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70 psi compression

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sarg314(at)gmail.com
Guest

Posted: Wed Jun 25, 2014 11:46 am Post subject: 70 psi compression

In the last compression test of my IO-360, after running the engine only a minute or two, showed 70 psi on cyl #4.Â  The A&P doing the measurement removed the dip stick and listened at the oil filler pipe. He could hear hissing which he says means it's leaking past the rings, which didn't seem to bother him much. Only 130 SMOH. Not using any oil.

 

Is it worth repeating the measurement after flying the thing a few hours?Â  I've been told the gaps in the rings can line up and affect the measurement.

Should I have run the engine longer than a couple minutes before doing the measurement?

 

How low is "low"?Â Â  At what point do I have to rebuild/replace the cylinder?



Thanks for any info/opinions/war stories.



-- 

Tom Sargent 

  [quote][b]

flying-nut(at)cfl.rr.com
Guest

Posted: Wed Jun 25, 2014 11:59 am Post subject: 70 psi compression

I'm no engine guru but my experience is       free .....

       On 6/25/2014 3:45 PM, Thomas Sargent wrote:

     

      	  Quote: 	
		                  In the last compression test of my IO-360, after running           the engine only a minute or two, showed 70 psi on cyl #4.Â  The           A&P doing the measurement removed the dip stick and           listened at the oil filler pipe. He could hear hissing which           he says means it's leaking past the rings, which didn't seem           to bother him much. Only 130 SMOH. Not using any oil.

           

           Is it worth repeating the measurement after flying the thing a           few hours?Â  I've been told the gaps in the rings can line up           and affect the measurement.

         

       

     	
     I'd run it againÂ  ...... a short flight around the patch should do     it ..... and the gaps aligning is possible, but IMHO not probable.

      	  Quote: 	
		                  

         

         Should I have run the engine longer than a couple minutes before         doing the measurement?

       

     	
     I would, just to get the cylinder temps up a bit.

      	  Quote: 	
		                  

           How low is "low"?Â Â  At what point do I have to rebuild/replace           the cylinder?         

       

     	
     That's up to your A&P/IA ....Â  but I believe 60 is a worry     point.

     [quote]                           

           

           Thanks for any info/opinions/war stories.

           

           -- 

             Tom Sargent           

         

       

        	  Quote: 	
		  

	
     [b]

carl.froehlich(at)verizon
Guest

Posted: Wed Jun 25, 2014 12:21 pm Post subject: 70 psi compression

I would throw this measurement away.

 

Go fly the airplane and get all engine up to normal temperatures then redo the compression test.Â  Do not be surprised if a cylinder changes ~2 psi or so from test to test.Â  Log the results in the engine log book after each test. Â I typically do a compression test at each oil change, but not less than at each annual. Â If you donâ€™t have a compression tester then perhaps you should.Â  This is something I view as a standard maintenance tool â€“ and are available at ACS for less than $100.Â  

 

Attached is the Lycoming SI on this.Â  



Carl

 

From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Thomas Sargent

Sent: Wednesday, June 25, 2014 3:45 PM

To: rv-list

Subject: 70 psi compression



 

In the last compression test of my IO-360, after running the engine only a minute or two, showed 70 psi on cyl #4.  The A&P doing the measurement removed the dip stick and listened at the oil filler pipe. He could hear hissing which he says means it's leaking past the rings, which didn't seem to bother him much. Only 130 SMOH. Not using any oil.



Is it worth repeating the measurement after flying the thing a few hours?  I've been told the gaps in the rings can line up and affect the measurement.



Should I have run the engine longer than a couple minutes before doing the measurement?



How low is "low"?   At what point do I have to rebuild/replace the cylinder?

 



Thanks for any info/opinions/war stories.



-- 

Tom Sargent 

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Cylinder_Compression.pdf

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Cylinder_Compression.pdf

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vshimsl(at)live.com
Guest

Posted: Wed Jun 25, 2014 12:41 pm Post subject: 70 psi compression

Thanks for the document!

VinceH

RV8-flying

--- Original Message ---



From: "Carl Froehlich" <carl.froehlich(at)verizon.net>

Sent: June 25, 2014 1:28 PM

To: rv-list(at)matronics.com

Subject: RE: 70 psi compression



I would throw this measurement away.



Go fly the airplane and get all engine up to normal temperatures then redo the compression test.  Do not be surprised if a cylinder changes ~2 psi or so from test to test.  Log the results in the engine log book after each test.  I typically do a compression test at each oil change, but not less than at each annual.  If you donâ€™t have a compression tester then perhaps you should.  This is something I view as a standard maintenance tool â€“ and are available at ACS for less than $100.



Attached is the Lycoming SI on this.

Carl



From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Thomas Sargent

Sent: Wednesday, June 25, 2014 3:45 PM

To: rv-list

Subject: 70 psi compression



In the last compression test of my IO-360, after running the engine only a minute or two, showed 70 psi on cyl #4.  The A&P doing the measurement removed the dip stick and listened at the oil filler pipe. He could hear hissing which he says means it's leaking past the rings, which didn't seem to bother him much. Only 130 SMOH. Not using any oil.



Is it worth repeating the measurement after flying the thing a few hours?  I've been told the gaps in the rings can line up and affect the measurement

Kellym

Joined: 10 Jan 2006
Posts: 1700
Location: Sun Lakes AZ

Posted: Wed Jun 25, 2014 2:09 pm Post subject: 70 psi compression

I assume we are talking an experimental here, so no IA involvement 

needed, just A&P  for condition inspection if you are not the builder.

If the only leakage is past the rings, oil consumption will guide you to 

when you feel the need to do something about the cylinder.

I would fly the engine hard for at least 10 hours, to see if the rings 

did not fully seat on that cylinder. Running it at 75% or even a bit 

higher, as long as you keep cylinder temps below 400 will not hurt 

anything, and may get those rings seated. 70/80 is nothing to worry 

about. Maybe a bit low for as low a time engine as you havel

As long as the leakage is not from a valve you can go down below 50/80 

and still make full rated power.

Kelly

A&P/IA

EAA Tech Counselor



On 6/25/2014 12:58 PM, Linn Walters wrote:

 	  Quote: 	
		   I'm no engine guru but my experience is free .....

 How low is "low"?   At what point do I have to rebuild/replace the 

 cylinder?

 That's up to your A&P/IA ....  but I believe 60 is a worry point.*\\*

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

sarg314(at)gmail.com
Guest

Posted: Wed Jun 25, 2014 3:11 pm Post subject: 70 psi compression

Thanks for all the good information. 



Reading the Lycoming Service instructions, I should note that cyl#1 showed 88psi.Â  I was doing the test as part of the annual inspection. Last year they were all in the 72 - 78 range I think.Â  What does an anomalously high reading indicate?Â  Off hand I would have guessed that the higher the better, but apparently not. Lyc. says more than 15psi difference is trouble.

 

I think I need to repeat this whole test soon after actually flying the plane. 



I'm still finishing the annual, I haven't flown it for a couple weeks.

  	  Quote: 	
		   

 



	


-- 

Tom Sargent 



  [quote][b]

wgreenley

Joined: 09 Jan 2010
Posts: 100
Location: Dowagiac, MI

Posted: Wed Jun 25, 2014 3:25 pm Post subject: 70 psi compression

An 88 means something is wrong with the equipment or the methodology. The max is 80 with the standardized orifice.

From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Thomas Sargent

Sent: Wednesday, June 25, 2014 7:11 PM

To: rv-list

Subject: Re: 70 psi compression

Thanks for all the good information. 

Reading the Lycoming Service instructions, I should note that cyl#1 showed 88psi.  I was doing the test as part of the annual inspection. Last year they were all in the 72 - 78 range I think.  What does an anomalously high reading indicate?  Off hand I would have guessed that the higher the better, but apparently not. Lyc. says more than 15psi difference is trouble.

I think I need to repeat this whole test soon after actually flying the plane. 

I'm still finishing the annual, I haven't flown it for a couple weeks. 	  Quote: 	

-- 

Tom Sargent 

 	  Quote: 	
		    http://www.matronics.com/Navigator?RV-List 	
0 	  Quote: 	

1 	  Quote: 	

2 	  Quote: 	

3 	  Quote: 	

4 	  Quote: 	

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  [quote][b]

carl.froehlich(at)verizon
Guest

Posted: Wed Jun 25, 2014 3:42 pm Post subject: 70 psi compression

Since the test rig provides regulated 80 psi input (if properly adjusted), your 88/80 reading makes no sense.  In other words zero leakage means you would read 80/80.  I suspect the test was done wrong.

Carl



On Jun 25, 2014, at 7:10 PM, Thomas Sargent <sarg314(at)gmail.com (sarg314(at)gmail.com)> wrote:

[quote]



Thanks for all the good information. 



Reading the Lycoming Service instructions, I should note that cyl#1 showed 88psi.  I was doing the test as part of the annual inspection. Last year they were all in the 72 - 78 range I think.  What does an anomalously high reading indicate?  Off hand I would have guessed that the higher the better, but apparently not. Lyc. says more than 15psi difference is trouble.

 

I think I need to repeat this whole test soon after actually flying the plane. 



I'm still finishing the annual, I haven't flown it for a couple weeks.

  	  Quote: 	
		   

 



	


-- 

Tom Sargent



 	  Quote: 	
		    is 



	
= 

[b]

vanremog(at)aol.com
Guest

Posted: Wed Jun 25, 2014 5:45 pm Post subject: 70 psi compression

Just a wild question since no one has asked it...How can one get an 88 psig aircraft bleed down type compression reading with 80 psig supplied air?

   

   

  --

Kellym

Joined: 10 Jan 2006
Posts: 1700
Location: Sun Lakes AZ

Posted: Wed Jun 25, 2014 7:06 pm Post subject: 70 psi compression

One needs to check the calibration of the compression tester. Easy way 

is to not connect the hose to the cylinder, then crank the primary gauge 

up to 80. The secondary should read 80 also. If more than a pound or so 

in either direction it needs to be recalibrated.

88 over 80 is not physically possible. 80/80 is the absolute best you 

can get.



On 6/25/2014 4:10 PM, Thomas Sargent wrote:

 	  Quote: 	
		  

 Thanks for all the good information.



 Reading the Lycoming Service instructions, I should note that cyl#1 

 showed 88psi.  I was doing the test as part of the annual inspection. 

 Last year they were all in the 72 - 78 range I think.  What does an 

 anomalously high reading indicate?  Off hand I would have guessed that 

 the higher the better, but apparently not. Lyc. says more than 15psi 

 difference is trouble.



 I think I need to repeat this whole test soon after actually flying 

 the plane.



 I'm still finishing the annual, I haven't flown it for a couple weeks.



 -- 

 Tom Sargent

 *

 *

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

flying-nut(at)cfl.rr.com
Guest

Posted: Wed Jun 25, 2014 7:12 pm Post subject: 70 psi compression

On 6/25/2014 9:44 PM, vanremog(at)aol.com (vanremog(at)aol.com)       wrote:

     

      	  Quote: 	
		           Just a wild             question since no one has asked it...How can one get an 88             psig aircraft bleed down type compression reading with 80             psig supplied air?

       	
            You             can't if you use the differential gauge         properly.  I can only surmise that 88 was a typo.

         Linn

       

          [quote]          

          

         --

sarg314(at)gmail.com
Guest

Posted: Thu Jun 26, 2014 6:47 am Post subject: 70 psi compression

Well 88 may well be a mistake, but that's what the A&P said.Â  He seemed a bit baffled.Â  I have my own compression tester now.Â  I will do it myself next time.



 On Wed, Jun 25, 2014 at 8:11 PM, Linn Walters <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)> wrote:

[quote]                    On 6/25/2014 9:44 PM, vanremog(at)aol.com (vanremog(at)aol.com)       wrote:

     

      	  Quote: 	
		           Just a wild             question since no one has asked it...How can one get an 88             psig aircraft bleed down type compression reading with 80             psig supplied air?

       	
            You             can't if you use the differential gauge         properly.Â  I can only surmise that 88 was a typo.

         Linn

       

          [quote]         Â 

         Â 

         --

sportav8r(at)gmail.com
Guest

Posted: Thu Jun 26, 2014 7:28 am Post subject: 70 psi compression

Be careful. Â Two-man job to do safely... 80 psi into one jug can be deadly if the prop gets away from you and your noggin is in the way. Â 



IIRC, the trend in the "literature" is away from compression testing altogether and toward boroscopy as a means of assessing engine health.

 --kind of like internal like medicine... the old standards of screening are giving way to the $$ passing-of-scopes $$ into various body cavities.

-Stormy



 On Thu, Jun 26, 2014 at 10:46 AM, Thomas Sargent <sarg314(at)gmail.com (sarg314(at)gmail.com)> wrote:

[quote] Well 88 may well be a mistake, but that's what the A&P said.Â  He seemed a bit baffled.Â  I have my own compression tester now.Â  I will do it myself next time.



  On Wed, Jun 25, 2014 at 8:11 PM, Linn Walters <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)> wrote:

[quote]                     On 6/25/2014 9:44 PM, vanremog(at)aol.com (vanremog(at)aol.com)       wrote:

     

      	  Quote: 	
		           Just a wild             question since no one has asked it...How can one get an 88             psig aircraft bleed down type compression reading with 80             psig supplied air?

       	
            You             can't if you use the differential gauge         properly.Â  I can only surmise that 88 was a typo.

         Linn

       

          [quote]         Â 

         Â 

         --

Kellym

Joined: 10 Jan 2006
Posts: 1700
Location: Sun Lakes AZ

Posted: Thu Jun 26, 2014 11:27 am Post subject: 70 psi compression

Not really. Until Appendix D of Part 43 gets re-written, compression 

tests are mandatory for both certified and experimental aircraft. Item 

(d) (3) of the appendix requires compression test, and AFAIK most all 

experimental operating limitations require condition inspect that meets 

requirements of Appendix D as a minimum. Yes, borescope is good addition 

to checking cylinder health, but FAA does not recognize it as a complete 

substitute.

IF one gains the experience to get a cylinder to TDC there will be no 

force on the prop. But allowing it to go very many degrees either side 

of TDC generates a dangerous force in the prop. I position prop near 

TDC, dial up about 20psi while adjusting prop for minimum  to no force 

at the prop, then bring the pressure on up to 80. I also make sure to 

hold prop such that if it got away from me it would hurt nothing. 

Especially keep rest of body besides hand outside the prop arc.I don't 

even pick up compression tester until I have prop in safe position.

On 6/26/2014 8:27 AM, Bill Boyd wrote:

[quote] Be careful.  Two-man job to do safely... 80 psi into one jug can be 

 deadly if the prop gets away from you and your noggin is in the way.

 IIRC, the trend in the "literature" is away from compression testing 

 altogether and toward boroscopy as a means of assessing engine health.

 --kind of like internal like medicine... the old standards of 

 screening are giving way to the $$ passing-of-scopes $$ into various 

 body cavities.

 -Stormy

 On Thu, Jun 26, 2014 at 10:46 AM, Thomas Sargent <sarg314(at)gmail.com 

 <mailto:sarg314(at)gmail.com>> wrote:

     Well 88 may well be a mistake, but that's what the A&P said.  He

     seemed a bit baffled.  I have my own compression tester now.  I

     will do it myself next time.

     On Wed, Jun 25, 2014 at 8:11 PM, Linn Walters

     <flying-nut(at)cfl.rr.com <mailto:flying-nut(at)cfl.rr.com>> wrote:

         On 6/25/2014 9:44 PM, vanremog(at)aol.com

         <mailto:vanremog(at)aol.com> wrote:

>         Just a wild question since no one has asked it...How can one

>         get an 88 psig aircraft bleed down type compression reading

>         with 80 psig supplied air?

         You can't if you use the differential gauge properly. I can

         only surmise that 88 was a typo.

         Linn

>         --

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

jluckey(at)pacbell.net
Guest

Posted: Thu Jun 26, 2014 2:25 pm Post subject: 70 psi compression

In addition to the regs - I can't see how a visual inspection w/ a bore scope/camera would be a good substitute for actually testing seals by putting actual air pressure on them.  I don't think the Compression Test is going to disappear anytime soon - it's such a great diagnostic.

-Jeff

     On Thursday, June 26, 2014 12:36 PM, Kelly McMullen <kellym(at)aviating.com> wrote:

 --> RV-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>

Not really. Until Appendix D of Part 43 gets re-written, compression 

tests are mandatory for both certified and experimental aircraft. Item 

(d) (3) of the appendix requires compression test, and AFAIK most all 

experimental operating limitations require condition inspect that meets 

requirements of Appendix D as a minimum. Yes, borescope is good addition 

to checking cylinder health, but FAA does not recognize it as a complete 

substitute.

IF one gains the experience to get a cylinder to TDC  there will be no 

force on the prop. But allowing it to go very many degrees either side 

of TDC generates a dangerous force in the prop. I position prop near 

TDC, dial up about 20psi while adjusting prop for minimum  to no force 

at the prop, then bring the pressure on up to 80. I also make sure to 

hold prop such that if it got away from me it would hurt nothing. 

Especially keep rest of body besides hand outside the prop arc.I don't 

even pick up compression tester until I have prop in safe position.

On 6/26/2014 8:27 AM, Bill Boyd wrote:

[quote] Be careful.  Two-man job to do safely... 80 psi into one jug can be 

 deadly if the prop gets away from you and your noggin is in the way.

 IIRC, the trend in the "literature" is away from compression testing 

 altogether and toward boroscopy as a means of assessing engine health.

 --kind of like internal like medicine... the old  standards of 

 screening are giving way to the $$ passing-of-scopes $$ into various 

 body cavities.

 -Stormy

 On Thu, Jun 26, 2014 at 10:46 AM, Thomas Sargent <sarg314(at)gmail.com (sarg314(at)gmail.com) 

 <mailto:sarg314(at)gmail.com (sarg314(at)gmail.com)>> wrote:

     Well 88 may well be a mistake, but that's what the A&P said.  He

     seemed a bit baffled.  I have my own compression tester now.  I

     will do it myself next time.

     On Wed, Jun 25, 2014 at 8:11 PM, Linn Walters

     <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com) <mailto:flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)>> wrote:

         On 6/25/2014 9:44 PM, vanremog(at)aol.com (vanremog(at)aol.com)

         <mailto:vanremog(at)aol.com (vanremog(at)aol.com)> wrote:

>         Just a wild question since no one has asked it...How can one

>         get an 88 psig aircraft bleed down type compression reading

>         with 80 psig supplied air?

         You can't if you use the differential gauge properly. I can

         only surmise that 88 was a typo.

         Linn

>         --

ceengland7(at)gmail.com
Guest

Posted: Thu Jun 26, 2014 2:28 pm Post subject: 70 psi compression

Even if you buy into the idea that a compression test is required during 

the condition inspection, it doesn't mean you have to give it any weight 

in your appraisal of the engine's health.  I suspect that Bill was 

saying that more recent research has shown the traditional compression 

test to be a very poor indicator of a cylinder's condition (unless, of 

course, it's very very low and you can hear a 'breeze' blowing out the 

exhaust or intake...).



I've gotten a 75+ reading on a cylinder that had a broken ring, and a 

low-70s reading followed the next year by a high-70s reading on the same 

cylinder, when checked 'cold'.



If you haven't done it already, I'd suggest reading everything you can 

find by Mike Busch (writes for Sport Aviation, in addition to seminars, 

webinars, etc).



Charlie

(If your mechanic insists that he got an 88/80 reading, then in the 

immortal words of Monty Python, 'Run away! Run away!' (from that mechanic).



On 6/26/2014 2:26 PM, Kelly McMullen wrote:

[quote] 



 Not really. Until Appendix D of Part 43 gets re-written, compression 

 tests are mandatory for both certified and experimental aircraft. Item 

 (d) (3) of the appendix requires compression test, and AFAIK most all 

 experimental operating limitations require condition inspect that 

 meets requirements of Appendix D as a minimum. Yes, borescope is good 

 addition to checking cylinder health, but FAA does not recognize it as 

 a complete substitute.

 IF one gains the experience to get a cylinder to TDC there will be no 

 force on the prop. But allowing it to go very many degrees either side 

 of TDC generates a dangerous force in the prop. I position prop near 

 TDC, dial up about 20psi while adjusting prop for minimum  to no force 

 at the prop, then bring the pressure on up to 80. I also make sure to 

 hold prop such that if it got away from me it would hurt nothing. 

 Especially keep rest of body besides hand outside the prop arc.I don't 

 even pick up compression tester until I have prop in safe position.



 On 6/26/2014 8:27 AM, Bill Boyd wrote:

> Be careful.  Two-man job to do safely... 80 psi into one jug can be 

> deadly if the prop gets away from you and your noggin is in the way.

>

> IIRC, the trend in the "literature" is away from compression testing 

> altogether and toward boroscopy as a means of assessing engine health.

> --kind of like internal like medicine... the old standards of 

> screening are giving way to the $$ passing-of-scopes $$ into various 

> body cavities.

>

> -Stormy

> On Thu, Jun 26, 2014 at 10:46 AM, Thomas Sargent <sarg314(at)gmail.com 

> <mailto:sarg314(at)gmail.com>> wrote:

>

>     Well 88 may well be a mistake, but that's what the A&P said.  He

>     seemed a bit baffled.  I have my own compression tester now.  I

>     will do it myself next time.

>     On Wed, Jun 25, 2014 at 8:11 PM, Linn Walters

>     <flying-nut(at)cfl.rr.com <mailto:flying-nut(at)cfl.rr.com>> wrote:

>

>         On 6/25/2014 9:44 PM, vanremog(at)aol.com

>         <mailto:vanremog(at)aol.com> wrote:

>>         Just a wild question since no one has asked it...How can one

>>         get an 88 psig aircraft bleed down type compression reading

>>         with 80 psig supplied air?

>         You can't if you use the differential gauge properly. I can

>         only surmise that 88 was a typo.

>         Linn

>>         --

vanremog(at)aol.com
Guest

Posted: Thu Jun 26, 2014 7:06 pm Post subject: 70 psi compression

baffled is not the word I was thinking of...

   

  -GV

   

   

  --

sarg314(at)gmail.com
Guest

Posted: Sun Jun 29, 2014 6:00 pm Post subject: 70 psi compression

I repeated the measurement myself this afternoon after running the engine until cyl. head temp hit 400 deg. (not hard when it's 105 outside).Â  I got all cylinders between 73 and 76.

The guy who did the first, obviously wrong,measurement is definitely an old hand,Â  I don't know what went wrong - I wasn't watching - but something certainly did.. 

 

On Thu, Jun 26, 2014 at 3:28 PM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

 [quote]--> RV-List message posted by: Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)>

  

 Even if you buy into the idea that a compression test is required during the condition inspection, it doesn't mean you have to give it any weight in your appraisal of the engine's health.  I suspect that Bill was saying that more recent research has shown the traditional compression test to be a very poor indicator of a cylinder's condition (unless, of course, it's very very low and you can hear a 'breeze' blowing out the exhaust or intake...).

  

 I've gotten a 75+ reading on a cylinder that had a broken ring, and a low-70s reading followed the next year by a high-70s reading on the same cylinder, when checked 'cold'.

 

 If you haven't done it already, I'd suggest reading everything you can find by Mike Busch (writes for Sport Aviation, in addition to seminars, webinars, etc).

 

 Charlie

 (If your mechanic insists that he got an 88/80 reading, then in the immortal words of Monty Python, 'Run away! Run away!' (from that mechanic).

 

 On 6/26/2014 2:26 PM, Kelly McMullen wrote:

 [quote] --> RV-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>

 

 Not really. Until Appendix D of Part 43 gets re-written, compression tests are mandatory for both certified and experimental aircraft. Item (d) (3) of the appendix requires compression test, and AFAIK most all experimental operating limitations require condition inspect that meets requirements of Appendix D as a minimum. Yes, borescope is good addition to checking cylinder health, but FAA does not recognize it as a complete substitute.

  IF one gains the experience to get a cylinder to TDC there will be no force on the prop. But allowing it to go very many degrees either side of TDC generates a dangerous force in the prop. I position prop near TDC, dial up about 20psi while adjusting prop for minimum Â to no force at the prop, then bring the pressure on up to 80. I also make sure to hold prop such that if it got away from me it would hurt nothing. Especially keep rest of body besides hand outside the prop arc.I don't even pick up compression tester until I have prop in safe position.

  

 On 6/26/2014 8:27 AM, Bill Boyd wrote:

 [quote] Be careful. Â Two-man job to do safely... 80 psi into one jug can be deadly if the prop gets away from you and your noggin is in the way.

 

 IIRC, the trend in the "literature" is away from compression testing altogether and toward boroscopy as a means of assessing engine health.

 --kind of like internal like medicine... the old standards of screening are giving way to the $$ passing-of-scopes $$ into various body cavities.

 

 -Stormy

 

 

 On Thu, Jun 26, 2014 at 10:46 AM, Thomas Sargent <sarg314(at)gmail.com (sarg314(at)gmail.com) <mailto:sarg314(at)gmail.com (sarg314(at)gmail.com)>> wrote:

  

 Â  Â  Well 88 may well be a mistake, but that's what the A&P said. Â He

 Â  Â  seemed a bit baffled. Â I have my own compression tester now. Â I

 Â  Â  will do it myself next time.

 

 

 Â  Â  On Wed, Jun 25, 2014 at 8:11 PM, Linn Walters

 Â  Â  <flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com) <mailto:flying-nut(at)cfl.rr.com (flying-nut(at)cfl.rr.com)>> wrote:

 

 Â  Â  Â  Â  On 6/25/2014 9:44 PM, vanremog(at)aol.com (vanremog(at)aol.com)

 Â  Â  Â  Â  <mailto:vanremog(at)aol.com (vanremog(at)aol.com)> wrote:

  	  Quote: 	
		   Â  Â  Â  Â  Just a wild question since no one has asked it..How can one

 Â  Â  Â  Â  get an 88 psig aircraft bleed down type compression reading

 Â  Â  Â  Â  with 80 psig supplied air?

 	
 Â  Â  Â  Â  You can't if you use the differential gauge properly. I can

 Â  Â  Â  Â  only surmise that 88 was a typo.

 Â  Â  Â  Â  Linn

 [quote] Â  Â  Â  Â  --

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