A Twin Squirrel helicopter was approaching Sydney Airport on a St Peters 2 Inbound helicopter route. As the helicopter approached the airport maintenance area, the pilot advised the aerodrome controller that he had a hydraulic problem and requested a fire tender to meet him on arrival. As this was being arranged, the pilot further advised that there was now a strong smell of hydraulic fluid in the cabin and requested confirmation that a fire tender was awaiting his arrival. However, as the helicopter passed over runway 25, the pilot advised that he had lost hydraulic power to the tail rotor and was landing immediately. The helicopter landed safely on helipad 03. There was no fire or reported damage to the helicopter. A ground inspection of the helicopter revealed that the right hydraulic system fluid reservoir outlet flange had cracked, resulting in loss of contents and subsequent loss of tail rotor control. The operator has submitted a Major Defect Report to the Civil Aviation Safety Authority.