Clean Sky 2 Deliverable D1.4.1.4-28 - Impact test campaign progress report on complex HTP Segments

Abstract

The European Union Horizon 2020 Clean Sky 2 research programme focuses on innovative technologies demonstrated on large passenger aircraft. The requested test series supports the maturity of the hybrid laminar flow control (HLFC) technology. It requires a suction technology for the outer surface which is here realised by a micro-perforated metal skin supported by a composite structure and multiple suction ducts in between. The tests with high complexity concerned a leading edge (LE) design at a sub-component level including a HLFC system. The testing was based on two identical LE demonstrators. The loft and size were adopted from the outer horizontal stabiliser segment of the reference long range aircraft configuration with a conventional design. In a preliminary series, several launching tests were performed and repeated over a realistic impact velocity range typical for passenger aircraft. The impact conditions were similar with small margins. The tests were performed back-to-back by artificial and real bird on identical generic leading edges (GLE) to study representativeness and repeatability. In the main test series, the technological maturity of the HLFC design was demonstrated on two full-scale demonstrators. The tests results showed a high degree of similarity and structural integrity. Furthermore, the results represent a comprehensive validation basis for numerical simulations of the impact behaviour, too. The key point of a back-to-back testing by artificial and real bird on an identical structure was fully accomplished. The test boundary conditions plus weight and velocity of the soft body impactors were similar. Under these conditions, it could be shown that no kinetic energy by impact is transferred behind the HLFC leading edge and no disintegration of parts occurs subsequent of the impact. For the artificial bird, the DLR reinforced artificial bird (DLRRAB) in the 3.6 kg (8 lbs) weight class in elliptical shape in the version Mk 2.3 was applied. For the real bird a new way of folding and fixation was applied. These types and preparations of projectiles were kept identical throughout these series. The bird strike safety of the structural concept with all constituents were shown. The boundary conditions for bird strike safety were considered with respect to the initial airworthiness requirements stated in EASA CS-25 but particularly FAA 14 CFR Part 25. This project receives funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. CS2-LPA-GAM-2020-2021-01.