| 摘要 |
The propellers 21 of the device each comprise two blades whose leading edges 43, 44 facing the loading are bevelled over the entire length of the blades or at least over the greater part of the latter. The trailing edges of the blades 41, 42 are provided with bends 45, 46 over the entire length of the blades or at least over the greater part of the latter. <IMAGE>
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