FM 1-506 Fundamentals of Aircraft Power Plants ... - Survival Books

WWW.SURVIVALEBOOKS.COMFM 1-506RequirementsThe primary requirements of the fuel system are —To control accurate and stable engine speed forsteady-state operations and to provide transientcontrol to achieve rapid power changes. Thissystem pumps, filters, and meters fuel inresponse to power-available spindle (PAS)position, load-demand spindle (LDS) position,sensed engine variables, and torque motor inputfrom the electrical control unit.To position the compressor variable stator vanesthroughout the engine operating range toachieve the required airflow and stall marginperformance by the compressor.To provide a schedule for starting bleed valve.To provide automatic start schedules from sealevel to 20,000 feet altitude.To protect the engine against destructive gasgenerator and power turbine overspeed.These requirements must be met over the full engineoperating envelope and environment.Fuel Boost PumpThe fuel boost pump is mounted on the AGBforward side (Figure 4-11). It is designed —To provide reliable suction feed from theaircraft fuel boost pump to the engine.To minimize vulnerability and fire hazard bycontinuous operation with fuel pressure in thelines from tank to engine at a pressure less thanatmospheric.To provide discharge pressure for high-pressurevane pump minimum inlet pressure requirements.At 100 percent Ng (44,700 RPM) the fuel boostpump operates at 10,678 RPM. Pump discharge pressureranges from 45 to 90 psi at maximum continuousspeed and 20 psi minimum at ground idle speed.4-10