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sam(at)fr8dog.net
Guest

Posted: Mon Jun 25, 2007 6:13 am Post subject: Static problems

I'm having static problems, I think, not sure where to look though. Indicated airspeed seams to be accurate on the bottom end but 20 to 30 knots slow at cruise, verified with chase plane. The static was checked and certified IFR by an avionics shop, with no leaks. Looking for ideas......

 Thanks,

 Sam

    [quote][b]

james.k.hovis(at)gmail.co
Guest

Posted: Mon Jun 25, 2007 6:43 am Post subject: Static problems

Most likely the place where your static source is portted to the

outside is experiencing some turbulence that is raising the

free-stream pressure of the air. Airspeed is measured by taking the

dynamic (pitot) and static pressure difference and calculating the

airspeed with a mechanical computer. Changing your static port

location, seeing if there's a skin mismatch or even a burr near the

port may help. Calibrating the airspeed indication systems is one

reason why production aircraft fly with an extremely long pitot/static

boom during initial flight testing.



Kevin H.



On 6/25/07, Sam Marlow <sam(at)fr8dog.net> wrote:

 	  Quote: 	
		   I'm having static problems, I think, not sure where to look though.

 Indicated airspeed seams to be accurate on the bottom end but 20 to 30

 knots slow at cruise, verified with chase plane. The static was checked

 and certified IFR by an avionics shop, with no leaks. Looking for

 ideas......

 Thanks,

 Sam

rene(at)felker.com
Guest

Posted: Mon Jun 25, 2007 6:44 am Post subject: Static problems

What type of static ports did you install.  Are they flush with the skin/paint?  

     

Rene' Felker  

N423CF  

40322  

801-721-6080  

        

  

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Sam Marlow

 Sent: Monday, June 25, 2007 8:13 AM

 To: rv10-list(at)matronics.com

 Subject: Static problems  

  

   

I'm having static problems, I think, not sure where to look though. Indicated airspeed seams to be accurate on the bottom end but 20 to 30 knots slow at cruise, verified with chase plane. The static was checked and certified IFR by an avionics shop, with no leaks. Looking for ideas......

 Thanks,

 Sam   	  Quote: 	
		    http://www.matronics.com/Navigator?RV10-List 	
0 	  Quote: 	
		   	
1 	  Quote: 	
		   	
2 	  Quote: 	
		   	
3 	  Quote: 	
		   	
4

       [quote][b]

Dave(at)AirCraftersLLC.co
Guest

Posted: Mon Jun 25, 2007 8:32 am Post subject: Static problems

Sam,

  

 You might have a pitot  leak.

  

 You can check by putting  a tiny bit of pressure on the pitot tube.  Be careful, it doesn't  take much to peg the instrument.  If you can get a piece of surgical  tubing over the pitot tube, then roll it up, you can set an airspeed on the  indicator.  Run it up to Vne.  It shouldn't bleed down more than  about 5 knots (mph) in 5 minutes.  Any worse than that, you might want to  look for a leak.

  

  Dave Saylor

 AirCrafters LLC

 140 Aviation Way

 Watsonville, CA 

 831-722-9141

 831-750-0284 CL

 www.AirCraftersLLC.com



  

  

   From: owner-rv10-list-server(at)matronics.com  [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Sam  Marlow

Sent: Monday, June 25, 2007 7:13 AM

To:  rv10-list(at)matronics.com

Subject: Static  problems

 

I'm having static problems, I think, not  sure where to look though. Indicated airspeed seams to be accurate on the bottom  end but 20 to 30 knots slow at cruise, verified with chase plane. The static was  checked and certified IFR by an avionics shop, with no leaks. Looking for  ideas......

Thanks,

Sam

[quote]



href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List

href="http://forums.matronics.com">http://forums.matronics.com



[b]

coop85(at)cableone.net
Guest

Posted: Mon Jun 25, 2007 1:02 pm Post subject: Static problems

As mentioned it could be a pitot leak.  I had one right behind the panel and could actually change my airspeed by grabbing the connection that was leaking (it was very pronounced though, not just 20 knots at the high end).  

   

Another thought depends on what indicator you have.  If it’s an EFIS, there may be some calibration errors that you can adjust.  

   

Marcus  

40286  

168 hours and can’t stand to park it long enough to paint it!  

         

  

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Sam Marlow

 Sent: Monday, June 25, 2007 9:13 AM

 To: rv10-list(at)matronics.com

 Subject: Static problems  

  

   

I'm having static problems, I think, not sure where to look though. Indicated airspeed seams to be accurate on the bottom end but 20 to 30 knots slow at cruise, verified with chase plane. The static was checked and certified IFR by an avionics shop, with no leaks. Looking for ideas......

 Thanks,

 Sam   	  Quote: 	
		    http://www.matronics.com/Navigator?RV10-List 	
0 	  Quote: 	
		   	
1 	  Quote: 	
		   	
2 	  Quote: 	
		   	
3 	  Quote: 	
		   	
4

        [quote][b]

GenGrumpy(at)aol.com
Guest

Posted: Mon Jun 25, 2007 6:44 pm Post subject: Static problems

Based on problems I had, if you have any 2 1/4 inch airspeed, VSI or 

altimeters, I would consider them likely suspects!

 

I went through 3 airspeed indicators to get a good one plus one VSI.  Both 

had leaks internally in them that affected my pitot and static systems.

 

Grumpy

do not archive

 

In a message dated 6/25/2007 4:04:58 PM Central Standard Time, 

coop85(at)cableone.net writes:



As mentioned it could be a pitot leak.  I had one right behind the panel and 

could actually change my airspeed by grabbing the connection that was leaking 

(it was very pronounced though, not just 20 knots at the high end). 

Another thought depends on what indicator you have.  If it’s an EFIS, there 

may be some calibration errors that you can adjust. 

Marcus 

40286 

168 hours and can’t stand to park it long enough to paint it! 

 

  

____________________________________



From: owner-rv10-list-server(at)matronics.com 

[mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Sam Marlow

Sent: Monday, June 25, 2007 9:13 AM

To: rv10-list(at)matronics.com

Subject: Static problems

I'm having static problems, I think, not sure where to look though. Indicated 

airspeed seams to be accurate on the bottom end but 20 to 30 knots slow at 

cruise, verified with chase plane. The static was checked and certified IFR by 

an avionics shop, with no leaks. Looking for ideas......

Thanks,

Sam



************************************** See what's free at http://www.aol.com

sam(at)fr8dog.net
Guest

Posted: Mon Jun 25, 2007 7:55 pm Post subject: Static problems

I have the static port in the Van's recommended position, I wouldn't have a clue where to move it, or even how. I can't just start drilling holes randomly. What should I do?

 

 James K Hovis wrote: [quote]--> RV10-List message posted by: "James K Hovis" <james.k.hovis(at)gmail.com> (james.k.hovis(at)gmail.com)   

   

 Most likely the place where your static source is portted to the   

 outside is experiencing some turbulence that is raising the   

 free-stream pressure of the air. Airspeed is measured by taking the   

 dynamic (pitot) and static pressure difference and calculating the   

 airspeed with a mechanical computer. Changing your static port   

 location, seeing if there's a skin mismatch or even a burr near the   

 port may help. Calibrating the airspeed indication systems is one   

 reason why production aircraft fly with an extremely long pitot/static   

 boom during initial flight testing.   

   

 Kevin H.   

   

 On 6/25/07, Sam Marlow <sam(at)fr8dog.net> (sam(at)fr8dog.net) wrote:   

    	  Quote: 	
		  I'm having static problems, I think, not sure where to look though.     

 Indicated airspeed seams to be accurate on the bottom end but 20 to 30     

 knots slow at cruise, verified with chase plane. The static was checked     

 and certified IFR by an avionics shop, with no leaks. Looking for     

 ideas......     

 Thanks,     

 Sam     

     

   	
   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

 [b]

sam(at)fr8dog.net
Guest

Posted: Mon Jun 25, 2007 7:56 pm Post subject: Static problems

I installed the Cleveland Tool flush ports.

 

 Rene Felker wrote: [quote]         v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);}  <![endif]-->   st1\:*{behavior:url(#default#ieooui) }  <![endif]-->          <![endif]-->       <![endif]-->         

What type of static ports did you install.  Are they flush with the skin/paint?   

       

Rene' Felker   

N423CF   

40322   

801-721-6080   

         

   

From: owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com) [mailto:owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com)] On Behalf Of Sam Marlow

   Sent: Monday, June 25, 2007 8:13 AM

   To: rv10-list(at)matronics.com (rv10-list(at)matronics.com)

   Subject: RV10-List: Static problems   

   

    

I'm having static problems, I think, not sure where to look though. Indicated airspeed seams to be accurate on the bottom end but 20 to 30 knots slow at cruise, verified with chase plane. The static was checked and certified IFR by an avionics shop, with no leaks. Looking for ideas......

 Thanks,

 Sam    	  Quote: 	
		    http://www.matronics.com/Navigator?RV10-Listhttp://forums.matronics.com 

	
 [b]

sam(at)fr8dog.net
Guest

Posted: Mon Jun 25, 2007 8:03 pm Post subject: Static problems

I just had a static check by an avionics shop, no leaks, IFR certified. I'm baffled.

 

 Dave Saylor wrote: [quote]         Sam,

    

   You might have a pitot leak.

    

   You can check by putting a tiny bit of pressure on the pitot tube.  Be careful, it doesn't take much to peg the instrument.  If you can get a piece of surgical tubing over the pitot tube, then roll it up, you can set an airspeed on the indicator.  Run it up to Vne.  It shouldn't bleed down more than about 5 knots (mph) in 5 minutes.  Any worse than that, you might want to look for a leak.

    

      Dave Saylor

   AirCrafters LLC

   140 Aviation Way

   Watsonville, CA 

   831-722-9141

   831-750-0284 CL

   www.AirCraftersLLC.com

   

    

    

      From: owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com) [mailto:owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com)] On Behalf Of Sam Marlow

   Sent: Monday, June 25, 2007 7:13 AM

   To: rv10-list(at)matronics.com (rv10-list(at)matronics.com)

   Subject: Static problems

   

   

   I'm having static problems, I think, not sure where to look though. Indicated airspeed seams to be accurate on the bottom end but 20 to 30 knots slow at cruise, verified with chase plane. The static was checked and certified IFR by an avionics shop, with no leaks. Looking for ideas......

 Thanks,

 Sam

    	  Quote: 	
		  



href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List

href="http://forums.matronics.com">http://forums.matronics.com





	
 [b]

sam(at)fr8dog.net
Guest

Posted: Mon Jun 25, 2007 8:05 pm Post subject: Static problems

I have both EFIS and analog, and they agree with each other.

 

 Marcus Cooper wrote: [quote]         v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);}  <![endif]-->   st1\:*{behavior:url(#default#ieooui) }  <![endif]-->          <![endif]-->       <![endif]-->         

As mentioned it could be a pitot leak.  I had one right behind the panel and could actually change my airspeed by grabbing the connection that was leaking (it was very pronounced though, not just 20 knots at the high end).   

    

Another thought depends on what indicator you have.  If it’s an EFIS, there may be some calibration errors that you can adjust.   

    

Marcus   

40286   

168 hours and can’t stand to park it long enough to paint it!   

          

   

From: owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com) [mailto:owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com)] On Behalf Of Sam Marlow

   Sent: Monday, June 25, 2007 9:13 AM

   To: rv10-list(at)matronics.com (rv10-list(at)matronics.com)

   Subject: RV10-List: Static problems   

   

    

I'm having static problems, I think, not sure where to look though. Indicated airspeed seams to be accurate on the bottom end but 20 to 30 knots slow at cruise, verified with chase plane. The static was checked and certified IFR by an avionics shop, with no leaks. Looking for ideas......

 Thanks,

 Sam    	  Quote: 	
		    http://www.matronics.com/Navigator?RV10-Listhttp://forums.matronics.com 

	
 [b]

sam(at)fr8dog.net
Guest

Posted: Mon Jun 25, 2007 8:10 pm Post subject: Static problems

Good thought but I have full size backup instruments, and the EFIS agrees with the analog readings.

 

 GenGrumpy(at)aol.com (GenGrumpy(at)aol.com) wrote: [quote]            Based on problems I had, if you have any 2 1/4 inch airspeed, VSI or altimeters, I would consider them likely suspects!

    

   I went through 3 airspeed indicators to get a good one plus one VSI.  Both had leaks internally in them that affected my pitot and static systems.

    

   Grumpy

   do not archive

    

   In a message dated 6/25/2007 4:04:58 PM Central Standard Time, coop85(at)cableone.net (coop85(at)cableone.net) writes:

    	  Quote: 	
		       

As mentioned it could be a pitot leak.  I had one right behind the panel and could actually change my airspeed by grabbing the connection that was leaking (it was very pronounced though, not just 20 knots at the high end).     

      

Another thought depends on what indicator you have.  If it’s an EFIS, there may be some calibration errors that you can adjust.     

      

Marcus     

40286     

168 hours and can’t stand to park it long enough to paint it!     

                

     

From: owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com) [mailto:owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com)] On Behalf Of Sam Marlow

     Sent: Monday, June 25, 2007 9:13 AM

     To: rv10-list(at)matronics.com (rv10-list(at)matronics.com)

     Subject: RV10-List: Static problems     

     

      

I'm having static problems, I think, not sure where to look though. Indicated airspeed seams to be accurate on the bottom end but 20 to 30 knots slow at cruise, verified with chase plane. The static was checked and certified IFR by an avionics shop, with no leaks. Looking for ideas......

 Thanks,

 Sam   	
   

   

   

   

      See what's free at AOL.com.   

    	  Quote: 	
		  

	
 [b]

AirMike

Joined: 27 Feb 2007
Posts: 514
Location: Nevada

Posted: Mon Jun 25, 2007 9:20 pm Post subject: Static problems

My I.A. friend suggested that it could be water accumulating.

He told me to put a sump in my system. Spruce sells a cheap sump.

I was directed to put a low point in the static lines for water to accumulate.

Had to run my lines up the port side, so after routing them high, they dropped down to the floor aft of the baggage bay.



Good luck - hope this helps

_________________
See you OSH '18
Q/B - sold.

Tim Olson

Joined: 25 Jan 2007
Posts: 2879

Posted: Tue Jun 26, 2007 3:08 am Post subject: Static problems

I'm going to combine 4 replies into one.

Sam Marlow wrote:

## I installed the Cleveland Tool flush ports.



Well, if they're the old flush flat Cleveland ports, then that's good

for at least about 1/3 of  your 20kt error right there.  If they're the

domed ones, they may have less error.

##I just had a static check by an avionics shop, no leaks, IFR 

certified. I'm baffled.



Did they check the PITOT system for leakdown too?  The IFR static

test is far far more relaxed on the pitot side than the static side,

and they really only bother to test for leaks in many cases.  The

suggestion given to use surgical tubing and check for leakdown is

a good one...even if they said it passed.

## I have both EFIS and analog, and they agree with each other.



Of course...even a leaky system could possibly have a pressure

inside it that's common along the whole system, so that doesn't

surprise me.

## Good thought but I have full size backup instruments, and the EFIS 

agrees with the analog readings.



Full size, or small, the leaks could be anywhere, if they exist.

 From what I've read, it's very hard to get pitot errors from

mis-angled pitots without it being a really big angle error.  If

your pitot is mounted in the standard way, and sits down low enough

from the wing, and there are no bugs and stuff in it, then it is

not likely the problem.  That really brings you back to either

a pitot leak, static problem, or port type/position problem.  There's

not going to be a silver bullet, so it's just time to roll up

the sleeves and start digging.  I replaced my static ports even

after the plane was painted.  If yours are the flat ones I'd

start there and then fly the 4-way GPS and see where you're at.

It's not going to come free, so it'll just take some time,

and eventually you should be able to get within a couple KTS.



Tim

k5wiv(at)amsat.org
Guest

Posted: Tue Jun 26, 2007 3:21 am Post subject: Static problems

How are your  altimeter and vertical speed indicators?  If they are correct then it's  unlikely that you have a static issue since they also use the static port for  their sensing.  Only the airspeed uses the pitot, however, so I'd start  looking there.  Possibly a kink in the pitot line, or a pinch, or something  restricting it.

  

 

Jack & Cecilia Sargeant 

1127 Patricia St. 

Wichita,  KS 67208-2642 

316/683-5268  [quote]   --

sam(at)fr8dog.net
Guest

Posted: Tue Jun 26, 2007 4:42 am Post subject: Static problems

Thanks.

Do not archive.



AirMike wrote:

 	  Quote: 	
		   



 My I.A. friend suggested that it could be water accumulating.

 He told me to put a sump in my system. Spruce sells a cheap sump.

 I was directed to put a low point in the static lines for water to accumulate.

 Had to run my lines up the port side, so after routing them high, they dropped down to the floor aft of the baggage bay.



 Good luck - hope this helps



 --------

 OSH '08 or Bust





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=120657#120657

sam(at)fr8dog.net
Guest

Posted: Tue Jun 26, 2007 4:45 am Post subject: Static problems

Thanks Tim, this is a tough one, I guess it'll just take some digging.

 Sam

 

 Tim Olson wrote: [quote]--> RV10-List message posted by: Tim Olson <Tim(at)MyRV10.com> (Tim(at)MyRV10.com)   

   

 I'm going to combine 4 replies into one.   

   

   

 Sam Marlow wrote:   

 ## I installed the Cleveland Tool flush ports.   

   

 Well, if they're the old flush flat Cleveland ports, then that's good   

 for at least about 1/3 of  your 20kt error right there.  If they're the   

 domed ones, they may have less error.   

   

   

 ##I just had a static check by an avionics shop, no leaks, IFR certified. I'm baffled.   

   

 Did they check the PITOT system for leakdown too?  The IFR static   

 test is far far more relaxed on the pitot side than the static side,   

 and they really only bother to test for leaks in many cases.  The   

 suggestion given to use surgical tubing and check for leakdown is   

 a good one...even if they said it passed.   

   

   

 ## I have both EFIS and analog, and they agree with each other.   

   

 Of course...even a leaky system could possibly have a pressure   

 inside it that's common along the whole system, so that doesn't   

 surprise me.   

   

   

 ## Good thought but I have full size backup instruments, and the EFIS agrees with the analog readings.   

   

 Full size, or small, the leaks could be anywhere, if they exist.   

 >From what I've read, it's very hard to get pitot errors from   

 mis-angled pitots without it being a really big angle error.  If   

 your pitot is mounted in the standard way, and sits down low enough   

 from the wing, and there are no bugs and stuff in it, then it is   

 not likely the problem.  That really brings you back to either   

 a pitot leak, static problem, or port type/position problem.  There's   

 not going to be a silver bullet, so it's just time to roll up   

 the sleeves and start digging.  I replaced my static ports even   

 after the plane was painted.  If yours are the flat ones I'd   

 start there and then fly the 4-way GPS and see where you're at.   

 It's not going to come free, so it'll just take some time,   

 and eventually you should be able to get within a couple KTS.   

   

 Tim   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

 [b]

sam(at)fr8dog.net
Guest

Posted: Tue Jun 26, 2007 4:47 am Post subject: Static problems

I've ran the lines to check for kinks etc, nothing I can see. It's a 

tough one for sure.



Jack Sargeant wrote:

[quote] How are your altimeter and vertical speed indicators?  If they are 

 correct then it's unlikely that you have a static issue since they 

 also use the static port for their sensing.  Only the airspeed uses 

 the pitot, however, so I'd start looking there.  Possibly a kink in 

 the pitot line, or a pinch, or something restricting it.

  



 Jack & Cecilia Sargeant

 1127 Patricia St.

 Wichita, KS 67208-2642

 316/683-5268



     --

sgesele(at)yahoo.com
Guest

Posted: Tue Jun 26, 2007 9:31 am Post subject: Static problems

 	  Quote: 	
		   Time: 07:13:44 AM PST US

 From: Sam Marlow <sam(at)fr8dog.net>

 Subject: Static problems

 I'm having static problems, I think, not sure where

 to look though. 

 Indicated airspeed seams to be accurate on the

 bottom end but 20 to 30 

 knots slow at cruise, verified with chase plane. The

 static was checked 

 and certified IFR by an avionics shop, with no

 leaks. Looking for 

 ideas......

 Thanks,

 Sam

There are three potential sources for your error:

pitot, static, or instrument.

Pitot:

Is your pitot installed exactly per Van's

instructions?  If not, what changes have been made?  A

pitot leak can be checked, and the instruments checked

for error, by using the method contained in the

following link:

http://www.iflyez.com/manometer.shtml

Many heated pitot tubes have a drain port.  Ensure

that it is covered when performing the test.  You may

want to try a test flight with the drain port covered.

 All the drain port does is allow an exit path for

water.  Don't fly in the rain with the drain covered.

Static:

Just because the system was checked for leaks during

an IFR cert, does not rule out static errors.  You

mentioned flush ports.  These have been the cause of

numerous static errors on the RV fleet.  Static errors

may be a function of airspeed.  You can use GPS

altitude to determine if you have a static error that

is a function of airspeed.  In VFR, severe clear,

conditions, start with the aircraft at rest on the

ground.  Adjust the altimeter setting until the

altimeter matches the GPS altitude.  Go fly.  Start at

a safe altitude and Vs+10 kts.  Record both the GPS

altitude and indicated altitude at various airspeeds

as the aircraft accelerates to cruise.  Repeat as the

aircraft is slowed from cruise to Vs+10 kts (power at

idle).  Perform this test while maintaining a specific

indicated altitude.  Obtain the local altimeter

setting and land.  If the above test shows the

indicated altitude to be less than the GPS altitude,

then your static port is reading a higher than ambient

pressure.  This will cause an airspeed error.  

Instrument:

The pitot test above will check both the pitot system

for leaks, and the accuracy of the instruments.

Now that's room service!  Choose from over 150,000 hotels

in 45,000 destinations on Yahoo! Travel to find your fit.

http://farechase.yahoo.com/promo-generic-14795097

Dave(at)AirCraftersLLC.co
Guest

Posted: Tue Jun 26, 2007 11:01 am Post subject: Static problems

Sam,

  

 When we get static  checks, they only test the pitot system if we ask.  Even then it's an  "information only" type check, no certification.  There's no requirement  for a pitot check in 91.411/413, so having the static system IFR certified  could still leave you with a pitot problem.

  

 If you are looking for a pitot leak,  remember that it won't show up as a low airspeed indication with the test I  suggested.  Airspeed will go to whatever you put in, then bleed  off.  If the leak is pretty big, you might not see any indication at  all, but since you are getting something close at lower speeds, I doubt you have  a huge leak.

  

 The fact that two instruments agree pretty  well rules out instrument error but not a leak common to both.

  

 What happens when you open the alternate  static port?

  

  Dave Saylor

 AirCrafters LLC

 140 Aviation Way

 Watsonville, CA 

 831-722-9141

 831-750-0284 CL

 www.AirCraftersLLC.com



 



   From: owner-rv10-list-server(at)matronics.com  [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Sam  Marlow

Sent: Monday, June 25, 2007 9:02 PM

To:  rv10-list(at)matronics.com

Subject: Re: Static  problems

 

I just had a static check by an avionics  shop, no leaks, IFR certified. I'm baffled.

[quote] [b]

sam(at)fr8dog.net
Guest

Posted: Tue Jun 26, 2007 3:38 pm Post subject: Static problems

Thanks Scott, I'll try that ASAP, will let the world know the results!

 

 Scott Gesele wrote: [quote]    	  Quote: 	
		  --> RV10-List message posted by: Scott Gesele <sgesele(at)yahoo.com> (sgesele(at)yahoo.com)

        	  Quote: 	
		  Time: 07:13:44 AM PST US

From: Sam Marlow <sam(at)fr8dog.net> (sam(at)fr8dog.net)

Subject: Static problems



I'm having static problems, I think, not sure where

to look though. 

Indicated airspeed seams to be accurate on the

bottom end but 20 to 30 

knots slow at cruise, verified with chase plane. The

static was checked 

and certified IFR by an avionics shop, with no

leaks. Looking for 

ideas......

Thanks,

Sam



    	
   There are three potential sources for your error:

pitot, static, or instrument.



Pitot:

Is your pitot installed exactly per Van's

instructions?  If not, what changes have been made?  A

pitot leak can be checked, and the instruments checked

for error, by using the method contained in the

following link:



http://www.iflyez.com/manometer.shtml



Many heated pitot tubes have a drain port.  Ensure

that it is covered when performing the test.  You may

want to try a test flight with the drain port covered.

 All the drain port does is allow an exit path for

water.  Don't fly in the rain with the drain covered.



Static:

Just because the system was checked for leaks during

an IFR cert, does not rule out static errors.  You

mentioned flush ports.  These have been the cause of

numerous static errors on the RV fleet.  Static errors

may be a function of airspeed.  You can use GPS

altitude to determine if you have a static error that

is a function of airspeed.  In VFR, severe clear,

conditions, start with the aircraft at rest on the

ground.  Adjust the altimeter setting until the

altimeter matches the GPS altitude.  Go fly.  Start at

a safe altitude and Vs+10 kts.  Record both the GPS

altitude and indicated altitude at various airspeeds

as the aircraft accelerates to cruise.  Repeat as the

aircraft is slowed from cruise to Vs+10 kts (power at

idle).  Perform this test while maintaining a specific

indicated altitude.  Obtain the local altimeter

setting and land.  If the above test shows the

indicated altitude to be less than the GPS altitude,

then your static port is reading a higher than ambient

pressure.  This will cause an airspeed error.  



Instrument:

The pitot test above will check both the pitot system

for leaks, and the accuracy of the instruments.



 

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