In case of emergency, it can be de-linked and jettisoned

A team of scientists from the Fatigue and Fracture Laboratory and the Advanced Seismic Testing and Research Laboratory, CSIR-Structural Engineering Research Centre (SERC), Chennai, conducted a crucial qualification test of the fuel drop tank of the Tejas Light Combat Aircraft (LCA).

The laboratory designed and developed the test in consultation with the Aeronautical Development Agency (ADA) and Hindustan Aeronautics Ltd. (HAL).

The LCA has been developed, designed and sponsored by the ADA and produced by HAL.

P. Gandhi, Chief Scientist and Head of the Fatigue and Fracture Laboratory, said the drop-tanks are attached to the aircraft externally and in case of emergency they can be de-linked and dropped, which gives them the name. The aircraft has other fuel tanks inside.

The 1,200 litre fuel drop-tank of Tejas needed to be qualified for sloshing of fuel when it is two-thirds full and vibrates during any air turbulence simultaneously as a mandatory requirement.

The test was carried out according to ‘U.S. Military Standard’ specifications and to prove that manoeuvring during flight would not be affected due to the sloshing around of fuel and additional vibration.

The tests were carried out using a specially fabricated test fixture, where a mechanical shaker mounted at the top vibrated the fuel tank to a specified frequency, and similarly, a computer-controlled servo-hydraulic actuator pitched it to an angle where the fuel would slosh.

The drop-tank made of glass fibre reinforced plastic composite material, withstood 25 hours of sloshing and vibration and 15 hours of only sloshing. These crucial tests are a final operation clearance requirement for enhancing the tank life to 3,000 flying hours and to obtain full certification.