Runway 17, Alpine County (M45)Reciprocating engines use petroleum oil to lubricate surfaces. A running engine's critical surfaces are kept apart by a very thin film of oil. A piston pushes on a rod which pushes on a crankshaft bearing surface (called a journal). This is where reciprocating movement is changed into rotational movement. The downward force by the fuel burn on the top of the piston is tremendous. It's 0.5-2 thousands of an inch of oil that keep metal-to-metal contact from occurring at the bearing surface when these forces occur. Also, protection of this surface under high load conditions requires that the oil is warm (usually around 180 degrees F.). Putting a high load on a cold engine immediately after starting is destructive because oil that was on the surface when the engine last ran has drained off, it is hard for the pump to move viscous cold oil to the bearing surface and when the oil flow reaches the surface its lubricating properties are poor until it warms up. Learn to position the throttle so that when the engine starts RPM is around 1000 or less.
On cold days with cold engines, prime the engine early, right after checking fuel quality. An engine will not start unless vaporized fuel is available to the cylinders. An engine will not start well or at all on atomized or liquid fuel. Trying to start an engine without vaporized fuel and flooding are the common causes of pilots grinding on the starter motor to get the engine to start. Grinding a starter motor for extended periods can deep cycle the battery. On a cold day with a cold engine, an early prime allows time for fuel vaporization. By doing this you will usually find that your engine starts up easily with very little load on the battery. Be sure to skip the priming item in your check list if you do an early prime. If you would rather to do it according to an approved check list, then prime, but wait a minute or so (with the master switch off!) before activating the starter motor. Large, high horsepower engines start noticeably easier when primed in this fashion. Bonus question: why wait until after checking fuel quality before doing an early prime?
Airplane batteries are not made for deep cycling. This means that if you severely draw an airplane battery down a few times, it's ready for the trash heap because it will never again hold a charge. (Cruising sailboats have deep-cycle batteries because they are drawn on for many hours between engine operation when the battery is recharged. Automotive batteries will fail after about 30 deep cycles whereas they will last for thousands of cycles if only used for starting, a 2-5% discharge. Marine batteries are designed to handle 80% discharges over and over.). If you find this topic electrifying, see http://www.windsun.com/Batteries/Battery_FAQ.htm.
If you have cowl flaps and it is a cold day, don't open the cowl flaps during start, taxi and run up. Most manufacturers state something to the effect: open cowl flaps as required. Watch your temperatures. Cowl flaps are required with high cylinder head and oil temperatures, not likely for a first start of the day and several minutes after on a 40 F. morning. With the cowl flaps closed, your engine oil will heat faster. Run ups should be done with the oil temperature needle in the green and this can take time with a cold start on a big engine especially on a cold day. When you cycle the prop you are making sure the governor and prop are functioning and at the same time applying warm oil to the prop hub cylinder. That oil isn't going to be very warm if you do the prop cycle with cold engine oil. (I won't get into the religion of prop cycling during run up)
Be kind to your engine and it will be kind to you (and your wallet).
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