The reason why the F- 15 adopts the conical delta wing airfoil is that the delta wing has great advantages in improving the wing structure and increasing the internal product of the aircraft. At the same time, it can make the drag increase of the aircraft more gentle in the transonic region, and the center of gravity deviation of the aircraft is also small at transonic speed, which reduces the trim resistance.
In order to improve the subsonic performance of the aircraft, F- 15 adopted the fixed leading-edge conical torsion design instead of the leading-edge maneuvering flap which was widely used at that time-this design was mainly considered from the aspects of weight, manufacturing technology and system complexity.
The aspect ratio of the wing is as high as 3, which is beneficial to delay the tip separation and obviously reduce the induced drag of the wing. At the same time, the larger aspect ratio increases the slope of the wing lift line and improves the wing lift characteristics.
This is consistent with the requirements of drag reduction and lift increase in energy maneuver theory. Of course, with the increase of aspect ratio, the supersonic zero-lift drag coefficient also increases, thus increasing the transonic/supersonic wave drag. This shortcoming is compensated by powerful engine thrust and other aspects of design.
The wing structure is a multi-beam torsion box damage safety structure, with the front beam made of aluminum alloy and the rear three beams made of titanium alloy. The lower skin of the internal integral fuel tank is a titanium alloy panel, and the rest are aluminum alloy machined integral panels. The leading and trailing edges, flaps and ailerons of the wing are all aluminum honeycomb sandwich structures. The damaged safety structure of the wing, combined with the load-bearing skin, can support the aircraft to continue flying as long as one spar is still intact, which greatly improves the survivability of the aircraft.