What would happen if lightning hit one of our planes while flying?

[kontiki]

Not really. Lightning protection paths need resistances of a fraction of a miliohm to ensure minimal resistive heating for the typical 200,000A currents encountered during a strike.
Conductive paint is good for antenna ground planes and HIRF protection (copper mesh is still the gold standard), but otherwise it will just turn into plasma when that kind of current goes through it.

A layer of metallic paint is in fact a required covering on some large transport aircraft components like flap fairings and the like. We used to get a lot of support requests for assistance with P-Static write ups. One of my coworkers bought a Dayton Granger Electrostatic test set for a radome project he was working on. I had also seen one in use at Pax river on the P3 when I worked civil service. We made the connections and had a lightning guru come out and show our avionics folks how to screen an airplane. One of the problems we found was that the people overhauling our flap fairings were not following the CMM manual for repainting the fairings. They skipped the layer of conductive paint. See -> https://daytongranger.com/products-lightning/edts10-843/

In fact this guy came out and trained our guys-> https://jdchapdelaine.com/charginginflight.htm

 

[Bell206]

Conductive paint is good for antenna ground planes and HIRF protection (copper mesh is still the gold standard), but otherwise it will just turn into plasma when that kind of current goes through it.

As mentioned above, there are specific metallic paints used for lightning protection on various aircraft. However, in the case of main rotor blades the paint tends to erode over time and it loses its conductive abilities. Which led some OEMs to add metal mesh to the blade production process or use the leading edge metal erosion strip as the grounding path.

 

[Velocity173]

<sotto voice>ahem, DA20...

The DA20 still has some protection designed into it under part 23. It just doesn’t meet the more stringent protection under IFR because of its composite (non mesh) airframe. Just like the helicopter I fly. It’s VFR only but still has part 27 requirements for lightning protection. Is going to get through unscathed? No, but it shouldn’t come from together either.

 

[kontiki]

Not really. Lightning protection paths need resistances of a fraction of a miliohm to ensure minimal resistive heating for the typical 200,000A currents encountered during a strike.
Conductive paint is good for antenna ground planes and HIRF protection (copper mesh is still the gold standard), but otherwise it will just turn into plasma when that kind of current goes through it.

I get involved with lightning questions on the job every once in a while. I cover 10 hour shifts in a cube on avionics engineering fire watch. This thread motivated me to do a little review. I've seen presentations that modeled the transmission of lightning through the skin of an aircraft as skin effect transmission. Doing a little surfing, I found lightning is a broad band electrical discharge with a frequency anywhere between 20Hz and 3GHz. Also out there, skin effect transmission starts to become significant somewhere around 350Hz. And, skin effect tends to increase the resistive heating because it effectively reduces the cross sectional area of a conductive path. Also it makes sense that Gigawatt power on a conductive coating that's maybe 0.010" thick, would no doubt be immediately vaporized. I did have Copilot show me the calculations and work up numbers, they seem plausible, I didn't check them. The broadband noise characteristic is the principle strike finders are based on. There's web sites devoted to that and DIY lightning detectors.

I do recall using a Simpson meter and a Wheatstone bridge to check the bonding of a fuel shutoff valve after installation way back. I think it was on an old 727-100. I really can't remember the process, I'm guessing the meter was just a power source. Did again, much later with much more modern equip on A300 fuel tank access plates after closing.

Not ground breaking stuff but a fun little distraction on a slow night.

 

[Crashnburn]

Back when i was very active in my training, I was blessed to have attended a presentation by Bruce Fisher. It was put on as part of an early FAA Wings program at my local field (KJGG), back when that program was first getting kicked off. Anyway, it was a fascinating lecture

F-106 Delta Dart NASA Lightening Strikes

Read the history of NASA Lightening Strike research using he F-106 Delta Dart Ultimate Interceptor as it serverd for 30 years in NASA projects.

www.f-106deltadart.com

basically they purposely flew into T-Storms to see what would happen
probably lots of other info on the study they did out there too, if you search for it...
The strike enters at whatever point and exits at some other point. The takeaway as I recall it anyway, was that mostly it's a non-event but sometimes stuff happens
One photo he had in his slideshow I remember clearly. It wasn't part of their study, just some side research or examples that he had. It was the leading edge of a small GA aircraft that had been hit on a wingtip in flight. The lightning got into the nav light power wire and traveled out the opposite wingtip. The magnetic field generated in the wire (look up "right-hand rule" if you're not familiar) collapsed the wing's leading edge. Basically...you know how the curve looks on the leading edge? To simplify, call the cross-section shape a half circle, right? Convex. Well, the newly modified wing was the same except it was concave! Apparently, the plan landed safely.

A personal story that I've often wondered about how this would apply to GA aircraft.... especially now with all the microchip stuff we use now...
When I was a kid, I was fishing offshore with my dad in his little boat, a 23ft Penn Yan flying bridge. We found ourselves inside a little thunderstorm. Visibility from the inside helm was just about to the bow of the boat. We were motoring at idle speed...flashBANG. I was standing in the cabin at the open door with rain splashing on my legs from the rain. I felt the electric buzz...like licking a 9-volt battery
Everything in the boat shut down...nothing worked... but we were still floating. So we dropped the anchor till the rain passed. Then started fishing again until someone happened by to tow us in.
Found out later that it had struck the top of the CB radio antenna. Everything electrical on the boat that was powered on was either burned up or literally a melted pile of goo. Lights that were switched on, the electronic ignition module, the windshield wiper motor, etc. Everything electrical that was switched off was still ok after we got power back.... every light, the other windshield wiper motor that was off, etc... So it got into the electrical system and traveled everywhere. I've never understood though how the little DC switches used to control the circuits that we off had enough interrupt rating to save those devices.

Mostly because the closed switches allowed all the energy to flow through them, and not enough voltage was developed from the closed switches' IR drop to jump the open contact gap. It probably would have been a different story (in that all of the equipment would have been fried) if all of the switches had been open.