The function of variable inlet guide vanes in a gas turbine engine is to prevent what condition?

• A. Increase Fuel Flow
• B. Prevent Compressor Blade Stall At Low RPM
• C. Improve Exhaust Velocity
• D. Reduce Oil Pressure

Answer: (B)

Variable inlet guide vanes adjust the angle of the air entering the compressor to match operating conditions. At low RPM, air can enter at an unfavorable angle, causing flow separation and compressor blade stall, which can lead to surge and unstable engine operation. By changing the vane angle, the incoming air is directed to maintain smooth, stable flow, increasing surge margin and preventing stall during start and idle. The other options don’t fit because they describe effects not controlled by the inlet guide vanes: fuel flow is governed by the fuel system, exhaust velocity is set by the turbine and nozzle, and oil pressure relates to the lubrication system.