1. Diameter of helideck : at least total length of largest helicopter no part of aircraft overhanging perimeter .
2. Approach/takeoff routes: adjacent structures below level of helideck – no tall structures.
3. Perimeter protection (to prevent personal from falling):handrail that can be lowered horizontal net- on fixed handrails.
4. Equirment to cope with bad weather/ poor visibility: perimeter landing lights and anchor points.