Why airplane have two vertical fin?

Question

Why airplane have two vertical fin?

Answer 1

http://en.wikipedia.org/wiki/Wingtip_dev...

Answer 2

I'll try and answer this without delving deep into aerodynamic babble. At high incidences / angles of attack, the airflow downstream of the main wing can interact with the airframe structure, and greatly exacerbate the loading on the fin. Obviously this brings fatigue and failure mechanisms into play, such are the forces that can be exerted on the fin.

Some aircraft manufacturers therefore either modify the airframe by using two vertical fins, which reduce the loadings on each fin and thus reduce the risk of fatigue failure. Different aircraft exhibit different aerodynamic effects at high incidence, hence the fact that you will see various tailplane configurations across all aircraft.

Answer 3

why do birds have 2 wings

Answer 4

First off, you'll notice that commercial planes DON"T have twin verticals.

As far as the MILITARY vertical tails, part of the reason if one tail/rudder becomes inop from battle damage, there is still another.

Answer 5

In WW2 aircraft, (for example, the B-24) the sole purpose was redundancy.

In supersonic jet aircraft, additional causes are reduction in airframe loading at trans-sonic speeds, reduced radar profile, and improved lateral balance.  Redundancy is still a strong reason.