FSX Erratic Slewing
Slewing in FSX is the process of rapidly moving the aircraft in order to relocate it. The default keyboard assignment to enable the slew function is 'Y'. When 'Y' is pressed the aircraft should freeze in its current position. Sometimes upon pressing the 'Y' key the aircraft may exhibit erratic behaviour such as rapidly accelerating away from its current location or rotating about its axis. This can be due to insufficient null zone on the controllers, joystick or yoke etc. The null zones can be increased or, rather than tampering with any preferred settings, the controllers can be disabled before going in to slew mode.
To disable the controllers use the key combination CTRL + K then go in to slew mode with 'Y' and the aircraft should be stationary. With the controllers now disabled slewing is achieved with the keyboard. There are several slew commands pre-set in the Options... Controls... BUTTONS / KEYS tab and it may be useful to look at them and set them to your own preferences.
The table shows some of the default settings that are probably going to be used the most but there are some commands that are not pre-set which I would think need adding e.g. (with my suggestions in brackets).
~ Rotate left (SHIFT + L)
~ Rotate right (SHIFT + R)
~ Move left (L)
~ Move right (R)
It should now be possible to accurately reposition the aircraft. Note that repeatedly pressing a key will increase the speed of the function. Press 'Y' to leave the slew mode and CTRL + K to re-enable the controllers.