Fatigue and Stress | Constant Speed Propeller Flashcards
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
The shaft power coming from the engine is ___ proportional the the RPM
directly
For a given throttle setting, the engine RPM depends on the load on the ___
crankshaft
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
The constant speed propeller changes the pitch automatically to keep the engine RPM ___
constant
A constant speed propeller can have its ___ adjusted for varying conditions
pitch
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
A ___ pitch is best for takeoff
fine
As forward speed increases on takeoff, the pitch angle is ___ by the governor to stop the engine from overspeeding
increased
For full speed in the cruise, a ___ pitch is selected and the engine speed can be ___ to a more comfortable level
coarse reduced
A double acting propeller users ___ ____ to move the blades towards both fine and coarse pitch angles
oil pressure
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
Engine overload when changing power is avoided by increasing the __ ___ prior to increasing the ___ __
propeller RPM, manifold pressure
If the engine oil pressure is lost, an ___ ___ can be used to feather the propeller only
electrical pump
The feathering pump is an electrically driven oil pump that suppliers the propeller with oil under pressure when the ___ ___ ___ ___.
engine is shut down
Unfeathering, with an engine failed, is done with an pressurised oil from an ___ or ___ ___.
accumulator or electric pump
The extremes of pitch in flight is limited by ___ ___
mechanical stops
In flight, the ___ pitch stop can be varied to prevent a sudden massive selection of fully fine.
fine
On the ground, the ___ pitch stop can be removed to allow the prop to go to ground fine and reverse pitch.
fine
The superfine pitch setting establishes ___ blade angle
zero
Early turboprop engines used a ___
reduction gearbox
Most modern turboprops use a ___
free turbine
A free turbine is (not) connected to the main spool of the engine.
not
A superfine pitch can be used to produce a great deal of extra drag in flight, called ___
discing
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
