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static system leak check procedure

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klehman(at)albedo.net
Guest

Posted: Wed Mar 05, 2008 11:06 am Post subject: static system leak check procedure

I started to do a preliminary static system leak check and noticed that 

it only takes about 500 feet of static vacuum to make the ASI read about 

100 knots. 10 or 20 thousand feet would peg the ASI pretty firmly. Is 

the pitot side subjected to the same vacuum as the static side of the 

system to prevent altimeter damage or is that not a concern? It seems 

prudent to check for obvious leaks before taking the plane to the radio 

shop.

thank you

Ken

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recapen(at)earthlink.net
Guest

Posted: Wed Mar 05, 2008 11:41 am Post subject: static system leak check procedure

I did a similar test with the ASI removed and its fittings plugged to verify the integrity of the rest of the system up to 20000ft.  Then I put it all back together and verified the leakdown integrity.



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trigo(at)mail.telepac.pt
Guest

Posted: Wed Mar 05, 2008 4:20 pm Post subject: static system leak check procedure

By the way, can somebody explain how is a static leak check performed?



Carlos

[quote] --

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bbradburry(at)bellsouth.n
Guest

Posted: Wed Mar 05, 2008 6:04 pm Post subject: static system leak check procedure

Carlos, check out the following website...



 http://www.kilohotel.com/rv8/rvlinks/ssec.html



Bill B



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recapen(at)earthlink.net
Guest

Posted: Thu Mar 06, 2008 5:32 am Post subject: static system leak check procedure

Here's how I did it:



I got a vacuum brake bleeding kit (JC Whitney IIRC) - it has a guage that will allow you to see an evacuation level and watch it change.



I disconnected my ASI, VSI, and capped off the rest of the static system.  The VSI has a built in leak and the ASI limits your altitude as the airspeed is artificially induced by the differential pressure.



I plugged one static port and attached the brake bleeder to the other port.



Pump the handle and watch the dial as you pull a vacuum.  (I did mine all the way to 20,000').



Start a stop watch and look for the dial to rotate downward indicating leakdown.  Swap static ports and start over.



I added the ASI and did another test with lower altitude levels to ensure the integrity of the ASI.  Swap static ports and start over.



You're allowed 100'/min IIRC from the regs - I ended up with 150'/hr so I think I'm OK......



Someone may convince me of the error of my ways and I'll re-do it differently - but noone's tried yet.



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khorton01(at)rogers.com
Guest

Posted: Thu Mar 06, 2008 6:16 am Post subject: static system leak check procedure

You can do an acceptable test much more simply than this.  The standard (as described in FAR 23.1325(b)(2)(i)) only calls for enough vacuum to raise the indicated altitude 1000 ft above the altitude of the test site.  On my RV-8, I put a piece of tape over one static port, and held a piece of rubber hose against the other static port.  I put the other end of the hose in my mouth, and sucked until I had increased the altitude more than 1000 ft.  I put my tongue over the end of hose to trap the pressure, and made sure to keep pushing the other end hard against the static port so no air leaked out there.  The altimeter dropped much less than 100 ft in a minute (the pass/fail criteria from FAR 23.1325), so my system was OK. 

There is no need to disconnect ASI or VSI (assuming you don't introduce excessive vacuum, which could damage an ASI).  In fact, doing it with instruments removed invalidates the test, as you might introduce a leak when you put those instruments back into the static system.  You really need to do an end-to-end leak check with the whole static system in the state it would be when you fly the airplane. 



Kevin Horton



On Thu, Mar 6, 2008 at 8:27 AM, Ralph E. Capen <recapen(at)earthlink.net (recapen(at)earthlink.net)> wrote:

 [quote]--> AeroElectric-List message posted by: "Ralph E. Capen" <recapen(at)earthlink.net (recapen(at)earthlink.net)>

  

 Here's how I did it:

 

 I got a vacuum brake bleeding kit (JC Whitney IIRC) - it has a guage that will allow you to see an evacuation level and watch it change.

 

 I disconnected my ASI, VSI, and capped off the rest of the static system.  The VSI has a built in leak and the ASI limits your altitude as the airspeed is artificially induced by the differential pressure.

 

 I plugged one static port and attached the brake bleeder to the other port.

 

 Pump the handle and watch the dial as you pull a vacuum.  (I did mine all the way to 20,000').

 

 Start a stop watch and look for the dial to rotate downward indicating leakdown.  Swap static ports and start over.

 

 I added the ASI and did another test with lower altitude levels to ensure the integrity of the ASI.  Swap static ports and start over.

 

 You're allowed 100'/min IIRC from the regs - I ended up with 150'/hr so I think I'm OK......

 

 Someone may convince me of the error of my ways and I'll re-do it differently - but noone's tried yet.

 

 --

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klehman(at)albedo.net
Guest

Posted: Thu Mar 06, 2008 7:08 pm Post subject: static system leak check procedure

I'm still wondering how the radio shop does a transponder check?

I'm guessing they connect their vacuum source to the static port AND the 

pitot port??  If so, I'm going to need to check the pitot side of things 

for leakage as well I think.

thank you

Ken



Kevin Horton wrote:

 	  Quote: 	
		   You can do an acceptable test much more simply than this.  The standard 

 (as described in FAR 23.1325(b)(2)(i)) only calls for enough vacuum to 

 raise the indicated altitude 1000 ft above the altitude of the test 

 site.  On my RV-8, I put a piece of tape over one static port, and held 

 a piece of rubber hose against the other static port.  I put the other 

 end of the hose in my mouth, and sucked until I had increased the 

 altitude more than 1000 ft.  I put my tongue over the end of hose to 

 trap the pressure, and made sure to keep pushing the other end hard 

 against the static port so no air leaked out there.  The altimeter 

 dropped much less than 100 ft in a minute (the pass/fail criteria from 

 FAR 23.1325), so my system was OK.

 

 There is no need to disconnect ASI or VSI (assuming you don't introduce 

 excessive vacuum, which could damage an ASI).  In fact, doing it with 

 instruments removed invalidates the test, as you might introduce a leak 

 when you put those instruments back into the static system.  You really 

 need to do an end-to-end leak check with the whole static system in the 

 state it would be when you fly the airplane.

 

 Kevin Horton

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khorton01(at)rogers.com
Guest

Posted: Sat Mar 08, 2008 6:56 am Post subject: static system leak check procedure

Yes, if they do the transponder check on the aircraft, they would  

have to also connect to the pitot to put vacuum there, or they could  

damage the ASI.



But, you really should do a pitot leak check anyway, as a leak in the  

pitot side could affect ASI accuracy.  Be aware that some pitot ports  

have a water drain on the tube, which introduces a very small at the  

tube.  This doesn't affect ASI accuracy as it is so close to the  

pitot tube, that any air that leaks out is quickly replaced without  

affecting the pressure in the pitot line.  But it does affect leak  

checks - you need to block the water drain during the leak check, or  

you'll end up looking for a phantom leak.



Kevin



On 6 Mar 2008, at 22:06, Ken wrote:



 	  Quote: 	
		   



 I'm still wondering how the radio shop does a transponder check?

 I'm guessing they connect their vacuum source to the static port  

 AND the pitot port??  If so, I'm going to need to check the pitot  

 side of things for leakage as well I think.

 thank you

 Ken



 Kevin Horton wrote:

> You can do an acceptable test much more simply than this.  The  

> standard (as described in FAR 23.1325(b)(2)(i)) only calls for  

> enough vacuum to raise the indicated altitude 1000 ft above the  

> altitude of the test site.  On my RV-8, I put a piece of tape over  

> one static port, and held a piece of rubber hose against the other  

> static port.  I put the other end of the hose in my mouth, and  

> sucked until I had increased the altitude more than 1000 ft.  I  

> put my tongue over the end of hose to trap the pressure, and made  

> sure to keep pushing the other end hard against the static port so  

> no air leaked out there.  The altimeter dropped much less than 100  

> ft in a minute (the pass/fail criteria from FAR 23.1325), so my  

> system was OK.

> There is no need to disconnect ASI or VSI (assuming you don't  

> introduce excessive vacuum, which could damage an ASI).  In fact,  

> doing it with instruments removed invalidates the test, as you  

> might introduce a leak when you put those instruments back into  

> the static system.  You really need to do an end-to-end leak check  

> with the whole static system in the state it would be when you fly  

> the airplane.

> Kevin Horton

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klehman(at)albedo.net
Guest

Posted: Sat Mar 08, 2008 7:32 am Post subject: static system leak check procedure

Thank you Kevin

Even with the water drain plugged, I suspect that my pitot probe will 

leak a bit with about 8 psi vacuum (for a 20k feet test) so I will have 

to address that.

Ken



do not archive



Kevin Horton wrote:

 	  Quote: 	
		   

 <khorton01(at)rogers.com>

 

 Yes, if they do the transponder check on the aircraft, they would have 

 to also connect to the pitot to put vacuum there, or they could damage 

 the ASI.

 

 But, you really should do a pitot leak check anyway, as a leak in the 

 pitot side could affect ASI accuracy.  Be aware that some pitot ports 

 have a water drain on the tube, which introduces a very small at the 

 tube.  This doesn't affect ASI accuracy as it is so close to the pitot 

 tube, that any air that leaks out is quickly replaced without affecting 

 the pressure in the pitot line.  But it does affect leak checks - you 

 need to block the water drain during the leak check, or you'll end up 

 looking for a phantom leak.

 

 Kevin

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