Descender rig
A controlled vertical descent rig where a centrifugal fan brake regulates rope payout. The reference rig for the Burj Khalifa work in Mission: Impossible — Ghost Protocol.
Mechanism
A fan descender is a fixed-rate descender mounted at the top anchor that pays out steel cable through a centrifugal-fan brake. The fan blades are calibrated to spin against air resistance at the descent rate — typically 6 to 12 feet per second — so the cable feeds smoothly without shock loads. The performer wears a full-body harness clipped through a load-distributing screamer and the cable terminates at a swaged thimble. Unlike a free-rappel where the operator controls speed manually, the fan descender's rate is mechanical and identical on every take, which is why coordinators use it for repeatable visual-effect frames where the descent must hit a mark.
Safety
The fan brake must be tested at the daily rated load before talent is rigged. A redundant secondary line — typically a dedicated arrest ratchet — runs in parallel so any single-point failure on the descender cable is caught within 18 inches. The performer must not be placed on the rig until both lines are pretensioned and the catch crew is in position. Cold-weather operation derates the fan's air resistance (denser air = faster descent), so winter work uses a slightly higher-rated brake than the calibrated nominal.
Variants
Same principle but with eddy-current braking via permanent magnets — more compact, no air-density sensitivity, but less heat tolerance for long descents.
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.
References
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