Gwinnett commissioners on Tuesday approved three contracts to replace both helicopters used by the police department’s aviation unit for less than half the cost of buying new ones. Both units date to the mid-1980s.

For just under $2.5 million, the county will keep both McDonnell Douglas MD500E airframes and replace most components with new equipment and more powerful engines, converting them to MD530F helicopters that will be considered new. McDonnell Douglas was awarded the contract to do the conversion work estimated by three suppliers to have cost between $7 million and $8.4 million for new machines.

Both helicopters will also get new digital thermal infrared imaging systems and the 1984 machine will also get upgraded digital avionics with night vision and a new spotlight to make both helicopters identical.