CS 25.479 Level landing conditions

ED Decision 2003/2/RM

(a)     In the level attitude, the aeroplane is assumed to contact the ground at forward velocity components, ranging from V_L1 to 1·25 V_L2 parallel to the ground under the conditions prescribed in CS 25.473 with:

(1)     V_L1 equal to V_S0(TAS) at the appropriate landing weight and in standard sea-level conditions; and

(2)     V_L2, equal to V_S0(TAS) at the appropriate landing weight and altitudes in a hot day temperature of 22.8°C (41°F) above standard.

(3)     The effects of increased contact speed must be investigated if approval of downwind landings exceeding 19 km/h (10 knots) is requested.

(b)     For the level landing attitude for aeroplanes with tail wheels, the conditions specified in this paragraph must be investigated with the aeroplane horizontal reference line horizontal in accordance with Figure 2 of Appendix A of CS-25.

(c)      For the level landing attitude for aeroplanes with nose wheels, shown in Figure 2 of Appendix A of CS-25, the conditions specified in this paragraph must be investigated assuming the following attitudes:

(1)     An attitude in which the main wheels are assumed to contact the ground with the nose wheel just clear of the ground; and

(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 sub-paragraph (a) of this paragraph, but with maximum vertical ground reactions calculated from paragraph (a), the following apply:

(1)     The landing gear and directly affected 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 CS 25.473(a)(2) 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 tyre deflections must be assumed to be 75% of the deflection corresponding to the maximum ground reaction of CS 25.473(a)(2). This load case need not be considered in combination with flat tyres.

(3)     The combination of vertical and drag components is considered to be acting at the wheel axle centreline.