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  #41  
Old 12-21-2010, 09:36 AM
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G34U G34U is offline
 
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Location: Hingham Mass.
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Quote:
Originally Posted by rleffler View Post
http://myrv10.com/tips/flight_testin...rts/index.html

Pretty easy to find via search......

I suspect there are more detailed conversations on the RV-10 matronics list as well, but I didn't look for that history.
Thank you Bob.
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  #42  
Old 12-21-2010, 02:04 PM
ChrisC ChrisC is offline
 
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Location: Palo Alto, CA
Posts: 22
Default Correct in software?

I'm curious -- with the combination of widely-used EFIS devices and static port errors... Why can't the errors be corrected in software?

I understand why a bad static port can't be fixed for an analog gage, since the gage assumes a fixed (linear?) relationship between static and pitot pressure. But what about for an EFIS? Can't you just do a series of flight tests at assorted known altitudes and airspeeds (say, flying in formation with a calibrated aircraft), plug in "this is how fast and high I am" and derive the pressure curves for your particular plane and installation?

I am a new builder, so please forgive my ignorance. I'm just curious why we have to go to such efforts with physical kludges when this sounds like a software problem to me.

Chris
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  #43  
Old 12-21-2010, 02:22 PM
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mark schoening mark schoening is offline
 
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Location: Rhinelander, Wi
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Default static ?

My question----Has anybody tried 2 ports, one on each side of fuse, tied to static system on left and right sides of the instrument plumbing? Sort of an "averaging" of pressures. ignorance is bliss
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  #44  
Old 12-21-2010, 03:54 PM
N427EF N427EF is offline
 
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Default Dual Static Ports

I thought everybody uses dual static ports?
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  #45  
Old 12-21-2010, 05:32 PM
rubber314chicken rubber314chicken is offline
 
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Quote:
Originally Posted by mark schoening View Post
My question----Has anybody tried 2 ports, one on each side of fuse, tied to static system on left and right sides of the instrument plumbing? Sort of an "averaging" of pressures. ignorance is bliss
Quote:
Originally Posted by N427EF View Post
I thought everybody uses dual static ports?
Yea, most planes have a static port on either side of the plane, and these are tied into a Tee, which then is the static tube. Just imagine only having one static port in a crosswind.
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  #46  
Old 12-22-2010, 10:53 AM
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David Shelton David Shelton is offline
 
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If you want to install an untested static port on an IFR airplane, it would be advisable to test it. I suppose you could do this with a home-made trailing static cone and use a water manometer to compare the two static sources.
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  #47  
Old 12-22-2010, 01:51 PM
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F1Boss F1Boss is offline
 
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Default easy fix!

Quote:
Originally Posted by jjconstant View Post
I have a heated pitot tube with the static ports on the tube as well. I have been calibrating my airspeed and there is a HUGE error in airspeed. I've made several attempts at a kluge fix and, while the airspeed is now within 2 1/2 kts at 160kts and 1 kt at 100kts, it indicates stall at 38 kts.

snip

Jeremy Constant
7A 95hrs, down for annual and squawk fixes
Hey Jeremy:

Homey Depot sells the fix for your expensive heated pitot/static -- 1/16" rubber O rings! Install aft of the static holes to fix a fast-reading ASI, or in front of the holes for a slow-reading ASI. Keep making low passes at your home field (or another with a known elevation) to check your 'calibration' using your altimeter as the reference instrument. Once you get it right, a bit of RTV or Pro-seal will hold the O ring in place.

Every aft mounted static port I checked netted a 15% error @ cruise: look at the MPH scale and read it as knots. This was true using factory parts and location...YMMV of course!

FWIW, the altimeter is the only instrument you can actually use to check your static system. Use the low-pass method to see what yours tells you, and adjust from there. Do not rely on a pitot/static check to tell you that your static system actually works as it should in flight!

Carry on!
Mark
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  #48  
Old 12-22-2010, 02:45 PM
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Mike S Mike S is offline
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Quote:
Originally Posted by F1Boss View Post
the fix for your expensive heated pitot/static -- 1/16" rubber O rings! Install aft of the static holes to fix a fast-reading ASI, or in front of the holes for a slow-reading ASI.

Mark
O.K., are you cutting them in half first? so they look like the setup in this photo I borrowed from David?

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  #49  
Old 12-22-2010, 02:58 PM
Sig600 Sig600 is offline
 
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I can't believe I'm asking this question, but I can't think of a good answer...

In an unpressurized vessel (i.e. an RV) why can't you get a source of static air from within the plane itself? Something like an open port within the empennage?
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  #50  
Old 12-22-2010, 03:24 PM
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Default

Because the air inside the structure is NOT static. It changes depending on air entering and/or departing the airplane.
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