Today I was flying and lost my air speed indications as well as getting both stall alarms..

 

I of course ignored them and continued on my flight ;-)... however as I was on final at about 2000' I disengaged my autopilot and nosedived into the ground..

 

Why did this happen.. If the autopilot can maintain altitude why did I loose all altitude control in manual mode?

Your pitot tubes probably froze.  Did you have your ice protection on?  Did the backup AS indicator (analog) also went dead?

"Diving to the ground" - can ignore that one, eh?  hihihih.  Most likely you stalled.  Hard to land without knowing your airspeed

No I was flying just fine, lined up on runway at about 2000 ft alt stable flight estimated at 140 knots or so.. until I turned off the autopilot... then extreme nose dive with no apparent elevator control..

Did you check your elevator trim?  I don't know what happens to the aircraft in FSX when it loses all airspeed indications.  But, if your trim was set hard nose down, you might not have had enough stick to pull out of it.  That's a problem with FSX, I think, since most RW airplanes use trim to maintain steady flight but FSX doesn't seem to.  I usually have to add some elevator trim right when I release the autopilot.

Stick pusher?

No big deal,, I was also thinking I lost the pitot tubes so other than the alarm wasn't too concerned until...

I was attempting to trim up but alas... lost a good plane that day...

 

now on to better flights...

 

Thanks all...

The trim issue is an annoying FSX issue and, seems to me, to be a bug.  When you take the airplane off of A/P, it should continue at the attitude that the A/P had it on (assuming you're stable).  You shouldn't need need to change it.  I almost always have to add some up-trim right away no matter what aircraft it is.