Friday, December 28, 2012

De-Preservation For Lycoming engines:


                        It is important to remember that long-term preservation of engines can result in trapping large amounts of oil in the combustion chambers of one or more cylinders. For this reason, engines should not be rotated until all of the preservative oil is drained away. Failure to do so can result in damage to the piston, connecting rod, and crankshaft of the flooded cylinder.
                         To return the aircraft to service, remove seals, tape, and desiccant bags. Use a solvent to remove tape residue. Remove spark plugs or dehydrator plugs. With the magnetos off, rotate the propeller by hand through sufficient rotations to remove excess preservative oil from the cylinders. Drain the remaining preservative through the sump.

                   Most engines are equipped with a quick-drain oil fitting on one side of the oil sump and a standard AN plug on the other. Remove both in order to drain as much of the preservative oil from the sump as possible. Uninstalled engines should be hoisted level, then tilted as required to aid in draining of the oil.
                      If the spark plugs were installed in the flooded cylinders, all traces of oil should be removed from the firing end and the external barrel with clean solvent or MEK prior to reinstallation.
              Remove all dehydrator bags, tape, plugs, and barrier paper from the induction system, exhaust ports, breather lines, and so on. Drain and flush the carburetor or other fuel components with fuel, and re-safety all drain and vent plugs as necessary. Check all fuel and oil hoses and intake ducts for security and leaks.
           After servicing the oil sump with the proper grade of oil, wash and pre-flight the engine and engine compart-ment, perform a ground run to operating temperature, and check for leaks. If all is satisfactory, install the cowling and make a logbook entry noting the reversal of the preservation process.
             Keep the first flight local to be sure there were no items missed or loose items. Double check for any pest dam-age or roosting, as well as hand operate all control surfaces to feel for any signs of binding or corrosion in hinges.

That includes a visual check and light thumping on the tail and control surfaces, as well as the gear wells and en-gine compartment to assure there are no stubborn tenants or nest residues. If there is any signs of varmints or in-sect activity, more serious investigation is called for such as panel removal and the use of a borescope. If you plan on not doing all these things for storage, at least consider doing some of them such as the dehydrator plugs and desiccants as well as the use of vapor corrosion inhibitors) VCI technology for the cabin and avionics.
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