Heavy-Lift Helicopter

Overview

A heavy-lift helicopter exists to move loads too large or too remote for a crane or a truck: a transformer onto a mountain ridge, a drill rig into the bush, a wildfire water bucket, or a stranded vehicle off a flooded road. It lifts these loads on a cable slung below the aircraft, which is why the airframe, rotor, and drive train are sized around lifting force rather than speed or range. The machine described here uses a single seven-blade Main Rotor System, twin Turboshaft Engine turboshafts feeding one Main Transmission, and an external External Cargo System rated for roughly ten tonnes. Everything else, the Fuselage Structure, the Landing Gear, the Hydraulic System, serves that lifting mission.

Main rotor system

Lift comes from the main rotor, and the more blades it carries the more thrust it produces without growing the disk diameter past what a confined site allows. The seven Main Rotor Blade blades are composite, each built around a Composite Blade Spar with a titanium Titanium Leading-Edge Cap that resists erosion from dust and rain. They bolt to a titanium Rotor Hub through Blade Grip grips on Elastomeric Bearing bearings that let each blade flap, feather, and lead-lag as it goes around. Pilot inputs reach the blades through the Swashplate Assembly: tilt it and the rotor disk tilts, raise it and every blade increases pitch together. A Pitch Control Link connects the swashplate to each blade, and a Lead-Lag Damper on every blade suppresses the in-plane oscillation that would otherwise build into ground resonance.

Engines and transmission

Two turboshaft engines drive the rotor through a single combining gearbox, so the loss of one engine still leaves enough power to fly. Each Turboshaft Engine is a free-turbine design: the Axial-Centrifugal Compressor and Gas Generator Turbine form a self-sustaining gas generator, and a separate Free Power Turbine downstream extracts shaft power and feeds it to the gearbox. Combustion happens in an annular Annular Combustor fed by twelve Fuel Nozzle nozzles, and a FADEC Engine Control meters fuel to hold rotor speed constant as the load changes. The Main Transmission is the most stressed component on the aircraft: it takes around 8,000 horsepower at engine speed and steps it down roughly 90:1 through the Main Gearbox and a Planetary Reduction Stage to the slow, high-torque Rotor Mast. A Freewheel Clutch in each engine drive lets the rotor keep turning and autorotate if both engines quit.

Anti-torque and tail rotor

A single main rotor wants to spin the fuselage the opposite way, so the Tail Rotor System pushes sideways at the end of the Tail Boom to cancel that torque and to steer the aircraft in a hover. It is driven off the main gearbox through a Tail Drive Shaft and a right-angle Tail Rotor Gearbox. The anti-torque pedals change tail rotor pitch directly, which is how the pilot points the nose while hovering over a pickup point. Tail rotor authority sets a real limit on how the aircraft can be flown in a crosswind with a heavy slung load.

Airframe, landing gear, and fuel

The Fuselage Structure is a semi-monocoque aluminium structure with a reinforced Reinforced Cargo Floor and titanium Engine Firewall (titanium) panels around the engines. The Landing Gear is a wheeled tricycle layout on Oleo-Pneumatic Strut oleo-pneumatic struts that soak up hard landings with heavy loads aboard. Fuel sits in crashworthy Self-Sealing Fuel Tank self-sealing tanks; the Fuel System uses redundant Boost Fuel Pump boost pumps so an engine never starves during the aggressive maneuvering that load placement demands. The Hydraulic System system is dual-redundant because the rotor control loads are far too high for a pilot to move the Flight Control Servo Actuator actuators by muscle alone.

External load handling

What makes this aircraft a heavy-lift type rather than a transport is the External Cargo System. The electric-release Cargo Hook (electric release) hangs on the aircraft centre of gravity and carries a Load Cell so the crew sees the exact weight before they commit to a lift. A loadmaster watches the Sling Leg Set sling legs and the load through a belly window or a remote camera and calls the pilot onto the pickup point inches at a time. A separate Rescue Hoist handles people and small payloads on a powered cable. The hook can be triggered to drop a load instantly, which is a safety feature: a swinging external load that starts to diverge can endanger the whole aircraft, so the pilot must be able to release it in an instant.

Operations and variants

Heavy-lift helicopters earn their keep in jobs with no road access. Logging operations fly logs out of steep terrain, power utilities set transmission towers and string conductor, construction crews place rooftop chillers and steel, and firefighting variants carry a belly tank or a Cargo Hook (electric release) bucket to drop water on a fire line. The same airframe appears in a firefighting fit with a refill snorkel, a utility fit with a passenger cabin, and a flying-crane fit stripped of everything not needed to lift. Because the Main Transmission and rotor are the cost and life-limiting items, operators track torque and rotor hours closely, and overhaul intervals on the gearbox and blades drive much of the operating cost. Pilots flying these loads work to fine tolerances: a load placed on a tower or a building must arrive slowly and without swing, which is a different skill from forward flight and is what the long-travel controls and precise Hydraulic System are tuned to support.