Helicopters used to lift heavy loads are called aerial cranes or skycranes. These are usually awkward-looking helicopters carrying loads connected to long cables or slings in order to place heavy equipment.
Aerial cranes are usually a last resort, deployed when all other methods have been exhausted, and it becomes economically feasible.
Often this means that the job in question must be accomplished in remote or inaccessible areas, such as the tops of tall buildings or the top of a hill or mountain, far from the nearest road.
Unsurprisingly skycranes have proved an enduring presence in the the logging industry, lifting large trees out of rugged terrain where vehicles aren’t able to reach or where environmental concerns prohibit the buildings of roads.
However there was a time when the helicopter, like the similarly aged jet engine, was seen as one of the revolutionary technologies that could re-shape a world recovering from the ravages of World War Two.
It seems ludicrous now, but there was a time when people envisioned helicopters replacing trains in the daily commute to dense urbanised areas such as Manhattan Island in the US.
Indeed, talking of New York, soon after the helicopter came into commercial use in 1950s it would was suggested it could be used in the construction of the skyscraper-shaped cities that were beginning to sprawl.
Having been first deployed as aerial cranes in the early part of the 1950s, helicopters found a natural role in construction in the 1960s. With popular use of skycranes in the construction and other industries beginning to catch on, for a while it really looked like a revolution, to use a bad pun, was taking off.
Bell 47 helicopters were the first, lightweight aerial cranes to be used in the early 1950s. Unfortunately, due to the helicopter’s limited power via its piston engine, it was never capable of carrying more than just a few hundred pounds of cargo.
In the 1960s, the Sikorsky S-58 replaced the Bell 47 because of its larger power margin. Even today, S-58s can be found carrying medium-size loads.
It was, however, the creation of the small jet turbine engine that transformed helicopter versatility and capabilities. With more power and a far lighter construction, plus the ability to operate at higher rpm for longer periods while using less fuel, turbine-powered helicopters ushered in a new age of construction-oriented uses.
The lattice-boomed 1955 Aérospatiale Alouette II was the first commercially available turbine powered helicopter, and its variant, the Aerospatiale Llama, became a popular choice for lifting duties because it was able to carry slingloads of up to 1000kg (2,205 lb).
The 1960s also brought the Bell 211 HueyTug, a specially produced commercial version of the UH-1C for lifting medium loads, and even the popular Bell 206 JetRanger and Hughes 500 were used for lighter loads. Both used variants of the Elison 250 C20 turbine engine, and they remain two of the most popular helicopters in commercial use today. Each carries just over 650kg in payload, making them perfect for small construction jobs in remote areas. Both are also widely used for a myriad of tasks, including stringing high-voltage wires across valleys.
But there continued to be a demand for aircraft able to lift even larger loads.
Larger helicopters became commercially available after the Vietnam War as helicopter manufacturers focused on selling commercial versions of their military aircraft.
For instance, Boeing Vertol Model 107 and Model 234 aircraft have been used to carry even heavier payloads than their lighter predecessors. But the heaviest loads required a pure aerial crane. The answer came from Sikorsky’s S-64 Skycrane.
Originally produced for the military as the CH-54 Tarhe for heavy lifting of downed aircraft and artillery pieces, the S-64 Skycrane was nothing more than just enough airframe to attach two powerful engines, the main and tail rotors and transmissions, a cockpit, and a cargo hook and winch system.
However its sheer power, simplicity and endurance helped make it one of the most successful of its breed.
When construction on the Chesapeake Bay Bridge – labelled as one of the seven wonders of the world at the time – started in 1960 the Skycrane proved that it could do length as well as height as it brought concrete and other supplies to the construction site across 17 miles of water.
The cost of aviation fuel and advances in cheaper ground-based alternatives means that the use of heavy-lift helicopter around sites has become rarer, but decades down the line there is always a buzz when one flies into town.