As big as necessary to be visible form a typical approach altitude. Normally about the size of the helicopter(s) expected there is enough.
16 meters
A helipad is a designated landing area for helicopters, typically marked with a large "H" symbol to indicate its purpose. It may be built on rooftops, open fields, or specially constructed areas and is often made of concrete or asphalt for durability. Helipads are generally clear of obstacles, with safety features like lighting for nighttime visibility and sometimes perimeter fencing. They can vary in size, depending on the type of helicopter they accommodate.
It's a place especially made for helicopters to land on and always marked with a big: 'H'.Very handy on ships or skyscrapers or even your garden.
helicopters
After you unlock free roam you need to complete the 2 missions then you will unlock a new Crib where there will be a helipad
A helipad
helipad
A "helipad" is a helicopter landing pad. The helipad provides a clearly marked hard surface away from obstacles for the helicopter to land.
Helipad, antenna, garden.Antenna, Flag, mobile phone tower, Satellite Dish, Helipad, Lightning Rod, Roof and a bird.
George H. Large died in 1939.
George H. Large was born in 1850.
You can access the police station in Algonquin area and go upstairs to the helipad. And have a immigration authority annihilator helicopter spawned on the helipad. And it is in one of the cut scenes