the engine's still going anyway. Whilespeed is of the essence, there isusually time enough to verify actualengine failure by looking at theinstruments while you're reducing toTechie Stuff 253autorotation speed to maintainheight, certainly in a Bell, unlessyou’re very heavy in a high hoversituation, such as long-lining, whereyou have no time to do anythingother than dump the pole.For all practical purposes, yourgliding distance is about equal toyour height or, put simply, what youcan see slightly above the bottom ofthe windscreen. If you keep yourlanding spot in the same place in thatarea, your speed watch needn’t be socritical (remember sight pictureapproaches?). In fact, once you'veset your speed, keeping a mentalnote of the attitude will enable youto look out more. Loss of RPM atthe entry into autorotation is moreimportant—a higher angle of attackfrom the new relative airflow as airrushes up through the rotors willcause enough drag to slow the rotorsdrastically, especially if your weight ishigh or air density low, meaning thatyour blades will be at a higher pitchangle anyway. Get that collective down,and bring the airspeed back to autorotationspeed. Then accept the inevitable, thatyou may hit something, so yourprimary focus now is to ensure youand your passengers' survival, that is,to protect the cabin area as much aspossible. Of course, it would be niceto save the whole ship, but don'tstretch the glide, for example,towards a clear area and risk losingthe RPM, or having less control overthe rate of sink. Clear areas shouldreally be within a normal glide.On this point, remember that thehelicopter is better able to cope witha vertical rather than a horizontalcrash (oops, sorry, landing), since thegear can usually take somepunishment, as is proven daily bystudent pilots. You can use the tailboom and main rotors, too,especially in trees, mentioned below.To ensure the horizontal element isreduced, the best tactic will be toland in a decelerating attitude, whichwill mean making sure that the rearskids hit first (this will also help youkeep straight. The reason a Jetrangerrequires to be levelled during normalautorotative landings is to preservethe gearbox mountings, but this isless of a consideration right now). Acouple of good reasons for avoidingrun-on landings are obstacles, andsoft ground, which would increaseyour chances of nosing over, due tothe inertia of the gearbox, engineand rotors, etc. against the drag ofthe skids.Reducing collective to compensatefor the extra drag will, of course,increase the rate of descent, at whichpoint the inner 25% of each blade isstalled, and the outer 30% isproviding a small drag force. Inother words, it is being driven:The right hand view above is whathappens to the lifting area if youvary the ideal speed – it moves
towards the retreating blade side,and when it reaches the edge, youget your VNE for autos. The best254 Operational Flyinglift/drag ratio in autorotation isobtained at best endurance speed,whatever that is (check the manual,but most helicopters are designedfor a speed of about 45 kts).Try to establish the cause of enginefailure—if it's fire, close the throttle,but, if not, consider initially closing itonly to idle speed (or not closing itat all) as the engine may be able toprovide enough power to help youout a little, but this point iscontroversial as many people thinkyou should secure the engine andfuel in case the landing gets hashedup, which may actually be caused bya playful engine, or a fire caused by ahot one (turbines cool down quitefast after they are turned off). Also,if the main drive shaft breaks in a206 or a 407 (and others), you willneed the engine to drive the tailrotor. However, the discussionbelow will consider it closed.Several factors may affect your rateof descent, such as gross weight, airdensity, airspeed and rotor RPM.Changing airspeed, though, is aboutthe only one you have direct controlover that gives you some flexibility,as the RPM must remain in a smallspeed band to be effective—remember that only the portions ofthe blades between 25-70% of theirlength provide any lift. In any case,every 1% reduction in rotor RPMresults in a 2% loss of thrust, whichwill be the same as if somebodythrew that weight in the back of yourmachine. The other significant pointabout keeping your RPM upconcerns the tail rotor, which runs ata fixed speed relative to the mainrotors – if they go slower, the tailrotor does too, and loses some of itseffectiveness.Changes in airspeed can havedramatic effects on the rate ofdescent. If the recommended IAS is60 knots (fairly common), forinstance, speeds of either 30 or 100could increase RoD to as much as3000 fpm, because the lift vector isreduced when you alter a relativelyhorizontal rotor disc, so if you wantto change your angle of approach,don't forget to use collective tocompensate (when going for range,you must use both collective andspeed to get the full effect—you canpull collective until you get nastynoises in your ear). As forwardairspeed increases, the driving regionof the autorotating blades movestowards the retreating blade side –the point where it meets the edge ofthe rotor disc is where power off Vneis found. If you go beyond it, yourdriving region gets smaller, so yourrotor RPM will decay.Turns will have a similar effect, butthe results will be worse if pedals areused. Steep turns are good ways oflosing height if you find yourselfovershooting—if you are seated onthe right, turn right first, then go left,so you have the best possible viewthrough the windscreen, and you
of collective, used with somemachines to level better. Otherwise,there should just be small pause in acontinuous movement, and youshould find the rear skids touchingthe ground gently well before yourun out. Get used to the visual cluesrequired for the correct approach256 Operational Flyingand flare attitude – there's no time tolook at the ASI, and the one on the407 is dampened anyway, so is fairlyuseless under these circumstances.Get up on a nice day and practiceautos to a cloud, getting used to thehorizon's position through thescreen during descent, flare andturns on your machine.In every flare there is a point calledthe apex, which is where the tradingoff of airspeed for lift is essentiallyall over and you just have to getyourself on the ground. Put anotherway, it is the point where there is nofurther benefit from the flaremanoeuvre, so you may as well pullthe pitch (a little later in a 206). Asthe flare ends, and the kinetic energyof the rotors is used when thecollective is raised, the airflowthrough the rotors is reversed,assisting the level, ready to cushionthe landing with collective. This iswhere correct use of airspeed duringthe descent will have had the mostbeneficial effects—as the kineticenergy stored in the blades is whatslows you down, it follows that anyyou have used already to slow anunnecessarily fast descent is notavailable for the final stages oftouching down.But what if you are going into aclearing? Or don't get that muchpractice? The above method is fine,but you need to be doing it a lot toget it right every time. One way thatwill cover both the above situationsis to start the flare very much earlier,so that you are virtually stoppedquite high up. Then carry on as ifyou had an engine failure in a highhover, that is, dump the pole to getgoing vertically downwards and haulit all in at the end. In a verticalautorotation, there is a phenomenonknown as dynamic stall that will help,where an aerofoil that is rapidlystalled can produce double thenormal lift, just for a moment,because the breakup of the boundarylayer on top is delayed for a while, ifindeed you don’t actually create alittle vortex along it that improveslift even further. Do not try to gainspeed, as you will split the lift vectorand increase your rate of descent.If you're likely to be ending up intrees, as you might if you have thechoice between them or power lines,aim between two tops, tail first orlow, or at least moving gentlybackwards. The worst thing to do isgo in nose first, because the engineand gearbox will hit the groundbefore you do. The height of the treeis less important than the height atwhich the branches start, and if youare over them regularly, you mightlike to carry a good length of rope tohelp yourself get down. Having saidthat, it will be easier for the SAR
guys to pick you up from the top.With short trees, denser areasprovide the most shock absorbency– don't worry about branchesoverlapping, as long as the trunks arefar enough to allow the fuselage tosettle and the main rotors to missthem (actually, the main rotors canbe used as an umbrella to reducedescent). Fewer trees in an areaactually become obstacles. Deadones provide no absorbency at all.Pull the collective when you are inthe trees.If the surface is sloping, try to landnose up. If you flare a little, you willincrease your chances of getting itright first time as the attitude of theTechie Stuff 257skids will match the slope of theground better.Whereas an aeroplane is better suitedto protecting the occupants fromforward impact, the helicopter isbetter suited to vertical motion, soforward movement should bereduced as much as possible,especially over hostile ground – thecabin can be distorted badly justfrom the couple between its forwardmotion against the drag from theskids on the ground. As it happens, azero speed touchdown at 1500 feetper minute on soft terrain wouldprobably not result in many injuries.If it looks like you are going to hithard vertically, do not lean forward,but brace your back against thecomplete area of the seat to maintaina natural curvature. Spinal injuriesare most often caused by flexing.In fact, there are two broad types ofinjury to consider. Contact injuriesarise when you hit something, orsomething hits you (such as loosearticles in the cockpit). Decelerativeinjuries result purely from motion ofthe body, or loads applied throughseats and safety belts. They areinternal in nature, such as the spinalinjuries mentioned above, or in theabdomen. Other injuries, likeburning, may occur after the crash.Although it helps to crash as slowlyas possible, dissipation of whateverspeed you have is the mainconsideration, and this is neverusually uniform. Every obstacle thefuselage hits is responsible for a peakdeceleration and the potential fordamage to the people inside, so itmakes sense to try and protect thisas much as possible at the expenseof rotors, undercarriage, tail booms,etc. This is where the proper use ofshoulder straps is important – if youdon't wear one, you will jackknifeover your lapstrap and your head willhit the instrument panel at a speedover 12 times that of the cockpitdeceleration. Also, when onlywearing a lapstrap, your tolerance toforward deceleration reduces tobelow 25G, from a normal total ofover 40.Some things you can do to preventinjuries can be done before you get aproblem, by selecting clear routeswherever possible, and flying higher,which increases your range ofchoices (but not so high that it takestoo long to get down in a hurry).
Once you've landed:·
Close throttle & fuel valve·
Turn off Battery·
Evacuate aircraftPower-On RecoveriesThese are an increasing trend inmany companies, intended to reducethe number of autorotative accidentswhen practicing engine-off landings,and ensuring that some pilots don'tget to practice real ones for years onend. The examiner is looking for acorrect entry into autorotation andflare initiation height, but, thereafter,the process is a coordinationexercise, and you should treat it as arather fast transition to the hover—be careful not to check and level, oryou can expect a large torque spike(in a 206, anyway), and looking at thetorquemeter is not what you want tobe doing at that late stage.258 Operational FlyingTail Rotor FailureWhen the tail rotor fails, it will be invarying degrees of positive, neutralor negative pitch, depending on whatyou were doing at the time, so if youcan remember what it was, you willhave an idea of the state of thepedals. Unless it’s a drive failure, oryou lose some of the components,the chances are that you won’tdiscover the problem until youchange your power setting, as it’svery unlikely you’ll be flying along inthe cruise, for instance, and find apedal forcing itself completely overto one side, as simulated byinstructors on test flights, unless youhave a motoring servo or similar, inwhich case your problem ishydraulics and not the tail rotor,although the effect might be thesame. More typically, you will be in adescent, climb, cruise or hover, withthe pedals where they should be andwon’t move when you want to dosomething else. When descending,for example, in the AS350, you willhave more left pedal (more right inthe Bell 206), both of which will aidthe natural movement of thefuselage against the main rotors. Thepedals would be in a neutral positionif you were flying at medium to highspeeds, and the power pedal wouldbe forward in high-power situations,like hovering. In any case, the spreadbetween the pedals is not likely to bemore than a couple of inches eitherway, certainly in a 206 – try anautorotation properly trimmed outto see what I mean. You will noticethe same in the hover. My point isthat the situation may not be as badas frequently painted.In fact, landing with a power pedaljammed forward is relatively easy,since the tail rotor is already in aposition to accept high powersettings (try also using a little leftforward cyclic in a 206, and pivotinground the left forward skid), so youmay be able to come in very slowlyand even hover. If the pedals jam theother way (right in a 206), look formore speed because there will not beenough antitorque thrust available.A drive failure, on the other hand, orloss of a component, will cause anuncontrollable yaw, and maybe anengine overspeed, so the immediatereaction should be to enterautorotation, keeping up forwardspeed to maintain some directionalcontrol (which is difficult in thehover, so try to get one skid on theground at least), if you have time. Ifyou lose a component, the C of Gmay shift as well, although an aft onein general has been found to helpwith this situation. Pilots who havebeen there report that there is asignificant increase in noise with adrive shaft failure, and that thecentrifugal force in the spin is quitesevere. Anyhow, an autorotation iscertainly part of the game plan, andas speed is reduced towardstouchdown, you will yawprogressively with less controlavailable in proportion, so it may beworth trying to strike the groundwith the tailwheel or skid first (ifyou’ve got one), which will help youto keep straight—according to theJetRanger flight manual, you shouldtouchdown with the throttle fullyclosed, as you would if the failureoccurs in the hover, to stop furtheryaw when pitch is pulled to cushionthe landing.However, in some circumstances,such as the cruise, suddenTechie Stuff 259movements like this may not be thebest solution. If you can reduce thethrottle and increase the collective,this would reduce the effect of thetail rotor at the same time as keepingthe lift from the main rotors, as does
beeping down to the bottom of thegovernor range (difficult in mostAS350s or Gazelles, where thethrottle is not on the collective). Thetail rotor is there to counteracttorque, so if you give it less work todo, you will be more successful.Otherwise, you might find a powerand speed combination that willmaintain height until you find asuitable landing area, then you've gotas much time as your fuel lasts tosolve the problem. Don't forget thatthe cyclic can be useful for changingdirection and enabling you to flysideways to create drag from the tailboom and vertical stabiliser, forexample. It's the sort of situationwhere it pays to be creativesometimes. After all, the aim is towalk away, not necessarily topreserve the machine. Two otherthings you can try if you finally makethe hover—stirring the cyclic so asto dump lift, and pumping thecollective to produce a similar effect.Both will serve to confuse themachine enough so it forgets whichway to turn! With a jammed powerpedal (left, in a 206), what also worksis to crab in the way the machinewants to, come to a high hoversideways and let the machine settleby itself. You will find very littleinput is required by you.If you want to run-on for landing,get the wind and/or nose off to theretreating blade side, so the fuselageis crabbing, and control your(shallow) descent with acombination of throttle andcollective, applying more of thelatter as the throttle is closed justbefore touchdown so you run onstraight. Note that some helicopters(such as twins, or the AStar) won’tlet you use the throttle as precisely asthat. Not only that, you may well beso busy that worrying about minordetails like the wind’s exact quarterwill be the last thing on your mind.For a running landing, on mostmachines, about 30% torque at 30kts will put you in a good positionfor landing at 30 ft, and a littlepower at the last minute will putyour nose nicely straight. For thenon-power pedal, keeping straightinvolves either more speed or lesspower, and you have to accept moreof a run-on.In an AStar (or TwinStar), therecommendation in the book is tocome in with some left sideslip (i.e.crabbing right). Slow down until thenose starts to move to the left, andyou have your landing speed.Loss of Tail Rotor EffectivenessThis is sometimes known as tail rotorbreakaway, or a stall, which is notstrictly correct, as thrust is still beingproduced – it’s just not enough forthe task in hand. It shows up as asudden, uncommanded right yaw(with North American rotation), andhas amongst its causes high densityaltitudes, high power settings, lowairspeeds (below about 30 kts) andaltitudes, and vortex ring, notforgetting turns in the oppositedirection of blade rotation. Yourhelicopter will be more susceptibleto it if the tail rotor is masked by atail surface, like a vertical fin, and itcan be especially triggered by tail andside winds (this is actually a260 Operational Flyingsignificant reason for maintainingmain rotor RPM – as the tail rotorruns at a fixed speed in relation to it,lower NR will reduce tail rotoreffectiveness in proportion).Recovery in this case comes from acombination of full power pedal,forward cyclic and reduction incollective, or autorotation.Prevention lies in keeping into windand always using the power pedal(left in a 206 or one with similarblade rotation). If you use the otherone, not only will the fuel governorensure that the aircraft will settleafter a short time (using the powerpedal by itself makes it climb), but alarge bootful of the power pedal in afast turn the other way will create alarge torque spike.Jammed ControlsAside from jammed tail rotor pedals,discussed above, your cyclic orcollective may jam as well. Bothcases will result in a run-on landing.To get out of a jammed collective,just bring the speed right back. Thiswill cause you to descend, and youcan use your speed to aim at theground. Hopefully, your cyclic willjam in the centre. Anyway, leaning inthe desired direction (passengers aswell) will cause enough of a shift inC of G to turn the ship in thedesired direction.Hydraulic Boost Failure
Indicated by feedback forces in thecontrols, which will be negligiblewhen they are held in a fixedposition. Hopefully, your failure willbe just from fluid leakage, but itcould be a hydraulic pump drivefailure—in a JetRanger, this will beconfirmed by looking at the NRgauge, as the pump is driven fromthe transmission. Note that theHydraulic CB sometimes relates tothe switch as the idea is to have itfail-on – electricity keeps the switchoff, so if it fails, it stays on and so dothe hydraulics. Reduce forwardspeed and control inputs to aminimum, making necessarymovements at a rate of travel notfaster than one full displacement,stop to stop, per second. The failurewon't be sudden, so switch off earlyto keep fluid in the system.If you ever have to leave thecontrols of a helicopter with theengine running, do not switch thehydraulics off, but use the controllocks only, in case the controlsmotor by themselves.OverpitchingIn a helicopter, overpitching iswhere the rotor RPM are too low tomaintain flight, giving the impressionof "labouring". It's the nearestequivalent to stalling and iscommonly caused by beingoverweight for the particularconditions. Reduce power tomaintain RPM.Engine HandlingOne of the biggest things to unlearnwhen transitioning from piston toturbine is to keep your finger on thestarter button once things starthappening (with a piston, you tendto take your finger off straight awaywhen the engine starts). You takeyour finger off when the enginebecomes self-sustaining. Before then, itrelies heavily on the battery or starttrolley to keep it turning. It followsthat, if the battery is weak to startwith, the engine won't spin as fast,Techie Stuff 261the airflow is reduced, the wholeprocess becomes hotter and youcould melt the back end with a hotstart. You should always check thevoltage available from the batterybefore starting a turbine engine. Ahung start exists when the engine failsto accelerate to normal idle RPM. Itjust sits there, weakening the batteryand leading to a hot start.Pulling full power just because it'sthere is not always a good idea.Limitations may be there for otherreasons—for example, thetransmission might not be able totake that much, which is why youcan’t go faster than 80 kts in aJetranger when pulling more than85% torque (actually, in this case, thetransmission ends up in a strangeattitude). Excessive use of power willtherefore ruin your gearbox wellbefore the engine (and will show upas metal particles in the oil). Manyturbine failures are the result ofpulling too many cycles fromminimum to maximum Ng, so if youdon't need 100% torque, it's best notto use it. It's also best not to reduce
the collective lever of yourhelicopter to the bottom whendescending, either, and to makepower changes gently, avoiding over-and undershoots.Maximum Continuous Power is thesetting that may be used indefinitely,but any between that and maximumpower (usually shown as a yellow arcon the instrument) will only beavailable for a set time limit.While I'm not suggesting for amoment that you should, pistonengines will accept their limits beingslightly exceeded from time to timewith no great harm being done.Having said that, the speed at whichthe average Lycoming enginedisintegrates is about 3450 RPM,which doesn't leave you an awful lotof room when it runs normally (in aBell 47, anyway) at 3300! Turbines,however, are less forgiving thanpistons and give fewer warnings oftrouble because of their closertolerances. This is why regular powerchecks are carried out on them tokeep an eye on their health. Theother difference is that damage to apiston engine caused by mishandlingtends to affect you, straight away,whereas that in a turbine tends toaffect others down the line.In a turbine-engined helicopter,power is indicated by the torquemeter.Apart from sympathetic handling,the greatest factor in preservingengine life is temperature and its rateof change. Over and under leaningare detrimental to engine life, andsudden cooling is as bad asoverheating—chopping the throttleat height causes the cylinder head toshrink and crack with the obviousresults—the thermal shock and extralead is worth about $100 in terms oflost engine life. In other words, don’tlet the machine drive the engine, butrather cut power to the point whereit’s doing a little work. This isbecause the reduced power lowersthe pressure that keeps piston ringsagainst the wall of the cylinder, so oilleaks past and glazes on the hotsurfaces, degrading any sealingobtained by compression. The onlyway to get rid of the glaze is byhoning, which means a top-endoverhaul. For the same reasons, anew (or rebuilt) engine should berun in hard, not less than 65%power, but preferably 70-75%,according to Textron Lycoming, so262 Operational Flyingthe rings are forced to seat inproperly. This means not flyingabove 8000 feet density altitude fornon-turbocharged engines. Richermixtures are important as well. Also,open the engine compartment aftershutting down on a hot day, as manyexternal components will havesuddenly lost their cooling. Withsome turbine engines (like on theAStar), you have to keep a track ofthe number of times you fluctuatebetween a range of power settingsbecause of the heat stress.In the cruise, better fuelconsumption may be obtained atslower speeds and lower powersettings, at the cost of extended
running time, so you might not reallysave that much. For example, leaningto 10° lean of peak Exhaust GasTemperature (EGT), withoutexceeding the maximum, loses about5 knots. Typically, EGT probes arefitted to one cylinder of the engine,which is not necessarily the one thatreaches peak temperature first, eventhough it may end up as the hottest,so a margin of 25° rich of peak maystill not be enough to stop anothercylinder from getting too close topeak for comfort, or even lean.One consideration with using lowpower when it's very cold is that theengine may not warm up properlyand water that forms fromcombustion may not evaporate, sooil won't lubricate properly.The reason the temperature coolseither side of the peak reading is thaton the one hand (rich), there is toomuch fuel and, on the other (lean),there is too much air (having saidthat, the hottest CHT is between 25-50° rich of peak EGT, because that'swhere the peak cylinder pressureoccurs, with a high rate of heattransfer to the cylinder head, so youneed to lean past it). However,although being lean of peak works,there is much more potential forcausing damage to the engine if it ismismanaged – it needs moremonitoring to be used effectively, asthe temperature at the exhaust willstill be high, which is not good forthe valves, particularly acute withhigh performance turbochargedengines – Australian authoritiesfound that leaning causes leadoxybromide deposits to cling tovarious parts inside the combustionchamber, which could becomehotspots and cause detonation (thelead appears as a result of chemicalchanges in avgas as it burns). Atricher settings, the lead either doesn'tform or is swept out of the cylinder(this may be true for lowerperformance engines, too).Don't forget to enrich the mixturesbefore increasing power when atpeak EGT or when increasing tomore than 75% power. Move theengine controls slowly and smoothly,particularly with a turbochargedengine. Harsh movements that (onolder engines) will result in a coughand splutter and having no powercan be embarrassing.Although many flight manuals statethat as soon an engine is runningwithout stuttering it's safe to use it toits fullest extent, try warming up fora few minutes before applying anyload, at least until you get a positiveindication on the oil temperature(and pressure) gauges. This ensures afilm of oil over all parts.Even better, warm it before you startit, because the insides contract atdifferent rates – in really coldTechie Stuff 263weather the engine may have thegrip of death on the pistons andcause some strain when you turn thestarter. Equally important is notletting an engine idle when it's cold,as it must be fast enough to create asplash (about 1,000 RPM is fine).
After flight, many engines have arundown period which must be strictlyobserved if you want to keep it forany length of time. As engines getsmaller relative to power output,they have to work harder. Also, inturbines, there are no heavy areas toact as heat sinks, like the fins on apiston engine, which results inlocalised hotspots which maydeform, but are safe if cooledproperly, with the help of circulatingoil inside the engine (75% of the airtaken into a turbine is for coolingpurposes). If you shut down tooquickly, the oil no longer circulates,which means that it may carboniseon the still-hot surfaces, and buildup enough to prevent the relevantparts from turning. This coking upcould sieze the engine within 50hours or less.If the starter light remains on afteryou release the starter button on apiston engine, you should shut itdown, as it indicates that the starteris still engaged with the engine and isbeing driven by it.The "LL" in 100LL stands for lowlead, but there is still about fourtimes more than is needed. As wellas the lead (in the form of TEL—Tetra-Ethyl Lead), a scavenging agent(Ethylene DiBromide, or EDB) is alsoadded to ensure that the lead isvapourised as far as possible, readyto be expelled from the cylinder withother gases. Unfortunately, this isnot 100% successful, but the resultsare best at high temperatures andworst at low ones - the unwantedextras result in fouling of sparkplugs, heavy deposits in thecombustion chamber, erosion ofvalve seats and stems, sticking valvesand piston rings and generalaccumulation of sludge andrestriction of flow through fine oilpassages, so it makes you wonderwhich is worse (in fact, petrol is notthe only fuel you can use – JapaneseZeros used to outfly Americanaeroplanes because they used ethylalcohol). TEL, by the way, is actuallya liquid gas, which was developed bya subsidiary company (Ethyl, Inc)belonging to General Motors and IG Farben sometime before WWII.In June, 1940, just before the Battleof Britain, it could only be obtainedthrough the Anglo-American OilCompany, or Esso - when the fuelwas changed from 87 octane to 100,German pilots got a real surprise,because the Spit could suddenlyclimb a whole lot quicker.OilAn engine that is not used enoughdevelops corrosion very quickly onthe inside, and rust flakes, which arevery abrasive, will circulate when theengine is started, which is why youhave to change the oil even whenyou don’t fly a lot. Another reason isan increased water content, whichwill have an acidic effect once itmixes with the byproducts ofcombustion. The most wear takesplace in the first seconds of a coldstart, after the oil has been allowedto settle. Priming will wash whateveris left off the cylinder walls, so don't
