Avidflyer2
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Have you ever wondered how Piper bent the wing spar to the proper dihedral angle? I did! I removed the two plates or doublers from the inboard end of the right wing spar from my Cherokee PA28-140. The photos below tell a story on how they were able to bend a large "I" beam without distorting the center web. There is a small wavy area at the bottom spar cap's center web which is covered up by the doublers. I suppose this was caused by bending the spar cap up which put the bottom web in compression. In contrast I did not discern any thinning of the top web where the top spar cap was bent which put the top web in tension.
These photos do help to explain Piper's letter on the SNPRM for the proposed wing spar inspection Airworthiness Directive. Piper has stated that ERAU should have seen cracks in the two side plates or doublers during the last 100H inspection and that the cracks should have been visible with unaided eyesight. There are differences in the wing spar shown here and that of the PA28R & other retractable gear model airplanes due to the absence of some of the center web lightening holes. This is the only wing spar (condemned due to corrosion) upon which I could remove the side plates to view the attachment bolt holes unencumbered by the side plates. The top photo shows the right wing spar as being viewed from front to rear - note that the radius of the cut-out area of the center web is less than that of the top "notch".
These photos do help to explain Piper's letter on the SNPRM for the proposed wing spar inspection Airworthiness Directive. Piper has stated that ERAU should have seen cracks in the two side plates or doublers during the last 100H inspection and that the cracks should have been visible with unaided eyesight. There are differences in the wing spar shown here and that of the PA28R & other retractable gear model airplanes due to the absence of some of the center web lightening holes. This is the only wing spar (condemned due to corrosion) upon which I could remove the side plates to view the attachment bolt holes unencumbered by the side plates. The top photo shows the right wing spar as being viewed from front to rear - note that the radius of the cut-out area of the center web is less than that of the top "notch".
