propellers - 101

Propellers - 101Propellers - 101

Presented byPresented by

Skip SeilaSkip Seila

FAASTeam Lead Rep.FAASTeam Lead Rep.

The propeller, though most reliable, The propeller, though most reliable, is still probably the single most is still probably the single most

neglected component on an aircraft.neglected component on an aircraft.

What is really unusual?

Hmmm. Give up?

Nope, not this

Not this, either

What is highly unusual is the fact that the engine is still in the aircraft.

In the majority of cases, this scenario will result in fatalities!

On takeoff, propeller tip speeds On takeoff, propeller tip speeds approach the speed of sound. The approach the speed of sound. The

blades must absorb not only the blades must absorb not only the punishing vibration of the engine’s power punishing vibration of the engine’s power pulses, but also vibration caused by the pulses, but also vibration caused by the oncoming airstream. Centrifugal loads – oncoming airstream. Centrifugal loads – those forces that try to pull the blade out those forces that try to pull the blade out of the hub – amount to of the hub – amount to 1010 to to 2020 tonstons per per

blade.blade.

The blades twist and flex. The stresses The blades twist and flex. The stresses imposed on the prop are more imposed on the prop are more

concentrated in the small areas that are concentrated in the small areas that are nicked or cut. These nicks and nicked or cut. These nicks and

scratches act as stress risers, which can scratches act as stress risers, which can weaken the blade enough to eventually weaken the blade enough to eventually

cause blade failure.cause blade failure.

Non-Feathering Constant Speed Non-Feathering Constant Speed Propellers – McCauley “Threadless”Propellers – McCauley “Threadless”

* Takes oil * Takes oil pressure to pressure to change pitch.change pitch.

* If it has a large * If it has a large snap ring at the snap ring at the base of the base of the blade – it is a blade – it is a “threadless”.“threadless”.

* Only lubricated* Only lubricated

at overhaul.at overhaul.


* The retainer (2 ea.) on the left are put in place on * The retainer (2 ea.) on the left are put in place on the blade and the blade is then allowed to drop the blade and the blade is then allowed to drop down in place. The blade “play” is then removed down in place. The blade “play” is then removed by installing shims under the large snap ring.by installing shims under the large snap ring.


* To inspect. Place the blade in the vertical position * To inspect. Place the blade in the vertical position and with your thumb and forefinger on the tip, and with your thumb and forefinger on the tip, check for fore & aft movement.check for fore & aft movement.

* Movement of 1/8 “ is acceptable.* Movement of 1/8 “ is acceptable.

* If movement exceeds 1/8”, do * If movement exceeds 1/8”, do notnot remove the remove the propeller. It is repaired right on the aircraft.propeller. It is repaired right on the aircraft.

* Excessive movement is * Excessive movement is notnot critical to flight. It critical to flight. It diminishes at the first rotation of the propeller and diminishes at the first rotation of the propeller and is purely psychological.is purely psychological.


* If it has a small allen screw in the middle of * If it has a small allen screw in the middle of the hub, it probably is “oil filled”.the hub, it probably is “oil filled”.

* The oil has a red dye in it to detect early * The oil has a red dye in it to detect early cracking in the hub.cracking in the hub.

* In order to prevent unwanted red dye * In order to prevent unwanted red dye indications when no possibility of cracking indications when no possibility of cracking exists, it is highly recommended to exists, it is highly recommended to dynamically balance the aircraft. dynamically balance the aircraft.

Full-Feathering Constant Full-Feathering Constant Speed PropellersSpeed Propellers

HartzellHartzell

Full-Feathering Constant Speed Full-Feathering Constant Speed Propellers - HartzellPropellers - Hartzell

* Lubricated at 100 hr.* Lubricated at 100 hr.

or annual inspectionor annual inspection

with Aeroshell 5.with Aeroshell 5.

* Attains pitch change * Attains pitch change on initial start from on initial start from oil pressure from oil pressure from the governor.the governor.

* Lack of oil pressure * Lack of oil pressure willwill result in result in feathering.feathering.

Full-Feathering Constant SpeedFull-Feathering Constant SpeedPropeller - HartzellPropeller - Hartzell

* This shows * This shows the propeller the propeller reaching the reaching the low pitch low pitch stop.stop.

Full-Feathering Constant Speed Full-Feathering Constant Speed Propeller - HartzellPropeller - Hartzell

* This * This shows the shows the propeller propeller at the at the feathering feathering stop. stop.


* Here’s a close up view of the feathering stop that * Here’s a close up view of the feathering stop that shows the elongated slots and the spring that from shows the elongated slots and the spring that from inertia allows the propeller to feather.inertia allows the propeller to feather.


* This view shows the * This view shows the propeller in the feather propeller in the feather position. However, the position. However, the spring had to be cut for spring had to be cut for us to demonstrate the us to demonstrate the actions of this actions of this propeller. Seeing this propeller. Seeing this spring as it really is spring as it really is should remove any should remove any doubt that this doubt that this propeller propeller willwill feather! feather!

Propellers for Turbine Aircraft

Hartzell

Hartzell Turbine Propeller

* Lubricated at

100 hr./annual

inspections

with Aeroshell 6.

* Lack of oil press.

will result

in feathering.

Turbo Propellers

Lightweight Turbine – 2nd Generation

* Hartzell Compact Aluminum Hub off a Piaggio Aircraft.

* Raysbeck Aircraft

STC’s

The M-TPropeller

M-T Care & Maintenance

* Do not file leading edge. It’s stainless steel. If it is damaged, have it replaced. If discolored or stained, use a scotch brite pad.

* Do not wash it but keep it well waxed. Auto wax is fine.

* Note that these bearings are lubricated at time of O/H only.

Propeller GovernorsPropeller Governors


* Simply put – it is a high * Simply put – it is a high pressure oil pump.pressure oil pump.

* An inertia flywheel * An inertia flywheel maintains the setting maintains the setting that you made in the that you made in the cockpit.cockpit.


* Notice that the tear-* Notice that the tear-drop arm has moved drop arm has moved allowing the flywheel allowing the flywheel arms to come into play arms to come into play and regulate the oil and regulate the oil pressure flow to the pressure flow to the propeller and thus propeller and thus regulating the pitch of regulating the pitch of the propeller.the propeller.

* IT’S AN OIL PUMP !* IT’S AN OIL PUMP !

Propeller Care and MaintenancePropeller Care and Maintenance

Proper Care and MaintenanceProper Care and Maintenance

* File the leading edges of the blades with a * File the leading edges of the blades with a fine file. No rasp or coarse file!fine file. No rasp or coarse file!

* Do * Do notnot use the shank of a screw driver for use the shank of a screw driver for burrs. That only rolls the metal back in and burrs. That only rolls the metal back in and does nothing to prevent further damage.does nothing to prevent further damage.

* Do * Do notnot wash propeller. Wipe it clean and wash propeller. Wipe it clean and finish with a clean oily rag.finish with a clean oily rag.• Keep in mind that to pass overhaul Keep in mind that to pass overhaul

requirements, blades are measured on requirements, blades are measured on width and thickness. Blades are expensive.width and thickness. Blades are expensive.

Proper Care and Maintenance

* Burrs or nicks (stress risers) * Burrs or nicks (stress risers) on leading or trailing edges on leading or trailing edges must be repaired by using must be repaired by using the formula of 10X the the formula of 10X the depth of the damaged area depth of the damaged area to determine the to determine the necessary area required to necessary area required to be repaired.be repaired.

* Start with a file, then emery * Start with a file, then emery cloth and then crocus cloth cloth and then crocus cloth to remove all file marksto remove all file marks


* Check to assure that the spinner is not * Check to assure that the spinner is not touching the blades.touching the blades.

* Check that the flyweights (if installed) are * Check that the flyweights (if installed) are not touching and damaging the spinner.not touching and damaging the spinner.

* Check for blade play at the tip by fore and * Check for blade play at the tip by fore and aft movement, in and out movement and aft movement, in and out movement and twist movement. Slight play is okay if the twist movement. Slight play is okay if the blade returns to it’s original position.blade returns to it’s original position.

* Check for grease leaks.* Check for grease leaks.

Propeller Care and MaintenancePropeller Care and Maintenance


* To “store” your propeller properly after flight:* To “store” your propeller properly after flight:– 2 bladers – horizontally.2 bladers – horizontally.– 3 bladers – 2 up and 1 straight down.3 bladers – 2 up and 1 straight down.– 4 bladers – 2 up and 2 down.4 bladers – 2 up and 2 down.

- Storage in this manner prevents rain or moisture from - Storage in this manner prevents rain or moisture from settling in the cavity at the base eliminating the settling in the cavity at the base eliminating the opportunity for moisture to seep in and case corrosion opportunity for moisture to seep in and case corrosion or destroy the affectivity of any lubrication.or destroy the affectivity of any lubrication.


* Stay out of tall grass. It’s not a lawnmower.* Stay out of tall grass. It’s not a lawnmower.

* It’s not to be used as a tow bar. Do * It’s not to be used as a tow bar. Do notnot use the use the

propeller tip to move the aircraft!propeller tip to move the aircraft!

* Stay away from water puddles. Why? Ever notice * Stay away from water puddles. Why? Ever notice the vortexing when running up over water? the vortexing when running up over water? The blades are so thin that one tip may decide to go The blades are so thin that one tip may decide to go to one side while the other blade tip takes to the to one side while the other blade tip takes to the other side and now the prop is out of track. Avoid other side and now the prop is out of track. Avoid the vortex scenario. This can be real costly.the vortex scenario. This can be real costly.

Proper Care and Maintenance

* Note: A.D. 2004-10-14 Lycoming Engines

Change in definition of propeller strike or

sudden stoppage.

“(3) A sudden RPM drop while impacting water, tall grass, or similar yielding medium

where propeller damage is not normally

incurred.”

Overhaul PeriodsOverhaul Periods* Hartzell Service Letter-----HC-SL-61-61Y* Hartzell Service Letter-----HC-SL-61-61Y “ “Propeller – Overhaul Periods and Service Propeller – Overhaul Periods and Service Life Limits for Hartzell Propellers, Life Limits for Hartzell Propellers, Governors, and Propeller Damper Governors, and Propeller Damper Assembllies”. Assembllies”. * McCauley Service Bulletin SB137Y----”Revised * McCauley Service Bulletin SB137Y----”Revised time between overhaul (TBO) specifications”. time between overhaul (TBO) specifications”.

Overhaul PeriodsOverhaul Periods

* Notice there is no “recommended” in * Notice there is no “recommended” in

there anywhere.there anywhere.

* If you exceed or go past the TBO limits, * If you exceed or go past the TBO limits,

you are all alone with no back-up oryou are all alone with no back-up or

support.support.

Dynamic Dynamic

Propeller Propeller

BalancingBalancing

Dynamic Propeller BalancingDynamic Propeller Balancing

* Understand Basics of Vibration* Understand Basics of Vibration

* Understand the Benefits of Balancing * Understand the Benefits of Balancing

* Understand Fundamentals of Dynamic * Understand Fundamentals of Dynamic Propeller BalancingPropeller Balancing


DefinitionDefinition For the purpose of For the purpose of

Propeller Balance, Propeller Balance, vibration can be vibration can be described as: described as: “the unwanted, “the unwanted, unproductive, cyclic unproductive, cyclic oscillation of the oscillation of the propeller and engine propeller and engine assembly about its assembly about its rotational axis.”rotational axis.”


* Understand that * Understand that anyany imbalance at the imbalance at the center of rotation amplifies itself as it travels center of rotation amplifies itself as it travels out to the tip of the propeller. The tips being out to the tip of the propeller. The tips being thin vibrate augmenting the vibration and thin vibrate augmenting the vibration and also show a lose in efficiency.also show a lose in efficiency.


Vibration-Related Complaints Vibration-Related Complaints * Passenger complaints of noise in the cabin* Passenger complaints of noise in the cabin

* Cracked exhaust stacks and sheet metal* Cracked exhaust stacks and sheet metal

* Higher than normal occurrence of engine and prop * Higher than normal occurrence of engine and prop oil leaks and light bulb failuresoil leaks and light bulb failures

* Physical movement of airframe (buzz in the seat, * Physical movement of airframe (buzz in the seat, yoke, rudder pedals)yoke, rudder pedals)

* Malfunctioning or failed avionics* Malfunctioning or failed avionics


How It Is MeasuredHow It Is Measured* The vibration sensor * The vibration sensor

generates a small generates a small voltage when the mass voltage when the mass compresses the compresses the piezoelectric element. piezoelectric element. That voltage is That voltage is proportional to the proportional to the force being exerted on force being exerted on the element.the element.


How It Is MeasuredHow It Is Measured

* Engineering Units * Engineering Units – MilsMils (0.001 inches) - displacement (0.001 inches) - displacement– IPS (Inches Per Second) - velocityIPS (Inches Per Second) - velocity– gsgs (equivalent gravities) - acceleration (equivalent gravities) - acceleration


Equipment RequiredEquipment Required* A device to collect * A device to collect

vibration and phase vibration and phase data.data.

* A phase angle /speed * A phase angle /speed sensing devicesensing device

* A vibration sensing * A vibration sensing devicedevice

* Accessories: Cables, * Accessories: Cables, balance weights, hand balance weights, hand tools.tools.


Data Collection & ProcessingData Collection & Processing* The vibration sensor is installed * The vibration sensor is installed

on the engine as near the front on the engine as near the front bearing as possible. The bearing as possible. The Phototach is mounted on the Phototach is mounted on the cowling, behind the propeller. cowling, behind the propeller. The reflective tape is applied to The reflective tape is applied to the back side of the target the back side of the target propeller blade in line with the propeller blade in line with the Phototach beam. The mass is Phototach beam. The mass is located by the relative located by the relative occurrence of tach trigger and occurrence of tach trigger and mass passage at the radial mass passage at the radial sensor location.sensor location.


The Balancing ProcessThe Balancing Process

* With the equipment * With the equipment installed and all installed and all previously installed previously installed trim weights (not static trim weights (not static weights) removed, weights) removed, head the airplane into head the airplane into the wind (10 kts the wind (10 kts maximum) and begin maximum) and begin the data collection.the data collection.


Data Collection & ProcessingData Collection & Processing* As the heavy spot on the * As the heavy spot on the

propeller passes the location of propeller passes the location of the vibration sensor, the sensor the vibration sensor, the sensor generates and sends an generates and sends an electrical pulse to the analyzer. electrical pulse to the analyzer. The Reflective tape triggers a The Reflective tape triggers a response as it passes the response as it passes the Phototach, which then sends an Phototach, which then sends an electrical signal to the analyzer. electrical signal to the analyzer.


Data Collection & ProcessingData Collection & Processing

* When sufficient data * When sufficient data has been collected, the has been collected, the process is stopped by process is stopped by the operator and the the operator and the averaged data averaged data displayed on screen. displayed on screen. Notice that you have Notice that you have the option to the option to Retake Retake the data if desired.the data if desired.


Data Collection & ProcessingData Collection & Processing* A solution is then * A solution is then

provided by the provided by the instrument based on a instrument based on a stored influence stored influence coefficient or a coefficient or a calculated test weight. calculated test weight. If required, the process If required, the process is then repeated for is then repeated for refinement of the refinement of the solution.solution.


The Balancing ProcessThe Balancing Process* Where to place the weights* Where to place the weights

– Test weights can be placed under the spinner Test weights can be placed under the spinner retention screws. It may be necessary to use retention screws. It may be necessary to use longer screws for the test weights. If doing so, longer screws for the test weights. If doing so, account for the delta between the normal and account for the delta between the normal and the longer screw. Be sure you are measuring the longer screw. Be sure you are measuring the angles in relation to the sensor or tape as the angles in relation to the sensor or tape as you specified in the setup being used.you specified in the setup being used.


The Balancing ProcessThe Balancing ProcessPermanent weights may be installed under the flange or on the bulkhead. If installed under the flange, offset from spinner attaching screws by four times the diameter of the spinner screws.


* There is no difference in the propeller * There is no difference in the propeller balance procedure for a radial engine, balance procedure for a radial engine, opposed engine, turboprop, geared, variable opposed engine, turboprop, geared, variable pitch, or fixed pitch propeller.pitch, or fixed pitch propeller.


* Remember that dynamic balancing will * Remember that dynamic balancing will prolong the life of the engine, propeller, prolong the life of the engine, propeller, airframe and avionics.airframe and avionics.

* Before dynamic balancing and right after * Before dynamic balancing and right after propeller installation, it is best to put a few propeller installation, it is best to put a few flight hours or good high end runs on it first. flight hours or good high end runs on it first. This will allow the blades to take their “set” This will allow the blades to take their “set” and eliminate the need to re-do the and eliminate the need to re-do the balancing later on.balancing later on.


* Remember that when dynamic balancing * Remember that when dynamic balancing you are balancing from the engine mounts you are balancing from the engine mounts forward.forward.

* Dynamic balancing is * Dynamic balancing is notnot a “cure all”, as it a “cure all”, as it can not compensate for gear doors that do can not compensate for gear doors that do not close properly, worn control surface rod not close properly, worn control surface rod ends, beta rings not exact, etc.ends, beta rings not exact, etc.

* It is becoming the professional opinion that * It is becoming the professional opinion that allall engines with propellers should be done. engines with propellers should be done.

Quick Question

* You spend countless hours, phone calls, referrals, and do whatever you feel necessary in selecting an overhaul facility for your engine. How much time do you take to select a propeller overhaul facility? All too often, not nearly enough and yet the ramifications can be extremely costly, if not deadly.

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propellers - 101

Documents

feathering stop

speed of sound

blade failure

blade play

propeller tip speeds

lack of oil pressure

pitch change

excessive movement