Is this unairworthy?
It is certainly embarrassing 
I think it may have a tendency to stop in the same place next time you brake hard. That’s what happened with mine. As for airworthiness, I heard something about number of visible ply layers when I replaced mine, but don’t recall the details.
It is pretty rough to even taxi on; you have to taxi slowly. The takeoff is quite exciting…
There is no fabric showing but I plan to change both tyres as soon as I can organise it.
It’s my understanding that the tire is airworthy until you see the first ply but I can’t find a FAR. AC20_97B_pdf however goes pretty much in the same way. Last time it happened to me I stretched it a month or two to do the change at the next annual, mostly because of the pain that it is to get the plane on jacks, but indeed it is embarrassing. Do you know how you did that?
I guess that’s one of the downsides of private ownership, you can’t put the blame on another renter :-)
AC20-97B is the generally referred to doc. A flat spot isn’t unairworthy (unless your maint manual says differently). Doesn’t mean it is a good idea to leave it though.
Few years ago I was a bit nervous on the breaks at LDLO landing downhill towards the sea with some tailwind and developed worse flat-spot (first layer of fabrics was visible). I replaced it immediately after coming back home.
Which brings the question, when you are changing tires has anyone established an easy way to balance them? I know the standard is not to balance them. I’ve been looking at YouTube videos and it seems like it can be done….
You just have 1/6 chance to land on that patch again with same crosswind again…
Mine from last year. It started with an insignificant flat spot and then took a couple of attempts to vacate via first taxiway to develop further.
I am having the one flat-spotted tyre changed.
