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Flaps Questions

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Are flaps usually design to take up about 50% of the wing length on aircraft? From looking at a variety of ac, that appears to be a favorite division point between the aileron and the flap. It is also the default in aircraft settings FSEd displays.I am trying to figure out how flaps are hinged. Looking at the plans for the Aviat Husky, it appears the flap is not hinged along the forward edge like an aileron but the hinge point is on an arm below the flap and the front of the flap unattached to the wing. Is that correct?On the Aviat you can see the flap actuator/hinge. On some ac, this appears to be covered by a streamlined housing. But on others, some in FS ac, it appears they are rotating the flap about the front edge like an aileron and now hinge or cover appears.Can you help me to understand how flaps generally are supported and supposed to move on light aircraft?Thanks,Steve

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What a simple question and what a mountain to climb! :-)There is no simple answer Steve. Flap can indeed be a very basic hinged affair (a simple flap) or they can be extremely complicated. I'm not just talking about the multi track systems on the heavies either - ordinary Cessnas use flap tracks to increase wing area as the flaps move out and down.Simple flaps, split flaps, Fowler flaps etc. etc. Many variations according to what each designer needs the flaps to do. You can get heavily involved and find out how all these systems work (it would be well worth the reading) but if you are only working on one aircraft and are short of time it might be best to find out the flap actuation mechanism for just the one aircraft.It's a good job we can't draw diagrams on these messages! I'd be here all night..

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Thanks for the example. What makes me curious is why the flap moves down and backward on these brackets leaving a gap between the wing and the flap. When it could be hinged along the axis of the flap front edge. It would not seem to make much difference in this case.The only explanation I have is that you want to extend, not just block, the airflow and perhaps the gap does not matter much in the flow of air? I suppose that is why they call it extending flaps.Well, I will leave all that for later. Right now I only need to know how to animate movement of the flap. This means I will likely have to attach the flap itself to the hinges and make it move with them instead of the other way around. IOW I need to name the hinge front arms l_flap and r_flap to animate the attached flap together. Right now the flap and flap motion is tied to the flap angle sim value.Steve

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Okay, I've learned a bit more about flaps.It appears they do move away from the wing with a seperation between the wing and the flap. I should have read your answer more closely because you did say it was to increase wing area. That must account for the sliding motion. The drooping probably acts like a spoiler.On the stock FS Cessna 182 they clearly model the sliding and drooping motions. The flap slides out from the wing on struts.I am making my flaps work like the Aviat or Europa where they are hinged and fall away from the wing rotating about a pivot point below the wing. They do not slide. For now, I model this by having the back flap support arm and the flap rotate according to the FS stock animation. This looks fairly accurate unless you go beyond my maximum flap angle, then the arm pokes through the top of the wing.If I have time, I will group the trailing arms with the flap and rotate the entire group itself. But the arms are grouped with the hinge right now.Steve

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ufo, there are many different kinds of flaps, both for the leading(front) and trailing(rear) edges. There are 3 main kinds of leading edge flap, slats, variable camber, and krueger. Slats are just sections of the leading edge(LE) that move forward and downward, like on the 737 or msot airbuses(DC-10 and MD-11 too). Variable camber flaps are only sued on the 747 outboard of the inner engien pylons. They are flat pieces of pyc that lie on the underside of the wing behind the LE and when the flaps are lowered, they are swing out and forward by actuator arms that add curve or camber to the otherwise flat sections. Kreuger flaps are pieces of the underside of the leading edge that swing forward but do not curve. All 747s use these inboard of the inboard engine pylons.As for trailing edge flaps, there are so many differnt kinds it would take me hours to explain them all. I'll just list a few common ones.Split flaps. These are very simple affairs and all they do is pivot downward to increase lift and drag. Most pre 1942 aircraft that had flaps used this kind of flap. They do not increase wing areaButterfly flaps. These flaps simply increase area, and do not pivot down. Some japanese fighters used these to increase manuverablitity in a dogfight.Fowler flaps. These are flaps that slide backwards as well as downwards. They came into use during WWII because aircraft that needed to go fast(and have small, thin wings) needed to land at reasonable speeds, so they were invented to increse wing area and lift. They come in several varieties, single and multi slotted, which means the number of segments. The B-29, B.52, 707, as well as many other pre 1955ish aircraft used single slotted fowler flaps, which mens just one section pivots, creating one "slot" above the flap section. The 747 introducted triple slotted flaps, which come in 3 segments and slide out and downward accodring to flap setting(check out a good FS 747 model and you'll see what i'm talking about). When airliners started to be built with very efficient airfoils, they started to go back to double, and single slotted flaps. For example, the 767's inner flaps are double slotted, but the outer ones are single. All fowler flaps have tracks to slide on. Single slotted ones can be contained within the wing, but multislotted ones need external tracks, which is why you see large fairings below flaps of many modern aircraft.Blown flaps. These are like fowler flaps, but are placed in the jet exhaust, which is forced through and downwards, greatly increasing lift. The YC-14, YC-15, C-17 and several other aircraft use these kind of flaps. They must withstand alot of heat and pressure, so they are often built from titanium.I think that's enough for the basics. Good luck.

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