I think the sound you mean is made by an overspeeding or runaway prop. I'm not convinced this is at all realistic. Like most things in films it's exaggerated for effect which makes real life seem rather dull.
I've always figured that typical "diving plane" sound from the movies is the sound of a plane diving with an air-driven siren- like the Junkers Ju87, aka the "Stuka".
I seem to recall a sound file for this effect included with a CFS2 Stuka. I never tried it & don't know if it would work in FS.
PS. This is the sound you mean from the same page as the Stuka.
Death Dive