(2)
Thepoint of application anddirectionof the upward component of theloadis the same as that in the symmetrical condition, and the point of application of the side component is at the same longitudinal station as the upward com-ponent but is directed inward perpendicularly to the plane of symmetry at a point midway between the keel and the chine lines.

(c)
Unsymmetricallanding; twin .oatseaplanes. The unsymmetrical loading consists of an upward load at the step of each .oat of 0.75 and a side load of 0.25 tanβ at one .oat times the step landing load reached under Sec. 23.527. The side load is directed inboard, perpendicularly to the plane of symmetry midway between the keel and chine lines of the .oat, at the same longitudinal station as the upward load.]

Amdt. 23-45, E.. 09/07/93
FAR23.531:[Hull andmain .oattakeo.condition.]
[For the wingand its attachment to the hull or main .oat–
(a)
The aerodynamic wing lift is assumed to be zero; and

(b)
Adownwardinertiaload, correspondingto aloadfactor computedfromthefollowing formula, must be applied :

2
CTO V11
n =
2313

(tanβ)
W

where– n :inertia load factor; CTO :empirical seaplane operations factor equal to 0.004; VS1 :seaplanestalling speed(knots) atthedesigntakeo. weight with the .apsextendedintheappropriatetakeo.position; β :angle ofdead rise atthe main step(degrees); and W :design water takeo. weight in pounds.]
Amdt. 23-45, E.. 09/07/93
FAR23.533:[Hull andmain .oatbottompressures.]
(a)
[General. The hull and main .oat structure, including frames and bulkheads, strin-gers, and bottom plating, must be designed under this section.

(b)
Local pressures. For the design of the bottom plating and stringers and their at-tachments to the supporting structure, the following pressure distributions must be applied :

′
Elodie Roux. Septembre 2003
Subpart C : Structure
(1) For an un.ared bottom, the pressure at the chine is 0.75 times the pressure at the keel, and the pressures between the keel and chine vary linearly, in accordance with .gure 3 of appendix I of this part. The pressure at the keel (p.s.i.)is computed as follows :
2
C2 K2 VS1
Pk =
tanβk
where-Pk :pressure(p.s.i.) atthekeel; C2 :Constant C2 =0.00213; K2 :hull station weighing factor, in accordance with .gure 2 of appendix I of this part; VS1 :seaplane stalling speed(knots) atthedesign watertakeo. weight with .aps extended in the appropriate takeo. posi-tion; and βk :angle of dead rise at keel, in accordance with .gure 1 of appendix I of this part.
(2) For a .ared bottom, the pressure at the beginning of the .are is the same as that for an un.ared bottom, and the pressure between the chine and the beginning of the .are varies linearly, in accordance with .gure 3 of appendix I of this part. The pressure distribution is the same at that prescribed in pa-ragraph(b)(1) of this sectionforan un.aredbottom exceptthatthepressure at the chine is computed as follows :
2
C3 K2 VS1
Pch =
tanβ
where-Pch :pressure(p.s.i) atthe chine; C3 :Constant C3 =0.0016; K2 :hull station weighing factor, in accordance with .gure 2 of appendix I of this part; VS1 :seaplane stalling speed(knots) atthedesign watertakeo. weight with .aps extended in the appropriate takeo. posi-tion; and β :angle of dead rise at appropriate station. The area over which these pressures are applied must simulate pressures oc-curringduringhighlocalizedimpactsonthehull or .oat,butneed not extend over an area that would induce critical stresses in the frames or in the overall structure.
(c) Distributed pressures. For the design of the frames, keel, and chine structure, the followingpressuredistributions apply :
(1) Symmetrical pressures as computed as follows–
2
　
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