X-Plane 10.45 beta 1 fixes a bug in X-Plane's flight model where props applied too much torque to the aircraft. The effect is most noticeable on single engine aircraft where the prop torque is applied along the center of the fuselage.
Authors: in order to have the new correct torque applied to your aircraft, you must resave your aircraft in Plane-Maker 10.45. When X-Plane finds an aircraft authored with an old Plane-Maker, which includes all existing aircraft already shipped, we preserve the old torque behavior.
We put in this compatibility because some aircraft have plugins and other work-arounds that try to get correct flight dynamics assuming X-Plane will apply too much torque. If we were to apply the fix to these planes, they'd then have too little torque (because we'd apply less torque and the work-around would already be in place). So this is an opt-in fix.
Authors: if you use Plane-Maker 10.45 to work on your aircraft, you will be opted in to the fix! There is no way to work on a new aircraft and preserve the old torque. Our thinking is: the old torque calculating is physically wrong, so we're not letting anyone preserve this mistake when working on a new aircraft.
So when you bring your aircraft in for its next feature update, note that you will be getting the torque fix and you should make sure the results are useful.