234 Powerplant Flashcards
(34 cards)
Power Plant
Two Avco Lycoming 5512 engines mounted externally
Horse Power
2975 SHP MCP
4355 SHP 30 min OEI
7 stage axial compressor
2 stage gas turbine
2 stage power turbine
Bleed Band
Located at the 6th stage to prevent compressor stall at low power settings
How is engine power transmitted
Via the N2 shaft coaxially located in the N1 shaft. Torque output is turned 90 degrees with an engine transmission mounted to the front of the engine. A sprag clutch isolates the engine and engine transmission from the rest of the system.
Engine lubrication
Self-lubricated by an independent, self-contained oil system. 3.75 gal of BP 2380
Overspeed production
N2 overspeed governor mounted to accessory gear case of the engine, driven by the N2 tech drive shaft, measures magnetic pulse counts , sending a signal to the overspeed controller. At 114% N2 the overspeed controller will power the fuel limiting valve, reducing fuel flow down to 310 lb/hr.
Inlet Section Components
Oil Reservoir with float and fill cap
Torque junction box
Overspeed controller
T2 pickup
Engine wash nozzles
Starter drive mount
No. 1,3,6,7 bearings
Accessory Drive
Driven by two shafts. One from the N1 section and one from N2
N1 drives:
FCU
Oil pump and N1 tach gen
Engine driven fuel pump
N2 drives:
FCU speed sensor
N2 tach gen
N2 Overspeed governor
Gear box also has a magnetic chip detector with fuz burn off capability that will illuminate the ENG CHIP light
Fuel System
Fuel goes through to engine driven boost pump. From there it goes to the low pressure side of the fuel preheater. To the main barrier filter with LRB. Then to the FCU. The FCU meters fuel and splits into two outputs:
1) direct to flow divider and to 2 start fuel nozzles.
2) through the heat exchanger (heats fuel/cools oil), then to the high pressure side of the fuel preheater, in line fuel filter with LRB, then to the fuel limiting valve and then flow divider sending it to 28 air blast fuel nozzles in combustion chamber
Fuel Control Unit
Hydro-mechanical computer with 6 imputes and 2 outputs.
Imputes:
T2 (air temp) P3 (compressor discharge pressure) N1 speed sensing, N2 speed sensing, N1 control inputs, N2 control inputs
Outputs:
Metered main fuel
Metered start fuel
The FCU varies fuel flow to maintain a pilot selected N2 speed
Oil System
3.75 gal of BP 2380
Reservoir in the intake section with a float type level indicator with micro switch that illuminates the OIL LOW annunciator light (2 hours of flight remaining)
Oil pump driven by the N1 accessory drive takes oil from the tank, runs it through a filter and by a temp probe, cooled by heat exchanger, than split in two directions.
Forward:
To the accessory gearbox, filtered again, No. 1,3,6,7 bearings, cockpit chip detector with fuzz burn off, scavenged back to reservoir.
Aft:
Filtered, sent to No. 2,4,5 bearings, dual chip detectors with no indication, scavenged back to reservoir.
ENG 1 or 2 OIL LEVEL annunciator
2 hours of flight time remaining at normal consumption
Cockpit Controls
ECLs, C/Bs, Boost pumps, Fire T-Handles, ENG MOTOR/START switch
ECLs
STOP:
Fuel shutoff valve is closed. Bite detection system is able to be tested
GROUND:
Fuel control shutoff valve is partially opened via the N1 control linkage
Flight:
Fuel control is governing N2 with inputs from N2 linkage, droop eliminator, N2 Logic or emergency engine trim
Overspeed Protection System
Magnetic pickups sense a the speed on the 17 tooth spur gear on the N2 tach drive shaft. When a speed of 114% N2 is reached, DC power is sent to the fuel limiting valve in the fuel control reducing fuel flow to 310lbs/hr
This system has a test switch in the overhead panel.
Compressor Section
7 stage axial compressor, single stage centrifugal compressor.
6th stage bleed band allows air to escape during low power settings to prevent compressor stall
Bleed Band Actuator
Operated by P3 air. Will close during all engine accelerations and any time above 82% N1.
Gas Producer Turbine
Expanding combustion gases pass through two turbine wheels extracting about 2/3rds of the engines power output to drive the compressor section.
Power Turbine
Expanding gases pass through two power turbine wheels extracting the remaining 1/3rd of available power to turn the power turbine shaft. The wheels turn in the opposite direction of the compressor. The power turbine shaft is coaxially mounted inside the compressor turbine shaft and extends out the front of the intake housing.
Engine Start Switches
Located on the overhead panel
MOTOR:
Opens the hydraulic start valve. Utility hydraulic system isolation. ENG STARTER light
START:
The 4 igniters are activated, start fuel solenoid opens, allowing fuel to flow to 2 start fuel nozzles.
Scenario — Single Engine Ground Run
The second engine needs to be started within 3 minutes or motored for 10 seconds.
The 4 and 5 bearings spin due to friction from the drive system but not enough to lube
Beep Trim Switches
Collective beeps make inputs to N2 logic to move N2 linkage to increase or decrease N1 speed.
Emergency Engine Trim Panelp
Emergency Engine Trim removes the AC portion of the signal and full 28VDC signal goes to the N2 actuator, making larger inputs
Torque Limits
5 Min — 77.5%
MCP — 74.4%
30 min OEI — 104%
