Section 6 Helicopter landing areas
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Special Service Craft, July 2022 - Part 7 Hull Construction in Aluminium - Chapter 5 Special Features - Section 6 Helicopter landing areas

Section 6 Helicopter landing areas

Parent topic: Chapter 5 Special Features

6.1 General

6.1.1 The landing area may be located on an appropriate area of the weather deck or on a platform specifically designed for this purpose and permanently connected to the craft structure.

6.1.2 Attention is drawn to the requirements and guidance of National and other Authorities concerning the construction of helicopter landing platforms and the operation of helicopters as they affect the ship. These include SOLAS Reg.II-2/18 and Reg.III/28 as applicable as well as the International Chamber of Shipping (ICS) Guide to Helicopter/Ship Operations and the International Aeronautical Search and Rescue Manual (IAMSAR) and CAP437 Standards for Offshore Helicopter Landing Areas.

6.1.3 Attention is drawn to the requirements of National and other Authorities concerning the construction of helicopter landing platforms and the operation of helicopters as they affect the craft.

6.1.4 Plans are to be submitted showing the proposed scantlings and arrangements of the structure. The type, size and weight of helicopters to be used are also to be indicated. Details of the helicopter types to be used are to be included in the craft's documentation, and be contained in a notice displayed on the helicopter landing deck.

6.1.5 Where the landing area forms part of a weather or erection deck, the scantlings are to be not less than those required for decks in the same position.

6.1.6 The requirements for fire protection, detection and extinction are outside the scope of classification, and are therefore to comply with requirements of the National Authority.

6.2 Arrangements

6.2.1 The landing area is to be sufficiently large to allow for the landing and manoeuvring of the helicopter, and is to be approached by a clear landing and take-off sector complying in extent with the applicable regulations.

6.2.2 The landing area is to be free of any projections above the level of the deck. Projections in the zone surrounding the landing area are to be kept below the heights permitted by the regulations.

6.2.3 Suitable arrangements are to be made to minimize the risk of personnel or machinery sliding off the landing area. A non-slip surface and anchoring devices, and in the case of independent platforms, safety nets, are to be provided.

6.2.4 Arrangements are to be made for drainage of the platform, including drainage of spilt fuel.

6.2.5 Details of arrangements for securing the helicopter to the deck are to be submitted for approval.

6.3 Landing area plating

6.3.1 The deck plate thickness, t p, within the landing area is to be not less than:

t p =
α = thickness coefficient obtained from Figure 5.3.1 Tyre print chart
βp = tyre print coefficient used in Figure 5.3.1 Tyre print chart
=
where

s and k a are as defined in Pt 7, Ch 5, 1.2 Symbols and definitions.

The plating is to be designed for the emergency landing case taking:

where

φ1, φ2, φ3 are to be determined from Table 5.3.1 Deck plate thickness calculation

f = 1,15 for landing decks over manned spaces, e.g. deckhouses, bridges, control rooms, etc.
= 1,0 elsewhere
P h = the maximum all up weight of the helicopter, in tonnes
P w = landing load on the tyre print, in tonnes
For helicopters with a single main rotor, P w is to be taken as P h divided equally between the two main undercarriage wheels.
For helicopters with tandem main rotors, P w is to be taken as P h distributed between all main undercarriage wheels in proportion to the static loads they carry.
For helicopters fitted with landing gear consisting of skids, P w is to be taken as P h distributed in accordance with the actual load distribution given by the airframe manufacturer. If this is unknown, P w is to be taken as 1/6P h for each of the two forward contact points and 1/3P h for each of the two aft contact points. The load may be assumed to act as a 300 mm x 10 mm line load at each end of each skid when applying Figure 5.3.1 Tyre print chart.
γ = a location factor given in Table 5.6.1 Location factor, γ

For wheeled undercarriages, the tyre print dimensions specified by the manufacturer are to be used for the calculation. Where these are unknown it may be assumed that the print area is 300 x 300 mm and this assumption is to be indicated on the submitted plan.

For skids and tyres with an asymmetric print, the print is to be considered oriented both parallel and perpendicular to the longest edge of the plate panel and the greatest corresponding value of α taken from Figure 5.3.1 Tyre print chart.

Table 5.6.1 Location factor, γ

Location γ
On decks forming part of the hull girder:    
(a) within 0,4L R amidships 0,71 Values for intermediate locations are to be determined by interpolation
(b) at the F.P. or A.P. 0,6
Elsewhere 0,6

6.4 Deck stiffening and supporting structure

6.4.1 The helicopter deck stiffening and the supporting structure are to be designed for the load cases given in Table 5.6.2 Design load cases for deck stiffening and supporting structure, with the helicopter being positioned so as to produce the most severe loading condition for each structural member under consideration.

6.4.2 The minimum requirements for section modulus, inertia and web area of secondary stiffeners are to be in accordance with Table 5.3.3 Secondary stiffener requirements.

6.4.3 For primary stiffening, and where a grillage arrangement is adopted, it is recommended that direct calculation procedures be used to determine the scantling requirements, in association with the limiting permissible stress criteria given in Pt 7, Ch 7 Failure Modes Control. A copy of the calculations is to be submitted for consideration.

Table 5.6.2 Design load cases for deck stiffening and supporting structure

Loadcase Loads (tonnes)
Landing area Supporting structure (see Note 1)
UDL, in kN/m2 Helicopter
patch load 		Self weight Horizontal load,
see Note 2 see Note 2
(1) Overall distributed loading 2 - - -
(2)Helicopter emergency landing 0,5 2,5P w f W h 0,5P h
(3) Normal Usage 0,5 1,5P w W h 0,5P h + 0,5W h
Symbols

P h, P w and f are as defined in Pt 7, Ch 5, 6.3 Landing area plating 6.3.1.

UDL = Uniformity distributed vertical load over entire landing area
W h = structural self-weight of helicopter platform, in tonnes

Note 1. For the design of the supporting structure for helicopter platforms applicable self weight and horizontal loads are to be added to the landing area loads.

Note 2. The helicopter is to be so positioned as to produce the most severe loading condition for each structural member under consideration.

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