Here comes the good news and the bad news The good news: the first alpha version flight was done by a real pilot. He was impressed how good is the flight model, but there were some minor things needs to be adjusted to match the real plane's flight and engine model. The engine model is completely wrong in x-plane. You can make the plane fly like the real one, but then the numbers won't match - or if the numbers match, the model is completely unusable. After some research, I found the Maintenance Manual of Walter M601E (with reference numbers and grapsh) and JSBSim (an open-source flight dynamics model). With those I can model the engine to match all the numbers and graphs during the takeoff, flight and landing - including water injection and IELU (Integrated Electronic Limiter Unit). The bad news: because of this, I've decided to write the engine model from scratch, based on real engine graphs and data - likewise the An-2. This takes time. And I don't know exactly how much. If I'm lucky, I can re-use code from the An-2 and make it in a relatively short time (about a week), but this is clearly not enough to include all the features I plan to implement to the engine model. I've been thinking on this for a week and made a tough decision: because I'd like to include this in the first release, I cannot release this plane this year. XP10 is coming too, and there will be lof of new features which I plan to include. A plane cannot be finished. You just stop working on it.