Aircraft Propellers

Engine Block and Magneto Check

• Engine block is the same as engine run-up.
• Check magnetos in block 14.
• In a constant speed variable propeller, set the pitch to low for high RPM to check the laminar.
• Checking the P-lead connections from the mags to the airframe structure.
• Ground and P-lead check on the magneto.
• Pitch should be low (high RPM) for proper magneto checks in a constant speed propeller.

Constant Speed Propeller Checks

• Ground checks for mags are done before flight or after maintenance.
• Engine run-up is always done after everything is done and in service.

Hydromatic Propeller System

• Hydromatic propeller testing differs from Hamilton counterweighting and McCauley non-counterweight designs.
• Exercise the propeller by moving the governor control through its entire travel several times to free the dome.
• Dome is another term for the propeller hub in hydromatic propellers.

Hydromatic Propeller Dome

• The dome in a hydromatic propeller lacks counterweights and springs, relying purely on hydraulic/oil pressure.
• Oil is supplied and drained on both lines of the dome.
• Dome has outboard and inboard sides.
• Middle contains a double actuating piston.
• Double action: piston can move forward and backward, requiring differential oil pressures from either side.

Oil Flow

• Oil can come in or out of the lines.
• Supplying oil causes the piston movement to go forward, pushing the oil out on the other side and vice versa.
• There is a component at the back end that causes the oil flow to change, working with the prop governor.

Pitch

• Supplying oil on the inward pitch moves it to high pitch.
• Changing the oil pressure with the assembly (working with the prop governor) changes something.
• Oil moving on the outboard side can potentially lead to reverse pitch after low pitch or feather after high pitch.

Air Bubbles

• Air can enter the system through the filter, creating air pockets.
• Air bubbles in the oil change viscosity, which is more exposed in temperature.
• Cycling the entire pitch range of a hydromatic propeller is necessary before running to remove air, similar to priming without pushing the primer body.

Hydromatic Propeller Characteristics

• Hydromatic Propellers are constant speed propellers, not fixed pitch.
• Made of hollow metal alloy.
• Degrees ranges of pitches:
  • Propeller blade angles represent feather, power, flight idle, ground idle, and reverse positions.

Blade Angle Positions

• Positions of propeller blade angles and their nomenclatures.
• Fine pitch = low pitch.
• Relative wind creates pressure behind, increasing power and thrust.

Thrust

• Low pitch produces forward thrust.
• Zero thrust produced in feather, locks, and ground idle positions.
• Positions not shown that slow down engine: High and low, between power and feather, high pitch, low RPM.
• Variables affecting propeller control lever movements: specific angle degrees cause more or less power production.
• Positions exist for zero thrust and reverse thrust (for water maneuvers).

Power Output

• Basic operation sequence for reducing power output:
  • Reduce manifold pressure first through the throttle lever.
  • Then, reduce the RPM with the prop lever.
  • Fuel air mixture: can remain rich or full rich to decrease amount of RPM without losing cooling integrity.

Instruments

• Decreasing power: throttle back (throttle down) causes manifold pressure decrease, affecting brake mean effective pressure (BMEP) inside the cylinder.
• Moving the prop control lever down affects RPMs.
• Two tach meters should go down.

Increasing Power

• Increasing power: set the pitch to low first, increasing RPM on both tach meters, then move the throttle.
• Decreasing power, blade angle is at high pitch; increasing power, blade angle is at low pitch.
• Option for reverse: pitch goes low to reverse.

Power Changes

• Reducing power: decrease manifold pressure via throttle lever, then increase pitch via prop control lever.
• High manifold pressure and low RPM can cause cylinder pressures similar to over boosting.
• Reciprocating engine with turbocharger and constant speed propeller: more susceptible to over boosting.

Potential Faults

• Over boosting and cylinder detonation more likely if differential pressure control and desiccant control fail.
• Prop governor malfunction increases over boosting susceptibility.
• Lubrication system affects all three components.

Proper Functioning

• Over-boosting

  • Delta-P
    • push it back
    • supply the correct type of oil

• Opening the throttle when the propeller is in its constant speed range while developing cruise power will cause an increase in blade angle.

Forces

• Aerodynamic twisting force > centrifugal twisting force

  • resulting in un even forces

• Aerodynamic twisting force causes the blade angle to go higher.

• Reaction of propeller when only the throttle lever is moved.

BMEP

• Opening up throttle valve allows more BMEP to flow in.

• Propeller spins faster, but there is a misalignment between the settings of throttle valve and prop control lever.

• Don't increase throttle, then prop lever.
  * can cause damage

• Blade Angle at high pitch isn't a good thing

Slide 10

• Move prop lever first and then throttle lever when are increasing power
• Adjustments will be made with the Prop Governor automatically
• Fuel remains constant for cylinder cooling reasons
  • Don't move the Mixer * *Constant speed propp
    • You can maintain the RPM and Increase blade Angle
      = prop governor preventing over speeding

Propeller Characteristics & Components:

• Constant speed propeller tries to maintain the pre-set speed (governor) by increasing blade angle to prevent over speeding.
• Maintains a low angle of attack.

Angle Of Attack

• Low angle of attack: relative wind is being taken more but smaller bites.

• High angle of attack: bigger bites.

• Increasing blade angle is not really going is a big one

• Increasing the blade angle is moving from 10 to 12 degrees to 20 to 35 degrees.

• Still in low Pitch

• Between 10-12 degrees am I increasing pitches slightly?Yes

• What general pitch am I still in? Low, so it keeps producing power.

Zero / Negative Thrust

• Ground Lock

Low Pitch

• Why is this so low?
  *Because its helping w/ Air flow
  *It does Not spin

*Feather position = glide through air

Constant Speed Propeller at lower speeds:

• Constant propeller = Propeller stays at low Pitch

Underspeed situation occurs

• Not just reacting on it.
• Also preventing it for happening.

Example:

*The Govener has to go to under-speed at 23RPM
*Exhibits

• Propeller goes into lower pitch
• So the engine can go into 25RPM

Constant speed Propeller

• Why do they all Go to locks / feather / idle

  • There dealing w/ CPS
    • CPS also is know as Vibration and blade shake
      * constant speed collage are more seceptibale to blade shakes. Than a fix Pitch metallic.

• Constantly changing the pitches?
  *yes
  More seceptible to Blade CPS

  • When blade vibrations occur = Engine Vibrate also

*Inches per/second vibrations = Vibration # and = to that

*Green Flag = Inches per second is between point 7.25/ Mean It Will Not shake at all

• Propeller
  *Ground
  *Bad balance (needs fix ASAP)

Why are we so meticulous when we sync prop?

• Everything that I taught you now is working w/ one propp engine.

  • Multi Engines:
    *All of it can go kaput if your not careful / so you MUST follow refrence manuals.

  • A specfic Prop has a specific propp manufactruer

  • Has instructions how to Grease / maintain It.

Given two types of propps:
· Hamilation tatter weighted
Macaulay cell

*hydromantic Propp can be made by cell
*Greese and oil comes with antifriction and plascting.
*We need friction where? joint
*Very HIGH friction
*Is Bearings inside PROP? yes
*We are the one Freaking Grease on Dome of Prop
*Greese is for Freak lubrication / and the OTHER.
*August said.
*We are the one servicing it.
*Oil is NOT be servicing In prop hub
*Oil Tank

Grease Point is also know as: Zerk Fittings.
Grease and zerk:

1. One is holding it onto wire
2. Less mess from it to drop

*Grease points and its going though them
*Make sue you know what the oil it looks like
Old Grease = Black(ish)
New Gerese = Light yellow is color

*waiting till yellow comes out
*Inboard/ Outerboard?
Pitch Changer.
What do we lube the pitch changer w/?
*Do NOT have add extra virgin Oil
Oil Tank
*Vegetable oil? Skindral? Even B1 ( are you going to check if the fluid is there, if so its at Travel check)
*Alpha Ranged & Beta
All goes Kapaht!
Which refrrenece we go to?
*Props MDS?
*Props Manufactruer Man.
*All infomational given on those paper.
*greese/oil spces

• reems
• Fixing
• The surfaces
  Given two types of propps: Hamilton Tartner Weighted: mccauly / hart cell
  Mircar Props are made of hart cell
  you have been given the greese and the oil
  whats oil characteristics? and why do joint need so much friction
  whats inside Propeller valve
  Barons = Grease all Baron/ and out