Wind speed and direction

[bobcaldwell]

Hi pilots,

I know this subject has been discussed in the past but I am not sure
if this particular issue has come up. I run a CAI 302 which drives
both Winpilot Pro and a 303 head. The wind speed and directions are
often differing by large margins on these two displays even though
they must be looking at similar information. This is true even after
turning such that both displays should be completely "updated".

What are your thoughts on this subject or can you direct me to the
archives where this question may have been already answered?

Also on the subject of Winpilot, myself and others have pushed on
Jerry to provide a navbox with speed-to-fly data. He is apparently
unwilling to do this even though the program must be calculating it.
I understand the reasoning behind not chasing the instantaneous STF
number but I often wish I knew exactly what that number was. Other
programs such as GN II do provide this number. If other WP users push
on Jerry as well maybe he will put this navbox in. Thoughts?

Thanks and fly safely,

Bob Caldwell

[[email protected]]

Ugh? If you have a 302 you have one of the best STF there is - so make
sure you have the right polar, ballast etc. loaded in the 302 and use
that STF - and then worry about how much to ignore what it is telling
you to do.

Anybody serious is going to have a good flight computer, the PDA
really is the wrong place to do STF-- and I would want an audio tone
not to be trying to read a PDA screen for this type of info.There is a
great thread on the SeeYou Mobile support forum that touches on why
PDA based solutions really can't provide good STF - they just don't
have fast and clean enough data. See
http://www.naviter.si/component/option,com_smf/Itemid,238/topic,2832.0
(BTW Naviter's responsiveness on their support forum is very good, and
one of the reasons I switched to SeeYou Mobile). But in this case
Jerry is likely doing the right thing by ignoring your request! I'm
not sure what GN is showing as I've never used it.

I am not aware of any detailed description of how WinPilot Pro
calculates wind and I've not used it enough (well not recently) to be
sure but I beleive that WinPilot Pro is reading the extended data in
the NEMA stream for the 302 that includes TAS, etc. and when you
change direction enough it can calculate the wind from that. This is
also how SeeYou Mobile does it - they don't read the computed wind
output from the 302 (which is also available in the NEMA steam).
Winpilot Pro can also give you near instant headwind/tailind component
just from the TAS vs. GS. When you thermal it will use circle drift.
WinPilot advance only uses circle drift. The raw TAS/GS/ etc. data is
more or less the same but both WinPilot Pro and the 302 calculate wind
using completely different software algorithms, which will have
different aging factors, different height bands, hence the difference
you see.

I'd not overly worry about these differences, they are all pretty
crude approximations to what the wind is going to do next. Worry about
knowing how to display wind vs. altitude, develop a feel for how
accurate each algorithm is, and on the PDA especially know how to
resent the calculated winds if you think they are going to run you
into the ground with overly optimistic tailwinds etc.

The 302 is calculating the wind that you see on the 303 - which is
just a display to look at what the 302 thinks is going on, it really
does little else.

Darryl

On Dec 5, 3:43 pm, bobcaldwell > wrote:
> Hi pilots,
>
> I know this subject has been discussed in the past but I am not sure
> if this particular issue has come up. I run a CAI 302 which drives
> both Winpilot Pro and a 303 head. The wind speed and directions are
> often differing by large margins on these two displays even though
> they must be looking at similar information. This is true even after
> turning such that both displays should be completely "updated".
>
> What are your thoughts on this subject or can you direct me to the
> archives where this question may have been already answered?
>
> Also on the subject of Winpilot, myself and others have pushed on
> Jerry to provide a navbox with speed-to-fly data. He is apparently
> unwilling to do this even though the program must be calculating it.
> I understand the reasoning behind not chasing the instantaneous STF
> number but I often wish I knew exactly what that number was. Other
> programs such as GN II do provide this number. If other WP users push
> on Jerry as well maybe he will put this navbox in. Thoughts?
>
> Thanks and fly safely,
>
> Bob Caldwell

[[email protected]]

On Dec 5, 3:43 pm, bobcaldwell > wrote:
> Hi pilots,
>
> I know this subject has been discussed in the past but I am not sure
> if this particular issue has come up. I run a CAI 302 which drives
> both Winpilot Pro and a 303 head. The wind speed and directions are
> often differing by large margins on these two displays even though
> they must be looking at similar information. This is true even after
> turning such that both displays should be completely "updated".
>
> What are your thoughts on this subject or can you direct me to the
> archives where this question may have been already answered?
>
> Also on the subject of Winpilot, myself and others have pushed on
> Jerry to provide a navbox with speed-to-fly data. He is apparently
> unwilling to do this even though the program must be calculating it.
> I understand the reasoning behind not chasing the instantaneous STF
> number but I often wish I knew exactly what that number was. Other
> programs such as GN II do provide this number. If other WP users push
> on Jerry as well maybe he will put this navbox in. Thoughts?
>
> Thanks and fly safely,
>
> Bob Caldwell

Hi Bob,
I am going to fly this oncoming season with Win Pilot Pro for the very
first time. In the mean time I am just playing with it. Past 2 seasons
I flew with GN II and before that I had Win Pilot Advanced. I agree
with you about the speed to fly issue. I also have the 302 which is
connected to iPAQ. In the case of GN II, you had a number displayed
for your STF. And that number was matching almost exactly the STF from
my MC ring on my Winter vario. In the case of WP there are arrows for
pull/push. I prefer number being displayed instead of the arrows. That
is why I flew with GN II instead of WP even though I had both of them
in my iPAQ. I asked Richard with Craggy Aero if "the numbers" could be
added to the options of WP, so the pilot could decide if he will fly
the "chevrons" or "the number", but he gave me about the same answer
you got from Jerry. But still, it would be nice to have that option.

Jacek
Pasco, WA

[Vic]

Surprisingly I'm not aware of any calculator having an integrated electronic
compass in addition to the GPS. Sailing calculators do that for ages ...
Jean

"bobcaldwell" > a écrit dans le message de
groupe de discussion :
...
> Hi pilots,
>
> I know this subject has been discussed in the past but I am not sure
> if this particular issue has come up. I run a CAI 302 which drives
> both Winpilot Pro and a 303 head. The wind speed and directions are
> often differing by large margins on these two displays even though
> they must be looking at similar information. This is true even after
> turning such that both displays should be completely "updated".
>
> What are your thoughts on this subject or can you direct me to the
> archives where this question may have been already answered?
>
> Also on the subject of Winpilot, myself and others have pushed on
> Jerry to provide a navbox with speed-to-fly data. He is apparently
> unwilling to do this even though the program must be calculating it.
> I understand the reasoning behind not chasing the instantaneous STF
> number but I often wish I knew exactly what that number was. Other
> programs such as GN II do provide this number. If other WP users push
> on Jerry as well maybe he will put this navbox in. Thoughts?
>
> Thanks and fly safely,
>
> Bob Caldwell