A Pratt and Whitney R-1830 radial engine, mounted on the left wing of an ex-military Douglas C-47 undergoing maintenance.
<a href="https://en.wikipedia.org/wiki/User:YSSYguy" class="extiw" title="wikipedia:User:YSSYguy">YSSYguy</a> at <a href="https://en.wikipedia.org/wiki/" class="extiw" title="wikipedia:">English Wikipedia</a>
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<span class="int-own-work" lang="en">Own work</span>, image edited using Picasa software.