A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Soaring
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Polar Analysis from flight logs?



 
 
Thread Tools Display Modes
Prev Previous Post   Next Post Next
  #11  
Old December 29th 04, 04:42 AM
Andy Blackburn
external usenet poster
 
Posts: n/a
Default

At 00:00 29 December 2004, Eric Greenwell wrote:
My example was for GPS distance, and pressure altitude,
to indicate that
a distance measurement wasn't a problem. That's why
a I later referred
to flying off at least 1000 feet if GPS altitude was
used.

What I don't know is how much error change one can
expect in GPS
altitudes taken 5 or 10 minutes apart. The difference
(GPS start height
minus GPS finish height) might have a much smaller
error than the
altitude itself, which would allow shorter glides
(500 foot loss if the
differential error was only 5 feet, for example).


Clarification noted - but distance measurement is a
problem with GPS with respect to polar calculations.

Without knowing the technique Dick Johnson uses, or
the specs on a specific pressure transducer, it's hard
to know if measuring pressure altitude through a digital
transducer is more or less accurate than the traditional
method. I'd guess it's a close call, but that has nothing
to do with GPS.

The main source of error, is being able to turn GPS
ground speed (or distance) into IAS reliably by subtracting
wind speed and adjust for altitude. An even greater
source of error is trying to use fixes from a typical
soaring day with airmass movements and pilot control
inputs, airspeed changes and flightpath deviations.

The empirical evidence is that there is way too much
randomness from the above noted effects to tease out
a anything much beyond just how much randomness there
in fact is on a typical flight.

Maybe if you did fifty 10-mile runs on a dead calm
day across five different airspeeds, you'd get less
scatter - but I think that's more or less what Dick
does, except he measures IAS directly, rather than
having to figure it out from ground speed.

9B



 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
RAF Blind/Beam Approach Training flights Geoffrey Sinclair Military Aviation 3 September 4th 09 06:31 PM
AOPA Stall/Spin Study -- Stowell's Review (8,000 words) Rich Stowell Aerobatics 28 January 2nd 09 02:26 PM
new theory of flight released Sept 2004 Mark Oliver Aerobatics 1 October 5th 04 10:20 PM
Flight Simulator 2004 pro 4CDs, Eurowings 2004, Sea Plane Adventures, Concorde, HONG KONG 2004, World Airlines, other Addons, Sky Ranch, Jumbo 747, Greece 2000 [include El.Venizelos], Polynesia 2000, Real Airports, Private Wings, FLITESTAR V8.5 - JEP vvcd Piloting 0 September 22nd 04 07:13 PM
AmeriFlight Crash C J Campbell Piloting 5 December 1st 03 02:13 PM


All times are GMT +1. The time now is 10:50 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004-2025 AviationBanter.
The comments are property of their posters.