Boeing’s Lost Jumbo: What Happened To The 747-500?

In 1989, the 747-400 entered service and was a massive success, with 18 airlines ordering it before rollout and nearly 700 units sold. The 747-400 cemented itself as the most popular variant in the 747 program.

However, Boeing had even bigger plans for its flagship airliner and, in the early 1990s, began dreaming up an even better 747: the 747-500.

A Desire To Innovate At Boeing

The earliest concepts for the 747-500 date back to before the 747-400 launched. Boeing had already seen the success of previous aircraft variants and planned to push the program’s limits in several unconventional, innovative ways.

Perhaps the most outlandish of these experimental changes was Boeing’s attempt to build a 747 variant with turboprop engines instead of conventional jet-liner turbofans.

Boeing proposed this alongside another project, the 7J7, a small short-haul narrowbody airliner similar to the 717 and 727. The only significant difference would be the bizarre counter-rotating turboprop engines. As a result, the plane would be laser-focused on maximum fuel efficiency.

The 7 in 7J7 stood for Japan, where Boeing predicted the airliner concept would be most popular. Boeing believed these new turboprops could be the future of air travel and started dreaming bigger than just the humble 7J7.

The Next Generation Of 747s At Boeing

Early concepts for the proposed next generation of 747s included four turboprops instead of conventional jet engines, and the projected numbers were impressive.

Boeing believed the 747-500 would have a range of up to 8,700 nautical miles, 1,000 more than the 747 -400, rivaling even most modern-day airliners.

Such an extensive range would’ve let it connect the world’s most distant cities, like New York and Singapore, or London and Sydney, in a single trip.

Because of this capability, the 747-500 gained much interest from Singapore Airlines and Qantas. The two airlines have historically been known for pushing the limits of non-stop commercial flights.

Today, in 2023, that only continues, with Qantas eyeing the launch of Project Sunrise with the A350-1000. Project Sunrise aims to fly non-stop from Sydney to New York and Sydney to London, among other destinations. n

Meanwhile, Singapore Airlines already stretches its legs with some of the world’s longest flights using the A350ULR. Notably, from New York through to Singapore without a single stop.

Concerns Present Around The 747-500

However, while Boeing seemed to think the experimental turboprops held great promise, several good reasons made them sceptical of their viability. The most glaring issue was that the engines were so new and unusual.

That is, deploying them on an airliner designed only for traditional turbofan jets was highly experimental and involved many unknown variables.

Research and development to maximize these engines’ fuel efficiency, and possible additional modifications to existing airframes to accommodate them, would make the project a costly endeavour, given the risks involved.

This is, of course, in addition to several other logistical issues that may have arisen from the new engines, such as maintenance and the potential to acquire spare parts.

The fuel efficiency aspect of the engines also began to seem less enticing to potential customers as oil prices stabilized in the late 80s and early 90s. On top of that, the engines were loud, especially as new advancements tried to move airliners away from excessive noise pollution.

A Decision To Scrap The Initial 747-500 Plans

Ultimately, Boeing scrapped the turboprop 747-500. However, despite the engine issues, the concept of a stretched 747-400 still seemed promising. Therefore, Boeing went ahead with the idea, only with the conventional turbofans like the 747-400.

The new 747-500 was dubbed the 747-500X and would feature a lengthened 250-foot (76.2-meter) fuselage with a capacity of 462 passengers.

Its wings would be based on the 777s rather than the 747-400s, meaning no winglets, and even without turboprops, it would still boast a range of 8700 nautical miles.

A Lack Of Interest in a New 747

However, the new features still do not attract significant enough attention to make the 747-500 program economically viable. This is despite the long-standing success of existing 747 variants.

Of course, when an aircraft manufacturer is launching an aircraft or is in the final stages, it must ensure market demand is high enough to make the program economically viable.

If an aircraft manufacturer, say Boeing, launched a 747-500 with very little interest, they would likely face losses.

Only two airlines showed genuine interest in the -500X: Qantas and Singapore Airlines, which had long been interested in ultra-long-haul flight capabilities.

With brief interest from just two customers, most airlines couldn’t make such a colossal plane profitable and opted for the existing 747-400 instead.

A Shifting Industry Removes The 747s Need

Around this time, the industry began a more substantial shift. Twin-engine airliners, such as the A300 and Boeing’s 767, were emerging with new ETOPS certification.

These aircraft could also cross oceans, like the four-engine 747-400s, but these planes had two. While capacity shrank, these planes became more attractive to a broader range of airlines because of their size.

For analysis, the 747-400 seemed to be the last hurrah of the Superjumbo Age, and planes like it would no longer define commercial air travel as twin-engine planes became the way forward.