How do you evaluate the structural safety of an aircraft after a lightning strike?
Lightning strikes are a common hazard for aircraft flying in stormy weather. They can cause damage to the electrical systems, the skin, and the internal structure of the aircraft. How do you evaluate the structural safety of an aircraft after a lightning strike? Here are some steps you can follow to assess the impact and the risks.
The first step is to inspect the exterior of the aircraft for any visible signs of damage, such as burn marks, holes, cracks, or dents. You should also check the lightning protection devices, such as static wicks, surge diverters, and bonding straps, to see if they are intact and functional. If you find any damage, you should document it and report it to the maintenance team.
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In my experience as a Maintenance Engineer, I have never encountered a situation where a lightning strike compromised the aircraft's structure. Typically, lightning strikes are dissipated by the conductive paint or skin of the airplane and discharged through static wicks located along the tips and trailing edges. Following pilot reports of lightning strikes, our initial course of action involves conducting visual inspections. During these inspections, we meticulously examine for any signs of burn marks, punctures, surface pitting, or irregularities. Bit tricky with composite surfaces, they do burn at times which then calls for extensive repair and down times. Hope this helps.
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Most cases it does not cause much physical damage to the plane, nor does it compromise its safety. Typically, lightning hits certain parts of an aircraft like a wingtip or the nose. The type and intensity of damage to a plane depend on several factors, including the strike’s energy discharge level. Lightning can cause minor damage to aerials, compasses, avionics, and leave small puncture holes in the fuselage, radomes, and tail fins. In addition, lightning flash, especially at night, can temporarily blind the flight crew. In more severe cases, the incident can result in engine shutdown.
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Visually inspect the aircraft at the Radome on the Nose, the Wingtips, Nacelle, and Empennage. Observe these points for a melt through, and test with a magnet as the strike may have magnetised the components. There will be pits, burnthrough, or small circular holes at the strike points. Depending on the strike severity it may cause rivet damage, showing melting, fastener damage, or even missing parts at the tips. Check the bonding straps for damage. On composite frames, inspect for burnt paint, and other damages indicative of the high heat levels. Test wire bundles for damage, and verify them and the bonding straps as airworthy.
The next step is to test the electrical systems of the aircraft, such as the avionics, the wiring, the instruments, and the sensors. You should use a multimeter, a continuity tester, and a voltmeter to check for any shorts, opens, or voltage spikes. You should also verify that the circuit breakers, the fuses, and the relays are working properly. If you detect any anomalies, you should isolate them and troubleshoot them.
The final step is to perform a structural analysis of the aircraft, using both analytical and numerical methods. You should use the finite element method (FEM) to model the aircraft and simulate the lightning strike scenario. You should also use the damage tolerance analysis (DTA) to evaluate the residual strength and fatigue life of the structure. You should compare the results with the design criteria and the safety factors, and identify any critical areas that need repair or reinforcement.
To ensure a consistent and reliable evaluation, you should follow the guidelines and standards provided by the regulatory authorities, such as the Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA). You should also consult the manufacturer's manuals and recommendations for specific aircraft models and components. You should document your findings and actions, and keep a record of the lightning strike events.
The last step is to communicate with the stakeholders involved in the aircraft operation, such as the pilots, the crew, the passengers, and the owners. You should inform them of the status and the results of the evaluation, and advise them of any precautions or limitations. You should also answer any questions or concerns they may have, and reassure them of the safety and reliability of the aircraft.
The final step is to learn from the experience and use it to improve your knowledge and skills. You should review the lessons learned and the best practices from the evaluation, and share them with your peers and colleagues. You should also update your training and education on the latest technologies and methods for lightning protection and structural analysis. You should always be prepared and proactive for the next lightning strike event.