3 Dynamic seat tests
Clasification Society 2023 - Version 9.37
Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC/Circular.1054 – Interim Guidelines for Wing-In-Ground (WIG) Craft - (adopted 16 December 2002)Amended by MSC/Circ.1126 - Annex - Interim Guidelines for Wing-In-Ground (WIG) Craft - Annex 6 - Criteria for Testing and Evaluation of Revenue and Crew Seats - 3 Dynamic seat tests

3 Dynamic seat tests

  3.1 The provisions of this section are applicable for crew and revenue seats in craft having a design collision load of 3g or greater.

  3.2 All seats for which this section applies, the seat supporting structure, the attachment to the deck structure, the lap belt, if installed, and shoulder harness, if installed, should be designed to withstand the maximum acceleration force that can be imposed upon them during a design collision. Consideration should be given to the orientation of the seat relative to the acceleration force (i.e. whether the seat is forward-, aft- or side-facing).

  3.3 The acceleration pulse to which the seat is subjected should be representative of the collision time-history of the craft. If the collision time-history is not known or cannot be simulated, the acceleration time-history envelope shown in the figure below can be used.

  3.4 In the test frame, each seat unit and its accessories (e.g., lap belts and shoulder harnesses) should be attached to the support structure similar to the manner in which it will be attached to the deck structure in the craft. The support structure can be a rigid surface; however, a support structure having the same strength and stiffness as the support structure in the craft is preferred. Other seats and/or tables with which an occupant may come in contact during a collision should be included in the test frame in an orientation and with a method of attachment typical of that in the craft.

Figure 1 Acceleration time-history envelope

  3.5 During the dynamic seat test, a fiftieth percentile anthropomorphic test dummy, corresponding to the Hybrid II or Hybrid III (preferred) human surrogate (unless a more advanced test dummy is available), should be placed in the seat in an upright seating position. If a typical seating unit is composed of more than one occupant seat, a test dummy should be placed in each occupant seat in the unit. The dummy, or dummies, should be secured in the seat unit in accordance with procedures of recognized national standardsfootnote and be secured using only the lap belt and shoulder harness if they are installed. Tray tables and other such devices should be placed in the position that would cause the greatest potential for an occupant to become injured.

  3.6 The test dummy should be instrumented and calibrated, in accordance with the requirements of a recognized national standard, so as to permit calculation of the head injury criterion, calculation of the thoracic trauma index, measurement of force in the femur, and measurement, if possible, of extension and flexion of the neck, measurement of the maximum relative pelvis acceleration, and measurement of the maximum pelvis load in the direction of the spine.

  3.7 If more than one dummy is used in the tests, the dummy located in the seat having the highest potential for an occupant to be injured should be the one instrumented. The other dummy or dummies need not be instrumented.

  3.8 The tests should be conducted and the instrumentation should be sampled at a rate sufficient to reliably show response of the dummy in accordance with the requirements of a recognized national standard.

  3.9 The seat unit tested in accordance with the provisions of this section should be considered acceptable if:

  • .1 The seat unit and tables installed in the seat unit or area do not become dislodged from the supporting deck structure and do not deform in a manner that would cause the occupant to become trapped or injured.

  • .2 The lap belt, if installed, remains attached and on the test dummy’s pelvis during the impact. The shoulder harness, if installed, remains attached and in the immediate vicinity of the test dummy’s shoulder during the impact. After the impact, the release mechanisms should be operative.

  • .3 The following acceptability criteria are met:

  • .3.1 the head injury criterion (HIC), calculated in accordance with the formula below, does not exceed 500

  • where:
  • tl and t2 are the beginning and ending times (in seconds) of the interval in which the HIC is a maximum. The term a(t) is the resultant measured acceleration in the head of the dummy in g;

  • .3.2 the thoracic trauma index (TTI), calculated in accordance with the formula below, does not exceed 30g except for periods totalling less than 3 ms

  • where:
  • gR is the acceleration in g of either the upper or lower rib
  • gLS is the acceleration in g of the lower spine;

  • .3.3 the maximum pelvis acceleration does not exceed 130g;

  • .3.4 the maximum pelvic load does not exceed 6.7 kN measured in the axis of the spine;

  • .3.5 neck flexion does not exceed 88 Nm, if measured;

  • 3.6 neck extension does not exceed 48 Nm, if measured; and

  • 3.7 the force in the femur does not exceed 10 kN, except that it cannot exceed 8 kN for periods totalling more than 20 ms.

  • .4 Loads on the upper torso harness straps do not exceed 7.8 kN or a total of 8.9 kN if dual straps are used.

Parent topic: Annex 6 - Criteria for Testing and Evaluation of Revenue and Crew Seats
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