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CAA Module 17 > Module 17.2 Propeller construction > Flashcards

Module 17.2 Propeller construction Flashcards

1
Q

What is the most commonly used wood propeller construction?

A

Birch

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2
Q

What forms a blank?

A

At least 5 layers of wood glued together

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3
Q

Why is the blank left for a week after being roughly shaped?

A

Equal moisture distribution

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4
Q

After the blank has been left for a week what is it now referred to as?

A

A white

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5
Q

A cotton fabric sheathing is then applied to the outer 12 to 15 in (30 to 38 cm) of the tip, for what purpose?

A

Reinforce the strength of the thin sections at the tip

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6
Q

What is done to the fabric to protect it?

A

Doped

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7
Q

To prevent damage what is rebated onto the leading edge?

A

Protective metal strip

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8
Q

What metals are used to protected the LE?

A

Brass, stainless steel, monel (nickel/copper alloy) or terneplate (steel coated with a lead/tin alloy).

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9
Q

How is the tipping secured in thick blade sections?

A

Countersunk screws

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10
Q

Where are copper rivets placed?

A

Near the tip

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11
Q

How are the rivets safetied?

A

Solder

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12
Q

What is the purpose of drilling small holes in the tip?

A

Release moisture and allow the wood to breathe

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13
Q

Some propellers have a final coating of polyurethane paint for which purpose?

A

Mechanical and UV protection

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14
Q

How are wooden controllable pitch propellers secured to the metal sleeve?

A

Using lag screws

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15
Q

What are the methods of securing the propeller to the engine?

A
  • Splined
  • Tapered
  • Forged steel hub
  • Bolted
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16
Q

What LE protection do composite propellers have?

A

Nickel or CRES

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17
Q

How can Composite blades with a spar be constructed?

A

Spar, coated in fibreglass, kevlar or carbon fibre shell with foam or honeycomb in front and behind the spar.

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18
Q

What loads does the spar absorb?

A

Centrifugal forces and bending loads

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19
Q

What does the composite shell give the propeller?

A

Torsional rigidity

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20
Q

What is on the inner and outer surface of the LE?

A

Heating element - inner
Metal guard - outer

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21
Q

How is the blade surface protected? (composite)

A

Conducting polyurethane paint

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22
Q

What purpose does the paint coat serve? (composite)

A

Erosion protection and prevents it from being statically charged

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23
Q

How are composite blades without a metal spar constructed?

A

Two carbon fibre components in the blade that form the spar. Hollow core filled with foam

24
Q

What is used to horizontally balance the blade?

A

Lead wool in a hollow balancing tube

25
Q

How is the lead wool retained in place?

A

Use of a rubber plug

26
Q

What are the two different types of metal propeller?

A

Aluminium alloy or steel

27
Q

What type of propeller has better cooling properties for reciprocating engines?

A

Aluminium alloy

28
Q

Are steel propellers commonly used?

A

No, not really anymore

29
Q

How do you make steel blades lighter?

A

Hollowed out

30
Q

How big is a blade station?

A

6 inches

31
Q

How are the blade stations numbered?

A

From root to tip

32
Q

Where is the master reference station on a fixed pitch propeller?

A

75% from centre of rotation

33
Q

Where is the master reference station on a variable pitch propeller?

A

50 to 75% from the centre of rotation

34
Q

What is the master reference station also a reference point for?

A

Where most of the thrust of the blade acts

35
Q

Can the pilot control the angle of a fixed pitch propeller?

A

No

36
Q

What are the two types of controllable pitch propellers?

A
  • Two position (high or low pitch)
  • Variable pitch
37
Q

How does the propeller control regulate engine RPM?

A

Manipulating blade angle

38
Q

Why is it necessary to change the blade angle?

A

To maximise the blade angle

39
Q

In older systems how is blade angle manipulated?

A

Crank handle which drives a pinion gear through a cable

40
Q

A constant speed propeller is what?

A

A propeller that is designed to automatically change its blade pitch to allow it to maintain a constant RPM

41
Q

How does a constant speed unit work?

A

Principle of centrifugal force and incorporates a speeder spring edna set of fly weights

42
Q

How is constant speed maintained?

A

Constant speed unit or governor

43
Q

In an engine overspeed condition what occurs to the piston? (Constant Speed Unit Governor)

A

Flyweights separate and piston rises. Allowing oil pressure to be directed to the propeller to push it to a coarser angle

44
Q

In an engine underspeed condition what occurs to the piston? (Constant Speed Unit Governor)

A

Flyweights come closer and piston sinks. Allowing oil pressure to leave the propeller to allow the blade to move to a finer blade angle

45
Q

What occurs at normal speed? (Constant Speed Unit Governor)

A

Hydraulic lock

46
Q

What are three types of shafts?

A
  • Tapered shaft
  • Splined shaft
  • Flanged shaft
47
Q

How is the drive transmitted in a tapered shaft?

A

Key that is seated

48
Q

When are splined shafts used?

A

High output radial engines

49
Q

Why is one end of the splined shaft threaded?

A

To accommodate the hub nut

50
Q

How may the propeller shaft be connected to the engine crankshaft?

A

Large aircraft - Reduction gearbox
Small aircraft - extension of crankshaft

51
Q

When are flanged shafts used?

A

Modern turboprop and reciprocating

52
Q

What does a flanged shaft have for synchronisation?

A

Index pins

53
Q

Why are spinners mounted?

A
  • Protection
  • Aerodynamics
  • Aesthetics
54
Q

What loads are extremely high on the spinner?

A

Dynamic loads

55
Q

How may cracks be stopped on a spinner?

A

Stop drilling

56
Q

On spinner installation, it must be ensure that there is no what?

A

Noticeable wobble

CAA Module 17 (6 decks)

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