Natural laminar flow leading edge: Requirements, design, and experimental validation under operational loads

Abstract

To unlock the potential of natural laminar flow aircraft wings, novel structural designs are necessary for the wing leading edge and its attachment. Those designs may not impinge on operability and maintenance of the aircraft. This paper presents a leading edge and attachment design for the natural laminar flow environment as well as the testing of this design on a large-scale ground-based demonstrator. The leading edge design is numerically verified by considering operational loads. For operational viability, the replacement of damaged leading edges without alterations to the spare part is desirable. In a series of tests, such interchange trials are made with two Image 1 full complexity leading edge segments and the aerodynamic step height at the interface of leading edge and wing cover is assessed in both ground and cruise deformation. The leading edge design and its attachment concept were proven to support natural laminar flow step height requirements even under global part deformations of a multi-material structure under thermal loading both numerically and experimentally. Interchangeability of the leading edge is demonstrated with very low mean variation in step height between different installations.