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11 Cards in this Set
- Front
- Back
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Briefly describe the propellers on the DA42?
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-They are MT propellers made from wood covered in GFRP with an acrylic lacquer painted finish.
-They have erosion protection on the leading edges. Inboard is a self adhesive rubber strip. Outboard is a bonded stainless steel sheath. -They are constant speed fully feathering propellers. -The model number is MTV-6-A-C-F/CF187-129 |
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Describe the gearbox on the DA42.
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-The gearbox reduces the engine RPM of 3800 to a prop RPM of 2300 via a ratio of 1.69:1.
-It uses a separate oil system from the engine. -It has an overload clutch to decouple engine vibration from propeller during normal operations. It decouples the rotating mass of propeller from crankshaft during start & shutdown. This limits impact load to the crankshaft. |
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Can you move the propellers by hand?
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No because it is geared! It can damage the gearbox.
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How is the pitch of the propeller blades controlled?
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-The ECU controls the pitch of propeller blades automatically through Constant Speed Unit (CSU).
-The RPM is based on pre-programmed power lever settings |
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What does the CSU do?
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It controls the oil pressure in the propeller pitch change mechanism.
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Where is the propeller pitch change mechanism located and how does it work?
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-The Propeller pitch change mechanism is located in the propeller hub.
-It moves a piston that reacts to changes in oil pressure. Movement of piston adjusts the pitch of the propeller blades. -Increasing oil pressure moves the blades towards fine pitch. -It uses oil from gearbox system. |
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What happens with a failure of oil pressure in the CSU?
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The propeller will automatically feather because the spring in the propeller pitch change mechanism pushes the piston back and forces oil out; resulting in a higher pitch.
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What are some characteristics of the unfeathering accumulator?
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-It holds a mixture of nitrogen & oil at 290 PSI when the engine is running.
It's used for: Unfeathering; and maintaining RPM as the engine slows down. |
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How does the engine feather?
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-The feathering of the propeller can only occur above 1300 RPM and is accomplished by shutting down the engine with the appropriate engine master switch.
-This opens the governor valve which allows oil to flow back from the propeller thereby allowing the propellers to move into the feathered position. -At the same time the accumulator valve closes and the oil pressure is restored in the accumulator. -The feathered angle is 81° |
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How does the engine unfeather?
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-To unfeather, the engine mater switch must be set to the ON position.
-This opens the electric valve at the pressure accumulator and the stored pressure will move the blades into a low pitch (high RPM) position. -As soon as the propeller starts turning and the gearbox oil operates, the pressure in the accumulator will be restored. |
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Upon a normal engine shut-down, will the propeller feather? Why or why not?
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No. The coarse pitch stops prevent the propeller from feathering below 1300RPM.
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