Skyblue CBT propeller system Flashcards
what controls the propeller?
PEC in conjunction with:
- overspeed governer
- autofeather system
- alternate autofeather system
- synchrophase system
- power and condition levers
what does the PEH provide for the pitch change mechanism?
closed loop control
what does the PEC do if it senses a system fault?
detects and isolates the fault
how many channels make up the PEC?
- Master and backup
where does the PEC get airspeed and altitude from?
EEC
what does the PEC use to calculate prop speed?
EEC data and NP
how does the EEC provides overspeed protection?
acts on HMU to limit NH via a stepper motor
how does the PEC control prop pitch angle?
through the propeller valve module (PVM)
what 4 components make up the PVM?
- electro hydraulic valve
- protection valve
- feather solenoid
- rotary variable differential transducer (RVDT)
what 6 things does the PVM provide?
- basic speed set
- beta scheduling
- reversing
- synchrophasing
- prop feathering
- low pitch protection
how is blade angle controlled by the PVM in constant speed and beta modes?
controlled metering of oil pressure
how is blade angle controlled by the PVM in feather and overspeed modes?
dumping oil pressure
what is unmetred oil pressure always opposed by?
metered oil pressure which is then applied to the opposite side of the assembly
where does aerodynamic force tend to drive the prop blade?
to low pitch angles
what does the prop pitch lock ensure if oil pressure is lost from the PVM?
prevents aerodynamic loads reducing the blade angle by more than 1 degree
prevents speed increasing by more than 2%
when the power levers are in the forward thrust range, how is RPM set?
condition lever position sets rpm via the EHV located in the PMV via oil pressure changes
when in flight governing mode how is RPM set?
power lever angle through the PVM
what min propeller speed is maintained by the EEC in the ground beta/fuel governing mode?
70.8% NP
what does power lever angle command when in the ground beta range?
commands PVM to incrase or decrease oil pressure
what happens when blade angle reaches the commanded position?
blade angle feedback acts on the PVM to hold the blades at the new position
what provides torque info to the MFD, MFC and FDAU?
auto feathering unit
what provides torque info to the MFD from the power turbine shaft?
signal conditioning unit
what handles the autofeather and uptrim logic?
the MFC
What does the MFC command when an EFATO occurs?
commands uptrim on live engines EEC
commands oil pressure to feather the failed engine through the feathering solenoid
when is ATPCS armed on the ground? (5)
- PWR MGT to takeoff
- ATPCS button pushed in
- both torques greater than 46%
- both PLA greater than 49 degrees
what is available when ATPCS is aremd in flight?
only autofeather
when is autofeather commanded?
when torque drops below 18%
what happens when ATPCS senses torque lower than 18% on the ground?
uptrim command is sent to EEC on unaffected engine and the live engine bleed is closed
2.15 seconds later the failed engine will autofeather
what happens when autofeather is triggered?
affected feather solenoid is activated and the affected feathering pump activates
autofeather is inhibited on the unaffected engine
when will ATPCS disarm under normal conditions?
- PWR MGT anywhere but takeoff
- both torques more than 46%
- either PLA more than 49 degrees
- ATPCS button off
what is NP?
prop rotation speed
what do the 2 sensors on the reduction geartrain sent outputs to?
EEC which controls torque counter
AFU which controls torque pointer
when will the torque pointer show amber?
100-106% torque
when will the torque pointer show red?
over 106%
what does an amber LAB under torque indication mean?
wrong EEC installed
what does an amber HBV under the torque indication mean?
associated handling bleed valve has failed
what does the FDAU calcualte and display on the torque indication?
target torque displayed in amber (or magenta on a G/A)
what do 3 amber xxx in the torque indication mean?
invalid PWR MGT value
when is NP shown in amber?
between 41.6% and 62.5%
when is NP shown in red>
NP above 107%
how is ITT sensed?
thermocouple sensros between the low pressure turbine and power turbine
what is the red range on the ITT gauge?
715C hotel mode
765C take off
800C in flight
what does a red S on the ITT gauge mean?
950C start limit
what is NH?
high pressure turbine RPM
what is normal NH range?
62-103.1%
what is amber NH range?
103.2-106.3%
when will NH show red?
above 106.4%
what is NL?
low pressure turbine RPM
what is amber NL range?
104.2-106.7%
what is red NL range?
greater than 106.8%
what does the PWR MGT supply info to?
- FDAU
- PIU
- EEC
What does the engine rating interface unit allow?
the crew to select an engine rating between the original rating and a boost rating by incraseing the thermal limit
when is the boost function available?
when on the ground
in flight following an engine failure
how much is torque increased by if boost is used with PWR MGT set to T/O?
4.5% up to 4000ft and then 4%
how much is torque increased by if boost is used with PWR MGT set to MCT?
4%
when do we get an ENG BOOST caution?
when there is a disagreement between button position and the rating of the EEC’s
when will we get an amber ENG 1 PEC caution?
both channels on the PEC have failed
when will we get an amber ENG 1 PEC SGL CH caution?
one of the PEC channels has failed
what will NP be blocked at when a PEC is turned off?
102%
What does the crank selection on the knob do?
motors the engine without ignition
what does turning the knob to start A and B do?
ignites both ignition exciter units regardless of on ground or in flight
what will the starter generator connect to when the START button is pushed?
either the main battery, operating generator or external power through the STARTER BUS depending on the power source
what des the starter generator drive during start?
the high pressure spool to an RPM of 20%NH
at what NH is the condition lever moved from fuel shut off to introduce fuel?
10%
what is self sustaining NH?
45.5%
what disconnects at 45.5% NH during start?
starter generator and ignition
what can cause a start fault?
starter gen remaining engaged past 45.5
failure of GCU
prop brake on
what is ignition powered by?
DC ESS BUS