Propellers

Question 1

What 3 parts make up a propeller

Answer 1

Blades
Spinner
Hub

Question 2

What is the chord reference point for a propeller

Answer 2

75% of the blade hub> tip

Question 3

What is the helix angle

Answer 3

Angle between the raf and axis of rotation

Question 4

What is geometric pitch

Answer 4

How far the blade would travel if put through a solid material

Question 5

What is effective pitch

Answer 5

Geometric pitch - slip

Question 6

What does torque do

Answer 6

The opposite of what the engine wants

Question 7

What happens to blade AOA with TAS and RPM

Answer 7

TAS up = blade AOA down

Rpm up = blade AOA up

Question 8

What should you do if engine failure on propeller aircraft

Answer 8

Stop propeller from windmilling

Feather

Question 9

What is the efficiency of a fixed pitch propeller throughout its flight envelope

Answer 9

Low efficiency at low speed

Good efficiency at cruise speed

Question 10

What are high aspect ratio blades good for

Answer 10

Efficiency

Question 11

What are low aspect ratio blades good for

Answer 11

Best force

Question 12

What are short dumpy blades good for

Answer 12

Acceleration

Question 13

What are long blades good for

Answer 13

Efficiency

Question 14

What happens if a blade is noisy

Answer 14

Less efficient

Question 15

What happens if there is too many blades

Answer 15

Turbulent air = less efficient

Question 16

What is blade solidity

Answer 16

How much of propeller disk has something solid in it

Question 17

How does blade solidity affect force

Answer 17

Solidity increase 
=
Torque absorption increase (better able to convert power to thrust)
= 
More force

Question 18

What’s the max number of blades per hub

Answer 18

Around 6 at present

Question 19

What are contra rotating propellers

Answer 19

2 sets of blades rotating in opposite directions

Question 20

What is torque reaction

Answer 20

Blades rotate to right

Aircraft wants to rotate to left

Question 21

On ground what effect does torque reaction have

Answer 21

Wheels on side torque is trying to turn plane have more weight

Question 22

What effect does the slipstream from propellers have on yaw

Answer 22

Sideslip on rudder = yaw left (if right hand turning propeller)

Question 23

What is asymmetric blade effect (p-factor)

Answer 23

When propeller disk is included (at a higher AOA)

Downgoing blade = fast than upgoing blade = more thrust = thrust line moves to the right = yaw to left

Question 24

What is the pitch difference for asymmetric blade effect (p- factor)

Answer 24

Downgoing blade = travels further (greater pitch)

Upgoing blade = travels less = less pitch

Question 25

What is the gyroscopic effect

Answer 25

Resulting force 90° to the imput Nazi symbol

Question 26

When is asymmetric flight at its worst

Answer 26

Slow speeds

Question 27

Why is propeller engine failure / asymmetric thrust worse

Answer 27

No prob wash from dead engine = less lift on wing Yaw due to asymmetric thrust = less lift on lost engine wing + Drag from prop

Question 28

What is the benefit of the wing down method for asymmetric flight

Answer 28

More streamlined

Question 29

What is the drawbacks of the wingdown method for asymmetric flight

Answer 29

Subjected to somatogyral illusion

Question 30

Benefits of wings level method

Answer 30

All horizons align

Question 31

What happens to Vx for a jet engine with critical engine failure

Answer 31

Slower

Question 32

What happens to Vx for a propeller aircraft during critical engine failure

Answer 32

Faster

Question 33

What is the critical engine

Answer 33

The engine opposite to direction of rotation (for propellers) Or for jet / counter / contra rotating propellers Engine on the windward side

Question 34

What is Vmc (A)

Answer 34

Velocity minimum control in a given configuration usually take off When the critical engine fails

Question 35

What is Vmcl

Answer 35

Velocity minimum control landing In landing configuration When the critical engine fails

Question 36

What is Vmcg

Answer 36

Velocity minimum control ground When on the ground of in (ground effect during take off only) When critical engine failed

Question 37

How does cg affect vmc speeds

Answer 37

Rear cg = higher Vmc speeds

Question 38

How is Vmc (a) determined

Answer 38

``` Max available take off thrust Worst cg position Trimmed for take off Max sea lever take off mass Most critical take off configuration (with gear up) No more than 5°bank towards live engine Out of ground effect Propeller windmilling or (if autofreather is fitted) ```

Question 39

How is Vmcl determined

Answer 39

``` Go around power Worst cg position Trimmed for approach Heaviest weight Critical landing configuration ``` Also need to roll control = faster speed

Question 40

How is Vmcg determined

Answer 40

If critical engine fail you need to maintain control with rudder only without deviating more than 30ft laterally from centre line ``` Max take off thrust Worst cg Trimmed for take off Heaviest mass Critical take off config ```

Question 41

What is the order (fastest to slowest) of the Vmc speeds

Answer 41

1) Vmcg 2) Vmcl 3) Vmc (a)

Question 42

How does a temperature affect Vmc speeds

Answer 42

Not day = Vmc speeds slower | Because eng produces less thrust = less rudder needed to counter

Question 43

How does altitude affect Vmc speeds

Answer 43

Slower = less engine thrust = less rudder needed to counter