Hi everyone!
New member here with very long story. I will try to make it short and hope that somebody knowledgeable will answer some of my questions.
Last summer I purchased myself ELSA Skyboy with 100hp Rotax and NACA 4412 wing. It is high wing pusher designed and built in Europe originally as ultralight trainer, side-by-side, with 50hp engine and different very thick high lift airfoil. To American markets they were installing 100hp engines and 138 sq ft wing. Only about hundred of them where are made and sold worldwide.
To satisfy the insurance company with 5 hour dual training I made appointment with local CFI and one day we were ready for first flight. Previous owner did give me 15 minutes ride and I found this airplane very stable with a very solid field on the controls. My instructor however didn't like this airplane at all. Biggest concern in flight was that at 80 miles an hour and about 5000 RPM bottom of the wing was showing very high angle of attack to the horizon.
I managed to contact original designer and we were trying to determine if they didn't make any mistakes at the factory in 2001. In the process of checking everything out I found that engine what's tilted forward 4 degrees, opposite from his recommendation. I did rebuild engine mounts and now my engine tilted back by 3° and it's blowing on the tale. However I didn't find that airplane behaves any different.
Next I discovered that when my airplane parked on perfectly level ground, which supposed to be more or less straight and level flight attitude. When I am holding Digital level to the bottom of the wing, which is almost flat, I can see 4.5 degrees positive angle (tilted up). When I put a level on horizontal stabilizer - I can see negative 5.7° (tilted down) . So total difference between this two flying surfaces 10.2°. we can assume that true decalage to the cord line is about 11° !!!. I did walk around airport and measured everybody else's airplanes and found that most of them with tractor configuration have 4-6 degrees difference between wing and tail. Original designer did tell me, don't change anything, everything is good.
Of course I didn't listen. Because flying all the time with such high angle of attack is resulting into very poor performance (low speed, poor glide ratio). I talk to many different people, EAA technical advisors, different designers and builders. My conclusion was that airplane configured into slow flight mode to comply with ultralight rules in Europe 25 years ago. Everybody I talk to suggest to raise horizontal stabilizer, do it in small increments and test flight in between.
So I did. I and up raising leading edge of horizontal stabilizer by 2° and on my first and second flight didn't see any changes on handling or improvements in speed. Angle of attack to the horizon at 5000 RPM = 92hp with 1000lb total was about 6° going 82mph (GPS speed avg. four different directions). Not very efficient way to fly. I was told by many people that 4412 wing at that speed and load should be just about level to the horizon.
Aeronca Champ with 85hp engine and exactly same wing and 200 pounds heavier with power of setting of 75% (64hp) moving faster than my airplane.
On my third test flight I discovered, that if I trim airplane for level flight and without holding the stick, controlling direction only with a rudder pedals. After a few seconds or so stick Will start making gentle movements back and forth and if you let it go it will progress, then in the few seconds and you will find yourself in pretty aggressive rocking chair. Pulling power back and pushing stick forward and 200 feet of altitude, Will get you back to normal flight.
As you probably can guess, I am done with that experiment, and I will put everything back to original position. However I am still looking for explanation of why my airplane needs to fly this way. It feels exactly like flying Cessna 172 with fully extended flaps. Feels like airplane locked in to slow flight mode, with high angle of attack, high-power Setting, maintaining altitude and moving a relatively slow.
I would appreciate any kind of input.
New member here with very long story. I will try to make it short and hope that somebody knowledgeable will answer some of my questions.
Last summer I purchased myself ELSA Skyboy with 100hp Rotax and NACA 4412 wing. It is high wing pusher designed and built in Europe originally as ultralight trainer, side-by-side, with 50hp engine and different very thick high lift airfoil. To American markets they were installing 100hp engines and 138 sq ft wing. Only about hundred of them where are made and sold worldwide.
To satisfy the insurance company with 5 hour dual training I made appointment with local CFI and one day we were ready for first flight. Previous owner did give me 15 minutes ride and I found this airplane very stable with a very solid field on the controls. My instructor however didn't like this airplane at all. Biggest concern in flight was that at 80 miles an hour and about 5000 RPM bottom of the wing was showing very high angle of attack to the horizon.
I managed to contact original designer and we were trying to determine if they didn't make any mistakes at the factory in 2001. In the process of checking everything out I found that engine what's tilted forward 4 degrees, opposite from his recommendation. I did rebuild engine mounts and now my engine tilted back by 3° and it's blowing on the tale. However I didn't find that airplane behaves any different.
Next I discovered that when my airplane parked on perfectly level ground, which supposed to be more or less straight and level flight attitude. When I am holding Digital level to the bottom of the wing, which is almost flat, I can see 4.5 degrees positive angle (tilted up). When I put a level on horizontal stabilizer - I can see negative 5.7° (tilted down) . So total difference between this two flying surfaces 10.2°. we can assume that true decalage to the cord line is about 11° !!!. I did walk around airport and measured everybody else's airplanes and found that most of them with tractor configuration have 4-6 degrees difference between wing and tail. Original designer did tell me, don't change anything, everything is good.
Of course I didn't listen. Because flying all the time with such high angle of attack is resulting into very poor performance (low speed, poor glide ratio). I talk to many different people, EAA technical advisors, different designers and builders. My conclusion was that airplane configured into slow flight mode to comply with ultralight rules in Europe 25 years ago. Everybody I talk to suggest to raise horizontal stabilizer, do it in small increments and test flight in between.
So I did. I and up raising leading edge of horizontal stabilizer by 2° and on my first and second flight didn't see any changes on handling or improvements in speed. Angle of attack to the horizon at 5000 RPM = 92hp with 1000lb total was about 6° going 82mph (GPS speed avg. four different directions). Not very efficient way to fly. I was told by many people that 4412 wing at that speed and load should be just about level to the horizon.
Aeronca Champ with 85hp engine and exactly same wing and 200 pounds heavier with power of setting of 75% (64hp) moving faster than my airplane.
On my third test flight I discovered, that if I trim airplane for level flight and without holding the stick, controlling direction only with a rudder pedals. After a few seconds or so stick Will start making gentle movements back and forth and if you let it go it will progress, then in the few seconds and you will find yourself in pretty aggressive rocking chair. Pulling power back and pushing stick forward and 200 feet of altitude, Will get you back to normal flight.
As you probably can guess, I am done with that experiment, and I will put everything back to original position. However I am still looking for explanation of why my airplane needs to fly this way. It feels exactly like flying Cessna 172 with fully extended flaps. Feels like airplane locked in to slow flight mode, with high angle of attack, high-power Setting, maintaining altitude and moving a relatively slow.
I would appreciate any kind of input.
