On Mon, 04 Aug 2003 18:13:25 +0000, Chris W wrote:

I got such a good answer on my question about flap design I thought I
would ask another design question. why would a plane that has two
engines have two vertical stabilizers. No in the case of the Aircoupe I
always thought the reason for the twin tail was so that the helical prop
wash wouldn't induce a yaw tendency from the prop wash hitting the
vertical stabilizer/rudder. It is my understanding that the Aircoupe
was designed so you wouldn't need rudder pedals, and the twin tail I
think would have helped that. But on a twin engine, what's the point?
having two vertical stabilizers and two rudders seems significantly more
complicated both structurally and mechanically so why do it if there
isn't some advantage? There must be one I don't know about.


--
Chris Woodhouse


Planes may have multiple vertical stabs for several different reasons.
Some (e.g. the Lockheed Constellation) may have them to facilitate fitting
them in existing hangars without hitting the top of the door opening.

Some multiple engine designs have multiple vertical tails so that one
portion is directly in the prop wash of the operating engine which may
help reduce the minimum control speed following an engine failure. At
least that is what Kelly Johnson says about the twin vertical tails of the
first Lockheed Electra (More Than My Share of it All, Kelly Johnson, pg.
24). And he says that they also acted as end plates on the horizontal
tail, which increased its effectiveness, and improved the static
longitudinal stability - same book, same page).

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/