Let’s toss the esoterica for the moment. A few months ago, I offered some winter flying tips. Now here are a few hot weather tips to enlist in the fight against rising fuel costs, fewer maintenance technicians, and staying on the sunny side of that line between an airworthy system and a boat anchor. This is not an exhaustive treatise, but most people don’t give too much thought to some very important and very valuable actions, including:
ACTION 1: Just because winter is gone doesn’t mean there’s no longer any benefit from pulling the prop through a few blades during your preflight. Just remember that the prop may be ‘live.’
- You’ll hear the magneto impulse couplings “snap,” indicating that they are operating correctly.
- You can feel each cylinder cycle through its compression stroke. You might notice the lower resistance of a weak cylinder and save yourself from an impending problem.
- You’ll be priming the oil pump, ensuring an earlier supply of oil to all moving parts of the engine, greatly improving the chances that the engine will be able to run its full rated service life. Every time you swing the prop a few times prior to engine start, you probably add an hour or two to the life expectancy of the engine.
Important: Always handle a prop as though the engine could start with the slightest provocation. Make sure that the fuel selector and ignition switch are both OFF, with the mixture at the cut off stop. The airplane must be tied down, with the parking brake on.
ACTION 2: A strong indication of oil pressure — at least to the bottom of the green — should be visible within 30 seconds of engine start (in cold weather, make this a minute).
Important: Be sure to keep the engine speed and load down for that first 30 seconds and don’t exceed idle speed until it’s well into the green. Try not to exceed 1500 RPM (and preferably 1000 RPM or slightly less) for that first 30 seconds. Keep your eyes on this — the throttle setting that gave 1000 at start-up will invariably result in faster revs a few seconds later as the engine loosens up.
During and shortly after startup, cold oil is being pumped and splashed through the engine to vital engine parts — even when it’s warm outside. Operation with heavy engine loading or high power settings, combined with low oil pressure, will reduce engine life and possibly lead to catastrophic damage. A little care is all it takes to avoid this.
ACTION 3: Leaning… While running the engine or taxiing in high density altitude conditions, lean as much as you can and still have the engine run smoothly. This will reduce lead fouling on the spark plugs, as well as lead and carbon build-up on the valves and lead contamination of engine oil.
Important: Be sure to enrich the mixture prior to run-up and takeoff! (With density altitudes above a few thousand feet though — or any extreme high density altitude conditions — leaning to peak rpm for fixed-pitch prop takeoffs, or best power for constant-speed props, often becomes necessary to ensure smooth engine operation.)
Proper leaning means proper operation of your engine. Proper mixture control extracts the maximum performance from the engine — in all phases of flight. A great deal has already been said about this and the more we know, the better off we all are.
ACTION 4: Another time to avoid overworking an engine is during the run-up. Don’t ‘deep-cycle’ the prop! (This applies in the winter, too.) That is, don’t allow the rpm to drop way down to a minimum before returning the prop back to the high rpm setting. Overworking an engine can de-tune crankshaft counterweights. One can generalize even further: avoid rapid throttle movements, period!
Important: While cycling the prop, the primary instrument to watch is the manifold pressure gauge — not the tachometer. An increase in manifold pressure is caused by increased engine load. The secondary instrument to check is the oil pressure gauge, which will drop as oil is diverted to the prop governor.
Rapid throttle movement and the resulting sudden changes in mixture and engine speed can have a devastating effect on the moving parts of an engine. That’s one reason why the typical life expectancy of most racecar (also racing-airplane) engines is approximately five to eight hours. On those engines equipped with internal dynamic counterweights, this is especially true. De-tuning the counterweight system of the engine is caused by operation of the engine outside its normal range and by abrupt throttle changes. When this happens, the dynamic counterweights cannot follow the spectrum of frequencies for which they were designed, and rapid and severe damage to the counterweights, rollers, and bushings may result, which could lead to engine failure or severely shortened engine life. Use gradual, smooth throttle movements (whether it’s a normal takeoff, a go-around, or whatever)—except of course, for emergencies. Learning to operate an engine conservatively and within safe parameters will keep you from overworking your engine.
ACTION 5: Keep your plane in the prop blast of the one ahead.
Important: This one is offered somewhat hesitantly. You should only put your aircraft in another’s prop blast if — and only if — you know your run-up area is clean. Otherwise, you will be subjecting yourself to flying debris.
The obvious benefit here is better engine cooling.
MONEY SAVERS: When you’re done flying for the day, leave the fuel levels approximately one to one and a half inches below the filler neck — especially if you’re getting fuel from a cool source and it’s likely to remain hot where your plane is kept. This will minimize dumping of fuel through the vent system as it expands when the sun heats the airplane fuel tanks. If you have sunshades, use them. (If you don’t, buy some!) They really do extend the life of avionics and interiors. And remember to use cowl plugs, pitot covers, and other coverings to discourage birds and insects from setting up house in your airplane. Leave two-bladed props in the horizontal position (and three-bladed props with one blade pointed straight down) when parking your plane in an external tie-down. This provides the lowest profile and may keep the prop from being struck by the wingtip of a plane passing by or maneuvering to park nearby.
BOTTOM LINE: Good preventive maintenance doesn’t always require that you have a wrench in your hand, but it could provide as much benefit as any maintenance that is done with one.