The most recent civil aircraft dominantly use composite structures such as in the ailerons. However, airworthiness authorities raise concerns about lightning strike damage and repairability if the aileron is made of composite material. Today, aerodynamic profiles of aircraft wings become more complex and challenging for designers who need adequate space to fit conventional “torque box” designs inside the wing surfaces. The aero-surfaces may become too shallow and curved in the trailing edge side of the wing which is highly exposed to edge impact and lightning strike damages. This paper presents a new design concept for Carbon Fiber Reinforced Plastic (CFRP) External Trailing Edge (CETE) structure for the trailing edge of the ailerons. CETE is attached to the main aileron torque box where the main load carrying composite spar, ribs and panels are located. The design objective of the CETE combines various important features such as better strength characteristics against lightning strike and edge impact, and easier repairability with a lighter aileron. This paper also discusses recurring and non-recurring costs and monetary benefits of the new design concept. The CETE concept is as simple as creating a secondary torque box on the trailing edge side of the aileron with two C-section parts; inner and outer parts of CETE. The inner part of CETE provides a secondary spar to the aileron to sustain the main torque box force flows and support the trailing edge panels. The main structural feature of CETE is to form a low loaded zone by its outer part which is located at the outermost region of the trailing edge where mechanical edge impact and lightning strike damages are frequently encountered. It is revealed during the lightning strike tests that, the resulting damages can be catastrophic and located at the trailing edge line where the metallic strips are located. In case of lightning strike damage on the CETE, the aileron is able to carry loads since the flows in the main torque box is minimally disturbed as the inner part of CETE is still intact while the outer part is damaged. Similarly, the damage after edge impact is trapped at the outer section of the CETE where the loads are minimized by CETE design. In case of a larger damage, CETE can be replaced easily instead of replacing the whole aileron which is cost effective in long term although the initial costs seem higher than the conventional designs.

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