曝光台 注意防骗
网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者
A minimum 210° obstacle free sector is required. Its Point of Origin (PO) on the inboard side of the deck is the apex of the chevron (see CAP 437 – Visual Aids).
On an existing helideck that, by unusual exception, does not meet the normal obstacle free sector of 210°, the accepted angle (less than 210°) should be clearly shown. In this case, operability may be compromised. Where the minimum 210° obstacle free sector can be exceeded (e.g. on a NUI), the increased angle may be declared. In this case operability may be improved.
By extending a line out from each leg of the chevron, a check is required to ensure freedom from obstructions within the 210° sector by identifying items that are above deck level. Such items may not exceed 250 mm in height, and even then must be restricted to specified essentials such as lighting fittings, safety net rails, etc. as specified in CAP 437. Generally, no obstructions of greater height are permitted within 1000 metres of the PO. However, in some operational circumstances it may be acceptable to permit obstacles within 250 metres of the PO, subject to CAA / BHAB Helidecks assessment and approval.
Achieving the obstruction clearances can be a problem, particularly with floating installations (e.g. floatels), vessels operating adjacent to fixed platforms and during shuttle tanker operations to FPSOs. Where uninfringed obstacle protection cannot be achieved this is likely to restrict or preclude operations to that helideck. See also Section 8.1 - Combined Operations.
6.6.3 Limited Obstacle Sector
Permitted obstruction heights should be calculated for the largest helicopter that the helideck is designed to accommodate.
The obstacle height restrictions applied to helidecks are provided in order to maintain safe helicopter rotor clearances. The dimensions will vary according to 'D' size and helicopter type (e.g. single main rotor or tandem rotor). Refer to CAP 437 for specific details.
6.6.4 Falling Gradient
Strict control is required over the size of obstructions projecting from the side profile of the installation / vessel below the helideck. These obstructions are typified by lifeboat arrangements, communications antenna, laydown platforms, exhaust systems, buoyancy tanks and windlasses and anchor systems (on MODUs).
Within an outboard arc of minimum 180° (preferably 210°) centred on the centre of the landing area, and lying centrally within the 210° unobstructed arc, such obstructions must not penetrate an imaginary surface which extends downwards and outwards from the edge of the helideck at a gradient of 1 unit outwards for every 5 units of vertical fall. This is shown in CAP 437 – Size and Obstacle Free Environment.
This unobstructed space permits the helicopter to descend safely after take off in the event of engine failure, so as to pick up climbing speed.
The 5 to 1 gradient is measured from the outer edge of the 1.5 metre helideck perimeter safety net.
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：
离岸直升机起落甲板设计指南 OFFSHORE HELIDECK DESIGN GUIDELINES 1(30)
