Fatigue and Stress | Constant Speed Propeller Flashcards by Robert Unknown

The constant speed propeller is based on the idea that the power available depends not only on the efficieny of the propeller, but also the ___

shaft power coming from the engine

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The shaft power coming from the engine is ___ proportional the the RPM

directly

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For a given throttle setting, the engine RPM depends on the load on the ___

crankshaft

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Aerodynamic torque comes from the ___ component of aerodynamic force exerted on the propeller in the ___ __ ___, acting through a moment arm to the shaft

plane of rotation, resistive

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The constant speed propeller changes the pitch automatically to keep the engine RPM ___

constant

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A constant speed propeller can have its ___ adjusted for varying conditions

pitch

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Most constant speed propellers are ___ operated with a centrifugal ___ operating a control valve that lets oil in to make the pitch ___ or releases it for ___ pitch

coarser, fine

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A ___ pitch is best for takeoff

fine

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As forward speed increases on takeoff, the pitch angle is ___ by the governor to stop the engine from overspeeding

increased

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For full speed in the cruise, a ___ pitch is selected and the engine speed can be ___ to a more comfortable level

coarse reduced

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A double acting propeller users ___ ____ to move the blades towards both fine and coarse pitch angles

oil pressure

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A single acting propeller uses ___ ___ to move the blades towards the smaller pitch angle. If the engine fails, the blade ___ automatically to produce ___ ___

oil pressure feather minimum drag

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Engine overload when changing power is avoided by increasing the __ ___ prior to increasing the ___ __

propeller RPM, manifold pressure

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If the engine oil pressure is lost, an ___ ___ can be used to feather the propeller only

electrical pump

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The feathering pump is an electrically driven oil pump that suppliers the propeller with oil under pressure when the ___ ___ ___ ___.

engine is shut down

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Unfeathering, with an engine failed, is done with an pressurised oil from an ___ or ___ ___.

accumulator or electric pump

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The extremes of pitch in flight is limited by ___ ___

mechanical stops

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In flight, the ___ pitch stop can be varied to prevent a sudden massive selection of fully fine.

fine

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On the ground, the ___ pitch stop can be removed to allow the prop to go to ground fine and reverse pitch.

fine

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The superfine pitch setting establishes ___ blade angle

zero

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Early turboprop engines used a ___

reduction gearbox

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Most modern turboprops use a ___

free turbine

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A free turbine is (not) connected to the main spool of the engine.

not

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A superfine pitch can be used to produce a great deal of extra drag in flight, called ___

discing

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The job of the propeller is to convert the ___ delivered form the rotation speed of the crankshaft into ___

torque, thrust

A crankshaft or power turbine runs at so high a speed that ___ ___ is needed to drive a transmission

reduction gearing

___ or ___ reduction gears are used on radial engines

Epicyclic planetary

___ reduction gearing is generally used with in-line engines

spur

___ ___ will support the propeller shaft

Roller bearings

A ___ or ___ ___ ___ transfers propeller thrust to the airframe, though ___ ___ and a ___ ___ may be used instead.

ball, roller thrust bearing, plain bearings, thrust washer

Lubrication is normally from the __ ___ system

engine oil

The torquemeter indicates the twisting force of the ___ against the ___

engine, transmission

Part of the ___ ___ can be used to measure the power output because ___ ___ is generated when helically cut gears are used to transfer power from one shaft to another

reduction gearing, axial thrust

The amount that the gears move when they rotate is proportional to the ___ ___

torque applied

Turbine engines in turboprops have a ___ and ___ torque output

smooth uniform

Torque is a measure of the ___ being used

power

Torque is measured between the ___ and the __ __

engine reduction gearbox

Torque can be expressed in ___ ___, ___ ___, or ___ ___, ___ ___, or ____ ____

Newton Metres, brake horsepower, shaft horsepower, inch pounds, or foot pounds

Torque may be shown on a torque gauge as a ___

percentage

Power = ___ x ___

Torque x RPM

Having the torquemeter on the ___ shaft allows the engine torque to be closely monitored.

output

Manifold pressure is measured on the ___ side of the engine

input

Manifold pressure is a ___ of engine power, whereas torque is a ___

predictor measurement

Changes in __ or ___ are the only way of determining whether the engine is meeting its specification

N1 TOT

An electronic torquemeter uses the same probe and phonic wheel system as an ___ ___ indicator, on two concentric shafts

engine RPM

The torque shaft is connected to the ___ and the ___ ___, whereas the reference shaft is only connected to the ___

engine, reduction gearbox, engine

There is a ___ wheel at the forward end of each shaft that rotates past the pickup to produce an _C voltage

toothed AC

As power changes, so does the ___ relationship between the voltages from the toothed wheels, in proportion to the power used.

phase

___ can be used to force the blades into ___ their angle of attack when power is lost

Counterweights increasing power

With counterweights, loss of oil pressure ___ the blades

feathers

Using ___ RPM in the cruise with a ___ manifold pressure will reduce fuel consumption

lower higher

Using too high of a manifold pressure against too low of an RPM makes the engine work ___ ___ and ___ ___

too hard, risks detonation

The constant speed range is (not) maintained at very low power settings

not

As the throttle setting is reduced, the CSU senses a reduction in RPM and ___ the propeller. With the PCU piston coming into contact with the fine pitch stop in the cyclinder and the blade angle ___

fines, remaining constant

The flight fine pitch stop is withdrawn when ___

on the ground

The travel of the PCU piston in the coarse pitch direction is limited, either to a maximum to prevent ___ or to feather the blade angle, typically about __ degrees

overtorquing 85

Windmilling is the phenomena where The airflow creates a ___ ___, causing it to rotate in the ___ direction

lifting force, normal

The finer the pitch of the propeller blades, the ___ the windmilling rotation

faster

To feather the propeller following an engine failure, the RPM lever is moved through the ___ position, and the throttle is ___

low, closed

Without a feathering system, the blades will tend to move towards the __ blade angle, using the centrifugal turning moment or spring forces.

smallest

___ stops prevent the blades moving past the feathering position

feathering

In turboprops, the power levers control the ___ and the prop levers control the ___

torque RPM

In a turboprop, higher oil pressures create a ___ pitch and ___ RPM

flatter higher

The turboprop uses ___ propeller governors:

3 - Primary - Overspeed - Fuel-topping

The FCU is the ___

Fuel Control Unit

The ___ and ___ work together to keep the propeller RPM constant over a range of power settings

FCU and turbine governor

As you push the levers forward, the FCU sends more fuel to the ___ ___ which makes the turbine spin ____. This is sensed by the governor which makes the blades ___ their pitch to absorb the extra energy and provide increased thrust.

compression chambers faster coarsen

The primary governor works using ___

Flyweights

If the engine RPM decreases, the flyweights on the primary governor ___ and are drawn ___, allowing ___ oil in to ___ the pitch.

slow down, inwards, more, reduce

The overspeed governor is a relief valve that ___ the blade angle automatically if the primary governor fails.

increases

The fuel-topping governor also prevents ___, by adjusting the ___ ___

overspeeding fuel flow

Changes in power output are not directly related to engine speed but to the ___ ___ ___, which is determined by the ___ ___

turbine inlet temperature, fuel flow

Increased fuel flow will ___ the turbine inlet temperature. The absorbed energy is transmitted to the propeller as ___, ___ the blade angle to maintain a constant RPM

increase, torque, increase

Negative torque occurs when the propeller spins ___ than the reduction gear and drives the engine instead of the other way around

faster

Negative torque may happen when:

- Fuel flow is interrupted - Gust loads on the prop - During descent with high compressor bleeds at low power - Shutdown

If the negative torque exceeds the maximum limit of the Negative Torque Signal, a safety coupling will ___

disengage the reduction gear from the engine

An autofeather system is armed during ___

takeoff and landing

The beta range is the __ range of the power lever that is accessed through a gate

aft

In the beta range, the propeller blade angle is not controlled by the RPM level through the governor, but by the power lever through an ___ ___ ___ system

oil pressure control

The beta value bypasses the ___ ___ to send more oil to the hub, and allows the power lever to control only propeller pitch in the beta range

primary governor

Low pitch stops/hydromechanical locking devices stop the propeller entering the ___ ___ or ___ ___ in the cruise

beta range, reverse pitch

In reverse range, the power lever controls ___ and ___

pitch and torque

In the alpha range, the power output and propeller RPM are controlled by ___

one lever

The condition lever provides ___ in the ___

residual control, alpha range

When the power lever is moved aft of ground idle, the pitch reduces to ___, then is ___ for reverse thrust

zero, reversed

Engine power will ___ as negative pitch is applied

increase

CSU means ___

Constant Speed Unit

CSUs can be matched to the exact speeds automatically with a ___ or ___

synchroniser synchroscope

A ____ on each engine generates a signal that is proportional to within 100 RPM of the engine speed.

tachogenerator

A ____ measures the difference in alternator output frequencies

syncroscope

A typical synchronisation system will consist of ___

- Phonic wheel - Magnetic pickup - Control box, to compare the two signals

The engine with the ___ voltage/frequency determines which way the actuator will rotate

higher

Synchronisation will (not) take place on takeoff or landing

not

___ allows you to set relative positions of the propeller blades

Synchrophasing

A synchroscope for a twin engine aircraft measures the ___ of both ___

difference in output frequencies of both alternators