2.
Mesh panel fixed to frames by a single wire wrapped around the perimeter. Single point failure of the wire will render the net unserviceable.
NOTE: On helideck inspections, it is frequently found that the securing ties are too long. In the event of a tie breaking and unravelling, a large section of the net can separate from its frame.
3.
Mesh panel intrusion by support members (no spacers to keep net mesh clear of supports).
4.
Existence of large gaps at the points where safety net panels abut against each other. There should only be a small gap sufficient to provide a clearance between the panel frames and, when fitted, to accommodate NDB loop aerial supports. Any gaps in the panel system should not be of such size as to impair catchment of a falling individual.
5.
On vessel helidecks, equipped with hinged perimeter safety net panels that follow the bow line, provision should be made in the design to ensure that large gaps are avoided in both raised and deployed positions.
6.
On square aft helidecks equipped with hinged perimeter safety net panels the design should also include an arrangement that ensures the corners are properly protected when perimeter safety net panels are in the deployed position.
(Photo courtesy of John Burt Associates Limited)
(Photo courtesy of John Burt Associates Limited)
9.10.7 Perimeter Safety Net Load Testing
It is necessary to load test the constructed perimeter safety net system to ensure design and construction integrity.
Generally, this test requires the net system to be strong enough to withstand, without damage, a 75 kg weight dropped from a height of 1 metre.
Ideally, the initial test should be carried out on an identical test panel, not a section that is to be installed on an operational helideck. During helideck inspections, often the date of the last drop test cannot be confirmed. A copy of the test document should be kept readily available on the installation / vessel.
The test can be achieved using a sandbag of suitable weight released from a suspension point above the panel.
9.11 TIEDOWN ARRANGEMENTS
9.11.1 Introduction
The tiedown fixings required on helidecks are an important and functional part of offshore helicopter operations safety.
There may be occasions when it is imperative that a helicopter that is parked on the helideck needs to be properly secured to prevent damage to the airframe, due to high winds or excessive helideck motions.
9.11.2 Main References
CAP 437, Chapter 3.
Helicopter Manufacturer Data Sheets.
9.11.3 Design Considerations
9.11.3.1 Tiedown pattern
Proper distribution of suitable tiedown fittings is essential and should comply with CAP 437. This arrangement ensures that the ‘tiedown’ pattern required for securing different helicopter types is adequate for obtaining the correct distribution of loads through the aircraft ‘picketing fixtures’ and for achieving the correct angles of tiedown strops relative to the helideck and aircraft.
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