Heli1: The notes I had for this photo indicated that it was a USAF airframe, perhaps loaned or detached to the US Army. Prompted by Baston's highlighting of the wording on the nose, I conceded that the craft was almost certainly US Army and quickly found related information. Earlier in the year I had contacted the USAF archives in connection with this image but no response was forthcoming.
It would have been a wonderful thing to meet Carter Harman. As the narrative suggests .. flying the R4 in such an environment must have been quite a trick!