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CAT B- Mod 17 Propellers > 17.3.1 Speed and Pitch Control > Flashcards

17.3.1 Speed and Pitch Control Flashcards

1
Q

What are the two main types of propellers?

A

Propellers are designed as either pusher or puller (tractor) propellers.

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2
Q

What are the categories of propellers?

A

They are subdivided into fixed pitch, adjustable pitch, controllable, and constant speeding propellers.

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3
Q

How are constant speed propellers categorized?

A

Constant speed propellers are categorized by the method of pitch change: hydraulic, mechanical, or electrical.

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4
Q

What is the pitch change range in constant speed variable pitch propellers?

A

The pitch can be adjusted between the low (fine) pitch stop and the high (coarse) pitch stop.

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5
Q

What is the feathering position in multi-engine aircraft?

A

Blades can be moved into the feathering position to produce as little drag as possible when the engine is shut down.

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6
Q

What is reverse thrust in large aircraft?

A

Reverse thrust is produced by turning propellers into reverse pitch, accelerating air forwards while the propellers turn in the same direction.

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7
Q

What types of propellers commonly have hydraulic pitch change mechanisms?

A

Constant speed propellers, constant speed propellers with feathering position, and constant speed propellers with feathering and reverse.

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8
Q

What is disc braking in propellers?

A

Some propellers can move their blades to a very fine (low) pitch on landing, causing a negative angle of attack and a braking force.

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9
Q

What is power ON braking in propellers?

A

Some propellers can move their blades to a negative angle, offering resistance to rotation and allowing controllable braking force.

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10
Q

What is feathering in the context of engine failure?

A

Feathering reduces drag by moving the propeller blades to a coarse pitch, placing the leading edge into the oncoming airflow.

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11
Q

What is the BETA range in propeller pitch control?

A

The pilot controls the pitch on the ground.

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12
Q

What is the ALPHA range in propeller pitch control?

A

Also known as the constant speed range, where the propeller governor controls the pitch.

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13
Q

What are single acting propellers?

A

Propellers that operate with oil pressure changing the pitch in one direction only, with the opposite direction resulting from spring force.

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14
Q

How do single acting propellers for single engine aircraft operate?

A

Oil pressure moves the blades to high (coarse) pitch, and springs move them to low pitch for optimal engine restart.

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15
Q

How do single acting propellers for multi-engine aircraft operate?

A

Oil pressure moves the blades to low (fine) pitch, while springs and torsional moments move them to high pitch.

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16
Q

What is the role of centrifugal force in pitch change moments?

A

Centrifugal force produces a pitch change moment that turns the blade towards low (fine) pitch.

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17
Q

What are double acting propellers?

A

Large propellers with pitch change mechanisms that allow oil pressure to change pitch in both directions.

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18
Q

What is the function of a propeller governor?

A

It senses engine RPM and directs oil under pressure to the propeller hydraulic cylinder to maintain RPM.

19
Q

What are the components of a propeller governor?

A

Includes a spur gear type pump, a pilot valve, and a safety spring.

20
Q

What happens during the on-speed condition of a governor?

A

The governor is balanced, and the pilot valve does not direct oil pressure, keeping the propeller blades from changing pitch.

21
Q

What occurs during the under-speed condition of a governor?

A

The pilot valve drains oil from the pitch change cylinder, allowing the pitch change spring to reduce the propeller brake moment.

22
Q

What occurs during the over-speed condition of a governor?

A

The pilot valve directs pressurized oil into the pitch change cylinder, increasing the propeller brake moment to decrease RPM.

23
Q

What is the governor’s behavior when the engine is stopped?

A

No centrifugal force acts on the flyweights, causing the speeder spring to push the landed valve down.

24
Q

What happens when the engine power is increased to cruise?

A

Increased power raises propeller RPM, causing the pilot valve to move up and bleed away fine pitch oil.

25
Q

What is the purpose of feathering the propeller?

A

To prevent windmilling in the event of an engine stopping in flight.

26
Q

What happens when speeder spring force on flyweights is reduced?

A

When the pilot increases fuel flow by moving the throttle forward, it results in an under-speed condition.

27
Q

What is a single acting, constant speed, counterweight propeller control?

A

It involves a counterweight attached at the root of each blade that overcomes CTM and exerts a force to turn the blade towards a coarser blade angle.

28
Q

How does the pitch change mechanism work in a counterweight propeller?

A

It consists of a fixed cylinder housing a sliding piston subjected to spring force on its front face and oil pressure on its rear face.

29
Q

What is the role of oil pressure in the pitch change mechanism?

A

Oil pressure at the rear of the piston creates a force to counteract spring and counterweight forces, moving the blades towards fine pitch.

30
Q

How does the governor pilot valve control the pitch change mechanism?

A

The governor pilot valve routes boosted oil pressure to and from the rear of the operating piston in the pitch change mechanism.

31
Q

What happens when oil pressure is routed to the piston?

A

It pushes the piston forwards, overcoming spring pressure and counterweight force to turn the blades towards fine pitch.

32
Q

What is the function of the electrical control in pitch change mechanisms?

A

It employs a reversible electric motor that drives a bevel gear through a high reduction ratio gear train.

33
Q

How is electrical power supplied to the pitch change mechanism?

A

Electrical power is supplied through a slip ring and brush assembly.

34
Q

What is the function of the solenoid operated friction brake in the motor?

A

It is released whenever a pitch change signal is received.

35
Q

How does the electrically operated pitch change mechanism differ from oil operated mechanisms?

A

The governor pilot valve supplies pressure oil selectively to either side of a servo piston in the governor instead of the propeller.

36
Q

What do flight deck switches allow in the pitch change mechanism?

A

They permit manual control inputs and feathering.

37
Q

How do some aircraft synchronize engine speeds?

A

A single propeller pitch lever controls the speed of a master electric motor, with each engine driving a generator producing three phase alternating current.

38
Q

What is the ARINC 429 system used for?

A

It is used to pass information in digital form for avionics data bus systems.

39
Q

What does the ECU do in an integrated digital electronic control?

A

It receives pilot-initiated engine speed demands and computes them against allowable engine parameters.

40
Q

What is the function of linear variable differential transducers (LVDT) in the ECU?

A

They measure servo valve movement and provide feedback to the ECU.

41
Q

What happens if the ECU detects an exceedance in torque, speed, or EGT?

A

It exercises a limiting function to reduce the parameter back into limits.

42
Q

How is the ECU powered during engine start-up?

A

It is powered through its test circuits by 28V DC power until the generator reaches sufficient output.

43
Q

What does the ECU do during approach and landing?

A

The servo valve will be bypassed, and the blade angle will be under control of the flight deck power lever.

44
Q

What happens if the ECU fails?

A

The entire system reverts back to manual control under a power lever.

CAT B- Mod 17 Propellers (7 decks)

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