Max, thanks for the quick resply. Indeed I always used bug factor to degrade my
polar with Winpilot, but just about anyone else uses MC to degrade, and since
bug factor is not persistent in XCSoar, I figured the safety MC will be
perfect for that, except those 2 issues, which I think can be addressed without
impacting the current functionality:
1 - Add an option in safety factors configuration (screen 9) to use safety MC
for Next infobox, and in screen 10 add an option to also use reach for next
Infobox. Both will default to 'Off' so not to impact current configuration.
2 - In screen 9 also add an option to default MC to safety MC (and default this
option to 'Yes' for backward compatability). In any case, I don't think that
the default MC should update the initial MC in 302. If this is the case, then I
think we definitely need an option to disable auto MC sync between 302 and
XCSoar. This is especially important for conservative pilots flying localy
which have no reason to fly faster than zero MC, and if they use a relatively
high safety MC it will work against them, since the 302 will dictate faster
speed which in turn may result in landout...
BTW, I just had an unpleasant surprise with 302 on my Dell Streak - all the
configuration I did recently disapeared and it default to the factory
configuration. I checked the xcsoar folder on the SD card and the previous
configuration file was overwritten. My only guess is that it may have been
related to my enabling the USB storage option after connecting the streak to my
computer. Maybe when I restarted XCSoar it could not access the config file and
reverted to the default configuration. Could this be the reason? Of course I
did not have a backup (now I will). We sure need an option to save a backup of
the config file, or better yet, save multiple config files similar to the
option to save multiple gliders. Having an option to only make backups via the
file system is problematic.
Thanks,
Ramy
>________________________________
>From: Max Kellermann <m...@duempel.org>
>To: Ramy Yanetz <ryan...@yahoo.com>
>Cc: "xcsoar-user@lists.sourceforge.net" <xcsoar-user@lists.sourceforge.net>
>Sent: Friday, November 4, 2011 10:33 PM
>Subject: Re: [Xcsoar-user] Arrival Altitude and MC setting
>
>On 2011/11/05 04:12, Ramy Yanetz <ryan...@yahoo.com> wrote:
>> Hi everyone,
>>
>> I have few more complicated questions:
>>
>> 1 - I believe many (most?) of us use XCsoar
>> mostly for 'casual' XC or OLC, and less for contest/record/badges, which
>> means in most flights no task is set. It is not clear to me what is the
>> recomended strategy to configure
>> XCSoar to this most common type of flying. The most important
>> information for the casual XC pilot is distance, direction and arrival
>> altitude at various landout places along the course, using conservative
>> glide angle (typically half to 2/3 of published polar). The best way to
>> accomplish this I believe is using the safety MC. Although the manual
>> recommends to set it slightly above zero, I find that I
need to select
>> safety MC=4 to degrade my polar by 1/3.
>
>Degrading the polar by increasing the MC is not a good idea, but
>unfortunately, that seems to be the official way suggested by XCSoar.
>With a higher MC, XCSoar will recommend higher flying speeds, and
>you'll be degrading your performance even more. Everything in that
>idea is just wrong.
>
>The "bugs" setting is the one that degrades your polar without
>suggesting higher speeds. The problem is that "bugs" is not
>persistent - it needs to be set on every startup. That is something
>that can be implemented easily.
>
>> This seem to work fine for the arrival labels, which
>> are taking wind, polar, safety MC, safety altitude and reach into account.
>> However, it is often very helpful to closely monitor arrival altitude
>> (even when negative) and distance to selected airport (typically the
>> home airport). I found
doing 'goto' and monitoring the Next infobox to
>> be the best method. However to my surprise the arrival altitude in the
>> Next InfoBox ignores safety MC and uses actual MC instead. This is a
>> problem, since if I fly at low MC, it will show an overly optimistic
>> arrival altitude, and if I fly at much higher MC, it will show overly
>> pasimistic number. I know I can set it manualy to the same value as my
>> safety MC, but then, I don't want to use this MC setting to determine my
>> speed to fly, and if I change the MC to a lower setting in my 302 it
>> will increase my arrival altitude in the infobox. So either my strategy is
>> wrong or we need an option to display in an Infobox the arrival altitude of
>> the next turnpoint taking MC safety into account instead of actual MC, and
>> possibly even taking reach into account.
>
>It is difficult for us to decide which MC to use, because after such a
>change,
other people will be confused, because if the final glide bar
>and "Next Alternate" happen to point to the same waypoint, the arrival
>height will be different.
>
>Anyway, whatever we decide, some people will be confused ;-)
>
>But we could say: all that's not directly related to the current task
>shall not use the task's MC setting, but safety MC. Write a ticket if
>you care.
>
>> 2 - I noticed that the MC setting always defaults to the safety MC, in
>> manual or auto mode. Is this by design? It sure looks wrong, especially when
>> the safety MC is set high to degrade the polar by 1/3. It will stay high
>> until either the pilot changes it or it changes automatically after the
>> first thermal. But until then, it will dictate a very high speed to fly
>> right of tow, which is obviously not a good idea. Am I missing something?
>
>It is a design decision, yes. If you were using MC the way MC is
>designed to be used by Paul
MacCready, your problem wouldn't exist
>... see above.
>
>Max
>
>
>
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