LBarron
Well-Known Member
I wonder if you guys who have done truss design can tell me if I’m on the right track with my analysis. For my hypothetical airplane (the picture below is not the actual truss) I’ve calculated the 4g internal loads (x 1.5 = red arrows), moments and reaction forces (RF 1 is the main spar, RF 2 is the smaller rear spar). At this point RF1 is roughly five times RF2, and the sum of the Y forces = 0. Good so far. Next I added the maneuvering load down force from the HS, the orange arrow. This increased RF2, so the ratio of RF1:RF2 is now 2:1. Ok, I guess. Next, I added the 4g wing root shear force which is positive (green arrow), and since the force is located at the spar there is no associated moment and RF2 doesn’t change. RF1 did change, and now nets to zero. I did not include inertia force so I suspect the end result will be a slightly positive RF1. Does this seem like a reasonable result?
Also, I recall a comment from Orion where he said in many cases it’s not the flight loads but the landing loads (my recollection, not his exact words) that determine the design of the truss, so in the case of a 4g landing (I believe 3g’s is usually used for analysis) the loads would be the same, right?
Just checking to see if I’ve made any glaring mistakes.....
Thanks,
Leland
Also, I recall a comment from Orion where he said in many cases it’s not the flight loads but the landing loads (my recollection, not his exact words) that determine the design of the truss, so in the case of a 4g landing (I believe 3g’s is usually used for analysis) the loads would be the same, right?
Just checking to see if I’ve made any glaring mistakes.....
Thanks,
Leland
