What you don't know about using carabiners.

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If you look in the back of any helicopter in the world, I think you will be hard pressed to not find a carabiner being used in some capacity. They are a versatile piece of equipment used for a multitude roles. They can simply hang a helmet bag, or they can be used on the winch to secure a crewman to the wire. As common as carabiners are in the helicopter environment, there are many professional crewman who lack a thorough understanding of the different types, their limits, and how to use them safely.

As we are all aware, incorrect use of equipment can result in serious consequences, and carabiners are no exception. What seem like a simple to use device, has many limitations and hazards if not used correctly. 

This article is a beginner’s guide to better understanding  carabiners in the Aircrewman work environment. I will not discuss load restraint, understanding safe working loads (SWL), or converting kilonewtons (kN) for static weight cargo. These are complex topics which require more than one article to understand and explain.

Shapes 
Although there are now hundreds of types and shapes of carabiners available, they are not all created equal. There are four common shapes which are used, each with its own advantages and disadvantages.

Oval: Smooth regular curves are gentle on equipment and allow easy repositioning of loads. Their greatest disadvantage is that a load is shared equally on both the strong solid spine and the weaker gated axis.

D: Asymmetric shape transfers the majority of the load onto the spine, the carabiner's strongest axis.

Offset-D: Variant of a D with a greater asymmetry, allowing for a wider gate opening.

Pear: Oversized offset-D shape used in the climbing environment. These are a climbing and roping carabiner. Pear shaped carabiners generally don’t have a lot of use in the helicopter industry, but are still regularly seen.

Gates

There are two types of gates, locking and non-locking. Both types of gates have several variations and ways of being operated, as with the shape of the carabiner there are advantages and disadvantages to both. 

Locking

Locking

The three most common locking mechanisms are screw-lock, Twist-lock, and Magnetic. 

Screw-lock: Have a threaded sleeve over the gate which must be engaged and disengaged manually. They have fewer moving parts than spring-loaded mechanisms, are less prone to malfunctioning due to contamination or component fatigue, easier to employ one-handed. They, however, require more total effort and are more time-consuming than twist-lock.

Twist-lock: Have a security sleeve which must be manually rotated to disengage, but which springs closed automatically upon release. They offer the advantage of re-engaging without additional user input, but being spring-loaded are prone to both spring fatigue and their more complex mechanisms becoming balky from dirt, ice, or other contamination. They are also difficult to engage one-handed and with gloves on.

Magnetic: Have two small levers with embedded magnets on either side of the locking gate which must be pushed or pinched simultaneously to disengage. Upon release the levers pull shut and into the locked position against a small steel insert in the carabiner nose. With the gate open the magnets in the two levers repel each other so they do not lock or stick together, which might prevent the gate from closing properly. Advantages are very easy one-handed operation, re-engaging without additional user input and few mechanical parts that can fail.

Non-Locking

Non-Locking

Non-locking carabiners have a spring loaded swinging gate which can be opened easily but has no way of being secured in the closed position.

Three gate types are common:

Straight gate: The most versatile, and hence most popular.

Bent gate: Curved gates allow for easier clipping in and out in special situations, such as connecting a rope to a quickdraw. Gate strength remains on a par with straight-gate carabiners.

Wire gate: The lightest type, with a strength roughly equal to the others, allowing more to be carried for a given weight.

Markings

Not being able to identify the capabilities and limitations of a carabiner should limit what you use it for. If you don’t know what amount of load it is rated to, how do you know it can perform the job you are about to use it for? There are a large amount on non-load bearing and “not for climbing” carabiners available and unfortunately not all alert you to this fact.

The information you should be looking for on a carabiner is kN or SWL. This is usually marked in three ways, gate open, closed and cross loaded. This will be your first indication of the suitability of your carabiner.

Other common marks which can help identify the quality of your carabiner are safety label certifications such as CE, UIAA and ANSI. These markings indicate that the item has met the minimum standard for that organisation. 

Dangers

Most carabiners are designed to attach two items and bear a straight load. Any variation of this will cause stress and force on the carabiner. The strongest part of a carabiner is along its spine. The load should be placed on the carabiner in order to use this strong axis. 

Even with a correctly loaded carabiner there are other dangers to consider:

Dynamic roll out;

Gate Flap;

Cross loading;

Shock loading;

SWL;

Compatible connection point;

Load shift.

All of these hazards can be avoided with an understanding of the equipment, and the environment in which you use it. 

Carabiners are a great piece of equipment, but can also provide a false sense of security if they are not used correctly. CrewEquip sell both locking and Non-locking carabiners that have been tested in the Aviation environment.

Fly Safe

CrewEquip

http://crewequip.com.au/