(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 :
(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 B. The pressure at the keel (psi) is computed as follows :
2
K2 VS1
Pk = C2
tanβk
where– Pk :pressure[(p.s.i.)] atthekeel; C2 =0.00213 : K2 : hull station weighing factor, in accordance with .gure 2 of Appendix B;
VS1 : seaplane stalling speed [(knots)] at the design [water] ta-keo. weight with .aps extended in the appropriate takeo. position; and
βk : angle of dead rise at keel, in accordance with .gure 1 of Appendix B.
(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
B. The pressure distribution is the same as that prescribed in subparagraph (1)of this paragraph for an un.ared bottom except that the pressure at the chine is computed as follows :
2
K2 VS1
Pch = C3
tanβ
where– Pch :pressure[(p.s.i.)] atthe chine; C3 =0.0016 :
K2 : hull station weighing factor, in accordance with .gure 2 of
Appendix B;
VS1 : seaplane stalling speed [(knots)] at the design [water] ta-
keo. weight with .aps extended in the appropriate takeo.
position; and
β : angle of dead rise at appropriate station.
The area over which thesepressures are applied must simulatepressures occurring duringhighlocalizedimpactsonthehull or .oat,butneed notextend overanarea 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 are computed as follows :
2
K2 VS0P = C4
tanβ
where–
P : pressure[(p.s.i.)]; C4 =0.078C1 :(with C1 computed under Sec. 25.527); K2 : hull station weighingfactor,determinedin accordance with .gure2 ofAppendixB;
VS0 :seaplanestalling speed[(knots)] withlanding .apsexten-ded in the appropriate position and with no slipstream ef-fect; and
β : angle of dead rise at appropriate station.
(2) The unsymmetrical pressure distribution consists of the pressures prescribed insubparagraph(1) ofthisparagraphononesideofthehullormain .oat centerline and one-half of that pressure on the other side of the hull or main .oat centerline, in accordance with .gure 3 of Appendix B.
These pressures are uniform and must be applied simultaneously over the entire hull or main .oat bottom. The loads obtained must be carried into the sidewall structure of the hullproper,but need notbetransmittedinaforeand aftdirectionasshearandbending loads. Amdt. 25-23, E.. 5/8/70
FAR 25.535 : Auxiliary .oat loads.
(a)
General. Auxiliary .oats and their attachments and supporting structures must be designedfor the conditionsprescribedin this section.In the cases speci.edinpara-graphs(b)through(e) ofthis section, theprescribed waterloads maybedistributed overthe .oatbottomtoavoid excessivelocalloads,usingbottompressuresnotless thanthoseprescribedinparagraph(g) of this section.
(b)
Step loading. The resultant water load must be applied in the plane of symmetry of the .oat at a point three-fourths of the distance from the bow to the step and mustbeperpendiculartothekeel.The resultantlimitloadis computed asfollows,
′
Elodie Roux. Septembre 2003
Subpart C : Structure
except that the value of L need not exceed three times the weight of the displaced water when the .oat is completely submerged :
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本文链接地址：FAA规章 美国联邦航空规章 Federal Aviation Regulations 3(64)
