Cap 10 Propeller Principle And Systems

Question 1

Propellers parts

Answer 1

Propeller disc
Spinner
Propeller blades

Question 2

High solidity

Answer 2

High solidity is when there are lot of blades covering the propeller disc

Question 3

AoA vs RPM

Answer 3

Rpm is proportional to the angle of attack

Question 4

TAS vs AoA

Answer 4

If tas goes up AoA goes down and viceversa

Answer 5

Negative angle of attack gives you drag and the total reaction is opposite ( pointing backward)

Question 6

Blade twist

Answer 6

To have a constant AoA of attack along the disk

Question 7

Blade pitch angle

Answer 7

Blade pitch or blade angle: Plane of rotation and plane of the chord

Question 8

Variable pitch propeller

Answer 8

~alpha range (flight range)
~beta range (ground range)
~feather condition
~engine start 0 degrees position

Answer 9

Generating reverse thrust on the ground -18 degrees
Fully fine 0 degrees
Feathered 90 degrees

Question 10

Propeller spinner

Answer 10

May susceptible for icing

Question 11

Rpm gauge

Answer 11

the rpm at the crankshaft is directly related to the propeller rpm at least for directly linked gearbox reduction props.

Reduction gearbox main purposes is to make the prop more efficient

Question 12

Power ,torque and thrust

Answer 12

~The propeller is driven by engine troque (RPM)
~Opposing this is torque drag which changes in magnitude with blade angle
~these forces are detected and balanced by the constant speed unit
~when the forces are equal and opposite a stable propeller RPM can be achieved

Question 13

CTM (centrifugal turning moment)

Answer 13

Natural tendency to fine off the blade angle due to centrifugal turning moment.

Question 14

ATM (Aereodynamic twisting moment)

Answer 14

Blade CP is ahed of the pitch change axis.
ATM tries to course the pitch of the propeller.
CTM force is greater than ATM

Question 15

Windmilling prop

Answer 15

When propellers is windmilling the ATM acts in the other way so making to fine off the pitch propeller with the CTM

Question 16

Single acting PCU (with the spring)

Answer 16

~Single eng&raquo_space; SPRING FORCE tends to FINE ,
OIL PRESSURE tends to COURSE

~multi engine&raquo_space;SPRING FORCE tends to COURSE,
OIL PRESSURE TENDS to FINE

Question 17

Centrifugal latches

Answer 17

~if the prop enter a feather engine need to overcome a large amount of drag in order to re start

~the centrifugal latch prevents the blades entering a feather condition during engine shut down under normal operation

~if feather conditions is selected during flight,the operation of the latch if overridden

~the latch sys can also be know as a LOW PITCH stop

Question 18

Csu

Answer 18

~over speed»the governor weights will detect the increase in speed and move outwards.as the weights move outwards the landed valve moves up.This will allow oil flow through the landed valve and towards the PCU.The PCU will drive the propeller towards a coarse condition,reducing the propeller RPM.

~under speed&raquo_space;if the engine RPM decreases the flyweights move inwards,lowering the landed valve.The valve directs oil pressure to the fine pitch side of the PCU.The blades move to a finer pitch ,torque drag reduces below engine torque-allowing the propeller to accelerate back to equilibrium

Question 19

Unfeathering

Answer 19

Can be an accumulutor or electric pump eill sen d some pressure to fine the prop to get out of the unfeather positon

Question 20

Syncronised adn syncroophase

Answer 20

Syncronising»>exactly the same rpm (only for 1% change in difference )

Syncrophase»Controlling Relative blade path against one another so they stay far from each other (less noise)