Aft swept wing loading

[george27]

Quick question:
I understand that in aft swept wings the load is higher on the inboard portion of the trailing edge than on that of the leading edge. Whilst this intuitively makes sense, I can't really explain to myself why and would be thankful for clarifications. I am also unsure whether this effect is more to do with the geometry or with the fact that the load on a wing is not uniform.

 

[rb1957]

haven't heard that before ... depends what you mean by "loading" ... with 2 seconds thought i can't see why the air load would be higher on the inbd, but the structural load would be higher inbd as the outbd aero. moment twists the inbd wing ... maybe ??

 

[Andries]

Hi George27,

If you mean that the internal loading of the rear spar is greater than for the front spar the reason is probably that with a swept wing the rear spar, being the shorter, stiffer element, and, therefore, load path, will experience larger internal loads than the front spar.

Regards

Andries

 

[george27]

I'm sorry, I didn't phrase the question very well...
I did mean what Andries said, i.e. that the stresses developing along the rear spar (not the edge!!) are larger.
Thanks a lot for the explanation Andries, it makes sense now!

Regards,
George

 

[rb1957]

except the rear spar isn't particularly shorter (or stiffer) than the front spar ... i think it's more to do with the CP being further aft compared with an unswept wing, and this increases the torque on the wing box; the couple opposing the normal force on the front spar and summing on the rear spar.

 

[george27]

Thanks for your reply.
Wouldn't that mean that the resulting aerodynamic force acts at a point further aft, in which case the rear part of the wing box would in fact be more loaded?
(what do you mean by "the couple opposing the normal force on the front spar and summing on the rear spar"?)

 

[rb1957]

yes, compared to an unswept wing a swept wing as the resultant Lift further aft of the wing root (along the 1/4 chord line, which is swept too)