caribeanbound
Well-Known Member
Guys: I need some help. As some of you may know, we lost a home builder in Spain Saturday morning. He was making the second flight on his Janowski J1-B. While the accident involved running off the runway , across a grass area, through a fence, and over an embankment, He had control issues during the first flight. He had the stick back the whole flight to keep the nose up.
Our entire Yahoo Janowski group have been working on the control issues on this aircraft for some time now. It is a high wing pusher. It has a fairly short tail with a low mounted stabilizer/elevator. When you add thrust you need more back elevator to counteract the pitch down. One of our members has solved the problems in his J-1 by lowering the thrust line a bit, sealing the stabilizer/elevator gap, and adding a gerney flap (7mm aluminum angle) to the trailing edge of the elevator. He has over 400 hours on his now and no control issues.
We are talking about the issue. The incidence angle is 2 1/2 degrees. We are trying to get our heads around the issues of the stabilizer being a downlifting wing of sorts. it supplies down force counteracting the nose down tendency as thrust is increased. The gerney flap idea works but Is it the best method? Some of us feel that increasing the tail moment(longer tail) will probably solve the problem. Some of us feel that changing the incidence angle will work. some feel that changing the trust line will help.
I know that a lot of old high wing aircraft change the angle of incidence with a stabilizer jack screw trim system.
While the J1-B may have several issues on pitch, it is not an odd design. There are several similar layout planes out there, i.e. Challenger and CGS Hawks to name two. Do they have major pitch problems with changing thrust? I am not going to give up on this fairly traditional aircraft because of rigging problems. personally the one I am building has a 15 inch longer tail. I also have a 33 % scale model almost ready for testing.
Please respond to this request for your thoughts if you have useful advice. I am not switching designs so save the advice start over on another design.
Our entire Yahoo Janowski group have been working on the control issues on this aircraft for some time now. It is a high wing pusher. It has a fairly short tail with a low mounted stabilizer/elevator. When you add thrust you need more back elevator to counteract the pitch down. One of our members has solved the problems in his J-1 by lowering the thrust line a bit, sealing the stabilizer/elevator gap, and adding a gerney flap (7mm aluminum angle) to the trailing edge of the elevator. He has over 400 hours on his now and no control issues.
We are talking about the issue. The incidence angle is 2 1/2 degrees. We are trying to get our heads around the issues of the stabilizer being a downlifting wing of sorts. it supplies down force counteracting the nose down tendency as thrust is increased. The gerney flap idea works but Is it the best method? Some of us feel that increasing the tail moment(longer tail) will probably solve the problem. Some of us feel that changing the incidence angle will work. some feel that changing the trust line will help.
I know that a lot of old high wing aircraft change the angle of incidence with a stabilizer jack screw trim system.
While the J1-B may have several issues on pitch, it is not an odd design. There are several similar layout planes out there, i.e. Challenger and CGS Hawks to name two. Do they have major pitch problems with changing thrust? I am not going to give up on this fairly traditional aircraft because of rigging problems. personally the one I am building has a 15 inch longer tail. I also have a 33 % scale model almost ready for testing.
Please respond to this request for your thoughts if you have useful advice. I am not switching designs so save the advice start over on another design.
