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Subscale Flight Testing

Subscale flight testing (SFT) is a mean of allowing a design team to evaluate the free flight characteristics of an aircraft design prior to building a full-scale prototype. It is a convenient way to investigate extreme, high risk portions of the flight envelope without exposing a pilot to risk or to danger an expensive prototype aircraft. There are several recent examples of this:

  • McDonnell Douglas X-36 (NASA funded)
  • Rockwell HiMAT
  • Saab UCAV
  • NASA X-43A-LS
  • Gulfstream Quiet Supersonic Jet.

In all cases the configurations are highly unconventional and thus there is a desire to demonstrate the configuration's feasibility without the cost and risk of a manned, full-scale vehicle.

The testing of subscale free flying models is not a new concept. Particularly for high risk testing such as high angle of attack and to study departure modes, the restrictions imposed by a rigid connection as in the wind tunnel has been prohibitive. Spin models for updraft wind tunnels have been a standard practice since the 1940s and remotely controlled drop models from helicopters have often been used to complement spin tunnel testing. Free-flight models have also been built for conventional wind tunnels, such as the NASA Langley Free Flight Facility. Also for fighter configurations, drop models have been widely used; recent examples being the X-31 and F/A-18E/F. Subscale drop models of space vehicles, such as the Lockheed Martin X-38 and Japanese HOPE-X, have also been employed. Recently the usage of subscale flight testing has been extended to civil aircraft such as the NASA AirStar research program, where a scale model is used to explore a larger then normal flight envelope for a civil transport aircraft. For the Blended Wing Body concept, the X-53 project from Boeing and NASA is currently using a scaled model to demonstrate the concept and obtain more data without going to full scale.

All the above mentioned projects are fairly complicated from a university perspective. The approach at Linköping University was to investigate what can be achieved with more common university funds and within educational programs.


The Test Fleet

Currently the flight line at Linköping University comprises:

Beside this research SFT models, there is a plenty of in-house developed subscale aircraft demonstrator designed and build during tour advanced aircraft courses. Up to today, students have developed ca. 20 different demonstators including flappping wing designs (flies like a bird), variable wing geometries, solar power aircraft, fuel cell propulsions and general aviation jet models. During this courses, the students make the holistic approach from the first sketch, via conceptual and preliminary design up to the detail design, the manufacturing and -after many hours spend on the PC and inthe laboratory- the maiden flight of the own devloped aircraft.

Page manager: david.lundstrom@liu.se
Last updated: Thu Jul 04 17:18:42 CEST 2013