The first by-pass engine in commercial service was the Rolls-Royce Conway. It had a very low by-pass ratio and had the same stove pipe exhausts as the JT3C and JT4A powered airplanes.
The first high by-pass ratio engines were developed for the Lockheed C-5A
by both GE
was teamed with Lockheed and P&WA
was teamed with Boeing.
With Lockheed winning the production contract for the GE
teamed with Boeing on the 747.
has a system of designating their "paper" engines, i.e. engines that are design studies only and never built. The study engine that was proposed for the USAF
heavy lift plane was built and tested.
The data from this engine was the basis for the JT9D for the 747. There were a couple of early big problems with that combination; first P&WA
, after making their performance guarantees, found out that there were errors in the test data from the study engine which affected their guarantees greatly; second the 747 came in much heavier than Boeing had estimated. These two items results in a badly underpowered 747 with the JT9D-1 engine.
rushed the development of the JT9D-3 engine in order to allow Boeing to keep its delivery schedule. This rushed development resulted in an engine with a lot of problems. The first major problem was that the engine would warp longitudinally on the pylon (this was not seem in the test stands due to the stiffness of the engine mounts there) at high engine power. This warping caused excessive blade clearances in one sector of the engine and heavy blade rubbing in the opposite sector. P&WA
designed a wye shaped external structural member, called a yoke, that installed on the outside of the engine to prevent or reduce the warping.
All available production capacity was dedicated to building these yokes including the shops that produced parts for the various other development programs that P&WA
had going on then. The program I was on was heavily impacted. We were having our own problems and between us the JT9D program, we had several nasty engine failures in the experimental test stands.
It was a busy and intense time at P&WA