Free flying scale model flight testing: future or fiction?

René Eveleens, Aircraft Systems Department, NLR, The Netherlands
Floris Bremmers, Aircraft Systems department, NLR, The Netherlands

Abstract

The state of the art in aeronautical engineering has been continually accelerated by the development of advanced analysis and design tools. Sophisticated new airflow measurement and visualization systems let the engineers conduct micro- and macro-studies of properties within flow fields on and off the surfaces of models. Knowledgeable applications of these tools dramatically reduce risk and redesign, and increase the marketability and safety of new aerospace vehicles. Arguably, one of the more viable and valuable design tools has been testing of scale models.

Scale models can be classified as “static” models or “dynamic” models. Static models are now routinely used in many applications and roles, including aerodynamic data gathering in wind tunnel investigations for the analysis of full-scale aircraft designs, proof-of-concept demonstrators for radical aircraft concepts, and problem-solving exercises for vehicles already in production. Progress in the technology associated with dynamic model testing in worldwide applications has firmly established model aircraft as a key element in new aerospace research and development programmes.

The trend in research of the dynamics of the new aircraft configurations is the use of free flying scale models. The role of free flying models for the evaluation of new aircraft configurations is therefore expected to be expanded for safe and efficient development of new aircraft concepts. To determine if free flying scale model flight testing is “future” or “fiction”, the Netherlands Aerospace Center NLR works on a Scaled Model Aircraft Research & Development (SMARD) programme. The programme focusses on the following question:

To what extent can scaled flight test results be mapped onto full scale flight test results?

To answer this question NLR develops a 1:4 free flying scale model of its research aircraft, the Cessna Citation II. The paper describes the programme goals and its challenges, elaborates on the design parameters of the scale model, and gives a future outlook of the flight test programme.