developed by the engine shaft and the horsepower in the  exiting thrust, the answer is equivalent shaft horsepower.  With regard to aircraft, the turboshaft engine is a gas turbine  engine made to transfer horsepower to a shaft that turns a  helicopter transmission or is an onboard auxiliary power  unit (APU). An APU is used on turbine-powered aircraft to  provide electrical power and bleed air on the ground and a  backup generator in flight. Turboshaft engines can come in  many different styles, shapes, and horsepower ranges. inlet on this type of engine is bolted to the front (A flange)  of the engine. These engines are mounted on the wings, or  nacelles, on the aft fuselage, and a few are in the vertical fin.  A typical turbofan inlet can be seen in  Figure 1-44 . Since on  most modern turbofan engines the huge fan is the first part of  the aircraft the incoming air comes into contact with, icing  protection must be provided. This prevents chunks of ice  from forming on the leading edge of the inlet, breaking loose,  and damaging the fan. Warm air is bled from the engine’s  compressor and is ducted through the inlet to prevent ice  from forming. If inlet guide vanes are used to straighten the  air flow, then they also have anti-icing air flowing through  them. The inlet also contains some sound-reducing materials  that absorb the fan noise and make the engine quieter. The air entrance is designed to conduct incoming air to the  compressor with a minimum energy loss resulting from  drag or ram pressure loss; that is, the flow of air into the  compressor should be free of turbulence to achieve maximum  operating efficiency. Proper inlet design contributes  materially to aircraft performance by increasing the ratio of  compressor discharge pressure to duct inlet pressure. Turboprops and turboshafts can use an inlet screen to help  filter out ice or debris from entering the engine. A deflector  vane and a heated inlet lip are used to prevent ice rom forming  and allowing large chunks to enter the engine. This is also referred to as the compressor pressure ratio. This  ratio is the outlet pressure divided by the inlet pressure. The  amount of air passing through the engine is dependent upon  three factors:  On military aircraft, the divided entrance permits the use of very  short ducts with a resultant small pressure drop through skin  friction. Military aircraft can fly at speeds above Mach 1, but  the airflow through the engine must always stay below Mach  1. Supersonic air flow in the engine would destroy the engine.  By using convergent and divergent shaped ducts, the air flow is  controlled and dropped to subsonic speeds before entering the  engine. Supersonic inlets are used to slow the incoming engine  air to less than Mach 1 before it enters the engine.  The accessory section of the gas turbine engine has various  functions. The primary function is to provide space for  Turbine inlet type is dictated by the type of gas turbine engine.  A high-bypass turbofan engine inlet is completely different  from a turboprop or turboshaft inlet. Large gas turbine- powered aircraft almost always have a turbofan engine. The  Accessory Section 1.  The compressor speed (rpm) 2.  The forward speed of the aircraft 3.  The density of the ambient (surrounding) air $^{ }$Air Entrance Figure 1-43. Turbofan engine with separate nozzles, fan, and core.  1-38