Cylinder Compression Check

The standard compression check using 80psi  air pressure upstream of a standard orifice and measuring the downstream pressure which the cylinder can maintain. The tester is connected upstream to a source of compressed air and the downstream connection is screwed into a spark plug hole. This can identify issues with wear of piston rings and  valve seats. Normally done when the engine has been warmed up to normal operating temperature  (preferably after a one hour flight).  However there are issues with repeatability and low compression readings should be followed up by a Borescope inspection to confirm if there is a real problem in terms of cylinder wear etc.( In other words we don't panic and decide to take off one or more cylinders just because we get a low compression reading.)

Compression Tester