Identification and Location

The variable inlet guide vane assembly is located in front of the first compressor rotor and consists of a series of hollow blades positioned by a synchronizing ring.

System Design

The variable inlet guide vanes change the angle of incidence between inlet air and compressor rotor blades to maintain the airflow requirements of the compressor rotor assembly. At low N1 speeds, a high angle of inlet is required, while at higher N1 speeds, the angle of inlet required decreases. Since it is the proper inlet airflow angle relative to rotor speed that we are concerned with, the inlet guide vanes must vary in position as a function of compressor rotor speed and air temperature. The inlet guide vane actuator is positioned by the inlet guide vane actuator pilot valve located in the Fuel Control as a function of N1 speed and compressor inlet temperature T1.