To get this achievement, you have to visit the Helitours location (southern part of the central island). There are 6 Helipads, but only 5 tours. The helipad closest to the bridge never gets a helicopter. Each helicopter has its own tour.
To get the achievement, simply go to the Helitours location and take the tour for each helicopter that is there (you can skip the cutscene of the tour).
Once you have done it for each of the helicopters that is currently there, take one of the helicopters and fly somewhere with it (I went to the nearest bridge) and then come back and some different helicopters will be there.
Keep doing this until you have had a chance to take a tour in each of the 5 helicopters and the achievement will pop after you get out of the helicopter from the 5th tour.
*Note* New helicopters only seem to show up during the day. At night, the same ones will be there if you leave and come back.