STOL wing loading question

[Geof180]

Good evening all,

I have a little project going on here which requires the estimation of the wing loads on the lower wing skins of a large STOL aircraft.

The actual structure is not needed, I am just using an idealized structural representation using a given aircraft weight, planform, aspect ratio, etc.

I planned on sketching out span and chord-wise cross sections (assuming the "substructure" carries all the axial loads and the skins carry only shear).

Provided I have an elliptical lift distribution, I planned on ascertaining shear flows in each direction through the skins.

Does this seem sound? Or does anyone else have a better plan?

Geof

 

[inertia4u]

My two cents.

Treat the wing as a torque box, accounting for a front and rear spar, and stringers and of course skins.

Consider accounting for additional discrete inputs @ the spars from flaps, slats etc as well as your lift distribution.

Lower skins also typically carry tension and upper skins compression during flight, but if I remember correctly, the torque box analysis will have those loads carried by your "axial" members.

Good luck.

OH, and make sure you use a balanced Free body


-----
Nert

 

[rb1957]

why "large STOL airplane" ? the question is so general that you should ask for "an airplane". STOL imples specialised structure (eg full span flpas) and has special design features (eg low speed yaw control is difficult).

estimating loads/stresses is really pretty straight forward (for someone who does it !) ...
instead of elliptical airload, use trapezoids ... they're easier to work with. the wing is "just" a beam, so it's "easy" to calc the bending moments, etc. assume a simple wing box (a single cell between front spar and rear spar). the wing bending is carried by the wing skins and concentrated elements (stringers and spar chords).

good luck with your project. read up on this in Bruhn.

 

[Sparweb]

"structural loads... structural stresses".... are you actually looking for surface pressure distributions? My first reading through the post left me with the mental picture of chord-wise pressure distribution on a wing at high angle of attack and/or with slats/flaps/etcetera.
Are you looking for aerodynamic or structural data?

Steven Fahey, CET