Complex sentence: The upper pair formed a three bay structure with pars of parallel interplane struts and the overhangs of the upper wing were supported by outward leaning parallel pairs; the central and lower wings formed a similar but two bay structure.
Split into simpler sentences: The upper pair formed a three bay structure with pairs of parallel interplane struts and with the overhangs of the upper wing supported by outward leaning parallel pairs. The central and lower wings formed a similar but two bay structure.