First of all you will need to progress through the campaign and complete Chapter 10.
For the achievement first of all see the location for the Helipad to unlock with 20,000 Super Build Bricks.
There are many other Helipads to unlock with the same amount of Super Build Bricks, however, this is very easy to gain access to and locate from the Police Station.
Once you have arrived at the location walk around to see the below image, which you need to open the the door by tapping
button with your Fire Chase McCain.
Now go into the door and push up to the left, you will then automatically go up onto the roof.
Move to the right and climb the wall via the White & Blue climbable section.
Now go onto pad and press the
to purchase with 20,000 super build studs.
You will unlock a new Helicopter HERA worth 3,000 studs which I used for the achievement.
Select your Helicopter and and jump in and fly slightly off the pad, now lower to the road until you are prompted with
again as vehicles pass by, then hit the button to transfer from Heli to a road vehicle.
Lower (fly down)
Raise (fly up)
Then pop achievement unlocked.
Please see Game clip below which I have provided for Clarity:
Sorry, this Game Clip has been removed