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Surviving the Invisible Lightning 15:32 Lena: We’ve talked about vibration and interference, but what about the big, dramatic stuff? Like lightning? I mean, planes get hit by lightning all the time, right?
15:41 Miles: More than you’d think. On average, every commercial plane gets hit at least once a year. And antennas are the perfect lightning rods—they’re often the highest point on the fuselage or sticking out from the wingtips.
15:53 Lena: That sounds like a recipe for frying the entire avionics suite in a millisecond.
15:58 Miles: It would be, if not for Section 22 and 23 of the DO-160 standards. There’s this whole manual—ED-158—that’s basically the bible for protecting against the "indirect effects" of lightning.
16:10 Lena: What’s an "indirect effect"? Is that like the "splash" from the main bolt?
0:47 Miles: Exactly. When lightning hits the airframe, the current flows over the skin. But that massive surge of electricity creates a huge electromagnetic pulse—an EMP. That pulse can "induce" currents in the wiring inside the plane. It’s like a surge protector on steroids. If your antenna cables aren't properly shielded or "transient-protected," that surge goes straight into your radio and melts the circuits.
16:39 Lena: So the antenna has to act as a shield and a receiver at the same time?
16:44 Miles: In a way. You use things like "lightning diverter strips" on radomes—those are the little buttons or strips you see on the nose of the plane. They’re designed to guide the lightning strike safely over the surface and away from the sensitive electronics.
16:56 Lena: And then there’s the "Direct Effect," right? Like if the bolt hits the antenna itself?
17:02 Miles: If a bolt hits a standard blade antenna directly, that antenna is usually toast. But the goal of the engineering is to make sure the *plane* survives even if the *antenna* doesn't. You need "lightning protection" that acts like a fuse.
17:14 Lena: It’s another one of those "Survival Rules." You have to assume the environment is actively trying to destroy the hardware.
17:21 Miles: It’s why the testing is so rigorous. They literally blast these things with artificial lightning in labs. And it’s not just one bolt. They test for "multiple stroke" and "multiple burst" scenarios, because lightning isn't always just one hit. It can be a rapid-fire sequence of pulses.
17:36 Lena: It’s fascinating that there’s a specific "Section 21" too, for "Emission of Radio Frequency Energy." So not only must the antenna survive lightning, but it also can't "leak" its own noise and mess with other systems.
17:50 Miles: Right! It’s the "Golden Rule" of avionics: Be a good neighbor. Your equipment can't emit interference that exceeds certain limits. They measure this in anechoic chambers—rooms covered in blue foam spikes that absorb all radio waves—to make sure the antenna is "quiet" where it’s supposed to be.
18:07 Lena: It feels like the antenna is constantly being tested for its "social skills"—does it play well with others, and can it survive a bully like a lightning bolt?
18:16 Miles: (Laughs) That’s a great way to put it. An antenna that’s a "loud neighbor" gets rejected by the FAA. An antenna that can't take a hit gets grounded.