Aircraft leveling off and overspeeding with IAS/MACH mode engaged

[SteamingSpoon]

Hello,

Been enjoying flying the TriStar but it seems that every time I select IAS and MACH on the pitch mode selector during a climb, the autopilot/FD initially holds the desired speed but then pitches down, causing the the aircraft to accelerate past the speed target and overspeed if I don't intervene with V/S. Over two flights this seems to have happened consistently in both IAS and MACH hold modes. At this point it seems that V/S is the only appropriate vertical mode that can be used for a climb - I can't imagine that this is realistic at all. Has anyone else experienced this?

[Nikita2024]

I have had success climbing in VNAV to a preset altitude with TM activated when the PMS has been fully set up.

[SteamingSpoon]

Hello,

I do understand that flying the aircraft in TM/VNAV could work around the issue, I’d still want the aircraft to function properly in a speed hold mode if I want to manage the climb manually, especially when I’m flying a departure procedure that has multiple altitude and speed constraints that (to my knowledge) the PMS can’t take into account. Even then, there seems to be a bug where the TM A/T mode commands idle thrust without the AP engaged which many on this forum have already reported it seems.