GB 9745-2025Aircraft tyres (English PDF)

4.2 Peripheral dimensions

4.2.1 Diagonal tyres The peripheral dimensions of tyres shall comply with the provisions of GB/T 9746 or the manufacturer's stated values. When the tyres are used for helicopters, the peripheral dimensions of the tyres may be increased by 4 %.

4.2.2 Radial tyres After completing 50 dynamic performance takeoff tests, the peripheral dimensions of tyres shall comply with the provisions of GB/T 9746 or the manufacturer's stated values. When the tyres are used for helicopters, the peripheral dimensions of the tyres may be increased by 4 %.

4.3 Static loaded radius The static loaded radius of tyres shall comply with the provisions of GB/T 9746.

4.4 Dynamic performance

4.4.1 Low-speed tyres The dynamic performance of low-speed tyres shall meet one of the following requirements.

a) Low-speed tyres shall pass 200 landing tests, including 100 low-speed landing tests and 100 high-speed landing tests;

b) Low-speed tyres shall pass the dynamic performance tests of high-speed tyres (4.4.2).

4.4.2 High-speed tyres High-speed tyres shall pass 61 takeoff and taxiing dynamic performance tests, including 50 takeoff tests at rated load, 8 taxis at rated load, 2 taxis at

1.2 times rated load, and 1 overload takeoff at

1.5 times rated load. When conducting dynamic performance tests, if the overload takeoff test is scheduled last in the dynamic performance test suite, the tyre tread does not need to remain intact after the test; if the overload takeoff test is not scheduled last, the tyre tread shall not show any visible damage other than normal tread wear after the test.

4.4.3 Air tightness check Within 24 h of completing the dynamic performance tests, the tyre's inflation pressure loss shall be less than 10 % of the initial inflation pressure.

4.5 Overpressure performance When inflated to at least 4 times the rated inflation pressure, the tyre shall remain inflated for at least 3 s without bursting, blisters, delamination, or steel wires or cords break.

4.6 Air tightness performance of tubeless tyres After inflating a tyre to its rated inflation pressure and allowing it to stand at ambient temperature for at least 12 h, then adjusting it to the rated inflation pressure and allowing it to stand at ambient temperature for at least 24 h, the rate of pressure drop shall not exceed 5 % of the rated inflation pressure. During inflation pressure measurement, the ambient temperature deviation shall not exceed ±3 °C.

4.7 Bead fit pressure of tubeless tyres The bead fit pressure values for tube tyres with different rated inflation pressures shall comply with the provisions in Table 1.