Hi, I've down loaded everything fine, issue is that once I take off the plane wants to dive down and left and I've got to fight to keep it straight and level. Any idea's?
Thanks

RB1 or RB3D?
Fpr RB3D, Multiplayer or Single Player?
Two things.
One is the flight model is set for Authentic which adds engine torque. Second is today's machines are "hot" for RB3D and cause the planes to move to fast and be too sensitive.
GOG has included a SetSpeed.exe in the RB3D folder which lets you 'slow down' your computer for the game and makes the planes more flyable. Adding graphic mods also helps slow the computer slow the planes are not so "hyper" and makes the games look better.

Preferences-->Realism Settings --> Realism Options --> Flight model -- easy
Slowing it down helped some but this fixed the problem for me. It seems too light on the back end in 3rd person view.

With the mods out there for SP, one has to use authentic else the AI can not fly the planes. I have seen entire squadrons crash into the hills on take off in RotJ because I had the setting on "Easy" :)

I've had this happen too. I think it has something to do with the autopilot which sometimes engages on its own and will often do this if you apply it at take off. If on its own, hitting "A" has fixed it for me. otherwise, hit "A" then "Cntrl A" again and it usually clears out the hiccup. Note - it likes to self engage when approaching the airbase at the end of a mission (when you receive permission to land) and will dive you into the ground unless you quickly disengage it. Seems to be a random bug. If the technical fix supplied doesn't work - try this - maybe it'll work (no promises :) ).
I should add, if you are purposely on autopilot and the "permission" thing happens, you will quickly dive but will land without incidence - only a problem when not on autopilot and it self engages.