Which two features provide automatic locking capabilities on most aerial apparatus?

The automatic locking capabilities on most aerial apparatus are primarily provided by holding valves and interlocks. Holding valves play a crucial role by maintaining hydraulic pressure and preventing movement in the aerial device when it is not in use or when the apparatus is in a stowed position. These valves ensure that, regardless of external forces or changes in weight distribution, the aerial ladder or platform remains securely in place.

Interlocks, on the other hand, serve as safety mechanisms that prevent certain operations unless specific conditions are met. For instance, an interlock may prevent the operator from extending the ladder if the hydraulics are not properly engaged or if the apparatus is not positioned correctly. This feature helps ensures safety by automatically locking the system in a safe state and preventing inadvertent movements that could lead to accidents.

Other options, while they may relate to various mechanical features of fire apparatus, do not encompass the primary systems designed for automatic locking in aerial devices. Therefore, the combination of holding valves and interlocks effectively delivers the required automatic locking capability, enhancing the safety and functionality of the aerial apparatus during emergency operations.