In such circumstances, where the helideck cannot be used, the ‘closed’ state of the helideck should be indicated by use of a Prohibited landing marker, according to CAP 437.
This signal is the standard ‘landing prohibited’ signal given in the Rules of the Air and Air Traffic Control Regulations, except that it has been altered in size to just cover the letter ‘H’ inside the TD/PM.
Contact us for prices and availability of the Prohibited landing marker.