The trouble was that at high altitudes where there is less oxygen, the propeller blades had little air to bite and engines still needed oxygen to burn petrol.

麻烦的是，高海拔的地段，氧气稀薄，螺旋桨叶片没有空气使其扇动，而且发动机燃烧汽油也需要氧气。

Having the chords of propeller blades parallel to the line of flight.

螺旋桨边缘弦的.

Test results provide an important basis for strength design and structural optimization of propeller blades.

为螺旋桨桨叶的强度设计与结构优化提供了重要依据。