Sentence:  In a flying machine, a supporting surface comprising a flexible body, a fixed front <WSD>wing bar</WSD>, a centrally pivoted rear <WSD>wing bar</WSD>, flexible ribs connecting said bars, slidable supports for the rear <WSD>wing bar</WSD>, and sustaining springs associated with said supports. 
Meaning of the word marked with <WSD> tags:  A support strut on for the wing of an airplane.