Federal Aviation Administration, DOT

Section 25.561

(e) Unsymmetrical bow loading. The resultant water load consists of a component equal to 0.75 times the load specified in paragraph (b) of this section and
a side component equal to 0.25 tan b
times the load specified in paragraph
(c) of this section. The side load must
be applied perpendicularly to the plane
of symmetry at a point midway between the keel and the chine.
(f) Immersed float condition. The resultant load must be applied at the
centroid of the cross section of the
float at a point one-third of the distance from the bow to the step. The
limit load components are as follows:

vertical= gV
2

3
aft = Cx 2 V  KVS 

0 
2

side =

3
Cy 2 V

 KV 
 S0 

2

2

where - 
r = mass density of water (slugs/ft.2);
V = volume of float (ft.2);
Cx = coefficient of drag force, equal to 0.133;
Cy = coefficient of side force, equal to 0.106;
K = 0.8, except that lower values may be used
if it is shown that the floats are incapable of submerging at a speed of 0.8 VS0 in
normal operations;
VS0 = seaplane stalling speed (knots) with
landing flaps extended in the appropriate
position and with no slipstream effect;
and
g = acceleration due to gravity (ft./sec.2).

(g) Float bottom pressures. The float
bottom pressures must be established
under Section 25.533, except that the value of
K2 in the formulae may be taken as 1.0.
The angle of dead rise to be used in determining the float bottom pressures is
set forth in paragraph (b) of this section.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-23, 35 FR 5673, Apr. 8,
1970]

Seawing loads.

Seawing design loads must be based
on applicable test data.

259

VerDate Sep<11>2014

12:50 Apr 30, 2019

Jkt 247046

PO 00000

Frm 00269

Fmt 8010

Sfmt 8010

Y:\SGML\247046.XXX

247046

EC28SE91.043</MATH>

spaschal on DSK3GDR082PROD with CFR

Section 25.537

EMERGENCY LANDING CONDITIONS
Section 25.561 General.
(a) The airplane, although it may be
damaged in emergency landing conditions on land or water, must be designed as prescribed in this section to
protect each occupant under those conditions.
(b) The structure must be designed to
give each occupant every reasonable
chance of escaping serious injury in a
minor crash landing when - 
(1) Proper use is made of seats, belts,
and all other safety design provisions;
(2) The wheels are retracted (where
applicable); and
(3) The occupant experiences the following ultimate inertia forces acting
separately relative to the surrounding
structure:
(i) Upward, 3.0g
(ii) Forward, 9.0g
(iii) Sideward, 3.0g on the airframe;
and 4.0g on the seats and their attachments.
(iv) Downward, 6.0g
(v) Rearward, 1.5g
(c) For equipment, cargo in the passenger compartments and any other
large masses, the following apply:
(1) Except as provided in paragraph
(c)(2) of this section, these items must
be positioned so that if they break
loose they will be unlikely to:
(i) Cause direct injury to occupants;
(ii) Penetrate fuel tanks or lines or
cause fire or explosion hazard by damage to adjacent systems; or
(iii) Nullify any of the escape facilities provided for use after an emergency landing.
(2) When such positioning is not practical (e.g. fuselage mounted engines or
auxiliary power units) each such item
of mass shall be restrained under all
loads up to those specified in paragraph
(b)(3) of this section. The local attachments for these items should be designed to withstand 1.33 times the specified loads if these items are subject to
severe wear and tear through frequent
removal (e.g. quick change interior
items).
(d) Seats and items of mass (and
their supporting structure) must not
deform under any loads up to those
specified in paragraph (b)(3) of this section in any manner that would impede