Engine Break-in Procedure (Post Flight)
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Understanding what happens in the engine during the break-in process allows us to comprehend the ideas behind how we should operate the engine after piston rings have been changed. The normal prescribed flight procedure after ring replacement is to keep ground running to a minimum, take off at full power and reduce to climb power at the first available safe altitude, all while keeping the climb angle flat and the climb airspeed higher to promote the best cooling possible.

At cruise altitude we should use 75% to 85% power.  At all times we are to remember that heat is the greatest enemy of engine break in, we should try to maintain all engine temperatures in the green, well away from the top of the green arc or red line.  This means step climbing the aircraft if necessary, and operating with the cowl flaps open or in trail position during cruise flight.  We should avoid running the engine above 85% power in cruise flight because the B.M.E.P is too great and the likelihood of glazing increases.  Periodic climbs at full power act to achieve a higher than cruise B.M.E.P. and helps to seat the rings.  As you can see, keeping the engine as cool as is practical and at a conducive power setting is the best combination for successful engine break in.

To properly seat the piston rings in a newly overhauled engine, takeoff at full throttle (or climb power), lean engine per operating handbook (be observant of the oil temperatures; do not let it get too high), cruise at 75% to 85% power.  Do not operate the engine for extended periods of time at a fixed power setting.  Very the RPM, manifold pressure (fly at various altitudes; i.e., descend 1000 feet and climb back to cruise altitude at full throttle (climb power)), and engine cylinder head temps for the first 30 hours.

Applying loads to the engine for short periods of time, such as during a climb, causes increased ring pressure against the cylinder walls and helps to seat the rings. This is especially important because you are "breaking-in" the engine with heavy duty oils. The deceleration (descending) increases vacuum in the combustion chamber and gives extra lubrication to the piston and ring assemblies.

Installation Checkout
Engine Test Runs
Flight Test
Post Flight

Post Flight: (After landing and shutdown)

1. Check for leaks at:
. . . a. Fuel and oil fittings
. . . b. Accessory section parting surfaces.
2. Check tightness of rocker box cover screws, oil scavenge, intake hoses, and exhaust system.

3. Remove oil suction screen and oil pressure screen or oil filter to check again for contamination
4. Compute fuel and oil consumption and compare to limits given in operator's manual.
. . . If consumptions vary from figures shown in manual:
. . . Determine the cause before releasing the aircraft for service.
5. After all discrepancies have been corrected and the aircraft and engine conform to manufacture's specifications:

. . . The aircraft may be returned to service

Return to Service: (The owner's responsibilities)

1. Before each flight
. . . a. Check engine for obvious leaks.
. . . b. Check baffles and baffle seals for integrity
. . . c. Monitor oil consumption
2. At 5 hours since major overhaul
. . . a. Inspect engine for leaks.
. . . b. Check engine operations on ground with normal run-up.
. . . c. Change oil, inspect suction and pressure screens or oil filter element.
. . . d. Check tightness and integrity of:

. . . . . . • rocker box cover screws
. . . . . . • baffle attaching screws and baffle seals
. . . . . . • oil breather tube
. . . . . . • intake hoses and exhaust system.
. . . e. Remove and inspect lower sparkplugs for oil or oil mist.
. . . f. Adjust lifter clearances of all engines not having hydraulic lifters per manufacturer's service manual.
3. Repeat step 2 at 15 hours since major overhaul
4. Repeat step 2 at 25 hours since major overhaul
5. Repeat step 2 at 50 hours since major overhaul
6. Each 25 hours thereafter
. . . a. Inspect engine for leaks.
. . . b. Change oil, inspect suction and pressure screens or oil filter element.
. . . c. Check tightness and integrity of:

. . . . . . • rocker box cover screws
. . . . . . • baffle attaching screws and baffle seals
. . . . . . • oil breather tube
. . . . . . • intake hoses and exhaust system.
7. Each 100 hours thereafter
. . . a. Remove and inspect lower sparkplugs for oil or oil mist.
. . . b. Adjust lifter clearances of all engines not having hydraulic lifters per manufacturer's service manual.
. . . c. Check tightness and integrity of:

. . . . . . • rocker box cover screws
. . . . . . • baffle attaching screws and baffle seals
. . . . . . • oil breather tube
. . . . . . • intake hoses and exhaust system.

Good luck.  Fly safe.