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