Intermittent Issue with IAS/IAS Prof
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I'm trying to narrow down how to reliably reproduce it, but I suspect it has to do with being within 1000ft of a target altitude and/or ALTS mode.
I have had an issue intermittently on several flights with 1.1 (and maybe 1.0, as well). I will engage IAS mode while climbing, however the FD/AP will simply level the aircraft instead of climbing and let the speed increase from the set target. I believe it has happened when I have been nearing an initial assigned altitude after takeoff, right around capture, before increasing the target altitude and engaging IAS/IAS Prof to climb to a higher one.
After takeoff at KBNA my last flight, I had 4000 as my target altitude. I took off in HDG/GA mode, and around 1000ft or so I switched from GA to IAS. While I was sorting the vectors to my first RNAV waypoint, I crossed 3000ft, which reminded me to increase my set altitude from 4000 up to 15000.
IAS showed engaged, but I discovered that the aircraft was not climbing, and the speed was increasing over my set target of 180. I fiddled with several modes, but I needed V/S mode to get me climbing again. Initially, this was just the FD, as I was hand flying, but of course when I engaged the AP the issue persisted.
While climbing, I was messing with the target altitude in order to try to solve the IAS issue and get it working right again, and I heard the chime as it approached my then setting of 12100. I increased the altitude again, and this time when I engaged IAS it started working properly. I'm about to do a second flight and see if engaging/reengaging IAS around altitude capture results in the same issue.
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Just had it happen again, again on the first flight. I was cruising at only a few thousand feet, surfing under a class B, climbing slowly in VS mode. I cleared the Bravo and switched to IAS mode, and she leveled out on me and stopped climbing.
Maybe it has to do with having a preset speed set before first engaging it? I dialed in 220 knots on the IAS gauge before switching from VS to IAS mode. When I turned off the selection on the IAS gauge and then enabled IAS mode it started working fine.
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That's it! I can repeat it. I was cruising at 13500 and set my new target to 15500. I engaged VS mode with a token 500, then dialed in 200 knots and engaged IAS. She leveled out on me.
@Black-Square Nick do you mind taking a look at this? It seems that having a preset speed dialed in before engaging IAS mode will sometimes break it, at least if you're in VS and then try to go to IAS.
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I just wanted to let you know that I will look into this and try to reproduce it before the next update. It's just been a busy weekend. If you could provide a step-by-step, since you say it's reproducible, that would be helpful, but please don't spend too much time on it. I can probably find the issue regardless.
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Thanks Nick. What I posted above is the best lead I have for reproducing it right now. In the next day or so I will give it another try; it seems to be happening to me fairly consistently, and that's the usual order of operations I do. GA off the runway, VS to capture any initial alt, then speed when I'm settled into the climb, usually by dialing in a speed before I engage IAS mode. I usually do 200 up until 10,000ft, then engage IAS Prof and let it decrease as I climb to whatever cruise altitude.
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Dammit, I thought I had something with that. I did two tests just now and haven't seen it since last Saturday or Sunday (about four flights total). When I posted I could reproduce it, I was able to make it happen at will that flight.
I did both a quick start on the runway and my steps above and a full cold and dark startup with the full suite of tests (my normal procedure on first flight of the day), and both times it went from GA to VS to IAS mode with the values selected beforehand flawlessly.
I will continue to play with it as time allows to see if I can get something concrete.
