Outriggers (also called supports, stabilizers, or outrigger legs) are hydraulically extendable supports on mobile cranes, truck-mounted concrete pumps, aerial work platforms, and truck cranes. They widen the support base of the machine and absorb the tipping moments when loads are lifted. Without fully extended outriggers, a mobile crane may only operate at drastically reduced load capacity.
The support system consists of telescopic beams (horizontally extendable) and vertical cylinders with support plates. The support load per jack on large mobile cranes can reach 60+ tons — ground pressure must be reduced to permissible values using load distribution plates (crane mats).
Modern mobile cranes feature variable outrigger widths: the crane can operate at different support widths, with the load chart specifying separate values for each width. Fully automatic leveling systems align the crane horizontally at the push of a button. On truck-mounted concrete pumps, the supports stabilize the machine against the recoil forces of pump operation and the slewing movements of the distribution boom.