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The HLL system operated by the British Helicopter Advisory Board (BHAB Helidecks) should ensure that landings on offshore helidecks are properly controlled when adverse environmental effects are present. On poorly designed helidecks, severe restrictions may be placed on operations resulting in reduced payloads or cancelled flights. This can lead to significant commercial penalties for the installation operator or vessel owner. Well-designed and ‘helicopter-friendly’ platform topsides and helidecks therefore result in efficient operations, and a saving in cost for the platform operator.
A survey based on pilot responses to a questionnaire on workload and safety hazards [Ref: 44] rated ‘turbulence around platforms’ as the largest source of workload and presenting the largest safety risk of all aspects of offshore flight operations. A review of offshore helideck environmental issues [Ref: 41] pointed out that many of the decisions leading to poor helideck performance were made by designers in the very early stages of design, and recommended that it would be easier for designers to get these decisions right if comprehensive helideck design guidance published by industry was available to run in parallel with CAP 437.
10.4 DESIGN ISSUES
10.4.1 Introduction
The design guidance in this section applies to all fixed installations (manned and normally unattended installations), floating installations (including semi-submersibles {e.g. MODUs, FPUs and specialist barges} and vessel hull based FPSOs) and any other specialist offshore support vessels with a helideck (e.g. seismic, diving support, pipelay).
The environmental effects described in this section fall into two classes;
.
aerodynamic effects, and
.
wave motion effects.
All offshore installations experience the aerodynamic affects described in Sections
10.4.3 to 10.4.7 but only floating systems experience the influences of wave motions on the helideck as described in Section 10.5.
Turbulent airflows and thermal effects are in effect 'invisible' obstructions in flight paths around installations and vessels. They can seriously affect flight operations onto a helideck. These effects must be identified, quantified and taken fully into account when establishing the operability of a helideck.
The environmental issues described in this section are clearly not the only factors in the selection of the helideck design or location. It is also strongly influenced by other important practical, safety and regulatory factors. For example, on many installations the helicopter will be designated the ‘primary means of escape’, and so the helideck must be close to the ‘temporary refuge’. Selection of the best helideck location is therefore invariably a compromise between a number of potentially conflicting requirements.
10.4.2 Aerodynamic Issues and Criteria
Helidecks are basically flat plates and so are relatively streamlined structures. In isolation they would present little disturbance to the wind flow, and helicopters would be able to operate to and from them in a more or less undisturbed air environment.
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