Knowledge Levels 1, 2, 3

Knowledge Levels

• Basic knowledge for categories A, B1 and B2 indicated by knowledge levels 1, 2, or 3.
• Category C applicants must meet either B1 or B2 basic knowledge levels.

Level 1

• Applicant should be familiar with the basic elements of the subject.
• Applicant should be able to give a simple description using common words and examples.
• Applicant should be able to use typical terms.

Level 2

• General knowledge of theoretical and practical aspects, with ability to apply knowledge.
• Applicant should be able to understand the theoretical fundamentals.
• Applicant should be able to give a general description using typical examples.
• Applicant should be able to use mathematical formulae with physical laws describing the subject.
• Applicant should be able to read and understand sketches, drawings, and schematics.
• Applicant should be able to apply knowledge in a practical manner using detailed procedures.

Level 3

• Applicant should have detailed knowledge of theoretical and practical aspects.
• Applicant should have the capacity to combine separate elements of knowledge in a logical manner.
• Applicant should know the theory of the subject and interrelationships with other subjects
• Applicant should be able to give a detailed description using theoretical fundamentals and specific examples
• Applicant should understand and be able to use mathematical formulae.
• Applicant should be able to read, understand and prepare sketches, drawings and schematics.
• Applicant should be able to apply knowledge using manufacturer's instructions.
• Applicant should be able to interpret results from various sources, and apply corrective action.

Propeller Forces

• Aerofoil prop or wing shape is designed to increase airflow velocity over its cambered surface, decreasing pressure.
• Reduced pressure above and higher pressure below produces upward force termed lift.

Lift

• Aerodynamic force caused by air flowing over an aerofoil.

Drag

• Force resisting thrust caused by disruption/impact of airflow.

Thrust

• Forward acting force.
• Reaction to mass of air accelerated rearwards.
• Felt on the blade face forming basis of momentum theory for propellers (Newton's Third Law of Motion).
• Momentum is quantity of motion of moving body measured by mass and velocity.

Total Reaction

• Resultant of two pairs of forces.
• Lift and drag.
• Thrust and torque.

Propeller Rotational Speed

• Increase in rotational speed increases forces equally
• Restricted to point where blade tip speed remains below sound speed

Blade Angle

• Angle between chord line (imaginary line through blade) and plane of rotation, measured in degrees.
• Varies from root-to-tip.
• Measured with reference to a datum point such as 75% of the radius.
• Aircraft Maintenance Manual/Aircraft Type Certificate give angles/positions.
• Example Sensenich propeller M74 DMSS-2-60, '74' is the propeller’s diameter in inches, '-60' signifies its pitch at 75% station in inches.

Angle of Attack

• Angle between chord line and angle of relative wind/airflow
• Should be 2-4° for best results, compressing incoming air, expanding it at trailing edge resulting in thrust.
• Combination of two airflows due to forward motion i.e. True Air Speed or TAS and rotational speed revolutions per minute (rpm).

Blade Twist

• Faster the section of the blade is traveling, the further the distance from the hub along the propeller blade.
• Blade manufactured with gradual twist from hub to tip for even thrust production.
• Blade angle decreases toward tip, ensuring correct angle of attack is maintained.
• Design consideration: shockwaves and vibration will be produced that prevents producing thrust if tip reaches sound speed.

Pitch

• Distance propeller moves forward in one revolution.
• Differs for variable pitch propellers.

Propeller Slip

• Defined as difference between geometric and effective pitch.
• Geometric pitch is calculated distance propeller advances in one revolution through solid medium.
• Effective pitch is distance propeller advances in one revolution moving through air.
• Slip represents loss of efficiency.
• Most propellers 75-85% efficient.
• Example: Prop with 50 in geometric pitch moving forward 35 in per revolution has effective pitch of 35 inches is 70% efficient.

Effects on Aircraft Stability

• Anti-clockwise propeller torque affects the aircraft structure tending to roll it clockwise.

Propeller Gyroscopic Effect

• Rotating mass of the propeller may cause gyroscopic effects which may cause resistance in plane of rotation.
• Body resists change in plane of rotation.

Propeller Slipstream

• Rotating propeller imparts rotational motion to slipstream in same direction as propeller.
• This has an adverse effect on aircraft's fin.

Contra-Rotating Effect

• Eliminates propeller torque, slipstream, and gyroscopic effect.
• Second propeller straightens first, increasing control with straight high-speed airflow.
• Propeller torque is cancelled because the propellers are spinning in opposite directions, therefore neutralizing gyroscopic effect.

Forces Acting on a Propeller

• Centrifugal
• Centrifugal Twisting Moment (CTM)
• Aerodynamic Twisting Moment (ATM)
• Bending
• Thrust and drag

Centrifugal Force

• Force throwing rotating propeller blades away from hub
• Can mount to many thousands of newtons

Centrifugal Twisting Moment(CTM)

• Force that rotates propeller blades toward a fine blade angle on variable pitch propellers.
• Propeller mass is located in front of rotational axis aligning itself with plane of rotation.
• Greater force compared to Aerodynamic Twisting Moment.
• Propeller manufacturers use this to alter the blade angle from coarse to fine.

Aerodynamic Twisting Moment (ATM)

• Force which tries to move propeller blades to a coarser blade angle.
• Centre of pressure resides in front of the rotational axis of the blade near the chord line midpoint.
• Tends to increase blade angle.
• Some designs use force for feathering.

Forces Bending

• Divided into two components, torque bending force and thrust bending force.

Torque Bending Force

• Resultant force coming from the load of drag or air resistance places against the blades
• Bends the propeller blades away from the direction of rotation.

Thrust Bending Force

• Force which bends blades forward aircraft is pulled through air
• This force bending the blades forward propels the plane.

Force Coupling

• Severe stress creating greater energy near the hub as a combination of centrifugal force and thrust.
• Because of tension from centrifugal and bending the blade face sustains exposure
• The design withstands these increasing stresses because blade must sustain rpms
• Simple scratch/dent will cause severe repercussions

Propeller Angle of Attack

• Vectors help in understanding its variance.
• Line that is drawn to scale shows velocity or force.
• Lines represent item speed
• Performance of fixed pitch propeller will vary given variance from Rotational velocity or rpm and aircraft velocity

Rotational Velocity

• (rpm) and aircraft velocity (TAS in kt) dictates design of desired results given correct design angle attack

Increased Rotational Velocity

• If forward velocity remains sustained, rotational velocity increase will result with the angle of attack will rise

Increased Forward Velocity

• If increase in forward velocity plus sustained rotational velocity then relative airflow will subside the angle effect.
• Rotate blades get negative angle effect that results when creating no thrust like brake

Blade Tip Speed Version Efficiency

• Absorbing engine power achieved by larger propellers, diameter will did not necessarily increase efficiency
• Larger propellers caused loss from tip vibration.
• Shockwaves caused vibration/flutter of 1200 ft/s (or 660 kt) at seal level for 15-dg C
• Important be under these conditions, and increase blade shape and section

Blade Vibration

• Final Force exerted when spinning propeller is blade vibration
• Blades vibrates when Thrust occurs when blade vibrations happen from aerodynamic forces
• Tendency of bending the blades forward near the tips, causing buffeting plus vibration
• Power pulses in piston engine causes mechanical vibrations
• Engine power pulses result with standing propellers the result with metal fatigue from structural cracks
• Detrimental concentration in blade stress is about 6inches.

Propeller Construction Materials

• Wood
• Steel
• Aluminium alloy
• Composite (non-metallic fibre)

Leading Edge

• Thick edge that first meets the air that rotates the propeller due to aerofoil shape

Trailing Edge

• Rear edge of propeller blade, where blade camber face and thrust faces connect after leaving leading edge.

Blade Back

• The curved face of a propeller aerofoil and joins the leading and trailing edge.

Blade Face

• Flat side of a propeller blade and thrust is created.

Chord Line

• Aids in set propeller blade angles with straight line from centre of LE & TE

Blade Stations

• Maintenance personal locates positions.
• Length measures distance measured from hub center that are tip to tip on blade
• Station lengths measured.
• Typically 6 inch intervals between blades, but locations are 18-24 inches

Hub assembly

• How propeller to engine is attached plus supports the blades.
• Barrel halves divide (forward & rear) then enable blades onto the spider, creating bearing support for variable pitch propellers.

Root Blade

• The round blade root, also known as the blade butt, is the part which fits into propeller hub

Blade shank

• Cylindrical part near the blade root.
• Thick for strength, but provides zero propulsion.

Blade

• Is the aerofoil part that creates torque into thrust.

The Tip

• portion in the blade furthest from the assembly’s hub
• Typically referred to last 6 inches.

Propeller Blade Cuffs

• Blade cuffs restores shape, and increases flow in the engine, usually bonding to the blade Wooden Propellers

Earliest Fitted

• Timber construction that were made from with layers and glue

Laminating

• Specially select timber and well-seasons
• Timber has zero imperfections
• Holes
• Loose Knots
• Decay.

Varnishing

• kiln that creates pressure and temperature to design
• coatings for the propeller such as varnish
• swelling,
• Shrinking
• Warping.

Leading edge Sheathing

• Shields at edge/tip create protection that is made from:plate
• Terneplate
• Monel
• Brass
• Stainless Steel

Metallic Propellers

• Main found on antique aircraft that normally create hollow construction
• Construction with rib, metal sheets, and filling

Aluminium Alloys

• A fixed-pitch aluminium propeller gets forge-in into its required shape , as a shape of referred to as profile, to the bar.
• A centre bore the middle creates fitment for adaptors , the fitters.

Anodising

• add the extra safeguard to alloy blades by using electroplating or by using hard coating which are: Corrosion resistant
• Waterproofs
• Airtight

Shot Peening

• Metal distributes at surface more in the equal way with steel strength
• Process create glassed steel.

Composite Propellers

• Involves resin that reinforces glass filament
• Glass
• Kevlar
• Carbon
• Boron

Fibre Reinforced Plastic (FRP) Moulding

• Kevlar sheet contains a form.
• Kevlar increase protection that reinforce Kevlar
• Leading & trailing that reinforce by the solid kevlar
• Resists flexing, to boost the strength of the sheet

Purpose of Flanged, tapered & spinner propeller installation

The purpose, correctly, is to avoid vibration, and to fit all

• Tapered installations. Smaller engines to flange in better
• Taper shaft, found on some propeller Installation needs
• Distortions on surfaces inspected
• bolt holes are in correct standing
• light coats help with flange
• Use of parts like nDT

Splined Shaft

• Found commonly on propeller shaft or turboprops Tight but sliding fit

Go not Go

• Gagues are required, like and especially during inspection of cracks or damage of these corners

Taper Bore

• Forging, with bushing and static balance.

Axial Lock Rotation

• Forcing with bearing or grease
• Propellers are fitted and bolted with the pilot

Installation Checks

• Ensure indexing proper before fitted
• Splines must
• Be with 4 and/or 10 for hand start
• Use manuals/washers before insertion
• Wood faceplate for wood propeller for compression
• Track test will provide if tips are balanced

Tractor Propellers

• Mounted to engine power plant
• pull through the wind.

Pusher Propeller

• Shaft with drive and rear.
• Mounted behind/above the wings
• Sea places with aquatic.

Fixed Pitch

• Specific use (cruise/accelerations)
• Performance stops to certain purpose of operation
• Wooded/metaled

Ground-Adjustable Propellers

• The blades were adjusted of specific height when being tightened
• Not changeable.

Controllable-Pitch Propeller

Ability to alter blade during rotation, to adjust for different settings and conditions of the blade

Constant-Speed Propeller

• Speed governors are additional fit with the air craft to permit turbine combination
• Variation is adjusted if engine revolutions per minute (RPM) to to bring
• Type protects from fluctuations

Contra-Rotating Propellers

• Two propellers are mounted in line
• For efficiency out put the two high powered engines.
• The cancelling torque & spiraling helps.

Counter Rotating Propellers

Must NOT be mistaken with counter application of engine turns.

Feathering

• controllable that turns multi air craft, so
• Pilot with single to help windmilling that will hurt the aircraft
• Rotation so thrust is a mechanism with
• Leading windmilling stoping

Reversing

• Aids to permit air craft to reduce: landing runs, broke or tyre wear.
• Slow landing for aircraft to travel to reverse of flight to help landing.

Negative pitch angle

• Thrust are negative or reverses thrust as the propeller nows acts the air flow with side rearwards
• Reversing prop, have positive in the air now be for side

Negative Torque Sensing

• Negative torque system acts as safety.

Propeller Brakes

• Designed to prevent damage or keep to long run due to the aircraft parking and the propellers downing.

Torquemeter

• Guages engine operating conditions, which sends electrical singles which process sensor with the level indicator

Manual Pitch Change Construction is what relates to being adjustable, but after, requires tight clamp, in replace adjustment Mechanical Concepts from 197 is a mechanic that provides a range for light aircraft conditions and flight.

Cockpit propeller

Helps pilot set flights conditions but rotate with the flex then drive the gears

Electric

Allows flight less horse power through speed and cost. Toggle of different controls for the user to managed

Unfeathering accumulates Increases governor and normal pressure

Contra Torque system

Has pump and beta.

• 2 levered 3 the
• Lever to select modes

Feathering

• controllable to support high flight, a 90' angle
• Prevent failures
• Aircraft flies preventing wind

Purpose of Governor

• To maintain RPM with conditions changing to provide with correct angle of speed for slowing that's selected

Single-Acting Governors

• Controls oil into what an action propeller. Used to control the flow using RPM for best speed

Governor Drive Shaft

• The governor drive shaft is connected directly to the engine drive train and rotates proportionally to the engine speed. It connects the governor oil pump, pilot valve and governor flyweights, all rotating as one unit, via a bearing to the bottom of the non-rotating speeder spring.

Governor Oil pump

Takes the engine oil and provides power to the vessel or device that needs propeller motion at the excess level.

Electrical

Valve is there to allow for propeller operation. Allows from shaft and speed in or out.

Hydro Mechanical (Oil pressure system)

• Low gear then with constant contact with all
• Blade
• -assembly for turbine

Speeder Speed

• Position

Balanced gear

• Protects the propeller where a useable power the control user.

Explanation of knowledge levels 1, 2, and 3. This includes familiarity with basic elements, general knowledge, and ability to apply knowledge practically. Outlines expectations for describing subjects, using terminology, and understanding schematics.