von klip tip 10 commandments of prop care

7/29/2019 Von Klip Tip 10 Commandments of Prop Care

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THE

10COMMANDMENTS

OF PROPELLER CAREALONG WITH ANSWERS TOTHE 16 MOST OFTEN ASKEDQUESTIONS ABOUT PROPELLERS


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1. Read and respect yourowners manualsknow

where to obtain serviceAh! There it is, your own plane. Bright, shinyand just begging for flight. But hold it! Haveyou read the owners manuals? Many of thecommandments in this booklet duplicateinstructions in other manuals. But you cant

repeat a good thou shalt or thou shaltnot too many times. We urge you to keepthe engine and aircraft in good shapeandto especially take care of the propeller. Andnow would be a good time to start a separatelog book just for the propeller so you have apermanent record of prop maintenance andoverhaul.

Sooner or later youll need service on yourprop, and youll want to locate an approvedpropeller repair station with proper equipmentto work on your McCauley propeller.* These

are stations approved and certified by theFederal Aviation Administration to service,recondition, repair, or overhaul propellers.These firms demonstrate that they have the

10 Commandments

*A listing of McCauley direct factory dealerscan be obtained by accessing our website at:www.mccauley.textron.com


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equipment, technical information, and skillsto perform such work. They are licensed andlimited to working only on specified propellermodels which are listed by manufacturer andmodel on their authorization. Know where

your home base prop repair station islocatedand also other stations in areaswhere you fly and land frequently.

2. Visually inspect the prop

before each flightYouve got the eye of an eagle or youwouldnt be flying! So it should be pure joyfor you to give the prop blades a visualinspection regularly, preferably before eachflight.

of Propeller Care

You should look for such surface damage andirregularities as dents, nicks, bruises,scratches, erosion, etc. When are theseserious enough to require professionalattention? Best rule is, when in doubt, let anapproved FAA-licensed A&P (airframe and

powerplant) mechanic look at the prop. Hecan correct minor damage by dressing itout. If you have a spinner, check externalsurfaces for damage and the attachmentparts for normal tightnessalso check theback surfaces of the hub. If no spinner isinstalled, visually examine the front and backsurfaces of the propeller hub and itsattachment onto the engine shaft for normaltightness.


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3. Dont rev the engine

over loose particlesUnless a gang of Bad Guys is chasing you andthe idea is to get away fast, you should avoidhigh static RPM when standing or taxiingover dirt, gravel or stony areas. Revving theengine to a cloud of dust may look dramatic

on the late movie, but high speed operationof the propeller can cause nicks and otherdamage to the blades and tips if particles aresucked up and hit the prop. Do you ever takeoff from runways of this type? If safeoperation permits, propeller speed controlshould not be opened to maximum RPMsuntil airspeed has picked up. Nicks and otherminor imperfections should be dressed outbefore cracks have a chance to develop.

4. Dont use prop blades

as handlesAn elephant may not mind being grabbed bythe nose and pushed or pulled into position.But it can do really jumbo-size harm to apropeller if you use the prop blades asconvenient handles for maneuvering theplane on the ground. If your plane isequipped with a steerable nose wheel andtow bar, use them as a means of jockeying


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the plane. If the plane is not so equipped,certain areas of the airframe have beendesignated by the manufacturer as safe forpush/pull pressure. Know where these pointsare, and just rememberfor positioning, thenose is a no-no!

5. Use oily rags for wipingdont hose the prop

A clean cloth dampened with light oil is yourpropellers best maintenance friend. Wipethe prop after each flight, or as regularly aspossible, especially if you operate near saltwater or fly a sea plane. An oily wipe-offremoves substances that cause corrosion andprepares the prop to repel corrosives and

water erosion. The oily rag wiping habit alsogives you the opportunity to inspect theblades for nicks, cracks, and tears. Neverscrape the blades or use abrasives as thesedamage the surface finish. And dont hosethe propeller down with water especiallydont stick a water nozzle in the spinneropening and squirt the hub to clean it. Thisact may force water into the hub and lead tocorrosion or lubricant breakdown.


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6. Clean and wax blades

oftenrepaint as requiredSaturday afternoons are great for messingaround with the plane. One of the tasks thatshould be maintenance regular is cleaningthe prop blades with a non-oil base solvent(Stoddard). Then wax the blades, using any

automotive type paste wax. The backs of theblades are painted a non-reflective black, andthis coating may have to be renewed fromtime to time. On the opposite side, blade tipsare painted a bright color.

7. Recondition prop whennecessary

The Bent Prop Club always welcomes newmembers. If you should happen to groundloop or hit a stray cows tail, chances are yourpropeller can be straightened and repaired.About 90% of accident-caused damage isrepairable. The need for reconditioningunder these circumstances is obviousitshould also be performed when prop bladeshave been damaged and filed often.

Reconditioning covers major and minor bladedamage from accident or other causes andincludes balancing the prop. This work isperformed on an as required basis by thepropeller manufacturer or an FAA-approvedpropeller repair station. For a one-piece fixedpitch prop, this operation is equivalent to anoverhaul. For other types of props, if damageis major but repairable, an overhaul shouldbe included with the reconditioning,although this is not mandatory.


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8. Check blade trackperiodically

Blade track is the ability of one blade tofollow the other in the same plane. Track isheld to reasonable limits to preventroughness. Excessive differences (more than

1/16 inch) may be an indication of bentblades or improper installation. To checktrack, a smooth board is blocked up justunder the tip of the lower blade. Oncontrollable props, the tip is moved fore andaft through its full blade shake travel (see

Question #15). Small pencil marks are madeat each position. Then center the bladebetween these marks, and draw a line the fullwidth of the blade. The other blade tip isrotated to the board, centered, and marked.The lines should be separated by not morethan 1/16 inch. If more, check for bent blades

or for foreign particles between hub andcrankshaft mounting faces.


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9. Make thorough visual

inspection yearly(or every 100 hours)

This is the same visual procedure you shouldbe conducting before each flight only thistime inspect the prop inch by inch in the bestpossible light, looking for any evidence ofdamage you may have overlooked previouslyduring your pre-flight inspections. This finetooth comb inspection should be done onceeach year for one-piece fixed pitch propellersand every 100 flight hours for all other typesof props. Have a licensed A&P mechanic

remove the spinner if installed and checkpropeller installation bolts for tightness witha torque wrench.


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10. Follow overhaulrecommendations

Much as you hate to part with yourcontrollable prop, the day finally comes whenthe men in white coats must remove it foroverhaul. Overhaul is the periodicdisassembly, inspection, reconditioning andreassembly of the propeller (except one-piece,fixed pitch props which do not require

overhaul). The overhaul interval is generallybased on hours of service (operating time),but a calendar limit also applies. After beingdisassembled, the propeller is inspected forwear, cracks, corrosion or other abnormalconditions. Certain parts are replaced, whileother parts are reconditioned and refinished.Reassembly and balancing complete the job.Overhaul is performed by the propellermanufacturer or by an approved propellerrepair station and follows manufacturersservice manual instructions and servicebulletins and letters, as applicable. A

subscription service is available fromMcCauley for those owners desiring their owncopies of these bulletins and letters.


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1. What is the propellers function?The propeller is a twisted wing or airfoil. Theprop converts the rotating power of theengine into thrust which propels theairplane through the air similar to the waythat the wing (also an airfoil) provides the

lift which enables the plane to be airborne.

2. What is the difference betweena tractor propeller and a pusher

propeller?A propeller mounted on the forward end of

the engine, relative to flight direction, is atractor type. A pusher type is one mountedbehind. A tractor propeller pulls the aircraft,while a pusher prop pushes it.

3. Classified by pitch, what are thebasic types of propellers?

*Fixed Pitchone piece prop with asingle fixed blade angle. The pitch must be highenough to offer good cruising performance andyet low enough to achieve acceptable takeoffand climb characteristics. With a fixed throttlesetting, the prop (and engine) RPM will change

as airspeed changes; with a constant airspeed,the prop (and engine) RPM will change if poweris increased or decreased.

16 Popular Questions

and Answers aboutPropellers


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Ground Adjustmentblade anglecan be adjusted on the ground but cannot be

altered in flight. Once fixed, this prop operateslike a fixed pitch propeller. Blade angle can beset low for short fields and/or high terrain or forbetter load carrying capability; it is set at ahigher angle for long runways, low terrain, orlight loads when a better cruising speed isdesired.

Two Positionblade angle may beadjusted during operation to either low angleor a high angle setting. Low angle is used fortakeoff and climb, then a shift is made to highangle for cruise.

Controllable Pitchblades may bealtered infinitely to any desired angle duringflight, starting with a low blade angle and thengradually increasing the angle during takeoff,climb, leveling out, and cruise.

Automatic Pitchblade angle changeoccurs automatically as a result of aerodynamic

forces acting on the blades, and the pilot has nocontrol over the changes.

*Constant Speeda governor is usedin conjunction with the propeller toautomatically provide constant RPM as the pilotselects the proper setting. Blade angle is

changed automatically and will increase ordecrease if RPM setting is decreased orincreased or if power is increased or decreased.With fixed RPM and power setting, the bladeangle changes automatically as airspeedincreases or decreases.

*Full Featheringblades can berotated to a high positive angle to stop rotation(windmilling). This feature is common on multi-engine aircraft, because it allows an engine tobe shut down and the prop stopped to reducedrag and asymmetric control forces.

Beta Controlnormally used for groundoperation, most often in taxiing, where thrust ismanually controlled by adjusting blade anglewith the power lever.

*Reversingblades can be rotated to anegative blade angle where they will providea rearward thrust to slow down, stop or movethe aircraft backward. This capability is normallyprovided for turbine installations.

*Types starred are available in various models.


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4. Why are props made of aluminumrather than wood?

Wood props were used almost exclusively onpersonal and business aircraft prior to WorldWar II. Lightweight aluminum props weredeveloped after the war. Compared to wood,an aluminum prop can be made with thinnerblade sections, which have higher efficiency

(more lift, less drag). The metal does notabsorb moisture, which can cause weightchange or warpage. High strength aluminumpropellers have good elongationcharacteristics and can be rather extensivelydamaged yet repaired. (They resistwoodpeckers, too!)

5. What other materials are usedfor props?During World War II, solid steel propellerswere made for the Armed Forces. Althoughno longer produced, some are still found onagricultural aircraft used for spraying anddusting. Fiberglass resins form the base fornew composite materials which may bespecified when reduced weight is critical.

6. Why are some prop blades tipsrounded and others square?

Round or elliptical tips are used for increasedground or fuselage clearance, certain noiseperameters, blade vibration resonantcharacteristics or special design conditions. Incontrolled tests, elliptical tips proved slightlymore efficient than square tips, but theincrease is insignificant. Most propellers havesquare tips to leave extra material which canbe removed after damage to make the bladeround or elliptical and still maintain diameter.


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7. Why are propellers painted?The faces of the propeller blades toward thepilot are painted non-reflective black so thespinning propeller is not seen as a shiny,hypnotic disc. The tips on the opposite sideare painted bright colors so the spinningpropeller can be more easily seen to warnthose on the ground about walking into it.

8. How are individual propellersidentified?McCauley propellers are identified by amodel designation and a serial number. Onone-piece fixed pitch props, the serial

number is stamped on the camber side of thehub face. Variable pitch propellers haveseparate numbers for hub (stamped on side)and each detachable blade (stamped on flatface at hub end).

9. What is feathering the prop?Changing the blade angle until the bladesoffer low resistance to flight and wontwindmill. On single engine aircraft, thefeathering feature adds cost and weight andoffers little advantage. Multi-engine aircraft

generally have full feathering props toeliminate asymmetric drag forces caused bywindmilling when an engine is shut down.


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10. What is meant by Beta Controland reversing the prop?Beta control is the manual repositioning ofthe propeller blade angle beyond the normallow pitch stop. Reversing means changingthe blade angle to a position less than thenormal positive low blade angle setting untila negative blade angle is obtained. A bladewith a negative blade angle produces athrust in the opposite direction to the normalforward thrust. This acts to slow down, stopor even reverse the airplane when on the

ground.

11. What is a spinner?A metal cover which encloses the propellerhub. It has a pleasing, low drag shape whichblends into the engine nacelle. Appearance isthe common reason for using spinners, buton some aircraft they streamline the airflowfor engine cooling purposes.

12. What is a governor, and how isit related to the propeller?The governor is a device generally mounted

on the engine, and driven by it, which sensesand controls engine speed (RPM) byhydraulically adjusting the blade angle ofthe propeller. This product is manufacturedby McCauley.

13. What is a governor, and how is itrelated to the propeller?On twin-engine aircraft, governors alsoprovide the means for synchronizing and


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sychrophasing the two propellers. Thesynchronizing option measures the RPM of

both propellers and adjusts one of them sothat both are turning at the same speed.Once the speeds are synchronized, thesynchrophaser option controls the phaserelationship of the two props to eliminateengine beats and minimize sound andvibration in the aircraft.

14. What is the difference betweenpropeller anti-ice and de-iceequipment?With anti-ice equipment, alcohol is permittedto flow over the propeller blades to prevent

ice formation. It is not effective after ice hasformed. A de-ice system applies electric heatto the blades after ice has formed so that it ismelted near the surface and centrifugal forcewill cause the ice to shed. De-ice systemsare made by McCauley.

15. What is blade shake?Blade shake is the tendency for the blade ofa variable pitch propeller to wobble slightlywhen the tip is moved by hand. This tendencyis the natural result of the fabrication ofretention parts to close tolerances. Very small

differences at the blade root are magnifiedmany times when measured at the tip. Bladeshake does not adversely affect prop strengthor performance and disappears when thepropeller rotates. With the first turn, thecentrifugal force of the spinning blades seatsthem rigidly against the retention bearing.

16. What causes prop roughness?All vibrate to some extent in operation.Assuming that the engine itself is not at fault,roughness relative to the propeller could becaused by bent blades, blades out of track

due to improper mounting of the prop onthe engine shaft, imbalance, propeller looselymounted on engine shaft, blade anglesbetween blades out of tolerance with respectto each other, and spinner imbalance due toimproper mounting, or to dirt, snow or iceinside the shell.


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This booklet is presented in the interest of

happier, safer and wiser flying by

PROPELLERS SPINNERS DEICERS

GOVERNORS & ACCUMULATORS

5800 E. Pawnee, Wichita, KS 67218Telephone: 800-621-7767 Fax: 316-831-3858

www.mccauley.textron.com

von klip tip 10 commandments of prop care

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