17.6.4 Propeller Treatment and Repair

Question 1

What is the nature of wood as a material?

Answer 1

Wood is a soft material that can be damaged easily and is at risk from stones, grit, and the environment.

Question 2

What types of damage can wooden propellers suffer during service?

Answer 2

Wooden propellers may suffer from scuffs, dents, bruising, nicks, scores, cracks, delamination, and warping.

Question 3

What should be checked during the periodic inspection of installed wooden propellers?

Answer 3

Checks for defects such as scuffs, dents, cracks, and loose or missing screws.

Question 4

What does the approved Maintenance Schedule specify?

Answer 4

It specifies the intervals when a wooden propeller is to be removed for inspection.

Question 5

What additional inspections are required on removed wooden propellers?

Answer 5

Inspect bolt holes for ovality, rough edges, cracks, boss faces for damage, center bore for cracks, and mounting hub for corrosion.

Question 6

What must be inspected on the blades of wooden propellers?

Answer 6

The surface protection coating must be 100% intact to prevent moisture penetration.

Question 7

What indicates significant damage on wooden propeller blades?

Answer 7

Cracks through the leading edge tipping require immediate replacement.

Question 8

What can be used to repair less significant damage on wooden propeller blades?

Answer 8

Less significant damage can be filled with plastics, and indentations in metal tipping can be filled by soldering.

Question 9

What must be checked after the installation of a new fixed-pitch wood propeller?

Answer 9

The attachment bolts must be re-tightened after 25 hours with the prescribed torque.

Question 10

What types of damage cannot be repaired on wooden propellers?

Answer 10

Cracks across the grain, splintered blades, delamination, missing material, cracks in the hub, and elliptical bolt holes.

Question 11

What are the typical damages observed on metal propellers?

Answer 11

Scratches, hairline cracks, impact marks, and corrosion.

Question 12

What measures are recommended for the care of metal propellers?

Answer 12

Strictly observe maintenance instructions, RPM limitations, and perform regular cleaning.

Question 13

What is the permissible repair limit on metal propellers?

Answer 13

Permissible repairs on blade width and thickness are specified in the manufacturer’s manuals.

Question 14

What must be checked during periodical inspections of the hub?

Answer 14

Check for cracks, corrosion, grease leaks, and excessive play on blade tips.

Question 15

How is damage classified for composite propellers?

Answer 15

Damage is classified into acceptable and unacceptable categories.

Question 16

What types of damage fall under ‘skin not perforated damage’ for composite blades?

Answer 16

Abrasion, scratches, gouges, nicks, debonding, delamination, and dents.

Question 17

What is the acceptable limit for gouges on the outer half of composite blades?

Answer 17

Typically less than two inches long and 0.02 in (0.508 mm) deep.

Question 18

What indicates unacceptable damage on composite blades?

Answer 18

Delamination accompanied by oil contamination or damage on the inner half of the blade.

Question 19

What is the significance of lightning strike damage on composite propellers?

Answer 19

Lightning strike damage renders the propeller unacceptable and is often indicated by a blackened area.