The AS907 turbofan engine is a 4.2 bypass ratio, two-spool, corotating turbofan engine. Bypass airflow represents 80% of the airflow, while the remaining 20% is dedicated to core airflow. The engine has two independent major assemblies. The N1 section consists of a fan rotor that is driven by a three-stage low-pressure turbine. The N2 section is comprised of four axial flow and one centrifugal compressor, combustor, accessory gearbox, and a two-stage high-pressure turbine. The high-pressure turbine drives the compressor.

The rotating system is fully held by a bearing and seal system containing two sump areas, which are found in the cool zones. The engine includes the full-authority digital engine control (FADEC) system, the customer bleed system and the accessory gearbox.

Engine airflow passes through the single-stage fan and is divided into two airflow paths, bypass and core air. Air is accelerated by the single stage N1 fan and is ducted around the engine nacelle to produce most of the thrust generated. Air entering the N2 core is compressed, mixed with fuel, and ignited. The resulting combustion gases are then exhausted onto the N2 turbine to drive the N2 assembly. The gases are then discharged onto the N1 turbine to drive the N1 fan. Jet pipe thrust accounts for a small portion of the thrust generated.

The engine subsections include an air inlet section, compressor section, combustion section, turbine section, accessory drives, and bypass section.

The primary function of the air inlet section is to move the air into the fan and compressor sections of the engine. The N1 fan consists of 22 titanium inserted blades. A fan containment system uses an aluminum honeycomb material surrounded by an aramid fiber wrap.

The high-pressure (HP) compressors are axial and centrifugal compressors. A variable geometry (VG) system regulates airflow across the N2 compressor by changing the position of the inlet guide vanes and the stator vanes for the inlet and first stage of the compressor. The compressors pressure ratio is 16:1.

The combustion section mixes the fuel from the fuel nozzles with high-pressure compressed air. Ignition occurs, and the fuel/air mixture burns in the combustor which expands and turns the high pressure turbine (HPT). The HPT changes this energy to mechanical energy to turn the compressor.

The turbine section comprises the HPT section and the low-pressure turbine (LPT) section. The HPT gives the mechanical energy to operate the high pressure compressor and accessory gearbox. The LTP gives mechanical energy to operate the fan rotor.

The accessory drives on the accessory gearbox supply the mechanical power necessary to operate the hydraulic pump, aircraft generator, air-oil separator, permanent magnet alternator (PMA), hydromechanical unit (HMU), and the cartridge oil pump. The accessory gearbox (AGB) also provides a drive pad for the air turbine starter (ATS).

The bypass section (ducts) controls the flow from the fan through the nacelle to give thrust. It also gives support for, and access to, the engine control systems, components, and engine build unit (EBU). The bypass section also helps decrease the engine noise and prevent the migration of an engine fire from the nacelle area to the pylon and the fuselage.

The engine has the primary functions that follow:

• Gives the thrust necessary to move the aircraft forward through the air on ground or in flight
• Gives the power supply necessary to operate the thrust-reverser actuating system to decrease the speed of the aircraft on the ground
  
• Gives the power supply necessary to operate the hydraulic pumps
• Supplies bleed air for cabin pressurization control and air-conditioning, heating and anti-ice systems
• Supplies electrical power for the aircraft systems

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