1. Why do airplanes have different tail-end designs and what effect, if any, does the shape have? I ask this because I notice the 777 has an MD "style" squared-off tail like the 717 whereas the 757 and 767 have rounded cone-style ends.
2. On a 3 or 4 engine aircraft, would it be possible to have engines of different thrust levels or sizes? In other words, would it be economical to have a 747 or 340 with two 777 size engines inboard and two 737/757 engines outboard? What about a trijet with a smaller thrust engine at the rear?
Thanks for your answers.