A few simple tasks performed each time you fly will help to identify potential problems before they become a safety issue and will also help to prolong your engine life.
VISUAL INSPECTION OF THE ENGINE
Conduct a thorough visual inspection of the engine. Check that there are no obviously loose or missing items (magnetos, starters alternators etc may have come loose on the previous flight). Check oil level and check for oil leaks. Check that the engine baffles and baffle rubbers are in place. Check that no lines or hoses have become chaffed. Check that no items are rubbing against the exhaust system.
PULL THE PROPELLER THROUGH
Caution: Ensure that the ignition/magneto switches are in the off position before pulling the propeller through and stand clear of the propeller at all times.
By pulling the propeller through 2 or 3 revolutions you will be able to feel the resistance from the compression stroke of each cylinder. The compression resistance of each cylinder should feel even. If you feel less resistance it indicates that a cylinder may have a compression leak past the exhaust or inlet valve or past the cylinder rings. If you do find a “soft cylinder” have it investigated and repaired. Operating an engine with cylinder compression leaks can lead to more serious problems such as burnt exhaust valves, holed pistons, and in some cases complete engine failure. Another advantage of pulling the propeller through is that is helps to spread a lubricating film of oil over internal engine surfaces prior to starting.
Start the engine and check the oil pressure is in its normal range. Keep RPM (and load on the engine) to a minimum while the engine warms up. High RPMs before the engine has had the opportunity to warm up can lead to the premature wear of internal parts due to lack of lubrication. Many of the internal engine parts are splash lubricated, most notably the camshaft lobes/tappet body faces in Lycoming engines. Sufficient time should be allowed for the splash lubricated parts to receive a good coating of oil and for the oil to warm up before increasing power above 1500 rpm. A second reason to properly warm up the engine is that until the engine reaches its minimum operating temperature, some of the important internal clearances may be outside the desired operating range. As a part gets hotter it expands. Operating the engine at high power settings before the engine has had the chance to warm up may lead to premature wear due to incorrect clearances.
Aggressive leaning on the ground at idle can help to avoid fouled spark plugs. If you do lean the mixture while idling and taxiing, lean it so much that if you open the throttle the engine will cut out. This helps to prevent the engine from being operated partially leaned at higher power settings. Remember unless you are at a very high density altitude most takeoffs should be performed at full throttle and full rich mixture setting.
RECORD ENGINE OPERATING PARAMETERS (DATA LOGGING)
Keeping a simple log of important engine operating parameters can be very useful in determining if any changes are occurring to your engine over time.
Logging engine parameters enables you to identify trends. For example, if idle oil pressure has consistently been around 45PSI at 700RPM with an oil temperature of 185°F and you then notice it slowing dropping to 35PSI, it is a good indication that something has changed within the engine.
Good information allows you and your maintenance personnel to identify potential problems before they seriously affect the engine operation, cost you a lot of money, or create a safety concern.
To obtain consistent information, try to record the parameters under the same operating conditions. For example, in most engines oil pressure changes with oil temperature and engine RPM. Therefore to obtain consistent oil pressure readings, always try to log the oil pressure at a given RPM and temperature.
An example of a simple manual Engine Condition Log is shown at the end of this section.
AVOID RAPID CHANGES TO POWER SETTINGS WHERE POSSIBLE
Where possible smoothly increase or decease the engine power.
Try to avoid rapid changes to power settings and engine RPM.
When cycling the propeller, do so slowly. On engines equipped with counterweights, rapid RPM changes can cause premature wear of the counterweight bushes and pins and the subsequent detuning of the counterweight system. Detuned counterweights no longer absorb the vibrational energy at the desired frequency. When not absorbed, this vibrational energy can cause many maintenance problems from cracked engine baffles and propeller spinners to broken crankshafts. On sandcast Continental IO-520 series engines, an alternator belt that keeps coming off is a sign that the counterweights have become detuned.
ALLOW THE ENGINE TO COOL DOWN BEFORE SHUT DOWN
Use your engine monitor as a guide to see when your engine is cool enough to shut down.
For many aircraft, the coolest your engine will be is at the end of your landing rollout, especially after a long descent. Taxiing to the parking area or your hanger may actually warm the engine up.
The above statement applies to both naturally aspirated and turbocharged engines.
Use your common sense, if the CHT are near 300°F, and the oil temperature is 170°F-180°F your engine is cool enough to shut down.
If you are sitting there with the engine idling (aggressively leaned) and after after a minute or two, the CHT’s and oil temperature is not decreasing at any appreciable rate, a longer period of idling the engine is not going to make the engine any cooler.
The one occasion when you many need to idle the engine for longer periods to allow the engine to cool before shutting the engine down, is after you have been out to the run-up bay and conducted a high power engine ground run. This is the one time where you may need to idle the engine for a few minutes to allow the engine to cool down, before you shut it down.
ENGINE OIL FILTERS
We also highly recommend that all engines are fitted with a full flow, paper element type oil filter. Many engines, especially older engines were made with only an oil screen. The old oil screens are generally only a fine wire mesh that will catch rocks and other large bits of debris, but essentially do nothing to filter smaller particles out of the engine oil.
Full flow paper element type oil filters are much better for the following reasons:-
Vastly improved oil filtration over an oil screen.
Much better protection, and less wear of critical engine components due to the superior oil filtration.
Improved detection of potential problems, from the ability of the filter element to hold contaminates which can then be identified when the filter element is inspected.
If your engine is not fitted with a full flow oil filter, and the engine oil system becomes contaminated for any reason, a full strip of the engine will be required to check the condition of the main and connecting bearings and other internal engine parts.
If a full flow oil filter is fitted, in some instances, the source of the engine oil contamination can be corrected and the engine returned to service without the need for the engine to be stripped.
STC’s are now available for nearly all engine and aircraft types to fit full flow paper element type oil filters.
If a full flow oil filter kit is available for your engine, and you elect not to have one fitted, there may also be warranty implications to be considered.