Updating my plane’s very old GPS data in a very modern way

No, you toe that line very carefully. You do mention removal (not sure if removing sleds is actually OK, I'll defer to you there, but in the general case avionics installation/removal is not OK), never mention flying on it, or quite explicitly state that this modification is legal. You just state that you have "a nice IFR-certified GPS" (not after this procedure you don't), and state that this procedure is "third option" to a legal-but-expensive service by a certified mechanic or illegally hacking in a connector for the official installation utility.

Again, to be clear, doing the mod is legal(-ish, probably violates DMCA but who cares). Flying IFR on it is not. Pulling and installing your own avionics is not. Flying VFR on it is... questionable, but not likely to end poorly.

This whole thing has giant red "DANGER" signs all over it and you should be making it very clear what the exact bounds of the law here are. Selling unpopulated PCBs is treading very close to the edge, that's farther than I would go personally. Selling finished units would definitely be over the line, you would certainly have liability if something happened to an aircraft because of your device. You need to be very clear about the fact that this database is not legal for IFR and the other caveats involved.

Again, I think the actual risk here is low for VFR flight, and I also think you got your reverse engineering correct and checked your work. But from the FAA's perspective: what if you actually did fuck up the reverse engineering, in-flight the unit hangs in a loop, overheats, and starts a fire in your cabin? That's not the perspective HackerNews likes to take, but it's the perspective the FAA does its regulation under. After all, until like 2012 you weren't even allowed to flash your own GPS database, you had to have a mechanic insert the connector and doubleclick the EXE for you. They are not DIY friendly people.

I don't think they'd be OK with a user-upgraded DB that was not done through an official installation tool. I think it's legally dubious even having that card installed in your aircraft (regardless of actual risk), flying IFR on it is right out.

Everyone in this business is 'more Catholic than the Pope' for a very good reason. Almost every single one of the rules we find so restrictive is so restrictive because it was bought and paid for with someone's life -- and often the lives of the innocent who trusted them as well.

Being certified and claiming to others to be certified is a promise. It's a position of trust in much the same way is anyone with a licence to practice medicine and who actually does practice is trusted.

We guard the system so jealously because have to trust in the system. Without it, it's far too dangerous for any rational person to even consider stepping foot on a plane or in an emergency room.

There's a reason for that. Quite a lot of people in this business end up splashed all over terra firma. Like I literally guarantee anyone who's an active pilot knows someone who has died or had some really fucking close calls.

I grew up in a house that's adjacent to a small grass airstrip. You walk across a grassy field for 50 feet and around a barbed wire fence, there's a barn on your right that opens onto the airstrip. The guy who owned that barn died when the wing fell off his buddy's ultralight down in Florida. Now it belongs to his kids and they're keeping some construction equipment in there until it finishes decaying and falls down.

My dad belonged to an aviation club at a municipal airport (different from the grass strip) with four aircraft for about a decade when I was a kid. I can remember no less than three major accidents.

Once, the mechanic was changing the oil and stuffed a paper towel into the oil drain cock to catch those last annoying drips of oil that gunk up the cowling. He forgot about it and it held well enough for the pilot to make it off the ground, then popped loose. She saw the oil pressure gauge drop and decided it was a bad gauge and proceeded on. She made it about 30 miles and seized the engine, then put it down on Milford Proving Grounds.

Another time, a club member was making a night approach into Lansing and got a little low. Apparently he noticed that the runway lights were starting to sparkle, and that's when he clipped the tree canopy (low-wing aircraft). He jerked the yoke back and floored it and managed to climb out. Thanks to the adrenaline rush he made the worst decision of his life. He called the 24/7 staffed tower at a mid-tier international airport with fire rescue service and requested direct clearance back to his home-field where the tower had closed at sundown, without mentioning that he'd flown his plane into a fucking tree. On the hour long flight back he had some time to cool off and think about it, which turned out to be the best decision of his life. He realized how totally fucked he was flying at night with a derelict aircraft into a municipal airport with no tower and no fire service, and started thinking. He reckoned that since he'd been doing 75 knots when he jerked the yoke back, the aircraft would be flyable at that speed. So his plan was to fly it all the way down to the ground at 75 knots. Turned out to be a great decision - a Piper Archer normally lands at 50kts, he flared at 75 kts and the aircraft fell out of the air onto the runway. When he could get some lights on he saw that he'd knocked several feet out of the leading edge of one of his wings. Repairable, the club fixed it and eventually sold the airplane.

Much simpler one, someone fucked up and ran the plane out of gas and parked it in a cornfield. That's the good kind of accident, everyone involved is real happy to walk away and come hire a trailer to come and get the plane.

That includes the FAA. To be brutally honest the FAA is the poster child of a cooperative regulatory agency. If you make an oopsie and have an accident, you come clean and tell them what happened. They track all that shit, they have probably the world's most accurate picture of the kind of accidents that happen in their field. They know everyone is human and mistakes happen, if you come clean and weren't grossly negligent then you are likely to walk away with a "this is a life lesson: do better next time". Or maybe some remedial flight training if you were a total knucklehead. But if they catch you doing something like modifying your avionics or pencil-whipping your maintenance logs they will come down on you like a fucking ton of bricks and you will never again set foot on any airplane where the flight attendants don't do a song-and-dance before takeoff.

I myself had a semi-close call when I was a kid. We had a father-son outing where my dad flew me, his instructor, and his instructor's kid across the state to a really cool aircraft museum attached to an airport (nowadays they have an SR-71). On the way back they noted the oil pressure was getting a little low, topped it up, and marked it in the log. The maintenance guy took a look at it. Cracked crankcase, don't remember if it was major service or a new engine. Could have been a problem if someone else had flown it for a couple more hours before us and hadn't noted it. That's the kind of shit that gets you if you're not careful about it. One pilot - not even the pilot actually flying the airplane at the time - making an oopsie at a bad time, or in too much hurry to mark that they added some oil in the maintenance log, and that could have been it. You're fucked if it seizes on climbout - and that's when you're pushing the engine hardest.

Ever heard the saying? There's old pilots and there's bold pilots, but there's no old, bold pilots. The truth is the FAA is just the hired gun here. Around good pilots - nobody pencilwhips the logs because if that's the norm then next time it might be them, or their buddy. The FAA rules are there for a reason, hard learned reasons, and airmen don't want to kill each other either or the public. The risks of flying around a several-ton missile full of fuel at 100kts are absolutely palpable in this hobby. A good airman will drive the plane down into the ground rather than hit something that might have people in it. That could be you or your friend.

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It's kind of sad because I know the airstrip is toast as soon as the 85 year old who owns it croaks. His son is raring to sell it.

On the other hand once I got to see someone bring this CASA-212 twin-engine cargo plane into this tiny grass strip, turn around, and do a takeoff. Must have been someone on their checkride - spec sheets says the plane can do it, so let's see it. Damndest thing I've ever seen, I wish I had video.

http://www.jetphotos.net/showphotos.php?regsearch=N687MA

Jack Roush (the racecar driver) also used to buzz the airfield in his T-6 Texan and P-51 Mustang. We would always run out and watch, and one time he landed and asked if it was cool if he buzzed the runway and we were like "hell yeah!?". Then our asshole neighbors who unknowingly bought airport-fronting real estate got butthurt because he was waking up their infant and reported reported him to the FAA for doing low level acrobatics. He got a suspension and never came back again.

Not strictly legal with the license he had, and that's how the FAA plays the game. He stepped over the line and he got slapped for it. But he wasn't really being dangerous and it was so cool to see, he'd dive and come by 30 feet off the deck, then do a sick climbout, maybe with like a roll or something. One time we heard him make a pass and then rushed my grandma out without telling her what was happening, and he came by and gave her the scare of her life. I miss you buzzing the field, buddy, come land again and say hi sometime :(

Another time, my sister and I witnessed a plane crash. Living next to an airfield you get a sense for how fast a plane needs to be going to take off. I saw this Cessna come by way fucking slow. Like probably 30mph, 150 feet from the end of the runway, on the ground. There's a point on the runway called V1 where you're committed , usually below the speed where you can take off safely, so you're in it for the long haul. There's a displaced threshold on that runway because of a gigantic fucking tree 50 feet off the end of the runway. This guy was way below where he needed to be, he was fucked, and he realized it, and he pushed it back onto the ground, jammed the brakes, and swerved into a field of soy (60 ft wide with a busy road on the other side). Clipped a wingtip (high wing), torqued it around 270 degrees, and ripped one of his gear off. But it was the good kind of crash. He walked away and the trailer came and picked up his plane.

We'd sometimes get Blackhawks from Selfridge ANGB and shit in the middle of night practicing their rustic-site operations. Never knew what you'd get, really. One time 7-year-old me helped launch a hot-air balloon that had decided to ride out some inclement weather on our field.

But yeah, in 10 years tops it'll all be a subdivision because the son of the owner is chomping at the bit to sell and develop that shit, since it's several hundred acres of woods with several lakes included. Used to take my dog running down the twotrack and see the lakes. 25 years ago a tornado ripped all the siding off the only permanent hanger and threw it into a tree, and it's only been getting worse since. The owner hardly ever plows the field anymore (used to use a vintage Korean War Deuce-and-a-half to plow and roll). We've been the ones who do the mowing for quite a while now. All those moments will be lost, like tears in rain. At least my parents tell me that they're filming a Netflix movie called "Crystal" there (production codename?) so I hope it will be immortalized.

https://en.wikipedia.org/wiki/GMC_CCKW#/media/File:GMC_2_Hal...

I should get a drone and do some flyarounds for posterity. I used to fly R/C airplanes there all the time, we get a landing like once a month nowadays and I'm 100% willing to trash the R/C airplane to avoid hitting a real plane if it comes down to it.

He has added an interesting disclaimer "Please note: I am in no way saying that you can, should, or are allowed to fly with a card updated in this way (even though the bits in it are identical). I am not claiming that I plan to or am flying with such a card. All experimentation was performed on a card and a GPS that is not used for IFR flight."

Also author appears to have commented on this thread with a similar disclaimer. Very neat hack, but yea, walking a very fine line with the relevant aviation authority :(

Because it's not just you reading this?

I found the reverse engineering part interesting too. Like I said, it's incredibly well done. But it's also legally problematic and anyone reading this should understand the risks they are taking. Fighting an FAA enforcement action will be far more expensive (think 5 figures) than just paying the money to do it the legally correct way. If someone does it wrong it might cost them their life (see paulmd's comments above).

Pilots operate in an complex regulatory environment and things that may seem okay from the outside are not okay to the government. It's so complex that otherwise well meaning and law abiding pilots each year run afoul of the various regulations, and there are few legal protections afforded to pilots facing an enforcement action. A good example of this is the relevant FARs about reimbursement for business expenses when flying yourself. They're not the same as driving and being caught breaking them could cost you your certificate.

Whole books are written about aviation law and attorneys specialize in it. And all pilots are expected to be familiar with them. But the devil is in the details, and that's where they'll get you,

He says he didn't put it in his plane, so he's fine. And it was a super interesting technical read. But others reading this need to understand the ramifications of doing this or something like it to an actual airplane is just asking for problems.

I think this conversation is kind of orthogonal to the actual issue, which is that setting up the hardware to shift 32 signals from 3.3v to 5v is pretty easy. I definitely wouldn't consider it a "major pain." Interfacing parts which use two different logic levels is incredibly common, and there are many inexpensive ICs that provide bidirectional level shifting.

That being said, I think choosing a microcontroller which uses the logic level you need is a perfectly acceptable solution. Minimizing the number of components goes a long way towards making a project easier to manage.