fowler wrote on Oct 22^nd, 2022 at 3:49am:

Another weird thing is how the aircraft react to thust change when A/T is off. In cruise when you do a very slight power up adjustment you can see the aircraft constantly accelerate for 10' minutes long and more. I got from 0.82 mach to 0.86 mach in more than 15 minutes with a very limited power change when I was stable at 0.82 mach. This is really unrealistic because the air resistance is not a linear function but a square function of speed. And that means that for a slight power change you should see a slight speed change rapidly that get amortized quickly and settle in the next equilibrium state of power/drag ratio. There should't be a large change of speed at a low rate how it occurs here.

I'll have to admit that I don't agree with this.

In real life, I fly an airliner which weighs a bit less than the Boeing 767, but has a very similar thrust to weight ratio. This is one of the scenarios we do in training to show the lack of excess thrust in high altitudes. In the another company simulator, we start at 250KT/0.75M at FL350 more or less, then we set the thrust to max power and see how long it takes to get to 270KT/0.80M, and it generally takes 90-120 seconds. If this is at MAX power, it almost makes sense that a slight power change would cause a 0.04M increase in 10 minutes. This issue isn't as much air resistance but lack of excess thrust. If you have excess thrust, yes it will equalize at a particular speed because of the exponential increase in drag, but how do you know how that is with a PW4060 at FL350 at 300,000lb, for example?