The prototyping process for a new aircraft is many things. It’s an expensive undertaking, it is an engineering challenge composed of tons of engineering challenges, and when you have outside factors like fuel prices actively ramping up the timetable, it becomes a race for each manufacturer: which one will be the first to market with a product that won’t come under the severe scrutiny of a late-night news investigation down the road because of a mis-step or two. If that sounds like stress by the boxcar, you are absolutely right. At the beginning of the 1980s, Boeing was reeling from the problems that the fuel crisis of the 1970s. Their aircraft lineup sold well, and they had a great position in the market, but if you don’t move forward you move out, and with a new airframe proposal on the drawing board that was meant to take over from the popular but aging Boeing 727 tri-jet. The project, known as the “7-7” proposal, was to be a 150-seat airframe that had fly-by-wire, a full glass cockpit with LCD display systems, an advanced avionics suite, and use of high-strength composites.
The ultimate peak of the program was the 7J7 proposal, which incorporated twin General Electric GT36 UDF contra-rotating turbine-driven unducted fan engines. The engines themselves were very interesting: a GE 404 turbofan drove two counter-rotating sets of blades (ten blades for Stage 1, eight blades for Stage 2) at speeds up to Mach .75 (approximately 575 MPH). The engine solved the fuel efficiency issue, but created two new ones: noise and cultural image issue. By their design, contra-rotating propellors are noisy, especially compared with the whine from a normal jet engine. While Boeing and McDonnell Douglas (who were both testing the UDF engine) figured that they could reduce the noise impact from the engines, the other problem was still present: how do you sell the flying public on the positives of a propellor-driven airframe when every propellor-driven plane seemed to be either too small or too antiquated to be safe?
The end game for the 7J7 project, however, was neither issue. It was fuel cost…after the pricing scares of the 1970s, fuel prices had slowly lowered back down and as a result, the 7J7 project continued on, but faced delay after delay before the project went from “new aircraft” to “new technology study”. The 7J7 never materialized outside of this test-frame Boeing 727…between the Boeing 737 platform and the McDonnell Douglas MD-80/90 series that became the Boeing 717 upon Boeing’s acquisition of their long-time rival in 1997, there was no need for a filler airframe. But the 7J7 program did give Boeing some technical leaps and bounds, and GE used the blade technology from the UDF engines in later engine developments.
