At least 20 operationally ready national servicemen (NSmen) and full-time national servicemen (NSFs) are standing shoulder-to-shoulder with regulars from the Republic of Singapore Air Force (RSAF) in a current multinational air combat exercise in Australia.

They are involved at different levels, including one who holds a senior appointment in the exercise - that of mission director.

Exercise Pitch Black, the largest multilateral air combat exercise held in the Australian continent, is hosted every two years by the Royal Australian Air Force (RAAF).

The latest one began on July 29 and will continue till Friday.

It involves the air forces of 10 countries, including the United States, Germany and Indonesia, and about 2,800 personnel and 115 aircraft.

Australia typically sends four mission directors from RAAF, said Lieutenant-Colonel (NS) Ong Swee Chuan, who is a mission director for this year's exercise.

In the RSAF, Lt-Col (NS) Ong is an NSman who is an F-16 pilot.

Singapore has sent one mission director for every Pitch Black exercise since 2008, and is the only country, apart from Australia, to have a mission director at this year's exercise, he added.

This role requires experience as it involves evaluating if plans developed by mission commanders of opposing teams are safe to execute and effective, said the former regular who retired from the air force in 2014 after serving for 24 years.

Lt-Col (NS) Ong, who turns 45 this year, added he thought Singapore was invited to provide a mission director because the RSAF was well regarded regionally. But he is not the only NSman to be involved.

NSmen and NSFs are involved elsewhere in the exercise. They include 16 NSFs and three NSmen who are part of 54 personnel supporting two RSAF I-Hawk surface-to-air missile systems.

They went up against planes from air forces like the US Air Force and RAAF, some of which deployed combat-tested techniques not normally seen by the personnel, Captain Benjamin Chua, 30, officer commanding for RSAF's 163 Squadron, said.

The RSAF personnel were praised by American aircraft operators for the way they adapted and performed, said Senior Lieutenant- Colonel David Lim, 42, the RSAF's exercise director.

He added that more NSFs and NS men have been brought to Exercise Pitch Black over the years.