Piston / turboprop engines?
They are piston engines. The whine at startup is just the starter motor. They are closely cowled and with ducted spinners. Imagine this (http://en.wikipedia.org/wiki/Republic_XF-12_Rainbow) aircraft with said ducted spinners. See a Tempest with ducted spinner here: http://www.hawkertempest.se/res/default/exp21.gif
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