oriol
Well-Known Member
Hi everyone!
I was told by an aircraft structure engineer, that you can consider the loads over the entire wing as homogeneous under the maximum possible load. Although this is not true, it serves to simplify the calculations, and albeit the structure weight would not be the most optimal, the extra weight is accceptable, and above all, the wing will be capable to bear the loads.
On a previous non related thread, I learned about the wing related accidents on the AMD Zodiac. I read an interesting article about that subject, in where the author came to the conclusion that:
"The FAA report, which is written in a colloquial style and is accessible even for lay readers, may be found online at faa.gov. What is interesting about it, apart from the details about one particular aircraft, is the general sense one gets that airplane design, at least at the LSA level, is not an exact science. Graphs of design wing loadings, in particular, display shockingly large disparities between the manufacturer’s assumptions and the feds’. Since the 601 is the work of a reputable designer and is produced by well-established firms, one has to suspect that if the FAA conducted an industrywide investigation of LSAs and homebuilts it would turn up a whole lot more of the same kinds of discrepancies."
In the glider book, Stelio Frati advices to size the wing according to the load distribution in different cases (maximum lift, maximum speed, zero lift and hard landing). He never talks about about an homogeneous distribution of lift, in fact he provides different graphics of lift distribution in 2d, but perhaps it is because he is designing a glider, and any bit of extra unnecessary weight is too much.
I assume that LSA manufacturers, in order to achieve a minimum weight penalty, perform more sophisticated calculations than the homogeneous lift distribution, but it shocking that the calculations from different engineers differ greatly.
In any case, are we safe as homebuilder by using the homogeneous lift distribution method?
Thanks for your replies,
Oriol
I was told by an aircraft structure engineer, that you can consider the loads over the entire wing as homogeneous under the maximum possible load. Although this is not true, it serves to simplify the calculations, and albeit the structure weight would not be the most optimal, the extra weight is accceptable, and above all, the wing will be capable to bear the loads.
On a previous non related thread, I learned about the wing related accidents on the AMD Zodiac. I read an interesting article about that subject, in where the author came to the conclusion that:
"The FAA report, which is written in a colloquial style and is accessible even for lay readers, may be found online at faa.gov. What is interesting about it, apart from the details about one particular aircraft, is the general sense one gets that airplane design, at least at the LSA level, is not an exact science. Graphs of design wing loadings, in particular, display shockingly large disparities between the manufacturer’s assumptions and the feds’. Since the 601 is the work of a reputable designer and is produced by well-established firms, one has to suspect that if the FAA conducted an industrywide investigation of LSAs and homebuilts it would turn up a whole lot more of the same kinds of discrepancies."
In the glider book, Stelio Frati advices to size the wing according to the load distribution in different cases (maximum lift, maximum speed, zero lift and hard landing). He never talks about about an homogeneous distribution of lift, in fact he provides different graphics of lift distribution in 2d, but perhaps it is because he is designing a glider, and any bit of extra unnecessary weight is too much.
I assume that LSA manufacturers, in order to achieve a minimum weight penalty, perform more sophisticated calculations than the homogeneous lift distribution, but it shocking that the calculations from different engineers differ greatly.
In any case, are we safe as homebuilder by using the homogeneous lift distribution method?
Thanks for your replies,
Oriol
