Originally Posted by
stilton
Not scientific at all but all you have to do is look at a 747s vertical fin to know it’s more than enough
Even on the 747, you can run out of tail. If you take a close look at the vertical tail on the 747SP, you'll notice there is a large 'extension' at the top compared to the regular 747s.
On the 747-400 - with the higher thrust options (and the 747-8), we had to limit go-around thrust because if you had two engines out on the same side, you could run out of tail doing a go-around with max thrust. However in the case of the 747, it wasn't foolproof - we simply modified the thrust target and how far the Autothrottle would push the levers - you could still override it by pushing the throttles fully forward.