About twenty years ago ...
Departed K017 late in the afternoon on Father's Day with 3 pax in a 172 that was down to about quarter tanks, so we were OK on CG & gross.
On departure at the far end of the runway, about 300' AGL, the engine power came back to 1600 or so and running rougher than a cob. Thankfully, airport is a "carrier" strip on a hill over town about 800' above average terrain, so I had some time to think.
Switch from both to left to right and wait a few seconds. No help. Switch both to right, both to left mags and wait a few seconds. No help.
Pull full carb heat, wait a few seconds. No help.
Squawk 7700 but I'm so far back up in the hills they have to pipe in sunshine. Called Unicom and told them to have an ambulance waiting on the little mountain "freeway" we are on.
Lined up on the freeway, came to WAY above best glide about 100 AGL to go over the cars to indicate that we were in trouble. Most of them stopped. One didn't.
Clapped out Datsun with three kids in the back seat, I could see their eyes getting bigger and bigger. Amazing what you can see under these circumstances.
Pulled out of the center lane into the passing lane to miss the Datsun -- kids didn't pay for the ride, I did. Took the wing off on the bridge overpass, airplane turned over, and four of us scrambled out. Two casualties. One video camera from the guy in the back seat (still have the video, all the way to impact) and my watchband, busted all to hell.
Kindly old FAA guy came out the next day when we had the carcass dragged onto the airport. We were trying to figure out what happened when he said words I'll never forget -- "If you guys figure it out, let me know."
Figured it out a few hours later ... single mag failure followed by multiple spark plug failures (long story, lead fuel involved).
The NTSB, in its infinite wisdom (LAX89LA221) came to the conclusion that it was improper maintenance. NOTWITHSTANDING the fact that I sent them the aircraft logbooks AND my personal notes showing when and where not only were the required inspections/maintenance performed but the manufacturer's own documents with annotations as to when the (not required) service bulletins were complied with.
If I am ever diagnosed with a terminal illness, I'll go back and raise holy hanna about this conclusion. Right now, if I did so, I'd probably stand a hell of a chance losing not only my IA, but my A&P as well while they "sorted it out" with glacial speed.
Miserable bastards, they are.
Jim