Qavion, I see your point. As you are familiar with the B-747 I do believe that the SP has a tail that is 10 feet wider then the –200 and of different aerodynamic design. It appears to have a higher sweep back angle with a possible extension of the chord (this latter part I’m not certain of). The tail volume is the tool used to determine CG range and is the product of the tail area and the moment arm about the aircraft CG. It is expressed mathematically as:
V = LSt/ cS
Where L is the tail arm, St is the area of the tail, c is the wing chord, and S is the wing area
Let’s say Boeing wants the same tail volume which is proportional to stability. If they decrease L by shortening the fuselage the stability will be directly affected, the CG range will be decreased, so they increase St to compensate. So much for stability and CG range.
The increased tail size on the SP is from many different factors, one being the tail volume, the other being the desire to retain an effective force moment with a reduced arm. You are correct. If they stretch the 747 again then the tail will also need to be bigger because of the increase in moment and inertia as discussed above. Tail size is not necessarily a linear relationship to fuselage length; there are many confounding factors.
I think it’s correct this time, thank you for your previous advisement.
