Abstract: It is a basic contradiction between decreasing the volume (Lightening the weight) of the landing gear and lowering the dynamic loads (fatigue loads) on the landing gear for the selection of the shock-strut compression ratios in landing gear design. To resolve the contradiction, the selected range of the compression ratios is discussed theoretically in this paper. It is pointed out that when the compression ratios (i.e. ther ratio of still to full expansion, qso and the ratio of full compression to still, qms) are taken from the range 2.5-4.5, not only can the volume of the shock-strut be decreased (the weight of the landing gear be lightened) as much as possible, but also the dynamic loads (fatigue loads) on the landing gear can be controlled in lower range. Therefore it is helpful to the selection of the compression ratios of the shock-strut in landing gear design, and it provides a theoretical basis with certainly significance for the experimental selection of the compression ratios in the past.

Key words: shock-strut, compression ratios, landing gear, aircraft design