In 1989, the 747-400 entered service, and it was a massive success, with 18 airlines placing orders for it even before rollout and almost 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 known as the 747-500.
A Desire To Innovate At Boeing
The earliest concepts of the 747-500 can be traced back to before the 747-400 was launched. Boeing had already seen the success of the previous aircraft variants and planned to push the program’s limits in several unconventional and innovative ways.
Perhaps the most outlandish of these experimental changes was Boeing’s attempt at a 747 variant with turboprop engines instead of conventional jet airliner turbofans.
This proposal was made with another Boeing project called the 7J7, a small short-haul narrowbody airliner similar to the 717 and 727. Only the most significant difference would be the bizarre counter-rotating turboprop engines. As a result, it would make the plane laser-focused on maximum fuel efficiency.
The 7 in 7J7 stood for Japan, where the airliner concept was predicted to be the 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
Therefore, early concepts of the proposed next generation of the 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 8700 nautical miles, 1000 more than the 747 -400, which rivals even modern-day most capable airliners.
Such an extensive range would’ve allowed it to connect the world’s most distant cities, like New York and Singapore, or London to Sydney in a single trip.
Because of this capability, the 747-500 gained much interest from Singapore Airlines and Qantas. The pair of airlines have historically been known for wanting to push 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 involves the ambition of flying non-stop from Sydney to New York and Sydney to London, among other destinations. n
Whereas, over at Singapore Airlines, the company already stretches its legs with some of the world’s longest flights utilising 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 that the experimental turboprops held great promise, there were several good reasons to be sceptical of their viability. The most glaring issue with the engines was that they were so new and unusual.
That is to say, their deployment on an airliner that was only designed to fly with traditional turbofan jets was highly experimental and involved many unknown variables.
Research and development on how to maximize the fuel efficiency of these engines and possible additional modifications of existing airframes to accommodate them would make the project a pretty costly endeavour, considering 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. To add to all of this, the engines were just plain loud, especially when, at the time, new advancements were trying to move airliners away from excessive noise pollution.
A Decision To Scrap The Initial 747-500 Plans
Ultimately, Boeing scrapped the idea of the turboprop 747-500. However, despite the issues with the engines, the concept of a stretched 747-400 still seemed to hold some promise. Therefore, Boeing went ahead with the idea, only with the conventional turbo fans like the 747-400.
This new 747-500 was dubbed the 747-500X and would feature a lengthened 250-foot or 76.2-meter fuselage with a capacity for 462 passengers.
Its wings would be based on the 777s as opposed to the 747-400s, which meant an absence of winglets and even without the turboprops, it would still boast a range of 8700 nautical miles.
A Lack Of Interest For 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 enjoyed with existing variants of the 747 program.
Of course, when an aircraft manufacturer is either looking to launch an aircraft or in the final stages, they must ensure that the 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.
The only airlines that did show genuine interest in the -500X were the customers Qantas and Singapore Airlines, who had always generally been interested in the 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, a more substantial change was beginning in the industry. Twin-engine airliners, such as the A300 and Boeing’s very own 767, were emerging onto the scene with their new ETOPS certification.
These aircraft could also cross oceans similarly, such as the 747-400s with four engines, but these planes had two. While there were capacity reductions, these planes became favourable with a broader scope of airlines thanks to size.
For analysis, it seemed as though the 747-400 success was the last hurrah of the Superjumbo Age, and planes of its kind would no longer define commercial air travel as twin-engine planes began being the way forward.