Herb wrote:

There were three B-17 airframes after the war that were given to
Curtiss-Wright, GE and Allison for testing turboprops. The one in
the pic is (I believe) the Wright engine, it was a 5500 hp
turboprop, they'd take off on the Cyclones, start the "5th engine"
and then
feather all 4 Cyclones and fly on the turboprop.

The ultimate example of that sort of testbed would have to be the
C-124C (54-1069) that Pratt & Whitney used to flight test the T-57
turboprop. (The T-57 was a turboprop version of the J57 (JT-3)
turbojet. It put out something like 15,000 SHP). Somewhere around
here I've got a picture of it cruising along on the T-57, with all 4
recips shut down. Given that Shakey was a 2-story beast about the
size of a medium-sized warehouse, it may well have been the largest
single-engine airplane. (Well, sort of.)

--
Pete Stickney
Java Man knew nothing about coffee.