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ATPL - [Mod 2] AGK - Engines > 10. Propeller Systems - Sections 5-8 > Flashcards

10. Propeller Systems - Sections 5-8 Flashcards

1
Q

Feathering and Unfeathering

Under normal conditions, when is a propeller normally feathered

A

AFTER ENGINE FAILURE

Pg 247

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2
Q

Feathering and Unfeathering

What is the main purpose to feathering a blade after an engine failure

A

PREVENT WINDMILLING

Pg 247

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3
Q

Feathering and Unfeathering

Feathering a blade after engine failure prevents windmilling. What is the purpose of this

A

PREVENT ENGINE TURNING

If an engine failed due to catastrophic event, you do not want the engine to turn, in particular as this could pull fuel over hot system and cause a fire

Pg 247

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4
Q

Feathering and Unfeathering

What is the simplest method for a pilot to feather a propeller

A

RPM LEVER

RPM lever can lift the pilot valve to the fully coarse position, bypassing the governor

Pg 247

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5
Q

Feathering and Unfeathering

In older aircraft types that have manual feathering, what is the significant control in place to prevent feathering by accident

A

GATE STOP

Gate stop prevents the lever being moved into the feather position without first lifting and moving the lever into position.

Pg 248

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6
Q

Feathering and Unfeathering

What component is used in modern aircraft to electrically operate the feathering system

A

ELECTRICALLY OPERATED SOLENOID VALVE

Directs pressure to the feather side of hte PCU

Pg 248

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7
Q

Feathering and Unfeathering

What is the key requirement of all feathering systems

A

SUPPLY HIGH PRESSURE OIL to PCU

Pitch Control Unit

Pg 249

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8
Q

Feathering and Unfeathering

High pressure oil is supplied by the engine typically. If the engine were to fail, this would result in high pressure oil being unavailable to supply the PCU. Subsequently, feathering systems must have what

A

SEPARATE OIL RESERVOIR

With sufficient oil to allow the propeller to be feathered

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9
Q

Feathering and Unfeathering

In the event of engine failure, to provide sufficient oil to a PCU, feathering systems must have a separate oil resrvoir. What else will this usually include in order to provide pressure

A

ELECTRIC PUMP

Pg 249

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10
Q

Feathering and Unfeathering

Large commercial aircraft will usually have what sort of feathering system

A

AUTO-FEATHERING

Pg 249

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11
Q

Feathering and Unfeathering

On commercial aircraft with auto-feathering systems, what must be done before take-off

A

SYSTEM ARMED

System must be armed before take-off

Pg 250

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12
Q

Feathering and Unfeathering

On commercial aircraft, when must the auto-feathering system be armed

A

BEFORE TAKE-OFF

Pg 250

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13
Q

Feathering and Unfeathering

Under what conditions on a commercial aircraft will the auto-feathering system be triggered

A

ENGINE TORQUE BELOW 25%
for more than 3 SECONDS

Pg 250

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14
Q

Feathering and Unfeathering

On commercial aircraft, when the auto-feathering system is triggered, what 4 things will it then do automatically

A
  1. FEATHER PROPELLER - feather on failed engine
  2. POWER AUX - power aux power on failed engine
  3. DISARM - disarm auto feather on live engine
  4. POWER - increase power on live engine (max take-off power)

Pg 250

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15
Q

Feathering and Unfeathering

What is the primary reason for unfeathering a propeller on an engine whilst airborne

A

ENGINE RESTART

Pg 251

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16
Q

Feathering and Unfeathering

How does unfeathering an engine in flight assist with engine-restart

A

WINDMILLING EFFECT

An unfeathered blade will cause airflow to move over the blades and turn the propeller through aerodynamic foces. This is called windmilling.
This will create sufficient turning in the propeller to assist with re-start, avoiding unncessary drain on the battery

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17
Q

Feathering and Unfeathering

What is a method or storing oil under high pressure to allow the PCU to drive the blades away from feather

A

UNFEATHERING ACCUMULATOR

Pg 252

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18
Q

Feathering and Unfeathering

How is the unfeathering accumulator isolated in the event of an engine shut down

A

NON RETURN VALVE

Pg 253

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19
Q

Feathering and Unfeathering

What component opens the supply from the accumulator to the PCU when the propeller lever is moved away from the feathered position

A

ELECTRICALLY OPERATED SOLENOID

Pg 253

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20
Q

Reverse Thrust

What name is given to the range of normal pitch angles for positive thrust

A

ALPHA RANGE

Pg 254

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21
Q

Reverse Thrust

What name is given to the range of flight idle pitch angles of a propeller

A

BETA RANGE

Pg 255

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22
Q

Reverse Thrust

What is the result to thrust if the AoA of a propeller blade falls below the 0° at higher airpseeds

A

THRUST GENERATED in OPPOSITE DIRECTION

relative to the aircraft movement

THrust will be generated in the opposite direction to the aircraft movement

Pg 254

23
Q

Reverse Thrust

What is the purpose of a fine pitch stop

A

MINIMUM PITCH SETTING

Prevents the propellers being put into such a fine pitch that this could cause dangerous excessive drag

Pg 254

24
Q

Reverse Thrust

Whatcomponents is the fine pitch stop linked to

A

POWER LEVER

The power lever is physically prevented from moving so far aft that excessive fine pitch would occur

Pg 254

25
Q

Reverse Thrust

What component is the flight idle stop linked to

A

WEIGHT ON WHEELS

When no weight on wheels, the power level cannot physically move into the flight idle position. Only when weight applied to wheels does this protection disengage

Pg 254

26
Q

As well as flight idle stop and fine pitch stop protections, what additional precaution measure can be used to prevent excessive flight idle position of the power lever

A

POWER LEVER GATE

Power lever has to be lifted through a gate in order to put it into a flight idle position

Pg 254

27
Q

Reverse Thrust

What is it important to understand regaridng the degrees of beta range

A

covers POSITIVE and NEGATIVE values

For example, on a Dash 8 Q 400, flight idle fine pitch stop is set from 16° and below

28
Q

Reverse Thrust

What sort of drag is produced in large amounts when a blade is moved into the negative pitch angle

A

TORQUE DRAG

Pg 256

29
Q

Reverse Thrust

To move the blade into the negative angle beta range, it produces reverse thrust. From the pilots perspective, they will want to retard the power. What is the problem from the engines perspective in regards to the power lever

A

WANTS TO WORK IN REVERSE

More power needed to produce reverse thrust to overcome torque drag

When the blade is at a negative angle, it is producing a lot of torque drag.
The desire is for a lot of thrust to be produced in the opposite direction of aircraft movement.
To overcome torque drag, more power is required.
From the engines perspective pulling back on the power lever would mean it wants more power to be produced, not less.

Pg 256

30
Q

Reverse Thrust

What is the purpose of an under-speed governor

A

SCHEDULES MORE FUEL in REVERSE THRUST

Pilot selects reverse thrust using the power level. Torque drag increases, RPM drops.
The under-speed governor activates and schedules more fuel to the engine to increase power output

Pg 257

31
Q

Reverse Thrust

When a pilot selects reverse thrust on a commercial propeller aircraft, torque drag INCREASES or DECREASES, and RPM INCREASES or DECREASES.
What component is then activiated to supply more fuel to the engine

A

UNDER-SPEED GOVERNOR

Pg 257

32
Q

Cabin noise and synchrophasing

What causes high level noise in the cabin on multi engine propeller aircraft

A

PRESSURE WAVES

Propellers in line with teh cabin rather than forward of the nose

Pg 258

33
Q

Cabin noise and synchrophasing

What is the term used for the number of times the blade of a multi engine aircraft passes the body of the aircraft, causing high levels of noise

A

BLADE PASS FREQUENCY

Pg 258

34
Q

Cabin noise and synchrophasing

If an aircraft has 2 or more propellers, when the blade frequencies are combined, what does this create

A

BEAT FREQUENCY

Pd 259

35
Q

Cabin noise and synchrophasing

What is a beat frequency

A

2 or more propellers combined blade pass frequency

Pg 259

36
Q

Cabin noise and synchrophasing

Very uncomfortable noise levels can be experienced in a multi engine aircraft when the beat frequency coincides with what

A

NATURAL RESONANT FREQUENCY
of the cabin structure

Pg 259

37
Q

Cabin noise and synchrophasing

When propellers are rotating at slightly different speads, what can this cause

A

Slow rise and fall beat frequency

Pg 259

38
Q

Cabin noise and synchrophasing

How can rhythmic noise pattern be cured

A

SYNCHRONISING PROPELLERS

Synchronising propellers so that they are totating at exact same RPM

Pg 259

39
Q

Cabin noise and synchrophasing

What does a synchronising unit do

A

SYNCHRONISES PROPELLERS

Makes propellers rotate at exact same RPM

Pg 259

40
Q

Cabin noise and synchrophasing

If there are 2 or more engines, in order to synchronise, what roles are assumed by the engines

A

1 x MASTER ENGINE
REST are SLAVES

Pg 259

41
Q

Cabin noise and synchrophasing

How does the syncrhonising unit use the relationship between the master engine and the slave(s)

A

COMPARES RPM of SLAVES to MASTER

Adjusts accordingly so slaves rotate same as master

Pg 259

42
Q

Cabin noise and synchrophasing

The synchronising unit can eliminate RHYTHMIC CHANGES or BEAT FREQUENCY

A

RHYTHMIC CHANGES

It does not effect beat frequency at all

Pg 260

43
Q

Cabin noise and synchrophasing

What does the synchrophasing unit do

A

ensure BEAT FREQUENCY
does not match
RESONANT FREQUENCIES

Pg 260

44
Q

Cabin noise and synchrophasing

What is the difference between a synchronising unit and a synchrophasing unit

A

Synchronising unit
Remedies RHYTHMIC CHANGES
Sychrophasing unit
Remedies BEAT FREQUENCIES

Pg 260

45
Q

Cabin noise and synchrophasing

How many decibles can good synchrophasing reduce cabin noise by

A

10dB

Pg 261

46
Q

Control, Indication and Operation

In each engine type, what gauge is used to indicate power;
1. Simple single engine
2. Constant Speed Propeller System
3. Turboprop engine

A
  1. RPM gauge
  2. MAP gauge
  3. TORQUE gauge

Pg 263

47
Q

Control, Indication and Operation

On a turboprop aircraft, a torque gauge is an indicator of power. What 2 methods can this be sensed

A
  1. ELECTRONICALLY
  2. MECHANICALLY

Pg 263

48
Q

Control, Indication and Operation

On the most common types types of piston and turboprop units, what are the 2 levers used for controll engine power

A
  1. RPM (gearbox)
  2. THROTTLE (power)

For the RPM lever, think that it is an infinite gearbox, with fully forward being similar to 1st gear or “fully fine”.
The further you retard the RPM lever, the “higher” the gear (coarser the blade)

Pg 264

49
Q

Control, Indication and Operation

Typically, what coloud is the RPM lever used for adjusting the propeller angle

A

BLUE

Pg 264

50
Q

Control, Indication and Operation

Fully fine setting on the RPM lever makes the propeller fine and minimises torque drag. What 3 phases of aircraft movement/flight is this important for

A
  1. TAXING
  2. TAKE-OFF
  3. GO AROUND

Pg 264

51
Q

Control, Indication and Operation

Essential pre-takeoff and pre-aldning checks should ensure that the RPM lever is set in what position

A

FULLY FINE
(MAX RPM)

Same as 1st gear. Ensure that prop is fully fine to reduce torque drag so that in the event of go around, response from increasing throttle is quick

Pg 264

52
Q

Control, Indication and Operation

What type of supercharged engine is particularly at risk of overboosting

A

TURBOCHARGER

Pg 266

53
Q

Control, Indication and Operation

Commercial turboprop modern aircraft have a condition lever per engine. What is the purpose of this

A

SHUT OFF FUEL
and
SET OPERATING MODE

There are several operating modes normally. For example, take off, climbe, cruis. The condition lever can be set to a mode and the engine will be governed accordingly

Pg 268

ATPL - [Mod 2] AGK - Engines (23 decks)

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