Hi,
Thanks for your great suggestions.
It listened through the sound files and It was the stall warning sound. I loaded a saved flight with a Mooney Bravo I had saved before this occurred and the sound was gone.
I loaded my latest saved flight with the DC-3 , loaded the Conquest and the sound was there again.
I am wildly guessing here but perhaps the angle of attack of the DC-3 when on the ground (It's a tail dragger) is tricking the stall warning to go off when I load the Conquest.
Anyway, thanks for your help. Now I can fly this excellent plane again / Jan