Five Black Hawk helicopters will join the country's fight against terrorism, their crews carrying out extensive drills over the next six weeks to prepare for a possible mass attack.

The imposing aircraft, manned by special forces officers, will hone their response to attacks on high-rise buildings, landmarks, big venues such as football stadiums and difficult terrains such as dam walls and cliff edges.

Crews will practise scenarios such as a possible attack from the sea or dropping officers into a well-lit stadium at night where they have to quickly adjust from darkness to light.

They will practise in rural areas around Nowra and Jervis Bay and urban areas in Sydney and Canberra.

Two Black Hawks from the 6th Aviation Regiment conducted a dramatic, 20-minute drill on Monday, taking off from a Mosman oval and performing low circles over Sydney Harbour before hugging the coastline up to Narrabeen and back.

Despite some of Australia's ageing Black Hawk fleet being replaced by European MRH90s, executive officer of the 6th Aviation Regiment Major Jeremy Mierendorff said the Black Hawks were "an extremely capable aircraft that have proved themselves since inception".

"It's fast, it's durable and it's got a lot of power so it's the ideal partner for what we want to do," he said.

The aircraft were designed more than 40 years ago and weigh about five tonnes yet can reach up to 350 km/h, carry up to 18 troops and are surprisingly agile.

Major Mierendorff said the people would probably hear the noisy helicopters before they saw them flying at low levels and hovering near buildings over the next six weeks. Flights will occur in the afternoon and evening, concluding by 11.30pm.

He said such drills were run several times a year in different spots around the country and Defence had sought to minimise the disturbance.

Australia's fleet of more than 30 Black Hawks remain on standby to attend terrorist attacks and major incidents such as disaster relief, medical evacuations and search and rescue. The last time they were used in action was in East Timor.

The former Howard government committed to replacing some of the fleet with MRH90s yet the acquisition of some has been marred by safety issues and delays.