Originally Posted by
BackPacker
As I said, the aerodynamics are beyond me, but I don't think this is the explanation. The DA-40, just like all aircraft, needs to be stable in speed vs. pitch and therefore, I think, has to have an aerodynamic downforce generated by the tail. A lifting tail needs some very fancy fly by wire or something else to make it dynamically stable. A380 territory.
Take it from a VC10 pilot - the 10 did not have fly by wire and yet was perfectly capable of having a lifting tail surface (all moving horizontal stabiliser and separate elevators).
Originally Posted by
IO540
Airliners reportedly often fly with the elevator pushing UP.
If at all possible, this would be the case. A tail pushing down creates extra drag, increasing fuel burn. If you can make the tail generate a little lift, total drag is reduced. It's usually done by managing the CofG by sticking fuel in the tail.
Pumping fuel around to manage CofG was very importanat to Concorde - drag management was an important aspect of that aeroplane's operation.