What component's compression changes when the propeller control is moved, causing the pilot valve to actuate?

What component's compression changes when the propeller control is moved, causing the pilot valve to actuate?

• A. Speeder spring
• B. Propeller hub
• C. Oil pressure
• D. Blade angle

Answer: (A)

When you move the propeller control, you change the compression on the speeder spring. That compression shift moves the pilot valve in the hydraulic propeller control, which modulates oil flow to the pitch-change mechanism. The altered oil pressure then changes blade angle to hold the desired RPM. The hub itself isn’t compressed by the control, and blade angle is the result of the oil pressure change, not the initial act of compression. Oil pressure changes as a consequence of the pilot valve movement driven by the speeder spring compression.

When you move the propeller control, you change the compression on the speeder spring. That compression shift moves the pilot valve in the hydraulic propeller control, which modulates oil flow to the pitch-change mechanism. The altered oil pressure then changes blade angle to hold the desired RPM. The hub itself isn’t compressed by the control, and blade angle is the result of the oil pressure change, not the initial act of compression. Oil pressure changes as a consequence of the pilot valve movement driven by the speeder spring compression.