Sec. 25.479 - Level landing conditions.
(a) In the level attitude, the airplane
is assumed to contact the ground at forward velocity components, ranging
from VL1 to 1.25 VL2 parallel to the ground under
the conditions prescribed in §25.473 with --
(1) VL1 equal to VS0
(TAS) at the appropriate landing weight and in standard sea level
(2) VL2 equal to VS0
(TAS) at the appropriate landing weight and altitudes in a hot day
temperature of 41 degrees F. above standard.
(3) The effects of increased contact
speed must be investigated if approval of downwind landings exceeding 10
knots is requested.
(b) For the level landing attitude for
airplanes with tail wheels, the conditions specified in this section must
be investigated with the airplane horizontal reference line horizontal in
accordance with Figure 2 of Appendix A of this part.
(c) For the level landing attitude for
airplanes with nose wheels, shown in Figure 2 of Appendix A of this part,
the conditions specified in this section must be investigated assuming the
(1) An attitude in which the main wheels
are assumed to contact the ground with the nose wheel just clear of the
(2) If reasonably attainable at the
specified descent and forward velocities, an attitude in which the nose
and main wheels are assumed to contact the ground simultaneously.
(d) In addition to the loading
conditions prescribed in paragraph (a) of this section, but with maximum
vertical ground reactions calculated from paragraph (a), the following
(1) The landing gear and directly
affected attaching structure must be designed for the maximum vertical
ground reaction combined with an aft acting drag component of not less
than 25% of this maximum vertical ground reaction.
(2) The most severe combination of loads
that are likely to arise during a lateral drift landing must be taken into
account. In absence of a more rational analysis of this condition, the
following must be investigated:
(i) A vertical load equal to 75% of the
maximum ground reaction of §25.473 must be considered in combination with
a drag and side load of 40% and 25% respectively of that vertical load.
(ii) The shock absorber and tire
deflections must be assumed to be 75% of the deflection corresponding to
the maximum ground reaction of §25.473(a)(2). This load case need not be
considered in combination with flat tires.
(3) The combination of vertical and drag
components is considered to be acting at the wheel axle centerline.
[Amdt. 25-91, 62 FR 40705, July 29, 1997; Amdt.
25-91, 62 FR 45481, Aug. 27, 1997]