Thanks for your reply...
At the moment (as I am fairly new to FS
) I fly with unlimited fuel, and my flaps were down at 5, which is normal for a take off roll.
And the same thing has just happened on a Britannia 757-200!!
There must be something within the files of certain downloaded aircraft that make them do this... I'd much rather do the lifting off the runway myself, as it takes some of the fun out of proceedings if its done for you!