#17 - Engine & Cylinder Break-In:
These instructions should be followed for freshly overhauled engines and/or replacement cylinders. These instructions apply to steel or nickel barrel cylinders.
RAM overhauled Continental engines are adjusted to meet engine specifications in our test cell prior to shipment, and the fuel system is set up on a flow bench. The installing mechanic must make final adjustments on the airframe in accordance with the Continental M-0 Standard Practice Maintenance Manual.
The break-in procedures below are excerpted from Continental’s M-0 Standard Practice Maintenance Manual:
(Items in yellow are RAM commentary)
RAM has completed the steps in 7-2.3 on overhauled engines. Skip to 7-2.4.
7-2.3. Engine Operation after Cylinder Replacement and/or Major Overhaul
Proper operation of the engine following cylinder replacement or major overhaul is extremely important. The following procedures should be followed to ensure that adequate lubrication is being provided to newly installed components and that the piston ring seating will occur as soon as possible.
1. Operation after Major Overhaul, Utilizing an Engine Test Cell:
a. Servicing and Pre-starting Procedures
1) Service the lubricating system with mineral oil of the appropriate grade depending on ambient temperature (Section 3-1).
2) Rotate the propeller by hand through several cycles with the spark plugs removed.
3) Pre-oil the lubrication system using an external pre-oiling pressure system according to the instructions in Section 5-2.9. Spark plugs are installed during the pre-oiling instructions.
b. Test Cell Operational Procedure 1) Perform the Post-Overhaul testing according to the instructions in the engine primary ICA (Ref: Section 1-1.1).
Start here if you have replaced one or more cylinders.
2. Operation after Major Overhaul, Utilizing The Aircraft (in lieu of an engine test cell): The aircraft can be considered a suitable test stand for running-in overhauled engines contingent on the following conditions.
a. Install engine cowling.
b. Each cylinder should be equipped with a temperature sensing device to monitor the head temperature. If the aircraft cylinder head temperature gauge monitors one cylinder, the following precaution must be adhered to: During ground runs do not permit monitored head temperatures to exceed 400°F or oil temperature to exceed 200°F. RAM recommends you follow these temperature limitations with single point or multi-point gauges.
c. The flight propeller may be used contingent on careful observation of cylinder temperatures. Head the aircraft into the wind for this test.
d. Calibration of the aircraft engine instruments must be performed.
3. Operation after New Cylinder Installation or Cylinder Overhaul:
CAUTION: Corrosion preventive mineral oil MIL-C-6529 can be used but must not be used after the first 25 hours, or six months, whichever occurs first as this oil can cause coking with extended use.
a. Service the lubricating system with mineral oil of the appropriate grade depending on ambient temperature. RAM recommends AeroShell Oil 100.
b. Ensure all engine and cylinder baffling is serviceable and properly installed.
c. Start the engine and verify oil pressure rises to within the specified limits within 30 seconds.
d. Operate the engine at 750 RPM for one minute; gradually increasing toward 1000 RPM in three minutes. Check the magneto circuit for grounding prior to a normal shut-down. Allow the engine to cool adequately and then perform a visual inspection for any irregularities.
e. Start the engine again and operate it at 750 RPM; gradually increasing to 1500 RPM over a period of four minutes.
1) If the engine is equipped with a controllable pitch propeller, cycle the propeller allowing only a 100 RPM drop.
2) Return to the idle range and make adjustments to the idle mixture and RPM as required on carburetor engines and to the low unmetered fuel pressure, idle RPM, and mixture on fuel injected engines.
3) Position the throttle to 1200 RPM to smooth the engine. Then, perform an idle mixture rise check. For continuous flow fuel injection systems, refer to Section 6-4.7 for fuel system specifications. For engines equipped with carburetors, refer to the primary ICA.
4) Run engine up to full power for a period not to exceed 10 seconds. Visually inspect and correct any discrepancies. Check the oil level and service if required.
5) Install aircraft accessories and cowling according to the aircraft manufacturer’s instructions.
f. Perform a “Flight Check” and “Engine Break-In” according to the instructions in Section 7-2.4.2 and Section 7-2.4.1.
7-2.4. Flight Check and Break-In
New and factory rebuilt Continental engines are adjusted to meet engine specifications in a test cell prior to shipment. A flight check ensures the engine meets operational specifications after installation in the airframe and prior to release for normal service.
Perform an “Engine Operational Check” according to instructions in Section 6-4.7 and a normal preflight, engine start and ground run-up in accordance with the Airplane Flight Manual or Pilot’s Operating Handbook (AFM/POH) before the A&P mechanic can approve the airplane for a Flight Check.
A flight check is required for engines with a standard fuel pump if rated, full power RPM cannot be verified during a ground run-up according to instructions in Section 7-2.4.2 after engine installation, inspection, fuel system repairs, or adjustments. Additionally, engines with an altitude compensating fuel pump require a “Flight Check” according to instructions in Section 7-2.4.2 after a significant change in geographic location from the last operational check (or if the auto-leaning function is suspect) and at twelve month intervals, in conjunction with the Annual/100-hour inspection. Follow the protocol in Section 7-2.4.1 to complete the recommended break-in period.
7-2.4.1. Engine Break-In
CAUTION: High power ground operation resulting in cylinder and oil temperatures exceeding normal operating limits can be detrimental to cylinders, pistons, valves, and rings.
The recommended break-in period for Continental engines is 25 hours. Adhere to the following instructions and the Engine Specifications and Operating Limits in the primary Instructions for Continued Airworthiness (Section 1-1.1) applicable to the engine model.
NOTE: Keep flying weight to a minimum to reduce power requirements.
1. For the initial flight after release to service, fast idle (850-1,000 RPM) engine for 3-4 minutes. Shut down and inspect for oil leaks. During ground runs, do not permit cylinder head temperatures to exceed 400°F or oil temperature to exceed 200°F.
2. Conduct a normal engine start, ground run-up and take-off according to the AFM/ POH (minimize ground time).
3. Monitor a) engine RPM, b) fuel flow and pressure (if equipped), c) oil pressure and temperature, d) cylinder head temperature (if equipped), e) exhaust gas temperature (if equipped), and f) turbine inlet temperature (if equipped) to verify the engine is operating within the parameters specified in the primary Instructions for Continued Airworthiness (Section 1-1.1).
4. Reduce the engine speed to climb power according to the AFM/POH instructions. Maintain a shallow climb attitude to achieve optimum airspeed and cooling airflow.
5. At cruise altitude:
a. Maintain level flight cruise at 75% power with best power or richer mixture for the first hour of operation.
b. For the second and subsequent hours of flight, alternate cruise power settings between 65% and 75% power with appropriate best power mixture settings.
NOTE: Best power mixture setting is 100°-150°F (38°-66°C) rich of peak exhaust gas temperature. Adjust engine controls or aircraft attitude to ensure engine instrumentation operates within specifications.
WARNING
Avoid long descents at high engine RPM to prevent undesirable engine cooling. If power must be reduced for long periods, adjust the propeller to minimum governing RPM to obtain desired performance levels. If outside air temperature is extremely cold, it may be desirable to increase drag to maintain engine power without gaining excess airspeed. Do not permit cylinder head temperature to drop below 300°F (149°C).
6. Descend at low cruise power settings. Avoid long descents or descents at cruise power RPM with manifold pressure below 18 in. Hg. If necessary, reduce engine RPM to the lower limit of the specified operating range to maintain sufficient manifold pressure. Carefully monitor engine instrumentation to maintain levels above the minimum specified cylinder head temperature and oil temperature.
7. Correct any discrepancies prior to releasing the aircraft for service.
7-2.4.2. Flight Check
Flight check instructions vary, depending on fuel system configuration, naturally aspirated engines with a carburetor:
• For Continental continuous flow fuel injection systems without altitude compensating fuel pump, or turbocharged engines regardless of fuel system configuration, follow the Standard Flight Check Instructions in Section 7-2.4.2.1.
• For naturally aspirated engines with Continental continuous flow fuel injection systems with an altitude compensating fuel pump, follow the Flight Check instructions in Section 7-2.4.2.2.
• For FADEC equipped engines, refer to the flight check in the primary ICA.
7-2.4.2.1. Standard Flight Check Instructions
NOTE: The accuracy of tachometer and fuel flow indicating device (if equipped) is critical to the outcome of the flight check. Verify tachometer and flow meter accuracy according to the aircraft manufacturer’s instructions prior to performing the flight check.
1. Conduct a normal engine start, ground run-up and take-off according to the AFM/ POH.
2. Monitor a) engine RPM, b) fuel flow and pressure (if equipped), c) oil pressure and temperature, d) cylinder head temperature (if equipped), e) exhaust gas temperature (if equipped), and f) turbine inlet temperature (if equipped) to verify the engine is operating within the parameters specified in the AFM/POH.
3. If the engine fails to reach the rated, full throttle RPM during ground operations, ascend to cruise altitude (>2000 feet above field elevation) and verify the engine achieves full throttle, full rich rated RPM at cruise altitude and operates within the limits specified in the AFM/POH; if the engine meets full power, rated RPM, proceed to step 4. If the aircraft indicated values fail to meet the published limits, repeat the Engine Operational Check and Flight Check.
WARNING
All abnormal conditions must be corrected prior to releasing the aircraft to normal operation.
4. Release the engine to normal service.
7-2.4.2.2. Flight Check for Continental Continuous Flow Fuel Injection Systems with Altitude Compensating Fuel Pump
NOTE: For engines equipped with Bendix/Precision servo controlled Fuel Systems with automatic density controllers, consult the primary ICA or AFM/POH for Flight Check instructions.
NOTE: The accuracy of tachometer and fuel flow indicating device (if equipped) is critical to the outcome of the flight check. Verify tachometer and flow meter accuracy according to the aircraft manufacturer’s instructions prior to performing the flight check.
1. Conduct a normal engine start, ground run-up and take-off according to the AFM/ POH.
2. Monitor
a) engine RPM,
b) fuel flow and pressure (if equipped),
c) oil pressure and temperature,
d) cylinder head temperature (if equipped),
e) exhaust gas temperature (if equipped) to verify the engine is operating according to the parameters specified in the AFM/POH.
3. Set altimeter to 29.92 in. Hg.
4. Navigate the aircraft to an area of low air traffic density. Ascend to the minimum pressure altitude which offers unobstructed straight and level flight within the altitude scale presented in the table applicable to the subject engine model shown in Section 7- 2.4.2.3. Record the altitude and corresponding fuel flow at 1000 ft. intervals depicted in Section 7-2.4.2.3 charts on a copy of the “Engine Operational Checklist” on page 6- 167 of this manual.
RESULT:
a. If the engine RPM and full power fuel flow meet the specifications depicted in the Altitude Leaning Schedule for engines equipped with altitude compensating fuel pumps, proceed to step 5.
b. If the engine fails to meet the operating specifications, repeat the “Engine Operational Check” in Section 6-3.7 and make necessary adjustments according to the “Fuel System Adjustment” and “Auto Leaning Schedule Adjustments” instructions in Section 6-3.10.2 and Section 6-3.10.3, respectively.
WARNING
All abnormal conditions must be corrected prior to releasing the aircraft to normal operation.
5. Release the engine to normal service.