What transfers aircraft electrical power for propeller deicer systems from the engine to the propeller hub assembly?

• A. Bus bars and connectors
• B. Magnetic couplings
• C. Hydraulic lines
• D. Slip rings and brushes

Answer: (D)

The mechanism being tested is slip rings and brushes. Propeller deicer systems need electrical power delivered to a rotating hub, since the propeller hub turns with the engine. A slip-ring assembly mounted on the hub provides conducting rings that rotate with the propeller, while stationary brushes connected to the aircraft’s power source press against those rings, allowing current to flow into the deicer heaters as the hub spins. This setup lets power transfer continuously without wires twisting around the shaft.

Bus bars and connectors would assume a fixed, nonrotating path and don’t itself provide a rotating connection. Magnetic couplings can transfer torque or enable non-contact power transfer in some systems but aren’t used to feed electrical power to a rotating hub in this context. Hydraulic lines carry fluid, not electricity. Therefore, slip rings and brushes are the correct method.