DA-42 Prop System

Question 1

What are the props made of?

Answer 1

Wood and covered in GFRP

Question 2

What do counter weights do?

Answer 2

Oppose centrifugal twisting of blades (fine pitch)

Question 3

What does the speeder spring want to do?

Answer 3

Move the blades to a coarse pitch, or feather

Question 4

What is the oil system in the prop pressurized to?

Answer 4

320 psi

Question 5

When the engine is over speeding, what does the prop. governor do?

Answer 5

Causes the fly weights to move out, and oil leaves the prop hub and goes back to the sump

Question 6

What will happen if you have a failure in the oil pressure system in the prop?

Answer 6

The blades will want to go to a feather position

Question 7

What angle is feathered? (or degree)

Answer 7

81

Question 8

What is the low pitch position/degree?

Answer 8

12

Question 9

What is the Start Lock position/degree?

Answer 9

15

Question 10

What are the two things that are trying to feather your blades?

Answer 10

Counter-weights, Spring

Question 11

What are the two things keeping it out of feather?

Answer 11

Oil Pressure from governor, course pitch stop

Question 12

Describe the function of the feathering accumulator during feathering and unfeathering

Answer 12

Feathering

All oil will flow back from the propeller hub, allowing the blades to move into the feathered pitch position. At the same time the electric valve at the pressure accumulator closes, and the oil pressure is restored in the accumulator. Feathering is only possible at propeller speeds above 1300 RPM.

CAUTION

If the engine is shut down below an RPM of 1300 the propeller pitch remains below the start lock position. In this case the speed must be increased to increase the propeller RPM.

Unfeathering:

pressure stored in the accumulator will move the propeller blades into a low pitch position. As soon as the propeller starts turning and the gearbox oil operates, the accumulator will be refilled.

Question 13

What does the aerodynamic twisting moment want to do to the blade angle?

Answer 13

Coarsen it

Question 14

What does the Centrifugal Twisting Moment want to do to the blade angle?

Answer 14

Fine it off

Question 15

Describe the prop pitch change mechanism on the Da42

Answer 15

• single acting counterweight
• DA42 has an oil pressure accumulator which is used to un-feather the props in flight. Activated when ENG MASTER ON