What was the NC-121D "Tripple Nipple"?

The WV-2 Warning Star began life as a long-range airborne radar aircraft for the US Navy. It was derived from the Lockheed L-1049 Super Constellation and carried Wright R-3350-34 or R-3350-42 engines of 3,400 hp (2,536 kW) each. It was first designated PO-2W, then WV-2 and, later, EC-121K. From that airframe came numerous specialized versions: the WV-2Q for electronic warfare, later EC-121M; the experimental WV-2E with a rotating radome, later EC-121L; and the RC-121D with wingtip tanks, which would end up as the EC-121D.

One of those versions was the NC-121D. The Constellation variant list describes it as a WV-2 converted to observe objects moving at high speed through the atmosphere. This was a very different task from the early-warning role for which the Warning Star had been conceived, and it shows just how far the Super Constellation airframe, spacious and with great range, could be adapted to carry measurement and observation equipment.

The aircraft became known as "Tripple Nipple," and the source records it with that spelling, with a double p, instead of the correct "triple." The Warning Star family had a long life: the US Navy and Air Force used its versions until 1978, more than forty years after work began on the first L-049. The NC-121D is a good example of how a 1940s airliner ended up converted, through successive modifications, into an observation platform in service with the Navy.