Well I went to the missions section and began with takeoff of a chopper. Oh I got it to ascend and descend using the throtle f3 and f4 keys. But as soon as you move it sideways the chopper becomes unstable and always likes to nose downward. Then you try to correct this and the chopper loses throttle. I have yet to complete this simple mission. Is there a bug in this sim?

No ... but maybe there's a bug in your approach.You simply can't fly a helicopter with a keyboard. You will need a joystick, and a lot of practice. FSX isn't a game ... it's a simulation. Helicopters take practice to learn how to fly, much moreso than fixed wing aircraft.Children as young as 13-14 have flown fixed wing aircraft across the United States without much effort in real life, primarily because airplanes are stable. An airplane is designed to fly all by itself.A helicopter, on the other hand, is designed to be unstable. This allows it to do things a fixed-wing aircraft can only dream about on rainy nights.Here's some video of someone who has practiced flying one of the helicopter missions in FSX:

Flying helicopters is hard, flying helicopters without a full set of controlers would be nearly impossible. You can try turning down realism settings.Gunner

I tried it with full realism settings and nothing but a joystick, and I'm 14. Yeah, you need pedals IMO.

just takes practice. I only use a joystick and i can fly a helicopter with out any problems at all.

pedals is best but twist rudder works as well. the chopper simulation is not the best in FS. They have toned down the difficulty in FSX compared to FS9 though which truly truly was a beast to fly if you don

I can fly a helicopter perfectly with a joystick, I'm 13. I think heli flying in MS FSX is much better than the other sims. You just have to be very gentle.

If by "better" you actually mean "easier", then you are definitely right. The physics engine in FSX when helicopters are involved is absolutely awful.The environment and the missions are the only things saving it at this point and the former advantage is being nibbled away by the competition (X-Plane 9 is an example) which also provide better physics simulation.The best way to view FSX is as a situational awareness simulation where you can learn what to watch in your surroundings, how ATC works (not entirely applicable to helicopters since it doesn't know about heliports), and how to use the instruments.Doesn't mean it isn't a lot of fun though! Just as long as you keep in mind that it's not a whole lot like the real thing. :)