Don and netters Something else came to mind the other day when considering the effects of raised or lowered thrust line. During flight training to become CFI's we were always told that the reason the Piper Seminole was made with a high "T" tail as compared to its sister plane the Piper Seneca which had a traditional tail (and 2 more seats, but that is another story) is because the Seminole was really ear marked for the training market, and so Piper wanted the tail in "clean air". This was supposed to make it safer to flight train in. I am told that the same designer, later worked for Beech and designed the Duchess, which is why so much of the configuration resembles the Seminole.
My point for this post is this: while in most cases planes are designed with the empennage "in the prop wash", some very successful designs are not. These planes seem to experience less pitch change due to the change in the amount of prop thrust over the elevator/stabilator, and the change is more a function of airspeed/airflow. If by raising the thrust line, one lessens the amount of prop wash over the elevator of a particular KR2 or S, that builder may find a nice softening of the effectiveness, without becoming dangerous. Then again it may favor one side only, causing good nose up authority, but lose some nose down authority. I would also think that if the builder then used a longer prop taking advantage of the greater ground clearance, he might not have any change in the behavior of the plane to speak of at all. Just some ideas for thought. I was once considering a PSRU or re-drive as some call them, for my 1915 cc VW original engine. Had I installed that, I would have been 4 to 5 inches higher. This may be an issue many builders have contemplated or evaluated. Colin Rainey brokerpi...@bellsouth.net
