How Aerial Crane Helicopters Suspend, Support and Hoist Utility and Construction Cargo
Helicopters often serve as aerial cranes for utility, construction, and heavy-lifting projects, typically a more precise and faster method of lifting than traditional ground cranes. Adaptable and efficient, helicopters are uniquely suited for heavy lifting, and the aircraft’s sky crane capabilities are among its most useful services in utility work.
Helicopters were first used for heavy lifting by the United States military and were initially only able to lift 2,000 or 3,000 pounds. Over time, helicopter manufacturers began building aircraft capable of lifting much more—up to 30,000 and 40,000 pounds—and aerial cranes quickly became a widely used and preferred method of heavy lifting for construction and utility companies.
They’re often employed to transport heavy cargo and construction materials; to install commercial HVAC units and ventilation systems; to repair or install power lines, cell towers, pipelines and water systems; and to perform forestry operations and restoration.
The use of aerial crane helicopters is far more complex than simply lifting things and setting them down, and helicopters use a variety of load suspension systems, slings, nets, and hoist systems to get the job done.
What kind of suspension systems do aerial crane helicopters use?
Nevertheless, a number of suspension systems are commonly used by helicopters, including cargo hooks, single-point suspension systems, and multi-point suspension systems.
While helicopter suspension initially used a four-cable configuration system affixed with a manual attachment and detachment system—known as a cargo sling—this basic suspension system was quickly improved by the addition of a cargo hook controlled by the pilot.
Today, cargo hooks feature electrical and automatic touchdown releases—improving helicopter stability on lift-off and allowing pilots to more easily and efficiently pick up and deposit loads. Cargo hooks are also frequently used on hoist systems, which allow aerial cranes to raise and lower a slung load.
Generally, primary, or “belly,” cargo hooks are mounted directly underneath a helicopter’s frame, affixed to the fuselage of the aircraft. Helicopter suspension systems also employ the use of remote hooks, which are suspended beneath the belly hook by a line or swivel.
Single-point suspension is the simplest and most common way of transporting external loads for aerial crane helicopters. Most often, single-point suspension systems attach the cargo to a helicopter’s cargo hook through a long line and ring pendant, which helps to disperse any twisting or wrenching of the load.
Sometimes, when it’s necessary to lift a load on a particularly long or short sling, single-point suspension systems affix the load to a swivel mechanism, which minimizes the risk of damage to the helicopter and suspension line.
Often, when extra stability is required to perform heavy lifting, aerial cranes employ a multi-point suspension system, using two, three or four-point configurations. Because single-point suspension offers only limited movement restraint, multi-point suspension allows greater control and stabilization during long or sensitive cargo trips.
Because helicopters are able to maneuver in tighter spaces, access harder-to-reach locations, and perform in all types of weather and terrain, the number and design of a multi-point suspension system can be augmented for various utility, construction and heavy-lifting scenarios.
For example, a four-point pickup system may provide significant advantages, since the load can be pulled up from the fuselage and considered a part of the aircraft’s structure. For cargo which is unstable during forward flight, a two-point system fastened to a single hook may be more practical, whereas a single system could prove simpler, cheaper and more reliable for transporting external cargo without significant load-bearing risks.
How do aerial crane helicopters employ slings and nets?
When working with a helicopter company like Helicopter Express on your next utility, construction or heavy-lifting project, our experienced pilots and experts will determine what kind of support equipment—most often a sling or a net—is best suited for your needs
While slings are the most common method of cargo transportation, cargo nets provide a much simpler means to restrain and support slung loads and may be suitable for your construction project.
While it may seem like an external load can be attached to a helicopter by any means that provides sufficient strength—like rope, steel cable, nylon webbing, etc.—slings are often the most significant and critical components in external load operations.
The most common method of supporting aerial crane cargo loads, slings are preferred for their:
Long shelf and service life
Ease of rigging to the load and helicopter
Adaptability to irregular loads
Freedom from periodic maintenance
Ease of inspection and replacement
Cargo nets provide a simple means to restrain and support cargo loads, and cargo nets are often used as load carriers on aerial cranes and helicopters when loads are relatively light—usually under two tons.
When nets containing cargo are picked up, items around the edges of the lend tend to shift upward and inward, causing the center to sag and the nets to impose some force on the contents. For this reason, cargo net support systems are often affixed with longer suspension lines, center rods, or spreader frames to reduce these forces.
While the first helicopter hoist systems were used by the U.S. Navy to rescue sailors from water, the utility of helicopter hoisting was quickly applied to utility and construction projects. Today, helicopter hoisting systems are routinely used to raise and lower cargo from a hovering helicopter.
Using cables wound around a hydraulic drum, helicopters usually employ capstan winches to increase the structural stability, efficiency and durability of hoist systems. Like most suspension systems, aerial crane hoisting can also employ single-point and multi-point hoist systems.
Single-Point Hoist Systems
Aerial crane helicopters most often use hoist systems to acquire a load from inaccessible places or when the helicopter must maintain some distance from the cargo it’s collecting. Hoisting systems are similarly used when the cargo, like a load positioned on a moving ship in undesirable sea conditions, is itself unstable.
While these tasks could be completed with a long suspension line, transporting cargo with unusually long lines can be dangerous to those below and hazardous to helicopter function. Single-point hoist systems, which work similarly to a single-point suspension system but are able to raise and lower cargo, are particularly helpful in this way: When using a single-point system, helicopters are able to acquire a load on a long line and then shorten the suspension for optimum flying.
In general, a single-point hoist system has load stability characteristics similar to those of single-point suspension systems. Efficient, uncomplicated and easy for loading and unloading, single-point hoisting systems are the most common hoisting mechanisms in practice, but may be replaced with multi-point systems when stability and cargo movement poses some problem.
Multi-Point Hoist Systems
Multi-point hoist systems are far less common, but are sometimes used to combine the load stability of multi-point suspension with the pickup and line positioning capabilities of hoisting.
While some two-point hoisting systems are used by aerial crane helicopters to lift complicated loads, most multi-point hoist systems couple multi-point suspension—using various points of suspension on a cargo hook—with a single cable hoisting system.
Contact Helicopter Express for all of your aerial crane needs.