G'day,I would like to discuss the design considerations required to design a belly landing UAV.The airframe will be roughly 5kg (~11lbs) with a 2.5-3m (100-120in) wingspan and made using composites.I have been throwing around quite a few different ideas, including using aluminum sheet as a skid, or a bow of aluminum to skid on as well as absorb some of the impact, using extra layers of kevlar and fibreglass, a foam padding, or even just a cut up plastic bottle.One pain is that we need at least two or three clover leaf antennas facing down under the fuselage.I am looking at both a skidding belly landing and a deep stall drop similar to the sky Lark but only a few feet above the ground and without the airbag.If you have any suggestions, advice, or experience that you can share I would like to hear them.
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Have you arrived at a conclusion on landing style. I surprised when I watch Skylark I-LE deep stalll drop landing style when I recently used the video on youtube. Do you think its cg is well below the airplane to enable the airplane drop in a succesfully levelled position?
Hey, so after my share of belly landings I would recommend keeping the CG as close to your skid surface as possible. A pontoon construction works well for a water landing plane, as the sheer force between the water and the pontoon is relatively low, however for gras it might be so high that your plane easily toples over if the pontoons are to high...
I actually had good experience with foam, works well especially if you try a lofty construction. Aerodynamic drag will be rising, but this solution is cheap, easy to construct and robust, thus for a experimental setup well suited.
If you want to have something more elaborated, why dont you try spring loaded skids, which in flight will be retracted in the centerbody. They could be released when approaching landing so that the spring will push out the skids, and also the spring would feather the impact shock. Much more complicated but much more elegant.
After reading your initial post some more I think that I have some some points that you may want to consider. You are going to want to focus on two obvious things; weight and shock absorption. If you want to focus on the drop stall landing method you are going to want to really focus on absorbing that shock. I would not recommend foam because that would create a rather bulky landing system, not as far as weight is concerned but as far as volume is concerned. This will definitely affect your flight characteristics. I would also not recommend a direct belly landing because all of the shock would be directly transmitted to the fuselage...which is not ideal. I would try to create a form of skid system similar to that of a helicopter using reinforced composites. That way you get the best of all worlds. You get the shock absorption that you need, the ground clearance you would need for the antennas, you would reduce the aerodynamic drag of most other systems, and your would still be able to land with both positive forward motion and zero forward motion conditions. Hope that helps.
Not sure if it'll work, but the first thing I thought of was one of the water-landing planes with pontoons on the wings, so it lands with 3-points down. That way you'd land on the belly with most of the force & have the pontoons to hold you level and protect the antennas, but I'm not sure how well they'd work on surfaces other than water.
Is there any reason in particular that you are interested in a belly landing and not a set of gear? Also, what media are you planning on landing on? I am assuming that you are going to shoot for grass but I want to make sure.
Replies
Hello Simon,
Have you arrived at a conclusion on landing style. I surprised when I watch Skylark I-LE deep stalll drop landing style when I recently used the video on youtube. Do you think its cg is well below the airplane to enable the airplane drop in a succesfully levelled position?
Hey, so after my share of belly landings I would recommend keeping the CG as close to your skid surface as possible. A pontoon construction works well for a water landing plane, as the sheer force between the water and the pontoon is relatively low, however for gras it might be so high that your plane easily toples over if the pontoons are to high...
I actually had good experience with foam, works well especially if you try a lofty construction. Aerodynamic drag will be rising, but this solution is cheap, easy to construct and robust, thus for a experimental setup well suited.
If you want to have something more elaborated, why dont you try spring loaded skids, which in flight will be retracted in the centerbody. They could be released when approaching landing so that the spring will push out the skids, and also the spring would feather the impact shock. Much more complicated but much more elegant.
These are my thoughts on this...
After reading your initial post some more I think that I have some some points that you may want to consider. You are going to want to focus on two obvious things; weight and shock absorption. If you want to focus on the drop stall landing method you are going to want to really focus on absorbing that shock. I would not recommend foam because that would create a rather bulky landing system, not as far as weight is concerned but as far as volume is concerned. This will definitely affect your flight characteristics. I would also not recommend a direct belly landing because all of the shock would be directly transmitted to the fuselage...which is not ideal. I would try to create a form of skid system similar to that of a helicopter using reinforced composites. That way you get the best of all worlds. You get the shock absorption that you need, the ground clearance you would need for the antennas, you would reduce the aerodynamic drag of most other systems, and your would still be able to land with both positive forward motion and zero forward motion conditions. Hope that helps.
Not sure if it'll work, but the first thing I thought of was one of the water-landing planes with pontoons on the wings, so it lands with 3-points down. That way you'd land on the belly with most of the force & have the pontoons to hold you level and protect the antennas, but I'm not sure how well they'd work on surfaces other than water.
Good luck!
Is there any reason in particular that you are interested in a belly landing and not a set of gear? Also, what media are you planning on landing on? I am assuming that you are going to shoot for grass but I want to make sure.