(Photos: Ajai Shukla)
Tejas LSP being prepared for a Structural Coupling Test)
Here’s one of the LSP Tejas fighters undergoing the Structural Coupling Test. Structural coupling is the disturbance that is caused by the flexibility in a fighter’s airframe to the aircraft’s inertial sensors. The frequencies that are generated by vibrations in the airframe structure interfere with the frequencies within the Flight Control Systems (FCS). If these frequencies are not neutralised (by introducing phase delays, or by dampers) they can cause serious malfunctions in the flight control systems of modern fighters.
The Structural Coupling Test involves suspending the aircraft by the flexible hangers that can be seen in the pictures. Then the airframe is made to vibrate in the manner in which it would during actual flight… and then the avionics sensors are checked one by one in order to see how they are responding.
Basically, the Structural Coupling Test Facility checks whether the airframe frequencies have been sufficiently neutralised or not.
Incidentally, the two-seater version is about to be taken for this test in a month or so.