Which 6 Aircraft Cylinder Tools Do You Really Need?

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Robe caraco chiffon Aircraft cylinders are an integral part of your engine and should be treated as such. Understanding which tools help you maintain and repair your cylinders can keep your aircraft healthy and safely flying.

Bordeauxrote trachtenkleider & landhauskleider This article will break down our top 6 aircraft cylinder tools and give a brief description of each.

1. Differential Cylinder Pressure Testers

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Differential compression testing is a tool that maintenance personnel use to check the health of an aircraft cylinder. The test uses two gauges to measure pressure. Compressed air is applied to the tester through the regulator gauge. This gauge indicates the air pressure being applied to the tester. The air then goes through a calibrated restrictor to the cylinder pressure gauge. This gauge indicates the actual pressure in the cylinder. Any compression loss in the cylinder would be shown by a pressure indication in the cylinder pressure gauge lower than that of the regulator gauge. A loss in excess of 25% of the 80 lbs. or a reading of 60/80 is the recommended maximum allowable loss.

The engine manufacturers have guidelines on inspection procedures to coincide with compression tests to help determine the health of the cylinder and the disposition should a reading be below the minimum limit. Be sure to refer to the manufacturer’s instructions for proper procedures and troubleshooting techniques to best determine what action is required.

The correct document for Continental Motors engines is CMI Service Bulletin 03-3. CMI’s procedure involves applying a known pressure into the cylinder bore with the piston at Top Dead Center (TDC) and measuring the reduced pressure in the combustion chamber due to leakage. For CMI engines, the pressure is generally input through the top spark plug port and the pressure is measured with the differential compression tester.

CMI requires the use of a master orifice tool , (use with the differential pressure tester 2EM2EM-60ETC’s E2A, or E2A-1000 depending on your bore size) to obtain the master orifice reading. Test results are unreliable unless the master orifice tool is utilized. SB 03-3 also states that you can also use ETC’s E2M or E2M-100, depending on your bore size, which incorporates the master orifice tool. There are so many factors in play regarding the differential compression test readings so make sure you follow, with discipline, CMI SB 03-3 which defines the procedures for obtaining accurate differential compression tests.

Lycoming’s maintenance manual follows closely with the FAA’s AC 43.13 which states that if a cylinder has less than a 60/80 reading on the differential test gauges (ETC’s differential pressure tester E2M or E2M-100 depending on your bore size) on a hot engine, and procedures in paragraphs 815b(5)(i) and (j) fail to raise the compression reading, the cylinder must be removed and inspected.

Most maintenance manuals allow an engine to continue to operate despite dropping below the 60/80 pressure differential but Lycoming offers a bit of caution and recommends further investigation. They encourage owners of aircraft not to readily accept a below 60/80 reading and to investigate the cylinder further before rejecting it.

The differential pressure test is the best method of checking compression, and particularly so when the readings are charted as a trend over a number of routine inspections. It is a good tool for preventive maintenance and aids in avoiding in-flight failures. Cross checking is good procedure, rather than relying on one source of information concerning the condition of the combustion chamber.


2. Cylinder Base Wrench Set


A.E.R.O. offers an ATS cylinder base wrench set which contains all 4 twelve-point cylinders base wrenches (sizes: 1/2”. 9/16”, 5/8”, and 3/4”) in 1/2” drive. These cylinders work on all Continental engines and all Lycoming wide-deck engines.

A.E.R.O. also offers a Lycoming cylinder base wrench set which contains a set of 2 internal hex wrenches specifically designed to install and remove Lycoming old style internal wrenching nuts found on narrow-deck Lycoming engines. These wrenches are bent to allow you to get to the cylinder base nuts when the cylinders are installed on the engine. There are different sizes required for different engines, so make sure to check which size you need.


3. Flex Hone Tool


The flex-hone tool is a resilient, flexible honing tool used to improve the internal surface finish of a bore or cylinder. It is comprised of abrasive globules laminated onto the ends of flexible nylon filaments. Its unique construction allows the tool to be self-aligning, self-centering, and self-compensating for wear. The tool provides the benefit of removing loose, torn and folded metal and creating a substantially flat or plateau surface. An additional important application for the Flex-Hone Tool is burr removal from cross-drilled holes.

The flex-hone tool is manufactured in 8 different abrasive types and 11 different grit selections in a wide selection of sizes to work on a broad variety of base materials and surface finish requirements. The tool is produced in diameters from 4mm to 36″. A flex-hone tool’s diameter is determined by the nominal bore size in which the tool is to operate. A cylinder hone is always produced and used in an oversized condition. Using an oversized hone creates pressure and a soft cutting action on the cylinder walls. For example, a 1” flex-hone tool is used to finish a 1” bore to provide the proper cut. If the bore size is between standard flex-hone sizes, the next larger standard flex-hone should be used.

The flex-hone tool always requires the use of a lubricant and it can be used until there is virtually no abrasive left on the filaments. Cutting curves can be plotted to show when to replace the tool.

4. Piston Ring Compressor Set


The piston ring compressor set  features a quick-change design to speed up piston ring installation. It includes the famous Hastings Ring-O-Matic pliers and bands that operate in all positions, not just vertically or horizontally. The pliers incorporate a precision locking action for exact holding and quick release.

The complete kit includes the Ring-O-Matic pliers and one of each of the following size bands: 3-7/8″ to 4-1/8″, 4-1/8″ to 4-1/2″, 4-1/2″ to 4-3/4″, 4-3/4″ to 5″, 5″ to 5-1/4″, and 5-1/4″ to 5-3/4″. These pliers and bands have useful agility and operate with ease. If you are looking for rapid piston ring installation, this tool kit is ideal.


5. Piston Ring Installer


Handling piston rings can be tricky at times. A piston ring installer is inexpensive and can be relatively easy to use. Just insert the ring ends into the wedge jaws, expand the ring gently, and slip the ring into the groove. You have successfully installed a piston ring! This tool can handle piston rings from 3/64” to ¼” wide and is also ideal for removing rings easily without damage, saving you time and money!


6. Valve Spring Compressor


The valve spring compressor is adjustable to service every Continental or Lycoming engine with ease. The ring installs on rockers and the “C” collar compressor spring to allow keeper removal. This is a great tool to keep handy. Do-it-yourself aircraft owners and professional technicians alike will love this efficient, hassle-free tool.

The next time you are removing, replacing, or repairing your aircraft cylinders employ some of the tools you just read about to help ease the process.

By making a job more enjoyable, you can make it something you do more often and won’t dread!

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  1. Robert Smith Jr Robert Smith Jr
    October 15, 2015    

    how about TORQUE WRENCHES?????

    • October 16, 2015    


      Great suggestion. Seems like a smart addition to any pilot or mechanic’s tool arsenal!

Have something to add? Commenting puts you in the pilot’s seat!

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