RTC Rope Systems & Rigging 2 — Questions and Answers
Question 1: In a theoretical 3:1 mechanical advantage (MA) system with no friction losses, if rescuers apply 100 lbs of force, what load can the system raise?
- 100 lbs
- 200 lbs
- 300 lbs (Correct answer)
- 400 lbs
Correct answer: 300 lbs
A 3:1 MA system multiplies applied force by three; 100 lbs of input force produces 300 lbs of theoretical output force, though friction reduces the actual load moved in practice.
Question 2: What type of rope rescue system is commonly called a 'Z-rig'?
- A 2:1 MA lowering system
- A 3:1 MA raising system where the rope path resembles the letter Z (Correct answer)
- A pre-rigged anchor system with three attachment points
- A redundant belay system using a Z-shaped configuration
Correct answer: A 3:1 MA raising system where the rope path resembles the letter Z
The Z-rig is a 3:1 mechanical advantage raising system named for the Z-shaped path the rope travels through two pulleys, with one pulley at the anchor and one on the load.
Question 3: Which device is commonly used as both a descender for controlled lowering and a belay device during rescue operations?
- Prussik loop
- Figure 8 descender
- Munter hitch on a locking carabiner
- Brake Bar Rack (Correct answer)
Correct answer: Brake Bar Rack
The Brake Bar Rack provides adjustable friction for smooth lowering of heavy rescue loads and can be configured as a belay device, making it highly versatile for rescue operations.
Question 4: In mechanical advantage haul systems, what term describes the additional rope that must be fed through the system each cycle as the haul team resets their grip?
- Tail rope
- Haul cam stroke
- Rope travel (Correct answer)
- System elongation
Correct answer: Rope travel
Rope travel refers to the amount of rope that must pass through the MA system to move the load a given distance; a 3:1 MA requires 3 feet of rope travel to raise the load 1 foot.
Question 5: In a high-directional (high-point) anchor system, what is the primary purpose of the elevated redirect pulley?
- To increase the mechanical advantage of the haul system
- To change the rope angle for easier edge clearance and reduce rope-on-edge friction (Correct answer)
- To serve as the primary load-bearing anchor
- To act as the belay device for the descending rescuer
Correct answer: To change the rope angle for easier edge clearance and reduce rope-on-edge friction
A high directional redirects the rope away from the edge and over the lip, reducing abrasion and enabling a cleaner angle of pull, though it transfers significant force to the high-point anchor.
Question 6: What effect does friction have on the actual mechanical advantage of a rope rescue haul system compared to its theoretical mechanical advantage?
- Friction increases actual MA above theoretical MA
- Friction has no effect because rescue pulleys are frictionless
- Friction reduces actual MA below theoretical MA (Correct answer)
- Friction only affects MA in systems with more than 4:1 ratios
Correct answer: Friction reduces actual MA below theoretical MA
Every pulley, bend, and friction point in the system reduces efficiency; actual MA is always lower than theoretical MA, which is why high-quality rescue pulleys with ball bearings are preferred.
Question 7: What is a 'pick-off strap' (or pick-off rescue strap) primarily used for in technical rope rescue?
- Attaching the haul line to the main anchor
- Quickly securing a patient to a rescuer for emergency removal from height (Correct answer)
- Creating an improvised chest harness for the rescuer
- Connecting two ropes together in a highline system
Correct answer: Quickly securing a patient to a rescuer for emergency removal from height
A pick-off strap is a short adjustable strap that allows a rescuer on rappel to quickly attach and secure a patient to themselves for an emergency removal when a litter is impractical.
RTC Rope Systems & Rigging 2
In a theoretical 3:1 mechanical advantage (MA) system with no friction losses, if rescuers apply 100 lbs of force, what load can the system raise?