The two sections of the fuel control unit are the ________ control and the hydro-________ control.

• A. Automatic; hydro-mechanical
• B. Automatic; hydraulic
• C. Manual; hydraulic
• D. Manual; hydro-mechanical

Answer: (D)

In this fuel control setup, two sections work together: a manual control and a hydro-mechanical control. The manual section gives the operator direct, mechanical control of fuel flow through the power lever, which is essential for starting, testing, or overriding automatic behavior when needed. The hydro-mechanical section uses hydraulic pressure combined with mechanical linkages to meter fuel automatically in response to engine demand, RPM, and other signals, providing smooth, controlled fuel delivery during normal operation. The term hydro-mechanical describes this blend of hydraulic actuation with mechanical metering, which is why the two sections are described as manual control and hydro-mechanical control. Automatic control isn’t listed here as a separate section in this configuration, since the emphasis is on the operator override via manual control alongside the hydraulic/mechanical metering.