17.3

Question 1

How is reverse thrust produced

Answer 1

Propellers turned into reverse pitch and propeller turns in same direction

Question 2

2 types of propeller

Answer 2

Push and tractor

Question 3

What is disc braking

Answer 3

Low pitch for landing

Creates negative angle of attack and braking force

Question 4

Power on braking

Answer 4

Negative blade angle resistnsce to rotation which gives proportional and controllable break force

Question 5

What is feathering

Answer 5

Moving blades to maximum coarse pitch until 90degress to plane of rotation

Question 6

In engine failure how does feathering occur

Answer 6

In one step

Pitch can’t be selected between max coarse pitch and feather

Question 7

In single acting propellers for single engine aircraft what controls pitch

Answer 7

Oil moves the blades to high pitch

Spring moves to low pitch

Question 8

In engine failure why does engine move to windmilling

Answer 8

Makes it easier to start engine

Question 9

Single acting propeller for multi engine what does the oil pressure and spring do

Answer 9

Moves the blades to low pitch

Spring and torsional moments move blades to high pitch

Question 10

CTM pitch

Answer 10

Low pitch

Question 11

Why does ctm give a low pitch

Answer 11

Due to distribution of propeller blade mass

Question 12

Negatives of low pitch

Answer 12

Unsafe

Windmilling

Overspeed

High drag

Question 13

What do counterweights do

Answer 13

Attached to blade to make centrifugal loads on the counterweights to drive blades to a higher pitch

Question 14

How are double acting propellers constructed

Answer 14

Oil pressure leads to pitch change in both directions

Question 15

What is a governor

Answer 15

Engine rpm sensing device and high pressure oil pump

Question 16

What does the governor do when it senses a change in engine rpm

Answer 16

Directs oil under pressure to the propeller hydraulic cylinder or by releasing oil from the hydraulic cylinder

Question 17

3 names for a governor

Answer 17

Constant speed unit

Propeller control unit

Propeller governor

Question 18

What does the governor control

Answer 18

Hydraulic servo system feeding high pressure oil via a pilot valve to a piston in the pcm

Question 19

What is on speed

Answer 19

Governor at neutral when engine operated at set rpm by pilot

Question 20

What’s underspeed condition

Answer 20

Pilot needs higher propeller rpm the propeller control (conditioning) lever is moved forwards to the new selected speed

Pilot valve down

Question 21

What’s an overspeed condition

Answer 21

Lower rpm required control (conditioning) lever is moved rear wards to new selected speed

Pilot valve up

Question 22

After max coarse what happens

Answer 22

Fixed feathered stop

Question 23

What’s full reverse stop

Answer 23

Blades go fine pitch and is required through zero angle to the fixed

Question 24

What happens when oil pressure is routed to the piston

Answer 24

Pushes it fowards and overcomes spring pressure and counterweight force to turn blades to fine

Question 25

What happens when the oil line is opened to return

Answer 25

Spring and counterweight forces push piston back towards coarse

Question 26

How is electrical power supplied for electrical control

Answer 26

Through and slip ring and brush assembly

Question 27

When is the friction brake released

Answer 27

When pitch change signal is received

Question 28

Why does the ecu have a crosstalk facility between the lanes

Answer 28

Compare and share information and a crosstalk link with the opposite engine ECU

Question 29

What system is used to send information in a digital form

Answer 29

Arinc 429

Question 30

How accurate is the system

Answer 30

Within 2 propeller revolutions

Question 31

What does the ecu receive

Answer 31

Pilot initiated engine speed demands

Question 32

Where is the output signal sent to

Answer 32

Torque motor on the servo valve that produces the correct metered oil supply to the propeller pitch change mechanism

Question 33

Why do we feather

Answer 33

To prevent excessive drag and negative torque (windmilling) if the engine fails

Question 34

How does manual featuring occur

Answer 34

Moving control in the cockpit against low speed stop

Question 35

How can feather be intiiamred

Answer 35

Depressing the feathering button which actions the auxilally pump and feather solenoid

Question 36

When is auto feathering used

Answer 36

During take off and cruise

Question 37

If the engine fails how does auto feathering happen

Answer 37

Centrifugal flyweights are overridden and electric feathering pump runs which drivers propeller to feathering position

Question 38

What’s up trim and when is it triggered

Answer 38

Engine adds more power to compensate for another engine loses power below 25% Rpm of propeller falls below 80%

Question 39

How much does dual up trim cause the engine to increase by

Answer 39

10%

Question 40

When auto feathering happens what does up trim do

Answer 40

Automatically signalled

Question 41

What pitch does the propeller need to be to unfeather

Answer 41

Low fine pitch

Question 42

What component unfeathers

Answer 42

Unfeathering accumulator to provide a reserve of pressure

Question 43

What does a centrifugal latch do

Answer 43

Locks piston in low pitch when engine not rotating

Question 44

What happen when oil is trapped in a single acting propellers when it’s shut down

Answer 44

Propeller blades are forced towards coarse pitch by the spring or gas pressure in the pitch change cylinder

Question 45

In beta mode why is the blade angle changed directly with the power lever

Answer 45

Any angle between zero thrust and flight idle can be selected

Question 46

What propellers use beta range

Answer 46

Propellers with reverse pitch capability

Question 47

When is the first overdosed backups

Answer 47

Primary propeller governor

Question 48

Primary governor works to what speed

Answer 48

102-103% of np speed

Question 49

Overspeed governor works when

Answer 49

104-106% np propeller speed

Question 50

Where is the additional Overspeed protection device

Answer 50

Inside main propeller governor and works at 106-107% and above

Question 51

How do the pt6a engine Overspeed governor work

Answer 51

Flyweights in the main propeller governor open a bleed aid link allowing pressurised air which is known as py pressure to leak into ambient air