Do you mean; "Slew" as in using the "Y" key, Or do you mean the; "Accelerate Time" option?
In both cases, as in normal flight
when not using the Autopilot, you will need to have full control over the aircraft with the joystick/Yoke at all times, as in a real aeroplane, to counteract wind direction, buffeting, engine torque, etc, effects.
I wouldn't worry about it, you will get used to the strange quirks of flying an aircraft after a while....
.....Use the Joystick to control and;
"fly" the aeroplane!...
...!
Remember...you are in control!
Paul.... 8-)...!
P.S. Note that even with the Autopilot engaged, you will still need to regularly correct the heading, (using the HSI heading bug), when being blown off course by the wind!
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.