If we are starting to look for the largest helicopter here it is. It is the Mil Mi-12.

General characteristics
Crew: six
Capacity: up to 25,000 kg (55,000 lb) of cargo
Length: 37.00 m (121 ft 4 in)
Main rotor diameter: 2x 35.00 m (114 ft 10 in)
Height: 12.50 m (41 ft 0 in)
Main rotor area: 1,924 m² (20,700 ft²)
Empty: 69,100 kg (152,020 lb)
Loaded: 97,000 kg (213,400 lb)
Maximum takeoff: 105,000 kg (231,000 lb)
Powerplant: 4x Aviadvigatel D-25VF turboshafts, 4,847 kW (6,497 shp) each
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Performance
Maximum speed: 260 km/h (163 mph)
Range: 1,000 km (625 miles)
Service ceiling: 3,500 m (11,480 ft)
Rate of climb: m/min ( ft/min)
Main rotor loading: 50 kg/m² (10 lb/ft²)
Power/Mass: 0.20 kW/kg (0.12 hp/lb)

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