Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Compression Checks  
User currently offlineFlyf15 From , joined Dec 1969, posts, RR:
Posted (10 years 3 months 4 days 3 hours ago) and read 1185 times:

Stemming off of the TBO post, I'd like to ask about compression checks.

I know basically what they are, but that is about it. What exactly is done? What are considered good and bad results?

Thanks guys!

2 replies: All unread, jump to last
 
User currently offlineChdmcmanus From United States of America, joined Mar 2001, 374 posts, RR: 2
Reply 1, posted (10 years 3 months 3 days 19 hours ago) and read 1076 times:

A differential compression check measures "seal" of the piston rings and valves for a given cylinder. They are required by 14CFR43 app.D as one of the minimum requirements for 100hr/Annual inspection. They are also in every manufacturers inspection requirements, sometimes more often than the minimum requirement.

The general procedure may be found in the AC-43 1A/2B, most of the time the specific procedure for the model of tester being used may be found on the case or body of the gauge set. Basically, a DPC tester is a set of air pressure gauges with a fixed orifice between them. To perform a check;
Run the motor, and warm it up to operating temperature,
Remove the most accessible spark plug from each cylinder,
Install the air adapter in the #1 cylinder,
Rotate the prop to find TDC (Top Dead Center) on #1 piston,
Connect the air source and gauge set,
Have someone hold the prop!!!! (VERY VERY Important)
Apply 80psi to set, open the air valve and observe pressure drop on the second gauge.
Move the prop slightly to ensure TDC, ring, and valve seating.
If the pressure drop is more than 20 psi (25%), it fails the check, listen for air leaking at the exhaust, intake, and crankcase.

If it fails there are some things you can do to seal up the valves and rings to troubleshoot, but that's it in a nutshell. There is another about this article in AMT, http://www.amtonline.com/ , same deal, Article archives, Technology-recip, #3 02/2004 and #30 5/2000. I'm not trying to advertise for AMT, but it has some really good articles from time to time.

Hope it helps
ChD



"Never trust a clean Crew Chief"
User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 2, posted (10 years 3 months 3 days 16 hours ago) and read 1048 times:

To add to the above, most TCM Continental big-bore turbocharged engines require the use of a specific part to assure accurate compression readings.
This master oriface tool is very important. In addition, Continental has recently released information that under certain circumstances, valve leakage may be allowed, to a small degree.
Under the TCM procedures, readings below 60 are allowed, in certain cases.


Top Of Page
Forum Index

Reply To This Topic Compression Checks
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Air Tahiti Nui A340 C-Checks posted Fri Oct 27 2006 03:41:34 by Corsair2
Air Compression And Combustion Chamber Question posted Fri Oct 6 2006 01:29:43 by Blackened
A, B, C, D Checks On 3rd World Airlines. posted Sat Jul 1 2006 11:34:38 by Jafa39
FIM & Transit Checks. posted Fri Jun 2 2006 12:02:55 by HAWK21M
Medical Checks - Mx Personnel. posted Fri Apr 14 2006 10:58:53 by HAWK21M
New EU Aviation Law / Security Checks posted Tue Dec 20 2005 03:10:32 by Starline
Maintenance Checks Deciphered? posted Mon Dec 5 2005 17:47:35 by DeltaGator
A320 Series Up For FAA Checks Following JetBlue posted Fri Nov 25 2005 14:07:43 by Julesmusician
Visual Checks On Aircraft In Quick Turnarounds posted Sat Oct 29 2005 01:14:41 by Julesmusician
C And D Checks posted Wed Aug 24 2005 19:23:18 by Amirs

Sponsor Message:
Printer friendly format