Simulink 3DoF model (Noob)

Hi,

I am having some serious understanding issues when trying to create a 3 DoF helicopter model. The goal is to create a model that starts from level flight (50 m/s) and then at a time=10s changes its pitch angle to zero. However, for the first 10 seconds I provide the 3DoF model Fx=Fy=M=0 but I still get that the helicopter has a constant acceleration in y of 10m/s^2! This of course results in an amplified altitude as well as velocities, even though I'm striving to keep the chopper level. Like I mentioned, I'm quite new to Simulink. I have attached dumps from the scopes (Scope 5 is altitude which is not seen on the plant dump). I also attached the Matlab file if there are any real heroes out there. Thanks in advance!