Rappelling refers to descending a vertical or steep pitch using an anchored rope. Different mechanical descending devices and techniques have been developed for emergency applications, helicopter rappels, and mountaineering abseiling. All types of rappelling have the intent of protecting the person on the rope from injuries like friction burns, as a considerable amount of heat is generated by rapid descent down a rope.
Helicopter Rappel
Helicopter rappelling is used in military and law enforcement as well as fighting forest fires. The Rappell Guide Working Group of the Geographic Area Coordination Center's National Interagency Fire Center (GACC) establishes uniform protocols for helicopter rappelling, so that all local, state, and federal firefighters will use the same equipment and techniques like hand signals during rappelling actions. GACC helicopter rappelling involves anchoring a double kernmantle rope with minimal stretch and high heat resistance to an anchor point within the helicopter, then running the double rope through a mechanical friction brake to control the descent. There are numerous mechanical descending devices on the market; the U.S. Forest Service and Bureau of Land Management only use the patented Sky Genie Model 14G-O descender for uniformity, which helps preclude user error that might occur with an unfamiliar device. The descending device is critical in helicopter rappelling, since the person descending is hanging freely on the rope with no ground on which to lean to relieve weight or descent speed.
Carabiner Brake Rappel
In the absence of a specific descender device, climbers can assemble a safe descender from a combination of four or five locking carabiners, according to Chockstone, a non-profit organization for climbers in Victoria, Australia. Place two locking carabiners together with their gates on opposite sides; poke a U-shaped loop of a single or doubled heat-resistant rope through the carabiners, then fasten two more D or oval carabiners under the rope across the center of the two other carabiners, in a cross shape. For better resistance, place a third crossing carabiner and run the rope over, under, and over the three crossing carabiners. Fasten the climber's harness to the dual carabiners used as the base for the brake with another pair of locking carabiners, and operate the rope for descent as with any other descending device.
Dulfersitz Rappel
According to Traditional Mountaineering, a non-profit dedicated to providing information about safe climbing techniques and alpine instruction, the Dulfersitz rappel is a basic safety skill, which should be familiar to all climbers and mountaineers. The Dulfersitz rappel uses rope only, wrapped around the climber's body to maximize friction for a controlled descent, while minimizing risk of entanglement with the rope. Pass a double or single rope through the climber's legs, then to the right side below the buttocks, up across the left shoulder, then across the back to the right side hip. Hold the rope with the left hand ahead and uphill of the climber and the right hand behind and downhill of the climber. Descend slowly, as the rope is likely to burn clothing and skin under rapid descent.
