From
www.adf-serials.comMirage IIIO(A) - Serial A3-69
Delivered 12/10/66. Served with 77 Sqn Williamtown NSW. Served with 75 Sqn Butterworth Malaysia. Collided with RSAF A-4 30/03/83 1 nm south of Tengah Airfield, Singapore Midair collision with RSAF Skyhawk A-4S No 636 whilst on finals for Rwy 36. Mirage pilot ejected at 400 ft and 190 kts with only minor injuries. Skyhawk pilot (LTA Foo Siew Ngan) also ejected successfully. One civilian on ground killed. Crew; FLGOFF J.T. O'Halloran.
Theres a book on the history of RAAF 75 Sqn called "Seek and Strike" (75 Sqn motto) and it describes the incident in more detail. The Mirage was grey painted and the Skyhawk in SEA scheme. The collision occurred on a hazy (ie. grey) afternoon and the Mirage was joining the TAB circuit during a complicated runway change procedure and came down onto the Skyhawk from above. Believe that the accident report stated that weather and camo may have been a factor (grey Mirage against grey sky; green/brown A-4 against green/brown terrain prevented both pilots from seeing one another clearly)
Performance wise the book states that the Mirage Hunters found low-flying RSAF Hunters and Skyhawks very hard to fight due to their effective camo and agility. While another book I've read on the English Electric Lightning stated that 74 Sqn RAF wiped the floor against the RAAF Mirages at all altitudes when 74 Sqn were based at Tengah.
The intercepted aircraft could have been Soviet Tu-16 Badgers, Tu-95 Bears, Il-38 Mays (ELINT) or even Tu-22M Backfires staging from Cam Ranh Bay in Vietnam in the 70s/80s. Since Soviet subs were known to transit through these waters its not surprising their aircraft flew this way too
BTW, I have seen a photo of a Tengah-based RAF Javelin intercepting an Indonesian Tu-16 Badger near Singapore during the Confrontation