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Saturday, March 2, 2013

Engine Overhaul - a Quick Overview

There are two reasons MMS Aviation overhauls reciprocating aircraft engines. One is to give the operators of airplanes used in Christian ministry a top quality engine overhaul at as reasonable a cost as possible (it's still expensive). The other reason is to give MMS' apprentice mechanics the experience of overhauling an engine. It isn't likely that any of them will perform an engine overhaul in the field, but having the experience will help them maintain the engines under their care.

Heartland Embrace, a ministry in Central Wisconsin, sent their Cessna Cardinal to MMS for an engine overhaul and some airframe work. The first step was to remove the engine from the plane after which the engine was disassembled in the engine shop.

Scott starts the process by removing the propeller.

Lots of photos are taken for reference at this stage.
A digital camera is a very important tool during engine removal and disassembly, as pictures are a great help in remembering how hoses, fittings, and wiring go back in the right place. Engine accessories and many parts that will be re-used are sent to specialty shops where non-destructive inspection, reconditioning, and certification take place. MMS does not do a volume of engine work to justify having these specialty services in-house. When all the parts to be re-used are back and new parts have arrived, measuring and reassembly begins. All dimensions are kept in the engine's work records.

Geoff measures a hole in the crankcase where a tappet body will ride.
Checking the camshaft timing on the partially assembled engine.
Once the engine is back together with its reconditioned and new parts, it must be tested. Part of MMS' engine overhaul facility is a test cell, a room designed to minimize noise and provide a place for safe engine operation.

In the test cell, instrumentation is connected to monitor engine condition throughout the test.
Nearly ready to run, the test propeller is on. An air scoop will be installed to direct the cooling air over the engine.

The "hood" is up so adjustments can be made.
The Heartland Embrace engine was operated briefly in the test cell yesterday afternoon. The full test will be performed Monday. Stay tuned.