The Scrapped Boeing 777 TriJet

Daniel Fowkes
30 Nov 2023
· Aircraft 
Boeing scrapped 777 with three engines dubbed the 777-100 to compete with the TriStar and MD-11

During the back half of the 1900s, Boeing studied several intriguing concepts that never got off the ground. However, ultimately, their studies would, in some cases, prove valuable to chart the next firm course for direction at the plane maker.

One of those concepts is that of a Boeing 777 with three engines, acting as Trijet and T-tail in a similar fashion to the popular series released at McDonnell Douglas.

But what was this concept aircraft? Why was it studied? Why wasn’t it released? Was it ultimately the right decision from a manufacturer trying to wow its customers with the next big thing?

Boeing Attempts To Compete With Emerging TriJets

The late 1970s and early 1980s saw Boeing releasing new aircraft to replace its older models and compete with new rivals in the sector.

It was during this period that the release of the 767 occurred. A plane made to compete with the Airbus A300. Additionally, Boeing proceeded with the 757, which was intended also to help replace some of the ageing 727s.

Thanks to the rapid evolution of technology, Boeing needed to outdo its previous aircraft quicker while studying emerging manufacturers that could be out to steal market share.

One sector that the company believed it lacked was that of a scene occupied by the DC-10 or Lockheed Tristar.

For better words, it believed there was a gap between the newly released 767 series and the queen of the skies and quad-engined 747, which had been taking the industry by storm.

Boeing Thinks A TriJet Is The Answer

The obvious solution to this problem seemed to be an aircraft with not two, not four, but three engines. At this point, aircraft with three engines made a lot more sense than what they do in the 21st century.

With ETOPS regulations in place restricting twin-engined aircraft from long overseas flights at the time, trijets made for a happy medium for airlines who wanted an aircraft capable of crossing oceans but not something as significant and costly to operate as the 747.

Boeing Begins Work On A 777-100, A TriJet

Therefore, around the time of emerging competition, Boeing began drawing up concepts for such an airplane that would slot between the 767 and 747

Such a concept was identified as the 777-100 and was conceived as a trijet. Using the 767 as a brace, the aircraft would be a scaled-up version of this series, with the same wide body and nose but a third engine on the tail.

Inspiration would no doubt be taken from other plane makers moving ahead with such trijet variants, and Boeing wanted to ensure it wouldn’t miss out on any available market. At the time, it had undoubtedly enjoyed capturing most of the long-haul demand thanks to its jet-powered aircraft.

S-Duct For The 777-100?

Similar to the Lockheed TriStar, the 777 Trijet was planned to feature an S-Duct for its third tail engine, although concepts were also drawn up for a straight-through engine, which would have made it a closer appearance to, say, the DC-10.

The S-Duct meant that while the intake was above the fuselage, the exhaust would be at the rear of the aircraft, with the entire engine tube being bent in an S shape, as opposed to traditional engines, which were straight through.

This design had numerous benefits, namely that the third engine would be closer to the ground, making it easier to service, and the technique reduced the Trijet’s overall drag, in contrast to the straight-through third engine design of the Douglas DC-10 and MD-11.

Boeing wanted to ensure that it would get the aircraft right if it proceeded with such a trijet. This era was where Boeing led the way for manufacturing standards and innovation.

ETOPS Removes The Need For A 777-100

However, as with the biggest changes to airliner design and the aviation industry, the decision not to proceed with the 777 trijet program came primarily from lifting ETOPS regulations on the allowed overseas flight distances of twin-engine planes.

With that, the very concept of the Trijet became obsolete, as any twin-engine aircraft could match its performance at a fraction of the cost.

While Boeing’s twin-engined programs, such as the 757 and 767, saw wild success with this new development, interest in a trijet from the American aircraft manufacturer dropped.

Add this to the fact that trijets were very complicated to design and maintain. Well, there were several important reasons why Boeing never proceeded with such a design.

A Gap In The Market Is Still Present

Nevertheless, Boeing still faced a gap in its fleet between the 767 and 747. While ideas were thrown around for a stretched 767, airlines clearly wanted a whole new aircraft.

Key airline executives made this opinion clear on several occasions in close communication with the American plane maker. Thus, Boeing returned to their 777 concept with some game-changing refinements.

This time, Boeing would head back to the drawing board and make the most significant change: removing the third engine and, thus, the trijet nature of the plane.

As a result of this change, the 777, as known today, was born. The life of the 777 is set to be extended for many decades with the newest iteration in the series, the upcoming 777X.

Was It The Right Decision For Boeing?

Most would argue Boeing not proceeding with a 777-100 featuring three engines was the right decision. While trijets are spectacular, if Boeing had launched a 777-100, it could’ve significantly altered their current 777 program and widebody offering.

Boeing was saved by the development of ETOPS on twin-engine aircraft that would eventually lead to the study of a much more refined and efficient 777 known today across the 777-200 and 777-300 series.

The success enjoyed with the refined 777 cannot be understated, and now, with the upcoming launch of the 777X, the life of this program will extend towards the end of this century. Had Boeing proceeded with a 777-100 and never released the current iteration, you’d be hard-pressed to find anyone who would agree that a similar fate would occur.

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