain the same number by either speeding up or
slowing down. Works perfect for me.


.... but is neither accurate, nor fast, not safer.

Most pilots don't want to waste time (or simply don't have the
weather) to climb extremely high in the last thermal, hence they
follow McCready's advice that has been proven for the last 50 years:
Set the average climb rate of the last thermal as MC setting, add the
bug factor, and leave the thermal once the arrival altitude is to your
liking. Works like a charm, and is extremely easy to use.
To be honest, I have difficulties to find an explanation why something
different (your settings, for example) should be less complicated.

What you are doing is simply to abandon the performance of your 56:1
ship and fly it like a 30:1 Ka-6. Works, but is far, far away from the
optimum.

Cheers
Andreas






  #30  
Old August 24th 10, 08:44 PM posted to rec.aviation.soaring
Ramy
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Posts: 746
Default required LD versus required MC to make it home

On Aug 24, 11:33*am, Andreas Maurer wrote:
On Tue, 24 Aug 2010 11:09:01 -0700 (PDT), Ramy
wrote:

Seems like many pilots are using multiple complicated methods to
determine their final glides. Most are using MC settings for that
purpose. Is it just me who never use MC setting to determine arrival,
but using bug factor instead? Following the KISS principal, this is
the simplest way. No need to compare L/D, guesstimate MC, disconnect
the vario or ignore the MC speed to fly, etc. Just set your bug factor
to degrade your polar to something you are comfortable with (I found
70-75% to work fine most of the time), set your MC to zero and watch
your arrival altitude. Once you are comfortable with the arrival
altitude just keep maintain the same number by either speeding up or
slowing down. Works perfect for me.


... but is neither accurate, nor fast, not safer.

Most pilots don't want to waste time (or simply don't have the
weather) to climb extremely high in the last thermal, hence they
follow McCready's advice that has been proven for the last 50 years:
Set the average climb rate of the last thermal as MC setting, add the
bug factor, and leave the thermal once the arrival altitude is to your
liking. Works like a charm, and is extremely easy to use.
To be honest, I have difficulties to find an explanation why something
different (your settings, for example) should be less complicated.

What you are doing is simply to abandon the performance of your 56:1
ship and fly it like a 30:1 Ka-6. Works, but is far, far away from the
optimum.

Cheers
Andreas


Nope. We both are going to leave the thermal at the same time and
glide at the same speed.
In my case the MC will be zero and the bug factor 75%, in your case
MC=3 and bug factor = 95-100%.
However you will need to ignore the speed to fly as John suggested
unless you are willing to risk landout to save couple of minutes
(which may make sense only in contest).
Using the last average climb in the thermal is often meaningless in my
opinion. In many places I fly (Truckee, Hollister, Byron), the last
average thermal is maybe 5 knots but the next is zero since this was
the last thermal. This is true for many soaring sites which are in the
valley and not on the top of the montain range you just left, as well
as long XC flight where the likelyhood to find another thermal late in
the day is small. So using the method of dialing MC = last average
climb and then follow STF is guaranty landout, and a very silly one...
So my recomendation to all non contest XC pilots will be to degrade
your performance using bug factor 70-75%, which will give you enough
buffer for unexpected sink or head wind (which can also be very
different from the wind measured in your last turn) and fly MC=0 until
you are comfrtable with your arrival altitude and then speed up if
your arrival altitude start increasing. This will usually result in
slower glide speed at the beginning of the final glide, gradually
increasing as you get closer, much safer than the other way around.

Ramy


 




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