Overview
The background of the general topic (multi-functional coatings) was to examine the wear behaviour of multi-functional coatings during real flight conditions.
Lufthansa Airline and Lufthansa Technik as MRO provider fulfilled all prerequisites itemised in the CfP and were an ideal participant partnership to perform the projected flight test program. Lufthansa was an active driver of general clean sky policy topics and would like to support also relevant technical topics regarding this aspect.
Lufthansa Airline operated its fleet world wide amongst others also to Asia and India. Lufthansa Technik as its main MRO provider has access to the aircraft and would cover all technical work packages (i.e. application of the multi-functional coatings supported by the ITD Topic leader, inspection of the coating areas during the test period including documentation of the measurement results, de-application of the coating etc.) most probably at its maintenance facilities in Frankfurt or Munich.
Funding
Results
Executive Summary:
Fuel Efficiency is a core topic in several research and development projects in the aviation industry. Environmental aspects as well as economic flight operations are the key driver for these projects.
One solution to reduce the drag of an aircraft and thereby increase the fuel efficiency is to focus on an optimisation of the aircraft’s surface by applying multi-functional coatings such as “riblets” (also called “shark-skin coatings”). These coatings essentially shall support natural laminarity of the air flow, besides providing the “normal” functions of an aircraft coating such as protection of the sheet metal or composite.
Former research projects have shown that by using riblet surfaces fuel consumption of an aircraft can be reduced by 1 % or more, which offers attractive saving potentials for aircraft operators.
Recently developed paint systems allow for embossing riblet structures directly into the paint itself. No additional riblet layers on foils are needed, therefore leading to a significant reduction of weight for the coating.
For a wide acceptance in commercial aviation, fine structured multi-functional coatings need to have a high durability comparable to those of a conventional coating system. If a fast degradation of the functionality occurs, frequent repairs or repaints are necessary, which significantly reduces or eliminates the cost saving potential of the shark-skin coating.
The project “LH-LHT-RFT— Flight-tests with multi-functional coatings” performed durability tests of riblet coatings under realistic environmental conditions. Intense inspections of riblet specimens applied on two commercially operated aircraft have provided basic data to judge the durability behaviour of multi-functional coatings. The positive results have led to the launch of further projects aiming at an industrial scale application of riblets on commercial aircraft.