It is very important to know the shape of the model during a test in the wind tunnel for the following reasons:

• To ensure that the model is accurately representing the full scale aircraft.
• To make sure that the geometry of the model under test is known to allow meaningful comparison with CFD work.

Non-intrusive optical techniques have been developed to enable accurate model shapes to be measured when the model is under aerodynamic loads.  ARA has undertaken a series of tests to determine the accuracy and repeatability of this measurement technique.

The tests included static deformation tests undertaken under laboratory conditions together with a wind tunnel test.  The performance of the system was found to be very high and provided data of the required standard.  Typical output acquired during the test is shown above.