Douglas DC-4 XC-112A

The XC-112 was the project for a pressurised variant of the C-54B with Pratt & Whitney R-2800 engines; none was built as such. One XC-112A, identical in concept, was built and later redesignated YC-112A, and out of it grew the whole DC-6 and C-118 family.

This is where the DC-4 lineage forks: the same wing and the same philosophy, now with a pressurised cabin and bigger engines, produce a new aircraft. Alongside it, the Skymaster's experimental list includes the XC-114 — a stretched C-54E with Allison V-1710 engines, one built — the XC-115 with Packard V-1650 engines, never built, the YC-116 with thermal de-icing instead of rubber boots, also one built, and the long-range XC-54K with Wright R-1820 engines.