What condition must be met for the landing gear transfer unit to function properly?

The landing gear transfer unit is designed to operate correctly only when specific mechanical conditions are met. For the unit to function properly, there must be at least one main landing gear that is not in the 'up and locked' position. This condition is crucial because the transfer unit's role involves managing and adjusting hydraulic pressure related to the landing gear system. If both main landing gears are locked in the 'up' position, the unit would not function as intended since it typically relies on feedback from the gear position to manage hydraulic flow and pressure effectively.

In the context of hydraulic systems, the presence of at least one gear not being locked ensures that the hydraulic actuation mechanisms remain active, allowing for the necessary adjustments in pressure and flow that facilitate safe landing gear operations. Hence, ensuring that not all gears are in a locked position is vital for the overall functionality and safety of the landing gear transfer unit.