Descender rig
The hydraulic ratchet rig used to arrest a high-fall in the last 6 to 10 feet, replacing or augmenting an airbag for daylight exterior work where the bag would be visible to camera.
Mechanism
A decelerator is a hydraulic cylinder that pays out cable under spring tension and arrests it under hydraulic damping. The performer wears a back-mounted carabiner clipped to the cable; on jump, the cable pays out freely through the spring-loaded reel, then transitions into the hydraulic chamber for the last meter or two of travel, producing a controlled negative-acceleration profile rather than the abrupt arrest of a static rope. The decelerator's payout length and damping rate are pre-tuned to the performer's mass and the fall height. Visually, the cable can be wire-rigged below the harness so it disappears against complex backgrounds or is removed in post.
Safety
Hydraulic decelerators must be bench-tested at the daily working load and the cable inspected for kink or strand failure before each take. The rig is not safe for falls greater than 60 feet without a parallel airbag underneath as a tertiary catch; the hydraulic chamber's heat dissipation degrades over consecutive takes. After three takes within ten minutes, the chamber temperature is checked and the rig is rested if it exceeds 140°F.
Variants
Two parallel hydraulic chambers used for performers above 200 lb or when the fall has horizontal momentum.
Lower-precision variant for falls under 25 feet — no hydraulics, just a long spring-loaded cable on a friction reel.
On screen
Sequences in the archive whose discipline tags overlap this technique's category. Click through for the full rigging breakdown of each set-piece.