Re: flapped ships flight model question - OP can't land
Posted: Fri Jun 14, 2019 9:04 pm
Oh I see the OP was refering to the 15 meter Ventus. The Ventus 15 meter (like the diana) has quite a high wingloading. Also the airbrakes of the Ventus are large, probably too large for the 15 meter version as they also have to meet the certification standards of the 18 meter wing.
As for the pitch down. Flaps have multiple effects. When you extend them you are effectively flying with too high an angle of attack because the flaps provide extra lift. Therefor you have to lower the nose to prevent ballooning and speed loss. They also cause drag, which also means you have to lower the nose to maintain speed. But to help you with this, the center of pressure on the wing moves back so it naturally causes the nose to pitch down when you apply flaps. Most gliders do however require a bit of nose down trim with flaps L.
As for procedures on approach. Use the max glide angle flaps for the traffic pattern. So for the ASG29 use 4, antares Flaps 0, JS1 flaps 4, Ventus flaps 0 or +1, Diana flaps +8 or + 14.
Only on final and after you are sure you can make the field, put the flaps in the maximum positive setting (L or whatever it is on the plane you are flying). If it is very windy and turbulent and you need more aileron effectiveness you can use the flap setting just below that. Aim, just like you would in a flapless glider to approach with half speed brakes.
The target speed is a tricky one. The yellow triangle denotes the recommended approach speed at maximum weight with the flaps in landing setting. Usually you will be approaching without water ballast. So the optimum approach speed can be up to 10 kph slower. It is safe to always use the yellow triangle, but this may cause some floating on landing. I just hold off the plane until i make a two point landing. I don't try to hold it off too long as that usually results in a hard landing (This is what I suspect you are doing). Due to the bigger ground effect from the flaps it will float a lot longer and you are able to reach a higher pitch. When it doesn't want to fly anymore it will set the tail down and rotate around the tailwheel causing a hard impact on the main gear. I think that is why you find it easier to land with less flaps.
After landing it is easier to keep the wings level when you put the flaps full negative. On the ASG29 the outboard flapperons automatically move to full negative when selecting flaps L. The inboard flapperons move to about 50 degrees. They did this to keep better roll control with flaps L.
Hope this helps you
As for the pitch down. Flaps have multiple effects. When you extend them you are effectively flying with too high an angle of attack because the flaps provide extra lift. Therefor you have to lower the nose to prevent ballooning and speed loss. They also cause drag, which also means you have to lower the nose to maintain speed. But to help you with this, the center of pressure on the wing moves back so it naturally causes the nose to pitch down when you apply flaps. Most gliders do however require a bit of nose down trim with flaps L.
As for procedures on approach. Use the max glide angle flaps for the traffic pattern. So for the ASG29 use 4, antares Flaps 0, JS1 flaps 4, Ventus flaps 0 or +1, Diana flaps +8 or + 14.
Only on final and after you are sure you can make the field, put the flaps in the maximum positive setting (L or whatever it is on the plane you are flying). If it is very windy and turbulent and you need more aileron effectiveness you can use the flap setting just below that. Aim, just like you would in a flapless glider to approach with half speed brakes.
The target speed is a tricky one. The yellow triangle denotes the recommended approach speed at maximum weight with the flaps in landing setting. Usually you will be approaching without water ballast. So the optimum approach speed can be up to 10 kph slower. It is safe to always use the yellow triangle, but this may cause some floating on landing. I just hold off the plane until i make a two point landing. I don't try to hold it off too long as that usually results in a hard landing (This is what I suspect you are doing). Due to the bigger ground effect from the flaps it will float a lot longer and you are able to reach a higher pitch. When it doesn't want to fly anymore it will set the tail down and rotate around the tailwheel causing a hard impact on the main gear. I think that is why you find it easier to land with less flaps.
After landing it is easier to keep the wings level when you put the flaps full negative. On the ASG29 the outboard flapperons automatically move to full negative when selecting flaps L. The inboard flapperons move to about 50 degrees. They did this to keep better roll control with flaps L.
Hope this helps you