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Pitot static port location

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mdnanwelch7(at)hotmail.co
Guest

Posted: Sat Jan 15, 2011 11:28 am Post subject: Pitot static port location

Guys,



  I'm VERY close to being able to permanently install my front instrument panel/console.  I have already installed the overhead panel.  Next will be the task of hooking up the various sending units, loose wires, etc., the stuff you can't do until the panel gets installed into the plane.   As far as all the wires between the two panels is concerned, this is simply a matter of plugging together two DB15 plugs.



  As many of you may recall, I recently installed my airspeed indicator pitot (under the front edge of the nosecone).

  Yesterday, I made the static pitot fitting (for the unpressurized static source)



  Here's my question;    Do any of you have a recommended place on the nosecone for the static pitot fitting?  Or is it okay to locate it ANYWHERE on the side of the nosecone?  The inlet hole for the static air is a drilled hole about .025 dia.   (It is TINY!!!!!, just slightly larger around than a pin)



  Here is a second question!   To make sure that the exterior fitting doesn't get either higher or lower pressure than static, would it be a good idea to drill an EXTRA hole into one of the interior static line "T's?  (the static line supplies air to 3 instruments)

  By drilling an extra hole into an interior T, I would be allowing for BOTH static air inside and outside of the cabin.  

  I know you are not supposed to rely ONLY on inside static air, because it is possible that the inside cabin MAY have slightly higher or lower static air, due to cabin design.  



  Anyone have some training on the pitot system, and at this point, the static part of it?



Thanks for any advice,

Mike Welch

MkIII

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Jan 15, 2011 11:50 am Post subject: Pitot static port location

Anyone have some training on the pitot system, and at this point, the 

static part of it?



Thanks for any advice,

Mike Welch

Mike W/Gang:



I have no training on the the pitot/static system, only practical experience 

that works for me.



If I was going to use a system similar to yours, I would use a static port 

on each side of the nose cone, combine these two ports into a T fitting, 

then into your instruments.  By doing this, you eliminate the pressurization 

or vacuum of a single port when the aircraft is not quite in yaw trim, one 

side or the other.



Once flying, the static ports can be calibrated by taking a tiny bit of 

material off the aft side of each static port, if they are pressurizing, or 

off the forward side of the hole if it is creating a vacuum.



The reason I settled on this system for my Firestar is because I tried it 

single first, then found it to be a more workable solution with two ports.



BTW:  I used 1/16" ID ports.



john h

mkIII

hauck's holler

Titus, Alabama

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

mdnanwelch7(at)hotmail.co
Guest

Posted: Sat Jan 15, 2011 12:42 pm Post subject: Pitot static port location

 	  Quote: 	
		   If I was going to use a system similar to yours, I would use a static port 

 on each side of the nose cone, combine these two ports into a T fitting, 

 then into your instruments. By doing this, you eliminate the pressurization 

 or vacuum of a single port when the aircraft is not quite in yaw trim, one 

 side or the other.

 

 Once flying, the static ports can be calibrated by taking a tiny bit of 

 material off the aft side of each static port, if they are pressurizing, or 

 off the forward side of the hole if it is creating a vacuum.

 

 The reason I settled on this system for my Firestar is because I tried it 

 single first, then found it to be a more workable solution with two ports.

 

 BTW: I used 1/16" ID ports.

 

 john h

 mkIII

 hauck's holler

 Titus, Alabama

 
	


John,

 

  I clearly see the logic in the "each side" of the fuselage idea.  It seems as

though if one side were being slightly pressurized, for the most part, the opposite

side would equally 'depressurized'.  I need to get another 'T'.

 

  What about the interior hole through one of the 'T's', which would include the

inside of the cabin into the static system?  A small hole into one of the 'T's'

(in the static source) would then be giving you three locations of "supposedly"

unpressurized air; left side fuselage, right side fuselage, interior fuselage.

 Is this unnecessary, would it help any?  Opinions???

  

   I did a quick check of A/C Spruce, and this is vitually identical to what I made, except that 

 my circular flat part is MUCH thinner than theirs;

 http://www.aircraftspruce.com/catalog/inpages/alumstaticports.php

   Also, from the looks of it in the photo, my drilled hole appears to be the exact 

 same size as in the photo.  I'm trying to keep the inlet hole as small as possible, to

 reduce any "ram air" affect.  I'll do some more research on the inlet hole size.

  

   Thanks for the pointers.....especially the 'each side of the fuselage' part.

  

 Mike Welch

 



 

 		 	   		    [quote][b]

by0ung(at)brigham.net
Guest

Posted: Sat Jan 15, 2011 1:08 pm Post subject: Pitot static port location

Here's my question;    Do any of you have a  recommended place on the nosecone for the static pitot fitting?  Or is it  okay to locate it ANYWHERE on the side of the nosecone?  The inlet hole for  the static air is a drilled hole about .025 dia.   (It is TINY!!!!!,  just slightly larger around than a pin)

  

  

 >>>>>>>>>>>>>>

  

 sorry about the drawing...   this is what  i did.

 boyd young

 mkiii

 



[img]cid:F828A39684FD4CCBB62CD87CC2EC205E(at)laptop1[/img]

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Description:

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mdnanwelch7(at)hotmail.co
Guest

Posted: Sat Jan 15, 2011 1:44 pm Post subject: Pitot static port location

Hi Boyd,

  

   Thanks for the drawing, your drawing is plenty good enough

 for us to get the idea of what you have.

  

   But, I would prefer to use those flush-mount type of static ports like 

 I previously showed the link of;  the ones that look like this;

 http://www.aircraftspruce.com/catalog/inpages/alumstaticports.php

  

   From what I've been researching, I think John has me headed in 

 the right direction, namely a port on each side of the fuselage.

 I'm afraid that if I had a port on the underside of the Xtra nosecone

 it would definitely be getting slightly pressurized air with the flush

 mounted type ports.

  

   I still not sure about the interior vent hole through one of the "T's", though.

 >From what I've been reading, it may not be all that necessary,

 especially if a guy went with two side ports!

  

   I did find that a Cessna 150 uses a .040" static hole (the guy said 1mm,

 which is .040")   Cessna also has only one outside port, too.  Some

 of them have an inside port, which I guess you can open by way of a knob

 or something, if you thought the outside was plugged, iced over, or whatever.

  

   Thanks for the input, guys.  I think I have enough good information to go

 ahead and finish the static line installation.

  

 Mike Welch

 MkIII

  

  

 		 	   		    [quote][b]

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Sat Jan 15, 2011 3:40 pm Post subject: Pitot static port location

Mike, I'd recommend you do either static ports or just vent them into the cockpit, not both, for the simple reason I think you'll play heck trying to tune the system if you have both.Yes, some Cessnas have an alternate static source valve with a knob on the panel to actuate it, for those that don't, student pilots are taught that should ice fowl the static ports the solution is to break the glass face of the VSI and vent the system that way.

 



Rick Girard



On Sat, Jan 15, 2011 at 3:41 PM, Mike Welch <mdnanwelch7(at)hotmail.com (mdnanwelch7(at)hotmail.com)> wrote:

 	  Quote: 	
		        Hi Boyd,

  

   Thanks for the drawing, your drawing is plenty good enough

 for us to get the idea of what you have.

  

   But, I would prefer to use those flush-mount type of static ports like 

 I previously showed the link of;  the ones that look like this;

 http://www.aircraftspruce.com/catalog/inpages/alumstaticports.php

  



   From what I've been researching, I think John has me headed in 

 the right direction, namely a port on each side of the fuselage.

 I'm afraid that if I had a port on the underside of the Xtra nosecone

 it would definitely be getting slightly pressurized air with the flush

 mounted type ports.

  

   I still not sure about the interior vent hole through one of the "T's", though.

 >From what I've been reading, it may not be all that necessary,

 especially if a guy went with two side ports!

  

   I did find that a Cessna 150 uses a .040" static hole (the guy said 1mm,

 which is .040")   Cessna also has only one outside port, too.  Some

 of them have an inside port, which I guess you can open by way of a knob

 or something, if you thought the outside was plugged, iced over, or whatever.

  

   Thanks for the input, guys.  I think I have enough good information to go

 ahead and finish the static line installation.

  

 Mike Welch

 MkIII

  

  

 		 	   		     	  Quote: 	
		  



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-- 

Zulu Delta

Kolb Mk IIIC

582 Gray head

4.00 C gearbox

3 blade WD

Thanks, Homer GBYM

 



It is not bigotry to be certain we are right; but it is bigotry to be unable to imagine how we might possibly have gone wrong.

  - G.K. Chesterton



 

  [quote][b]

_________________
The smallest miracle right in front of you is enough to make you happy....

mdnanwelch7(at)hotmail.co
Guest

Posted: Sat Jan 15, 2011 6:46 pm Post subject: Pitot static port location

>Mike, I'd recommend you do either static ports or just vent them into the cockpit, not both, for the simple reason I think you'll play heck >trying to tune the system if you have both.

 >>Rick Girard

  

 Hi Rick,

  

   I'd say at this point I agree with you and John, I ought to go with just the 

 two side ports.

  

   I'm just thinking out-loud here........

  

    At the risk of over-thinking this I was just wondering, since the main

 objective of the 'static' source is simply that,  "static" , what we want is

 absolutely uncharged, unpressurized air.  I definitely see the logic in John's 

 suggestion of the two side ports, but just the fact that the air is rushing past 

 a nosecone has GOT to have some kind of slight pressurization, whether it 

 be positive or negative, however slight it may be.

  

   When I try to wrap my mind around the objective of getting an "ambient"

 static air source, I can't picture how having both (two side port fittings and

 an inside hole in a fitting 'T') would do anything but create an even better

 balance to having zero pressure.

   I'm not arguing with you, I just don't see it intuitively.  You might be absolutely

 correct.

  

   It was my intention all along to try out the whole airspeed indicator(s) system

 in the car.  Since my entire panel is somewhat portable at this point, and I do have

 the entire pitot system 100% built, hoses, tubes, fittings and all, I could set the 

 entire arrangement on the seat of my truck, and go buzzing down the highway.  

 I could try a couple of pitot designs and try to get a feel for what might work best in 

 my situation.

  

   I think the thing I'm trying to get a good handle on is if the airspeed indicator is 

 going to be 'reasonably' accurate on my first time out.  I don't expect it to be 

 gnat's ass perfect, but then I'd rather it wasn't off by 25 mph, either.  Maybe taking 

 it for a spin down the highway will give me a little indication of it's approximate 

 accuracy.

   (BTW, I do realize that when flight testing the plane, the important point is

 to know what the airspeed indicator says for certain flight functions (like stall

 speed, for instance), and learn those readings, regardless of how accurate they 

 are.  In other words, if the ASI says stall happens at 37 mph, then never try to 

 fly less than 37 mph.....period!!!

  

   Hey, thanks for the help, guys.  I'm going to try to get some 'down the highway'

 readings.  I'll let you know what I come up with.  I also include various static

 pitot  source designs.   More later.......

  

 Mike Welch

   

  

 		 	   		    [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Jan 15, 2011 7:05 pm Post subject: Pitot static port location

When I try to wrap my mind around the objective of getting an "ambient"

static air source, I can't picture how having both (two side port fittings 

and

an inside hole in a fitting 'T') would do anything but create an even better

balance to having zero pressure.



Mike Welch



Mike W/Gang:



That is why I said you can fine tune the static ports after you fly the 

airplane by taking a little material off the fore or aft side of the port, 

depending on whether the ASI is reading high or low, pressure or vacuum. 

There are also other ways to fine tune the static system.  Use your 

imagination.



You are looking for one static source that will read the same air pressure 

as the pitot tube is flying in.



Testing your ASI in your truck will do nothing for the installation in your 

airplane.



If you take a static source inside the cockpit of a MKIII or FS, it will be 

low pressure.  It is the nature of the nose pod flying through the air.



What I shared with you is a proven system that worked well for me.



john h

mkIII

hauck's holler

Titus, Alabama

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

gpabruce(at)gmail.com
Guest

Posted: Sat Jan 15, 2011 7:49 pm Post subject: Pitot static port location

Nice drawing of a vulture with whiskers . . . just kidding . . . 



 On Sat, Jan 15, 2011 at 1:05 PM, b young <by0ung(at)brigham.net (by0ung(at)brigham.net)> wrote:

 [quote]  

  Here's my question;    Do any of you have a recommended place on the nosecone for the static pitot fitting?  Or is it okay to locate it ANYWHERE on the side of the nosecone?  The inlet hole for the static air is a drilled hole about .025 dia.   (It is TINY!!!!!, just slightly larger around than a pin)

   

  

 >>>>>>>>>>>>>>

  

 sorry about the drawing...   this is what i did.

 boyd young

 mkiii

 



[img]https://mail.google.com/mail/html/compose/static_files/blank_quirks.html?ui=2&ik=1f31465df0&view=att&th=12d8b8bd3bc78d96&attid=0.1&disp=emb&zw[/img]



[b]

mdnanwelch7(at)hotmail.co
Guest

Posted: Sat Jan 15, 2011 9:06 pm Post subject: Pitot static port location

John,

  

   Okay!!  I got the message!  I'll proceed as you suggested.

 Two side ports, 1/16" fitting holes, adjust as needed.  Got it.

  

 Thanks,

  

 Mike W

 		 	   		    [quote][b]

kuffel(at)cyberport.net
Guest

Posted: Sun Jan 16, 2011 1:49 am Post subject: Pitot static port location

Mike,



Strongly endorse Hauck's suggestions for a static system of two side ports 

connected by a T.  It has been a well proven industry standard for many 

years.



To expand slightly:



Put the ports as far aft on the nose cone as reasonable.  You want the air 

at the port to be going parallel to the surface, not accelerating around a 

curve.



<<   Once flying, the static ports can be calibrated by taking a tiny bit of

material off the aft side of each static port, if they are pressurizing, or

off the forward side of the hole if it is creating a vacuum. >>



There is a simpler way of determining which way to trim the ports than 

airspeed error.  Go to a long, level runway and make a takeoff keeping the 

aircraft planted on the runway as long as possible.  Just before liftoff 

note any change in *altitude*.  If the altimeter goes up you have a vacuum, 

if it goes down you have static pressurization.  This maneuver does take 

some practice and should be repeated several times to be sure of correct 

indication.



Instead of removing material you can add wedges on the other side:  front 

side if static is high, back side if static is low.  You can also buy static 

ports with a wedge built in.  Much more professional looking than balsa 

wedges glued on.  These you rotate to get most accurate readings.



Tom Kuffel

Richard Pike

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

Posted: Sun Jan 16, 2011 6:00 am Post subject: Re: Pitot static port location

Boyd's drawing looks like what I am using. One is the pitot, the other is static port, both are out away from the airframe in clean air, seems to make life simpler. Worked right the first time, needed no tuning. Your results may vary...

Details here:

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



Richard Pike

MKIII N420P (420ldPoops)

mdnanwelch7(at)hotmail.co
Guest

Posted: Sun Jan 16, 2011 6:39 am Post subject: Pitot static port location

> Boyd's drawing looks like what I am using.  

 	  Quote: 	
		   Richard Pike

 MKIII N420P (420ldPoops)


	


 Bro. Richard,

  

   Although I do agree Boyd's and your suggestion of the static inlet 

 works well out on an extended tube, I would prefer to go with the

 type of fitting that mounts on the surface of the fuselage.  But, thanks

 for your input!!

  

   At this point, I concede I know when I'm given good advice.  John H

 was generous enough to offer what says worked well for him.  Although

 I did agree, I was curious if a slight (unnecessary) modification would be 

 better.  He, Rick G, and Ted K didn't think so!!  (probably others, too)

 That's good enough for me!!

  

   I appreciate everyone's input, and value the advice I have been given.

 I think I'll go with the two, side fuselage, surface mount ports, no inside 

 cabin venting, and 1/16" vent holes.  

  

   Thanks, guys.

  

 Mike Welch

 		 	   		    [quote][b]

Dana

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

Posted: Sun Jan 16, 2011 5:51 pm Post subject: Pitot static port location

Mike,



 I'm coming into this discussion late, sounds like you already have a plan, but I'll add my two cents:



 Putting ports on both sides helps to cancel out any variation as the aircraft yaws.  On the bottom wouldn't be good as it'd change as AOA changes.  Inside the cockpit is a bad place because the air inside is nearly always _not_ at static pressure.  



 I built a concentric pitot/static tube, with the inner tube for the pitot and the outer one (sealed at front and back) with four holes spaced around the center for static air.  Mounted on the nose such a system will give very good undisturbed static air.



 -Dana

 --

 Congress shall make no law....What part of NO didn't you understand?   

    [quote][b]

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Jan 17, 2011 5:12 am Post subject: Re: Pitot static port location

I have had good success in changing the pressure seen by the static ports using a dab of RTV either fore or aft of the port.



My current Slingshot setup has the dual pitot/static tubes mounted below the nose cone with an extender for the pitot mounted flexibly and going out about six inches forward of the nose. My static tube has a Tee in side the cockpit so it is sensing both the pressure outside the at the static port and under the panel. With this setup, it reads TAS on the ASI at about 2,000' - 2,500' density altitude. 



Speaking of density altitude, I calculated it this morning and here at KBUF, the DA at 7 AM was negative(-)3,675'. Coldest yet this winter here at 1 degree.... but clear skies for a change and low winds. About -4F at my house.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

mdnanwelch7(at)hotmail.co
Guest

Posted: Mon Jan 17, 2011 6:22 am Post subject: Pitot static port location

 > Speaking of density altitude, I calculated it this morning and here at KBUF, the DA at 7 AM was -3,675'. > 

 	  Quote: 	
		   --------

 Thom Riddle

 Buffalo, NY (9G0)

 Kolb Slingshot SS-021

 Jabiru 2200A #1574

 Tennessee Prop 64x32


	


 Hi Thom,

  

   Thanks for the pitot info.

  

   -3,675' density altitude??  I think even Capt Nemo would have trouble flying

 at that level!!   (think about it, it'll come to you)

  

   BTW,  thanks for the pitot comments, everyone, but I think I'll proceed with

 what I mentioned previously (2 side ports, etc, etc.)  If that design needs some adjustment,

 then I'll work on it later.  Cheers!!

  

 Mike Welch

 		 	   		    [quote][b]

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