Vertical stabilizers have been breaking off airplans for a long time. The Navy Tacamo program lost a vstab off of a 707 during flight testing, a B-52 came home without the vstab, there has been combat damage that left airplanes coming home without it as well. Also crop dusters regularly slice off the vstab flying under wires they shouldn't be flying under. The metal ones break off sometimes, why would we think a composite part isn't subject to the same failures.
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And I'll throw in my 2 cents on pitot tubes. I cant think of any pilot in cruise flight who would change power settings due to an erratic airspeed indication, particularly if it wasn't associated with groundspeed deviations on the FMS. You just leave the power set and evaluate the problem. If 1.80 EPR got you there, it keeps you there. And in a thunderstorm, erratic altitude and rate of climb info isn't too unusual, but if it correlates to the direction the airplane is tossed around, it is ok, and pilots are trained to hold pitch and bank. And the aiutopilot will do the same with altitude hold off. And as long as the airplane has the structure to handle it, they pop out the other side off altitude and heading, but in one piece.
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And if the tail comes off for any reason in a thunderstorm, there would be no way to keep the pointy end in front, and any of the big airplanes would begin to turn side on to the relative wind and begin breaking up.
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But then noone knows if the tail came off, of if it did, why.