Which system does T-54A hydraulics not support?

The T-54A is equipped with various hydraulic systems that perform specific functions within the tank's operation. Among these, options such as landing gear operation, flap extension, and rudder movement are commonly associated with aircraft systems, while brake de-ice refers to a function that is generally not utilized in tank operations.

In the context of the T-54A, the hydraulic system is primarily designed to support the tank's internal mechanisms, such as its gun control, turret rotation, and suspension adjustments, rather than functions found in aviation systems like flaps and landing gear. Brake de-icing is not applicable because tanks do not have the same types of braking systems that might require such a function. The tank's braking system is typically mechanical rather than hydraulic and does not involve de-icing mechanisms.

Therefore, the correct choice represents a function that is specifically outside the operational capabilities of the T-54A hydraulic systems, which are not responsible for controlling functions like brake de-ice that are unnecessary in a ground vehicle context.