17.2

Question 1

What is the most common wood used to make a wooden propeller?

Answer 1

Birch

Question 2

A minimum of 5 laminates are bonded with what?

Answer 2

Aeroglue

Question 3

A minimum of how many laminates is bonded with aero glue?

Answer 3

5

Question 4

How long are wooden propellers left for and why in construction?

Answer 4

Left for one week for even moisture distribution

Question 5

What is it known as when a wooden propeller has been left for a week for even moisture distribution?

Answer 5

Propeller white

Question 6

What is added to wooden propellers for added strength?

Answer 6

Fabric sheathing

Question 7

How is metal tipping secured at leading edge of wooden propeller?

Answer 7

Tipping secured using countersink screws
Tips secured with copper rivets

Question 8

What can tipping be made from?

Answer 8

Brass
Stainless steel
Monel (nickel and copper alloy)
Terneplate (steel coated with a lead/tin alloy)

Question 9

Why are three 3/16” holes drilled in wooden propellers?

Answer 9

Draining
Allow wood to breathe

Question 10

Final stages of wooden propeller construction?

Answer 10

Balanced and varnished

Question 11

Modern propellers are painted with what for mechanical and ultraviolet protection?

Answer 11

Polyurethane

Question 12

What is metal spar made from?

Answer 12

Titanium
Aluminium
Stainless steel

Question 13

What is a composite propeller filled with?

Answer 13

Low density foam or honeycomb

Question 14

On a composite propeller what is the shell made from?

Answer 14

Fibreglass
Kevlar
Carbon fibre

Question 15

Does composite propeller always have a metal spar?

Answer 15

No
Some just filled with complete foam or honeycomb

Question 16

What is an aluminium blade made from?

Answer 16

Made from extruded formers of aluminium alloy
Shaped from a master blade

Question 17

Most common surface finish process for aluminium propellers?

Answer 17

Anodising
Stops corrosion

Question 18

Two grinding methods for aluminium propellors?

Answer 18

Manual grinding by a master blade as a template
Modern grinding done by CNC machine as more accurate

Question 19

Where are steel propellers found?

Answer 19

Old propeller aircraft

Question 20

Advantage of hollow steel propeller?

Answer 20

Saves weight

Question 21

Propeller blade station

Answer 21

Numbered from 1 onwards or the number of inches or centimetres from the root to its tip

Question 22

Propeller master reference station?

Answer 22

Measured from the centre of rotation
Normally 75% in a fixed pitch propeller
Can be 50%-75% on variable pitch propeller

Question 23

Propeller blade angle?

Answer 23

The angle between the blade chord line and the plane of rotation

Question 24

Propeller face?

Answer 24

The flat thrust producing side of a propeller blade

Question 25

Propeller blade root/shank?

Answer 25

The thickened portion of the blade nearest to the hub

Question 26

Propeller blade butt?

Answer 26

The base of the propeller blade where the root ends

Question 27

Propeller back?

Answer 27

The curved side of the propeller blade facing the direction of flight.

Question 28

Propeller hub?

Answer 28

Central portion of a propeller which carries the blades.

Question 29

Dome assembly?

Answer 29

Encases the pitch change mechanism

Question 30

Fixed pitch propellers are used up to what speeds?

Answer 30

250km/h

Question 31

Fixed propellers are favoured why?

Answer 31

Easier to produce Cheaper to maintain

Question 32

What conditions are fixed pitch propellers best suited for?

Answer 32

Best suited for cruising conditions

Question 33

Optimum angle of attack for fixed pitch propellers?

Answer 33

4 degrees

Question 34

What are disadvantages of a fixed pitch propeller?

Answer 34

-Maximum propeller efficiency only achieved in one phase of flight (take off or cruise) -Power available at take off is reduced because of lower RPM -The efficiency of propeller widely fluctuates -Pilot intensive (Must constantly be checking engine output power to RPM keeping within acceptable ranges)

Question 35

Why are blade angles adjusted on ground?

Answer 35

Change for desired conditions such as needing a short take off

Question 36

Variable blade angles change between what degrees?

Answer 36

7 and 15 degrees

Question 37

New blade angle is checked with what?

Answer 37

A propeller protractor at the master reference station

Question 38

There should be no more than what degrees variation between individual blades and desired blade angle?

Answer 38

0.1 degrees

Question 39

Two propeller aircraft controls?

Answer 39

-Throttle control, regulates power output of engine, registered on the manifold pressure gauge -Propeller control which is regulates engine RPM and therefore propeller RPM

Question 40

Constant speeding propellers are designed to do what?

Answer 40

Automatically change its blade pitch to allow it to maintain a constant RPM -Accomplished by means of constant speed unit or governor

Question 41

How does constant speed unit work?

Answer 41

Work on principle of centrifugal force Uses a speeder ring and a set of fly weights Can be electronically governed

Question 42

Advantages of constant speeding propeller?

Answer 42

-Maximum power in a narrow speed band -allows efficient use -Blade angle reduced torque required reduced- increase in RPM/ airspeed -Allowing propeller and engine to be set to optimum

Question 43

A spinner does what for the engine?

Answer 43

Gives better aerodynamics Protects the hub Aesthetic reasons

Question 44

Is the dynamic loads on spinner very high or low?

Answer 44

High Inspected regularly

Question 45

A spinner has no wobble on rotation, how will this help at higher RPM?

Answer 45

Magnify stresses

Question 46

What is the critical engine?

Answer 46

The engine that causes the smallest yaw moment