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The aileron push-pull control tube is a great example to look at the tradeoffs in materials, tolerances, costs, weights, certification, manufacturing, etc. and how each of these is related to each other. I probably won't think of everything but here's a conversation starter. 1) weight - aluminum, composite then steel, but I think that they would all be fairly close. 2) cost - steel, aluminum then composite. 3) manufacturing - steel/aluminum then composite 4) Stiffness - composite, steel then aluminum The problem is they all relate to each other and all have very strong positives and negatives. Here's some random thoughts. Steel produces the smallest diameter. Flexibility (buckling) is both good and bad. For metallic tubes, it allows less binding (and resulting lower control force); for composite (very stiff), alignment has to be perfect or it won't move. To back this, the 3 hinges on the aileron are rarely in perfect alignment, but when installed they move easily because the aluminum aileron flexes slightly to allow for it. A composite aileron does not (an M10 learning experience). Certification would be a large expense for composite as the material and processes would need to be qualified and tested. BUT (and this is where OEMs today are missing it) if one could find an off-the-shelf, commercially-produced tube that would work, end pieces could be designed to mate with the tube and the current attach points. Each tube assembly would need to be strength tested, but that is A LOT less work than certifying an original design. The match has been lit. Go!