Hi,

I'm not advocating using them at all costs or when it's mechanically impractical, I just think that sometimes, broadbrushed 'rules' drive some companies to do things certain ways even when it doesn't make things any safer. For example, the ailerons on our F-16 have an internal torque rod. One of my customers ended up cutting a hole in the wing and installing his servo there because, as he reported to me, some friends of his at his club urged him to for safety's sake. In the end, the size of the lever arm on his external linkage (the control horn) was half the size of the stock one which cut his mechanical advantage (for slop and torque) in half. Additionally, he cut through the carbon cloth layer, rendering that extra strength in the wing itself meaningless. Moral: Just because it's external doesn't mean it's stronger or safer. It depends on the design.