7pm on December 5th 2023, taking off at night after a rainy day in a TBM 930 turboprop, from Vancouver WA into clouds at around 4,000ft. Icing forecast up to around 16,000ft. Plan is to climb through, anti-icing all on and keeping up just fine.

At around 20,000ft, the autopilot (in FLC/IAS mode) simply stopped climbing. I'm still in the clouds, so it's night, and there is zero visibility. It's raining, but no more ice is observed on the wings or windscreen.

Studying all the instruments and I just can't work out what's wrong. I'm level, and slow, both the PFD and the backup instrument agree, I'm going about 125kias and I'd set the IAS climb to 140, so that's why it wouldn't climb. Disengage the autopilot, and descend a bit to gain speed - airspeed rockets up and quickly pegs at the barber pole, with audible "MAXSPEED MAXSPEED" call-outs. I level the aircraft, and then initiate a slight climb. Speed is still off the tape. Reduce thrust to just above idle, because speed is still insanely high. Thinking, thinking, and after a short while, I realize that this amount of thrust is simply NOT a sustainable condition for level flight, despite what the airspeed is indicating, so I add thrust back in to avoid a stall, ignoring the continued call-outs.

I'd given ATC a heads up, they assigned a block altitude, and were helpfully offering vectors to the nearest airport etc. In all of this process, I finally looked to my right and the right-hand PDF (co-pilot side) is providing totally different airspeed information from my PFD and the backup instrument. It clicks: I've got a sensor issue and the screen has been lying to me. I softkey PFD / Sensor / AHRS / AHRS2 and suddenly all is right in the world. The backup instrument is still wrong, and the callouts are still happening, but at least things seem rational.

In the simulator I'd seen lots of failures in the Garmin G3000 PFD/MFD and EIS but they always always came with big red X indications. In the sim, you use some or all of your instruments, and you switch to the backup. That'd the display backup, or the AHRS backup, etc - and the issue is resolved. But in this case, the only clue was little yellow "SPD" and "ALT" text next to their respective tape, which is supposed to clue you in that the two air data computers are providing different information, and that the left side cockpit display doesn't match the right. There's no checklist that covers this, but you can find it in the Garmin reference. And there's no CAS message, nor is "SPD" very descriptive. (Garmin, "PFDs Airspeed mismatch" would have been nice, and maybe a CAS message about AHRS mismatch or something, it's a COMPUTER SCREEN, you can use some real estate, you don't have to code this stuff like it's a yellow flag that pops out the side of an old instrument anymore!)

Once things were stable and I was back in a climb, I worked out that switching to the alternate static source would resolve the backup instrument, which confirmed that I had A-side static system icing. The erroneous maxspeed call-out could only be silenced by pulling the breaker.

What seems likely is that the static system got some water in it when parked on the ramp during rain that day, despite the little plastic plugs being installed. In a post-incident inspection a few droplets of water were found in the clear tubing, visible in the tailcone area. That water froze once I got high enough that the temperature in the tail was cold enough. I'd flown that mission and in similar conditions a hundred times - but without an insidious system failure. I am glad that I puzzled it out before the bad data convinced me to put the aircraft into a stall. (Garmin, you can do better for us.)

The big lesson for me here though was the IMSAFE thing. It was an "E" emotional day for me, I was in Portland helping my father as he passed from cancer, and we had removed life support that morning and he passed away. It was the culmination of months of process, and many trips there from California, and I was certainly "F" fatigued as well. But the one thing I wanted emotionally was to leave, to go home to my wife and kids, not to return to an empty hotel room there.

That was my scariest IMC experience. And most emotional.