Board index

Sport Pilot Talk

The discussion forum for Sport Pilots and Light Sport Aircraft
* * * CHECK Out the Sport Pilot Talk Flight School and Rental Finder Map! * * * It is currently Fri May 24, 2013 7:32 am

All times are UTC - 5 hours




Post new topic Reply to topic  [ 7 posts ] 
Author Message
 Post subject: Winds Aloft
PostPosted: Fri Feb 03, 2012 11:29 am 
Offline

Joined: Tue Jan 17, 2012 4:49 pm
Posts: 18
Location: Canton, GA
How do you figure wind direction and speed for a altitude in between reported altitudes?

Example:

If winds at 3,000ft are 120 at 21kts and at 6,000ft are 180 at 14kts, what would it be at 4,500ft?


Top
 Profile  
 
 Post subject:
PostPosted: Fri Feb 03, 2012 11:53 am 
Offline

Joined: Tue Nov 30, 2010 8:58 am
Posts: 514
Location: Iowa
The easy answer is that you interpolate. In your example, the winds at 4500 would be 150 at 17.5 knots. Interpolation works well in a perfect world. It is typical but not a lock that winds increase with altitude up to a point, so I'd be cautious about the readings in your example. Further, that is a pretty good shift in direction although not out of reason.
For those reasons, in this example, I'd be looking to the bigger picture. What are the winds and weather at other weather stations? It might be a cold front is moving through and the two altitudes are in different parts of the front. See this graphic.
http://www.crh.noaa.gov/lmk/soo/docu/basicwx.php
Another source is a skew-t if you are close to a balloon launching weather station. The skew-t shows altitudes other than those depicted by the AWS.
http://weather.unisys.com/upper_air/skew/
The FSS will give you interpolated winds. I do not know what programs they use to arrive at them.


Top
 Profile  
 
 Post subject:
PostPosted: Fri Feb 03, 2012 12:04 pm 
Offline
User avatar

Joined: Sat Nov 28, 2009 6:42 pm
Posts: 2481
Location: Lock Haven PA
jnmeade wrote:
The skew-t shows altitudes other than those depicted by the AWS.
http://weather.unisys.com/upper_air/skew/


That link is a great resource. Thanks for posting it!

Quote:
The FSS will give you interpolated winds. I do not know what programs they use to arrive at them.


Programs? I thought they just guessed. :wink:

_________________
The opinions expressed in this post are those of one CFI, and do not necessarily represent the position of the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS
AvSport of Lock Haven
http://AvSport.org fly@AvSport.org


Top
 Profile  
 
 Post subject:
PostPosted: Fri Feb 03, 2012 2:16 pm 
Offline

Joined: Tue Jan 17, 2012 4:49 pm
Posts: 18
Location: Canton, GA
jnmeade wrote:
The easy answer is that you interpolate. In your example, the winds at 4500 would be 150 at 17.5 knots. Interpolation works well in a perfect world. It is typical but not a lock that winds increase with altitude up to a point, so I'd be cautious about the readings in your example. Further, that is a pretty good shift in direction although not out of reason.
For those reasons, in this example, I'd be looking to the bigger picture. What are the winds and weather at other weather stations? It might be a cold front is moving through and the two altitudes are in different parts of the front. See this graphic.
http://www.crh.noaa.gov/lmk/soo/docu/basicwx.php
Another source is a skew-t if you are close to a balloon launching weather station. The skew-t shows altitudes other than those depicted by the AWS.
http://weather.unisys.com/upper_air/skew/
The FSS will give you interpolated winds. I do not know what programs they use to arrive at them.


Interpolation is what I assumed, but it seems that there may be a more finite line where the shift takes place. Those were ATL centers numbers from this morning. I guess you fly your WCA based on interpolated numbers and adjust if necessary? I'm getting ready for my first dual x-country and it seems like a handful to be on the E6B, checking landmarks, and flying all at the same time.


Top
 Profile  
 
 Post subject:
PostPosted: Fri Feb 03, 2012 2:24 pm 
Offline
User avatar

Joined: Sat Nov 28, 2009 6:42 pm
Posts: 2481
Location: Lock Haven PA
hink wrote:
it seems like a handful to be on the E6B, checking landmarks, and flying all at the same time.


It is a handful. Multitasking always is. Just remember that your brain has two frontal lobes. You need (consciously or unconsciously) to assign one of them to flying the airplane. The other frontal lobe has to be able to shift between navigation, communication, chart work, E6B computations, monitoring time and fuel, and everything else. Fortunately, with experience, this allocation of neural resources will become automatic.

_________________
The opinions expressed in this post are those of one CFI, and do not necessarily represent the position of the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS
AvSport of Lock Haven
http://AvSport.org fly@AvSport.org


Top
 Profile  
 
 Post subject:
PostPosted: Sat Feb 04, 2012 12:15 pm 
Offline
User avatar

Joined: Wed Sep 23, 2009 9:57 pm
Posts: 379
ForeFlight on iPad!!!

:o

_________________
Richard, Student Sport Pilot
Magazine Quality Photography and Imaging
http://www.agreatimage.com


Top
 Profile  
 
 Post subject:
PostPosted: Sat Feb 04, 2012 1:23 pm 
Offline

Joined: Tue Nov 30, 2010 8:58 am
Posts: 514
Location: Iowa
Interpolating is what you will do when planning your trip to see what your times and fuel burn will likely be. After you get in the air, you fly according to reality and you can check the WCA against the forecast numbers if you wish.
The key to staying on top of things is to keep your brain ahead of the airplane. Have a good idea of what things you are doing at various times and places as you fly. If things don't go according to plan make sure that you prioritize the tasks so the important ones are done first.
Sometimes if you are too busy to do something but there is not a problem, you can skip it but be sure to catch up at the next checkpoint or opportunity.
If you find as you fly that the WCA was markedly different than you planned, you may have to revisit plans such as fuel or time usage to be sure you are still OK.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 7 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group

Archive