FTB(A) has an income test...
For Family Tax Benefit Part A, if your family's actual annual family income for this financial year is $42,559 or less, your payment will not be affected by the income test.

If your actual annual family income is more than $42,559 for this financial year, your payment will reduce by 20 cents for each dollar above $42,559, until your payment reaches the base rate of Family Tax Benefit Part A.

Your Family Tax Benefit Part A will stay at that rate until your actual annual family income reaches $94,316 a year (plus $3796 for each Family Tax Benefit child after the first). Family Tax Benefit Part A will reduce by 30 cents for every dollar over that amount until your payment reaches nil.
(can you tell I'm bored I'm searching the CENTRELINK website LOL