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Pitot-static system

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capt_riney(at)yahoo.com
Guest

Posted: Tue Jul 20, 2010 8:12 am Post subject: Pitot-static system

I'm installing my ASI and Altimeter for my Mark IIIC.  I'll install a pitot tube under the nose for total pressure, but am thinking I will not have a separate static port but just leave the instruments open to the cockpit for static pressure. Anyone have experience with that?  I'm assuming that since the cockpit isn't sealed, the static pressure inside is fairly close to outside ambient.



Mark Rinehart

Indianapolis

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Tue Jul 20, 2010 8:37 am Post subject: Pitot-static system

At 12:12 PM 7/20/2010, mark rinehart wrote:

  	  Quote: 	
		  --> Kolb-List message posted by: mark rinehart <capt_riney(at)yahoo.com>



 I'm installing my ASI and Altimeter for my Mark IIIC.  I'll install a pitot tube under the nose for total pressure, but am thinking I will not have a separate static port but just leave the instruments open to the cockpit for static pressure. Anyone have experience with that?  I'm assuming that since the cockpit isn't sealed, the static pressure inside is fairly close to outside ambient. 	


 Don't assume that.  Depending on the shape of the cockpit fairing and openings, the pressure inside can be considerably higher or lower than the static pressure... and it can change as AOA changes.  Still, many do that and sometimes it works fine.



 I don't have a cockpit on my UltraStar, just an instrument pod between my legs, and it was vented there.  Every time I moved my foot the indicated airspeed changed.  I've since made a concentric tube pitot tube, with four holes in the outer tube for static air.  Works great.



 -Dana

 --

  Exceeding the legal fun limit on a regular basis    [quote][b]

by0ung(at)brigham.net
Guest

Posted: Tue Jul 20, 2010 8:43 am Post subject: Pitot-static system

I'm installing my ASI and Altimeter for my Mark IIIC.  I'll install a  pitot tube under the nose for total pressure, but am thinking I will not have a  separate static port but just leave the instruments open to the cockpit for  static pressure. Anyone have experience with that?  I'm assuming that since  the cockpit isn't sealed, the static pressure inside is fairly close to outside  ambient.



Mark Rinehart

Indianapolis  

 	  Quote: 	
		  >>>>>>>>>>>>>>>>>>>>>>>>>>>

  
	


 it seems the concencus is that the readings will be  off,   each one is different depending on the  instalation.

  

 boyd mkiii

  

 do not archive

   [quote][b]

tclongo(at)att.net
Guest

Posted: Tue Jul 20, 2010 9:32 am Post subject: Pitot-static system

My  MKIII read 10 mph too high with my static vented inside cockpit (Low pressure)  in my case. I ordered pitot/static combo (L shaped unit) from Aircraft Spruce  that was inexpensive and Airspeed was correct. 

 [quote]   --

Dennis.Kirby(at)kirtland.
Guest

Posted: Wed Jul 21, 2010 7:17 am Post subject: Pitot-static system

mark rinehart wrote: << I'm installing my ASI and Altimeter for my Mark IIIC.  I'll install a pitot tube under the nose for total pressure, but am thinking I will not have a separate static port but just leave the instruments open to the cockpit for static pressure. >>  

   

   

Mark –  

   

As others have mentioned, air pressure variations in a semi-open cockpit can be extreme, resulting in drastic inaccuracies in you’re A/S indicator if you leave the static port open on the back of your instrument.  

   

On my Kolb, the pitot is on the tip of the nosecone, and I use a static port on the left side of the nosecone.  The static port face does not have to be at exactly 90 degrees to the airflow to be accurate – anywhere within 15 degrees is OK.  As you know, the sides of our Kolb nosecones are slightly tapered, but not enough to matter for making it a suitable location of a static port.  My indicated airspeeds are right on the money, using the static port in this way.  

   

Got the static port from A/C Spruce, for under $12 if I recall.  Very short plumbing run from the nosecone side to the back of your instrument panel.  A nice, clean installation.  

   

By the way – if you decide to put the pitot on the nose, have the rigid alum tube stick out only about an inch.  The remaining forward six inches of aluminum tube can be connected to the one-inch stub with a short piece rubber (or vinyl) hose.  That way it won’t break off when someone brushes against it with their leg.  When, not if.  Good luck with your installation –  

   

Dennis Kirby  

Mark-3C, 912ul, in  

Sandia Park, NM  

   

      [quote][b]

lhaggerty(at)tampabay.rr.
Guest

Posted: Wed Jul 21, 2010 8:57 am Post subject: Pitot-static system

Which L shaped unit did you use. Pete

 [quote]   ---

tclongo(at)att.net
Guest

Posted: Wed Jul 21, 2010 4:26 pm Post subject: Pitot-static system

I used Aircraft Spruce part # 15144   $25



--

lhaggerty(at)tampabay.rr.
Guest

Posted: Thu Jul 22, 2010 7:19 am Post subject: Pitot-static system

Thank You.  Pete

 [quote]   ---

capt_riney(at)yahoo.com
Guest

Posted: Sun Jul 25, 2010 6:14 pm Post subject: Pitot-static system

Thanks for all the responses.  For those of you who are using the inexpensive pitot-static probe from Aircraft Spruce (p/n 15144), what are the dimensions of it? Is the position of the flange adjustable? If not, how far below the nose cone does it hang?  Thanks.



Mark Rinehart

N68MR reserved for my Mark 3 Classic

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Mon Jul 26, 2010 6:29 am Post subject: Re: Pitot-static system

Pretty easy to make your own pitot and static tubes with one length of steel brake line tubing cut in half and a couple of flat washers. 



http://www.bcchapel.org/pages/0003/pg7.htm



Richard Pike

MKIII N420P (420ldPoops)

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