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Static ports, was: Gretz GA-1000 Pitot Experience?

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khorton01(at)rogers.com
Guest

Posted: Thu Oct 05, 2006 1:46 pm Post subject: Static ports, was: Gretz GA-1000 Pitot Experience?

 	  Quote: 	
		   



 I've got one installed and flying.  It seems to work fine.

 The thermostatic control works as advertised.  Somewhere in

 my pitot static system I have something causing an airspeed

 error of -1 to -2 kts, but that's pretty minimal.  I had

 lots more until I got new static ports installed.


	


Tim - tell us more about the static ports.  Which static ports gave  

the errors?  How much error, and in which speed range?  Which ports  

do you have now?



Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

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Tim(at)MyRV10.com
Guest

Posted: Thu Oct 05, 2006 5:11 pm Post subject: Static ports, was: Gretz GA-1000 Pitot Experience?

I had the original Cleaveland ports that were flat.  I didn't get

any instructions with them, so I just riveted them in, and

painted around them...they were flush with the painted part of

the fuselage.  As it turned out, they were supposedly to be installed

on an un-primed inner surface, so they'd not have that super

thick primer (sarcastic) keeping them from sticking out, and then

they were supposed to be painted with the fuselage so the end

result was that they were to stick out .010" or so.  Well, with

mine being flush, I had a -6.5 to -7.5 kt error.  I had no idea

until thanks to your site I used your 4-way spreadsheet and

did a bunch of test flights.  I was consistently off by that

amount, with st.dev. numbers near zero.

I cut some .040 or .050" penny sized discs and taped them over

the ports (had a hole in the discs), and then my airspeed error

was -4 kts or so....a good improvement, but a messy kludge.

I then removed the discs and made some horseshoe bridges to put

in front of the ports, which brought the error to -4 to -4.5

kts or so.

Finally I gave up doing the messy fixes and installed the newer

style Cleaveland ports.  They stick out a bit, and are rounded

in shape on the outside.  When I test flew with those ports, my

error was -1.8 on your spreadsheet.  With 1kt resolution on the

airspeed indicator, I think this is the best I can expect to get.

I did a pitot system leak check when I had the IFR pitot static

done, and both were tight.  I did a simulated test of the pitot

system by blowing into it to 170kts and plugging the pitot with

a piece of rubber.  I couldn't get a perfect seal, but it only

leaked down by 1kt every 20+ seconds or so....so it was tight

enough to be pretty accurate I'd think.

I need to say thank you for your website.  I used it during my

quest for good airspeed numbers.  I'd love to get rid of the

-1.8 kt error, but I think I'd be a little obsessive if I put

much more time into that small of an error.

Thanks again Kevin,

Tim

Tim Olson - RV-10 N104CD - Flying

do not archive

Kevin Horton wrote:

 	  Quote: 	

> 

>

> I've got one installed and flying.  It seems to work fine.

> The thermostatic control works as advertised.  Somewhere in

> my pitot static system I have something causing an airspeed

> error of -1 to -2 kts, but that's pretty minimal.  I had

> lots more until I got new static ports installed.

 Tim - tell us more about the static ports.  Which static ports gave the 

 errors?  How much error, and in which speed range?  Which ports do you 

 have now?

 Kevin Horton         RV-8 (finishing kit)

 Ottawa, Canada

 http://www.kilohotel.com/rv8

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khorton01(at)rogers.com
Guest

Posted: Fri Oct 06, 2006 1:40 am Post subject: Static ports, was: Gretz GA-1000 Pitot Experience?

Thanks for the additional info.  It is good to learn that Cleaveland  

has updated the design of their static ports, and that the new ones  

appear to be much more suited to RVs, or at least RV-10s.  I'd love  

to get any reports from people who have done comprehensive static  

system error testing with the new Cleaveland static ports on other RVs.

I wouldn't try to chase your -1.8 kt error - that is actually pretty  

good.  A lot of type-certificated aircraft have errors larger than  

that.  You would probably have to experiment with machining the  

static port to change how much it protruded from the fuselage surface.

The ultimate answer is for EFIS manufacturers to add a feature where  

the user can define a static pressure correction.  The corrected  

static pressure would be used for the displayed airspeed and  

altitude.  There are several classical ways to describe the static  

pressure correction.

Fly safe,

Kevin Horton

On 5 Oct 2006, at 21:10, Tim Olson wrote:

 	  Quote: 	

 I had the original Cleaveland ports that were flat.  I didn't get

 any instructions with them, so I just riveted them in, and

 painted around them...they were flush with the painted part of

 the fuselage.  As it turned out, they were supposedly to be installed

 on an un-primed inner surface, so they'd not have that super

 thick primer (sarcastic) keeping them from sticking out, and then

 they were supposed to be painted with the fuselage so the end

 result was that they were to stick out .010" or so.  Well, with

 mine being flush, I had a -6.5 to -7.5 kt error.  I had no idea

 until thanks to your site I used your 4-way spreadsheet and

 did a bunch of test flights.  I was consistently off by that

 amount, with st.dev. numbers near zero.

 I cut some .040 or .050" penny sized discs and taped them over

 the ports (had a hole in the discs), and then my airspeed error

 was -4 kts or so....a good improvement, but a messy kludge.

 I then removed the discs and made some horseshoe bridges to put

 in front of the ports, which brought the error to -4 to -4.5

 kts or so.

 Finally I gave up doing the messy fixes and installed the newer

 style Cleaveland ports.  They stick out a bit, and are rounded

 in shape on the outside.  When I test flew with those ports, my

 error was -1.8 on your spreadsheet.  With 1kt resolution on the

 airspeed indicator, I think this is the best I can expect to get.

 I did a pitot system leak check when I had the IFR pitot static

 done, and both were tight.  I did a simulated test of the pitot

 system by blowing into it to 170kts and plugging the pitot with

 a piece of rubber.  I couldn't get a perfect seal, but it only

 leaked down by 1kt every 20+ seconds or so....so it was tight

 enough to be pretty accurate I'd think.

 I need to say thank you for your website.  I used it during my

 quest for good airspeed numbers.  I'd love to get rid of the

 -1.8 kt error, but I think I'd be a little obsessive if I put

 much more time into that small of an error.

 Thanks again Kevin,

 Tim

 Tim Olson - RV-10 N104CD - Flying

 do not archive

 Kevin Horton wrote:

> 

>> 

>>

>> I've got one installed and flying.  It seems to work fine.

>> The thermostatic control works as advertised.  Somewhere in

>> my pitot static system I have something causing an airspeed

>> error of -1 to -2 kts, but that's pretty minimal.  I had

>> lots more until I got new static ports installed.

> Tim - tell us more about the static ports.  Which static ports  

> gave the errors?  How much error, and in which speed range?  Which  

> ports do you have now?

> Kevin Horton         RV-8 (finishing kit)

> Ottawa, Canada

> http://www.kilohotel.com/rv8

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rvbuilder(at)sausen.net
Guest

Posted: Fri Oct 06, 2006 6:18 am Post subject: Static ports, was: Gretz GA-1000 Pitot Experience?

I got to see Tim's updated static ports last weekend (thanks again for

the ride) and the first thing I noticed is they are styled very much

like the Van's pop rivet ports.  They are like a little mound sticking

out of the skin a tiny bit.



A while back I made the decision to go with the SafeAir static and pitot

tubing along with their ports.  I asked lots of people about the

possible error I could see and had a wide range of answers but most

people didn't seem to have a problem with them.  If I had to guess the

RV-10 might be a tad more sensitive to the static port position than the

other RV's and it really wants the port sticking out into the slipstream

a little more.



I'm probably at least a year from flying but I will be sure to post back

any errors that I see after careful calculations and multiple runs.  One

solution I have heard for the people that had flush ports with errors

was to take the Vans pop rivet version, cut the head off, and glue it

over the flush ports.



I also have the Gretz GA-1000 Pitot and it is very nicely styled.  It is

sandable and you can also paint it to match whatever color.



Michael Sausen

-10 #352 Buildus Interuptus



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