Aviation Dictionary
تیر حامل چهارگوش ، عضو اصلی و قوی بال که در امتداد طول آن بوده و شبیه به نردبان است
The main spanwise structural member of a wing made in the form of a box. Tensile and compressive stresses are carried in the top and the bottom of the box beam, and the sides act as webs to give the beam rigidity. The top and bottom of the box beam oppose the greatest loads and are the strongest parts of the beam. A box beam is also called a box spar.