www.algodoo.com

That site helped me finally decide what airplane to do.

Really great. You don't have a sig, you should put the Early Aircraft Collab sig, like mine.

Anyway more on topic, I plane on building a V2 of my Albatros D.V, with realistic aerodynamics and even more features.

Here is the V1 in case you never played it:

Variable speed prop engine. Probably can't be implemented into anything, but it is nice.