Head to Higgins Helitours in south-east Algonquin (southern part of the central island) and take a tour on each of the five helicopters. There are 6 Helipads, but only 5 tours. At the Helitours icon, you will see five helicopter landing locations in the shape of a "T." Come up with an order you are going to do them in or memorize which helipads you have already taken a tour from so you don’t redo the same tour again. The helipad closest to the bridge never gets a helicopter. Each helicopter has its own tour. 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 should 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. You must complete each individual different tour of the 5. Re-doing a tour you have already completed to get to 5 will not count towards the achievement/trophy.
*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.
*This can be done after completing story mode**