It’s not impossible, you just have to hit the key that the command is bound to. I couldn’t figure out the default one though, so I just bound them to + and -.
Side note: You can’t adjust the simulation rate with AI controlling the aircraft. You have to fly it by hand or engage the aircraft’s autopilot.
It’s also worth mentioning that there’s nothing to indicate what the simulation rate actually is. You might be able to use the aircraft’s clock, but even that can be a little whack at times.