Engine + Prop Flashcards
What type of prop is it? Describe some features of the propeller
Dowty R391 six blade, coarse seeking, counter-weight, variable pitch controllable pitch in the ground operating range, constant speed in the flight and reverse ranges, full feathering
What are the propeller counterweights for?
they act as a safety device to drive the propeller blades towards feather if there is a loss of hydraulic pressure
What is the purpose of the propeller hub assembly?
provide an attachment point for the blades and a means of attaching the propeller to the PGB and to transmit engine HP to the blades
What is the purpose of the propeller pitch actuator? where is it located? what is it controlled by?
used to control fine and coarse blade angles on the front hub PCU
What is fine pitch? What direction is it driving the propeller?
refers to oil transferred, thru the beta tube, to the AFT side of the prop piston Towards reverse position
What is coarse pitch? What direction is it driving the propeller?
refers to oil transferred, thru the beta tube, to the FORWARD side of the propeller piston Towards feather position
What does the servo valve in the PCU do?
primary control device that changes blade angle in response to FADEC signals and operates in all modes except for manual feathering.
What does the auxiliary feather pump do?
provides backup oil pressure for full feathering when the FADEC-controlled feathering system is inoperative, when the high-pressure pump oil pressure is insufficient, and for ground maintenance purposes.
What is the purpose of the Magnetic Pulse Unit?
detects the passing of each blade and the propeller rotates and also provides backup NP sensing should the primary and secondary sensors fail.
Describe the three positions of the PROPELLER CONTROL switch and what they each do.
FEATHER - activates the aux feather pump and feathers the prop NORMAL - shuts off the pump UNFEATHER - commands prop to unfeather and drives it to full reverse unless the switch is released
How is propeller blade angle controlled?
by the PCU controlling the flow of oil to the pitch actuator in response to the FADEC signals. The FADEC controls engine fuel flow by providing signals to the FPMU
Positioning a power lever below FLT IDLE while airborne can cause what?
extreme propeller overspeed with damage to components, loss of electrical generators, and high drag levels.
Aux feather pump operating limit
80 seconds
Exceeding the 80 second aux feather pump operation limit could cause what to occur?
may cause oil to enter the compressor rotor. This creates a rotating imbalance when the engine is run and will likely result in severe engine damage.
Static propeller feathering is limited to how many cycles? When is a cycle counted?
2 each time the aux feather pump is used to drive the prop from feather to reverse to feather
The prop counterweights will stabilize the blade angle at approx. how many degrees?
66
The prop will windmill on the counterweights at up to what percent NP?
40
At what percent does the propeller speed digital readout change to red?
106
At what percentage are the propellers maintained thru fuel flow changes when the power levers are between FLT IDLE and reverse range?
99
At what percentage are the propellers maintained thru fuel flow changes when the power levers are above FLT IDLE?
100
At what percentage are the propellers maintained thru fuel flow changes when the power levers are in the reverse range?
101
What are the 3 major assemblies of the engine?
PGB torquemeter power section
What does the PGB do?
transmits shaft power from the torquemeter, reduces shaft rpm to run the propeller, and provides shaft power to the GMAD
What does the GMAD provide drive pads for?
AC generator Hydraulic pump PGB oil supply and scavenge pump PCU Prop high px oil pump OSG
Where is the GMAD located?
rear of the propeller gearbox
What does the torquemeter do?
transmits engine output power to the PGB and supplies torque reference to the FADECs
What are the major components of the power section of the engine?
variable flow 14 stage compressor 2 stage gas generator turbine 2 stage free power turbine
What does the PUAD provide drive pads for?
FPMU PMA Oil px and scavenge pumps Air turbine starter
Where is the PUAD located?
lower forward portion of the engine power section
What does the NIU do?
provides conditioning and processing of engine monitoring system sensor data signals provides engine, nacelle, and propeller sensor signal conditioning and nacelle component control
What does the FPMU do?
delivers filtered, metered fuel necessary for engine operation, and pressurized fuel for the CVG hydraulic actuator
What does the CVG do?
changes the angle of the compressor stator blades to assist with engine power control
What does the FCOC do?
cools engine return oil and heats the fuel to minimize engine fuel system icing
How big is the oil tank?
20 gallons 12 gallons of oil, 8 gallons of air
How big is the oil reservoir for the emergency feather pump oil supply?
0.66 gallon
What does the air oil cooler use on the ground to cool the engine oil? In flight?
Ground - propeller air flow In flight - ram air
What does the feather valve do?
allows the auxiliary feather pump to override the PCU servo valve to fx the prop. This override function protects against system failures in which the primary system is incapable of feathering the prop.
What happens if the high pressure oil pump loses pressure completely?
The counterweights will move the blade angles toward 66 degrees and will stabilize NP at less than 40 percent. Drag in this configuration is very low.
