/",.:,. SPORTPLANE BUILDER ~.

GOOD SENSEENGINE OPERATIONS

BY TONY BINGELIS

e learn a little about operat-ing our a i r c ra f t engineproperly during our initial

exposure to flight t r a in ing . A l i t t lemore is learned through experience aswe build up flying hours. And, right orwrong, we "learn" even more fromothers dur ing "bull sessions" andhangar discussions where spirited ex-changes of opinions, experiences, and"superior" knowledge on the subjectof aviating abound.

The best and most reliable advice,as always, regarding how to operateyour engine sensibly is naturally ob-tained from the manufacturer's enginemanual for the particular engine youhave installed in your aircraft. It wil lprovide you with the ultimate guid-ance you need.

Unfortunately, such manuals seldomanswer all the questions you may en-counter in the day-to-day operations ofyour engine. I find it most interestingand encouraging to learn that the smallair cooled aircraft engines most of usfly are very reliable and perform quitepredictably when operated properly.

These 4-cylinder aircraft engineswere first introduced many years agoand have changed very little up to thepresent. Among the more plentiful ofthese engines are the 4-cylinder Conti-nenta ls (A65s, C85s, C90s, andO-200s) and the Lycomings (O-235s,O-290s, O-32()s and O-36()s).

They have been operated by liter-ally thousands of owners, operatorsand mechanics for mil l ions of hoursunder a myriad of conditions.

Many operational lessons have beenlearned and many opinions have longsince been formed regarding howthese engines can be operated safelyand efficiently. Do the engine manu-facturers, experts and "old timers"agree? Let's see what you think.

NOTE: To keep this discussionbrief, I will try to confine my subjec-

Turning the prop through four or five blades before attempting to start the engineeach day will give you a number of important cues as to the condition of your engine.How many can you think of? Refer to the text under "Engine Starts."

Don't blast your throttle to get the airplane rolling. Prop vortices will suck up dirt andpebbles even on paved surfaces, use minimum power to get the airplanemoving...then smoothly increase power to keep it rolling.

SPORT AVIATION 81

ENGINE BREATHERAIR/OIL SEPARATOR

OIL CONDENSATERETURNS TOCRANKCASE

PROPELLERGOVERNOR PAD

ENGINE BREATHER

HOSE CLAMPS

AIR/OIL SEPARATORENGINE BREATHER

OIL CONDENSATERETURNS THRU OILFILLER NECK

ALUMINUM TUBINGEXTENSION

OIL BREATHER/SEPARATOR INST'L(CRANKCASE RECOVERY OPTIONS)

FIGURE 1.

live comments and observations to the4-cylinder air cooled carbureted en-gines driven by fixed pitch propellers.These are the most frequently used byhomcbuilders.DON'T BABY THAT ENGINE

That's what most of them say. Sur-prised?

Do you really believe you are treatingyour engine kindly by not using full throt-tle for takeoff... and habitually operate itat very low cruise rpm? If you do, you aremistaken. You will be saving a bit on fuelcosts but may be setting the stage for fu-ture operational problems.. .and possiblyincreased maintenance bills.

Low power settings tend to deprive82 SEPTEMBER 1995

the engine of adequate cooling air andinvite spark plug fouling as well as thebuild-up of cylinder varnish ... none ofwhich is good for a long engine life.

Your aircraft engine, unlike an autoengine, is designed to operate under highpower output conditions. This meansyou can operate your engine at 75% ofits rated power indefinitely. At pressurealtitudes above 7,000 ft. this may requirefull throttle to achieve and maintain. Bycomparison, auto engines are designedfor operations within a much lower 25 to30% range of their rated power.

Before an aircraft engine is issued itsType Certificate by the FAA, it has to becapable of operating at full throttle formany hours during a test stand endurance

run. This must be successfully accom-plished with its oil temperature and cylinderhead temperatures maintained within theirnormal operating range. In view of all this,running your engine for a mere five min-utes at full power during takeoff and climbwill hardly faze your engine.

AS FOR OIL CHANGEFREQUENCY...

The general consensus is that oilshould be changed regularly. Ordinar-ily this is after every 25 hours of flightfor an engine not equipped with an oilfilter—and 50 hours for an enginesporting an oil filter.

Like all generalities there are excep-t ions, aren' t there? What if yourairplane is flown only an hour or soonce a month? Would you let the en-gine go for two years before changingoil? I hope not.

As bad as infrequent flight is on anengine, infrequent oil change is just asharmful... if not more so.

To remove accumulated moisture,contaminates and sludge from the oil,consider changing your oil every fourmonths even if the recommended oilchange hours aren't reached in that time.

OIL CAPACITY VSOIL LEVEL

Your engine's oil capacity may begreater than it needs to be for safe op-eration.

For example, most 4-cylinder Ly-coming engines have an oil capacity of 8quarts. But, did you know that the manu-facturer also states that the oil level canbe as low as 2 quarts and the enginewould be safe to operate?

Certainly, I wouldn't advocate takingoff on a long flight with such a low oillevel in the engine. However, mosthomebuilders soon learn that the ideal oillevel in their Lyeoming is about 6 quarts.

If you try to maintain a full 8 quartlevel, the engine will quickly spew out atleast one quart in short order. Thisequates to a higher oil consumption thannecessary, doesn't it?

THE ENGINE BREATHERFUNCTION

If the belly of your aircraft is dirtywith an oil slick, you can generallyblame that on the copious air-oil va-pors expelled through the enginecrankcase breather.

It could be that an oil separator canhelp keep the belly of your airplane clean

and, also, minimize the loss of oil whileallowing the engine to breath freely.

The usual practice is to install an oilseparator on the f i rewal l and run asmall oil drain line from the separatorback to the engine. Some builders ac-complish this by attaching the drainline to a fitting screwed into a tapped(3/8" NPT) hole in the base of the oilfiller neck, or into a cover plate wherea prop governor would have been in-stalled for a constant speed prop.

A few builders don't like to reintro-duce the excess breather oil residueback into the engine because the oilmay still contain moisture and contam-inants that have passed through a lessthan efficient oil separator.

Rather than returning the expelled oilto the crankcase, why not collect thatsmall amount of oil condensate into acontainer which you can empty periodi-cally ... say at every oil change (seeFigure 1).

And what an ugly looking mess it is...no wonder many builders don't wantthat stuff draining back into their engine.

ENGINE STARTS ANDGROUND OPERATION

Quite a few pilots make a habit ofturning their propeller through about 5blades or more before starting the en-gine. Of course, they are careful tocheck that the ignition switch if OFF.

Even so. care must be taken any timeyou propeller is moved.. .even with theswitch OFF because a "P" lead mayhave become disconnected and the hotmagneto will fire when least expectedunder the right (wrong?) circumstances.

Anyhow, turning the prop throughbefore starting the engine can be use-ful as it will:

1. Help lubricate the cylinder walls,especially if the engine has been idlefor a week or so.

2. Prove that you have compressionon all cylinders.

3. Give you the opportunity to inspectthe condition of the propeller closely.

4. Tip you off if you have a leakyvalve.

5. Verify that your impulse coupleris working.

For better cooling always try to facethe aircraft into the wind especiallywhen awaiting your turn for takeoff.

Avoid high power run-ups on theground because the engine wil l notcool as well as it would in flight.

High power run-ups, if they are

necessary, must be kept brief.After any high power operation, al-

low your engine to idle for a minute ortwo before shutting it down to helpdissipate excess heat.

Avoid r u n n i n g your eng ine un-cowled because it is not good for theengine...the cylinders will cool un-evenly and hot spots may develop.

If it is necessary to check the idlemixture, try to do it quickly, runningthe engine only briefly.

TAXIINGDon't blast the throttle to get your

airplane rolling. Prop vortices willsuck up dirt and pebbles even on pavedsurfaces. The consequence could bebadly chipped propeller blades.

A safer procedure would be to use aminimum of power to get the airplaneroll ing. . . then smoothly increase thepower to keep it moving. This techniquehelps reduce the ability of the propellerblades to suck up damaging particles.

Taxiing at too high an rpm is poorpractice because you will be controllingyour speed by riding the brakes. This is,usually, unnecessary. Even with a freeswiveling nose gear, only an occasional

tap of a brake pedal will be needed tokeep it rolling straight.

Of course, taxiing in a crosswind mayrequire a slightly high rpm ... but beaware of the need for what you are doing.

TAKEOFF AND CLIMBAvoid following another aircraft too

closely down a dusty/dirt runway becauseeven the best air filter won't protect yourengine from ingesting a lot of crud.

Many pilots pull the power back im-mediately after takeoff. I consider thisto be rather risky because it seems moreengine failures occur during the firstpower reduction than at any other time.

For that matter, I see nothing wrongin NOT retarding the takeoff poweru n t i l a safe al t i tude has been gainedand that first turn in traffic is made.

Remember, we are talking about thesmall engined, fixed pitch jobs—notthe big powerful types that are capableof shattering windows unless powerand props are pulled back for climb.Actually, you should be able to climbto a reasonable cruise altitude withoutreducing power.

Many homebuilts, and some ultra-lights, will climb about 1000 fpm.

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SPORT AVIATION 83

OIL RETURN HOSE

OIL BREATHER SEPARATOR

METAL CAN(1 PINT)

STAINLESS STEELHOSE CLAMPS

RESHAPE TO FITCONTAINER

EXHAUST PIPES

•roif '

OIL BREATHER SEPARATOR(OIL CONDENSATE COLLECTOR)

(SCHEMATIC)FIGURE 2.

Therefore, in five minutes of ful lthrottle operation you can usuallyclimb to 5000 feet.. .if you want to gothat high.

My Lycoming O-320A Fuel and PowerChart indicates that with full throttle, myengine, at 8000 ft., will be producing only76.2% of its sea level horsepower...this

Formation flying can be especially hard on the engine and throttle control linkage dueto the frequent throttle movements from full power to idle ... especially at the handsof a pilot new to formation flying.

84 SEPTEMBER 1995

with 23.4" Hg and 2400 rpm, or 24.5" Hgand 2300 rpm. Therefore, 1 can lean aggres-sively even though I may be tooling alongat full throttle.

For safety's sake your electric fuel pump(booster pump), if you have one, should beturned ON for takeoffs and landings.

ON LEANINGI believe in leaning my Lycoming al-

most from the ground, certainly as soonas the throttle is partially retarded. Ly-coming recommends "aggressive"leaning for all power settings of 75%and below.

The higher the field elevation themore useful the initial leaning effort be-comes. . .actually it might be essential forsmoothing the engine for takeoff. Natu-rally, you would not, ordinarily, lean theengine anytime it is putting out full ratedpower (2700 rpm) as detonation be-comes a potential risk.

Anyway, when you come right downto it, most homebuilts flying with a fixedpitch cruise propeller will seldom de-velop full power for takeoff, therefore, ajudicious leaning of the engine duringthe climb should never be a problem.

LET DOWNSAn engine can cool excessively dur-

ing a let down, especially in coldweather. This could be bad as it inviteslead fouling and can lead to cylindercracking and excessive wear.

Start your let down early. By reduc-ing your man i fo ld pressure two orthree inches from your cruise setting,or the rpm by a couple hundred, youcan establish a leisurely let-down with-out causing the engine to coolexcessively. As you lose altitude, don'tforget to readjust your mixture in orderto maintain smooth engine operationduring the descent.

Chopping the throttle and allowingthe airspeed to build up to the pointwhere the windmilling propeller is dri-ving the engine is bad, bad, bad. Keepyour engine warm especially duringcold weather operations.

USE OFCARBURETOR HEAT

The general belief is that enginesequipped with pressure carburetors orfuel injectors are more or less immunefrom carburetor icing problems and needno carburetor heat provision.

There is no doubt however that car-bureted engines are vulnerable to

Don't follow another aircraft too closely down a dusty/dirt run-way because even the best air filter won't protect your enginefrom ultimately ingesting a lot of crud.

carburetor icing and that they must have some provision forcarburetor heat.

Induction system icing problems can crop up even in thesummer when humidity is high and the temperatures areranging up to 90°F simply because the mixture chamber tem-perature can drop as much as 70°F from that of the inlet air.

I learned that my Continental engines were more proneto carburetor icing than are the Lycoming engines I cur-rently fly. I suppose this is partly because the Lycoming'sintake manifolds are routed through the sheltered warmth ofthe engine crankcase. Continental engines, on the otherhand, have no similar set up.

Always apply the carburetor heat before reducing thepower, otherwise, the engine won't produce enough heat toprevent carburetor icing. It really doesn't do much good try-ing to apply carburetor heat when the engine is idling ...there won't be much, if any.

No need to use carburetor heat for takeoff and climbs be-cause icing at full throttle is most unlikely. As for cruise andother flight conditions, you would ordinarily leave the carbure-tor heat in the cold position.

If you experience a loss of power on a damp hazy summerday, suspect the formation of carburetor ice. Use full carbure-tor heat, or none at all, unless you have a mixture temperaturegauge to help you adjust your carburetor throat mixture toabove the 32°F freezing level.

ON SWITCHINGFUEL TANKS

I don't know about you, but I don't look lightly on the sim-ple matter of switching fuel tanks in flight. No, I have never

Start your let downs early. Reduce manifold pressure two orthree inches from your cruise setting and rpm by a couple hun-dred rpm to establish a leisurely let down without subjectingthe engine to excessive ("shock") cooling.

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SPORT AVIATION 85

had a bad experience in this regard, norhave I ever switched to an OFF position,or an empty tank inadvertently. Yet, thereluctance remains. I also avoid walkingunder ladders.

If I have the option, I try to timeswitching tanks when passing by asu i tab le forced l and ing area or anairstrip of some sort.

Following the same line of reason-ing, I always avoid switching tanks inthe traffic pattern just before landingand just before takeoff ... risky prac-tices at best.

As you switch tanks, it is a goodidea to look at the selector valve toconfirm the tank selected and that theselector is not incorrectly positionedbetween tanks.. .it does happen.

On switching tanks, be sure to mon-itor the fuel pressure gauge for a fewmoments, assuming, of course, youraircraft is equipped with one. It wil lquickly show whether or not the tankswitching is successful.

FORMATION FLYINGThis type of flying can be especially

hard on the engine and throttle control

linkage, particularly at the hands ofone inexperienced in the art of forma-tion flying.

Rapid throttle movements, from fullpower to idle, either on the ground orin the air, cause various parts of theengine to expand and contract at dif-ferent rates with engine temperaturechanges. Abnormal wear takes place inthe control linkage and elsewhere eachtime this is done because of the erratictorsional stresses and temperaturestresses induced.

Incidentally, throttle chopping is amajor factor in cylinder head crackingand other engine problems. The prac-tice is equally damaging in fl ightregimes other than formation flying.

IN SUMMARYThese few random thoughts only touch

lightly on the subject of sensible engineoperations. There are many additionalconsiderations that come into play, espe-cially with so-called "high-performance"aircraft where the engine drives a con-stant speed propeller, is equipped with afuel injector instead of a carburetor andmay even be turbocharged.

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As I pointed out in the beginning,when in doubt consult the engine manu-facturer's engine manual for guidance.

In addition, any homebuilder whowants to operate his engine in an effi-cient and professional manner shouldobtain and study the book by KasThomas, entitled, Aircraft Engine Op-erating Guide (Belvoir Publications,Inc., 1 1 1 1 E. Putnam Ave., Riverside,CT 06878). I recommend it highly. •*

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If you wish to contact the author ofthis column for additional infor-mation, please send a SASE to:

Tony Bingelis8509 Greenflint Ln.Austin, TX 78759

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86 SEPTEMBER 1995