Iranian Classification Society Rules
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Section 5 Helicopter Deck
501. Design loads
Plans showing the arrangement, scantlings and details of the helicopter deck are to be submitted. The arrangement plan is to show the overall size of the helicopter deck and the designated landing area. The design load in determining the scantlings of the members of helicopter deck is to be in accordance with following (1) to (3).
(1) Helicopter landing impact loading
(A) As for the deck loads in the range where a helicopter takes off or lands, a load of 75 % of the helicopter maximum take-off weight is to be taken on each of two square areas, 0.3 m × 0.3 m .
(B) For girders, stanchions, etc., the structural weight of the helicopter deck is to be considered
in addition to the helicopter impact loading specified in (A).
(C) Where the upper deck of a structure or deck house is used as a helicopter deck and the
spaces below are normally manned, the impact loading specified in (A) is to be multiplied by a factor of 1.15.
(2) Stowed helicopter loading
(A) The deck loads in the space where a helicopter is stowed are to be taken as wheel load- ings at maximum take-off weight. In this case, the dynamical effect due to the motion of the unit is also to be taken into account.
(B) In addition to (A), a uniformly distributed loading of 0.5 kNÕmĪ, representing wet snow or ice is to be considered, if necessary.
(C) For girders, stanchions, etc., the structural weight of the helicopter deck is to be considered
in addition to the loads specified in (A).
(3) Minimum deck load
The minimum deck load for helicopter deck is to be taken as 2 kNÕmĪ.
502. Allowable stresses
Allowable stresses of the structural members of the helicopter deck are not to exceed the values in
Table 4.5 in association with the design loads prescribed in 501.
Table 4.5 Allowable Stresses
Structural members Design loads | Deck plating | Deck beams | Girders, stanchions, truss supports, etc. |
Helicopter landing impact load | * | ſſ← | 0.9 × ſſ ′ ← |
Stowed helicopter load | ſſ← | 1.9 × ſſ← | 0.8 × ſſ ′ ← |
Overall distributed load | 0.6 × ſſ← | 0.6 × ſſ← | 0.6 × ſſ ′ ← |
* : At the discretion of the Society. ſſ : As specified in 302. (NÕmm Ī). ←′ Ī ſſ← : For members subjected to axial compression, ſſ← or critical buckling stress, whichever is the smaller(NÕmm ). | |||
503. Minimum thickness
The minimum thickness of helicopter deck plating is not to be less than 6 mm .
504. Landing appliances other than wheels
In case where a helicopter is provided with any other landing appliances other than wheels, the de- sign loads are to be at the discretion of the Society.
505. Loadings on helicopter deck
Wind loadings and possible wave impact loadings on helicopter decks are to be considered. Where in this case, those loadings are in accordance with the discretion of the Society.
Ch 4 Design Condition Ch 4
