Skinner designed an auxiliary power group for large military aircraft during WWII. It was licensed to Jack & Heintz (see).

“Skinner Auxiliary Motor”

-It gave 95 HP at 7,000 rpm and it had 6 air-cooled horizontal cylinders. They were valveless with sliding sleeves.

“Compact and light engine, aluminum”

“Engine section” (Redrawing of De Rouse)