The LCA employs composite materials to realise better
strength-to-weight ratio and avionics systems, such as full authority digital engine
control and digital fly-by-wire flight control systems to perform functions which are
critical from flight safety considerations. Further, the aircraft with improved instrument
fit aims at operating in adverse weather to match the user requirements. All these
desirable features from the performance point of view make the aircraft more vulnerable to
Based on these considerations, a comprehensive lightning protection plan was evolved to
ensure that the lightning hardness of LCA is adequately addressed and demonstrated.
Vulnerable structures and systems in it, such as radome, wing, fin, and rudder were
identified from direct effects point-of-view and have been lightning qualified. Flight
control systems and engine control unit are being qualified against indirect effects of
The nose cone radome houses the radar antenna. The antenna inside the dielectric radome is a major
electric field stress raiser at the front of the aircraft and will always be a potential
lightning attachment point. Unless suitable protection scheme is in place, the lightning
strike will puncture the radome wall and attach to the radar antenna,with the risk of
severe damage to the radar antenna equipment as well as the radome. The protection scheme
for the radome to protect it against the direct effects of lightning has been evolved
through design studies and detailed experimentation. An optimum scheme has been worked out
considering both radar performance and lightning protection .
The radome with the evolved scheme has successfully withstood high voltage and high
current tests carried out as a part of qualification testing.
The high voltage tests proved the adequacy of protection scheme in preventing attachment
to the radar antenna structure inside by puncturing the radome.
The high current tests carried out have verified the adequacy and efficiency of the scheme
while ensuring the structural integrity of the radome.
The wings of modern combat aircraft also serve as integral fuel tanks. In case of
lightning strike to the wing, there
could be sparks inside the wing that may trigger fuel ignition and cause explosion of the
aircraft. Carbon fiber composite (CFC) spars, CFC top and bottom skins are used for wing
construction.This results in a large number of CFC-to-CFC joints and CFC-to-metal joints.
The chances of sparking due to lightning currents across joints involving CFC are more, as
its conductivity is three orders of magnitude less than that of aluminium.
The lightning protection for wings was evolved through detailed studies and
experimentation and considering the critical spars and zones. Towards this, current
distribution in the wing was also evaluated by carrying out high current tests on an
electrical equivalent engineering model of the wing.
As a part of the design of protection scheme, techniques were evolved for realising good
electrical joints of CFC-CFC,CFC-metal and metal-metal.
The protection scheme has been implemented exhaustively in the actual wing based on the
studies as detailed above.
LCA fin and rudder is of co-cured co-bonded composite construction. Lightning protection scheme was evolved
through detailed design studies and experimentation and include metal foils, strips and
mesh to establish good electrical continuity. High voltage attachments test and High
Current tests were carried out as a part of qualification exercise from direct effects of