An incredible never built Boeing 747500 with propfan engines. It would have an impressive range to go London to Sydney nonstop and be ultra fuelefficient. Despite all of these advantages, Boeing never chose to follow through with the concept.

Watch part 1 here:    • Boeing 747X  The New Large Airplane ...  
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In today's video, we will look at what the Boeing 747500 was, how it improved on the Boeing 747400, who would have bought it, and ultimately, why it was never built.

You see, the Boeing 747500 was a design that was going to take advantage of the engine of the future the prop fan. It was a new take on the jet engine that put used counterrotating props behind the engine and would bring with it a host of advantages but this story actually starts with another plane the Boeing 727.

At the time, Boeing was also redesigning its successful 727 series with the new propfan engine in mind.

The plane was called the Boeing 7J7 and it would have been incredible for the world burned by the fuel crisis. it would have a longrange and unmatched fuel efficiency, especially against rival plane makers.

I've actually done an entire video on the Boeing 7J7 program that you can check out here, needless to say the concept was simultaneous cutting edge, and also a backward step for aviation.

This leads us to the 747500.

Like the 7J7 program, Boeing needed a successor to the Boeing 747400, its best selling version yet.

While it had also been working on new large aircraft, N650 and others include a strange partnership with Airbus, it was also flirting with the idea of taking the propfan engines and slapping it on the Boeing 747. After all, why not scale up the technology and call it a day, in a new engine option way.

Essentially, making a doubledecker jet with propeller engines in the early 90s.

let's talk specifics. This 747500 model would have a range of 8,700 nautical miles or around 16,000 km. This range would have made it perfect for routes such as LHRSYD, JFKSYD, EWRSIN and LAXSIN and would have been the 7778X of its time and could have possibly been bought by airlines such as Qantas and Singapore. By comparison, the 747400 could only 7,670 nmi 14,200 km. Boeing felt that the program was very doable, cheap to build, and will result in approximately 10% reduced costs on a seatmile basis compared to the 747400.

The plane would also have a new winglike the Boeing 777, and a stretched upper deck to accommodate 500 passengers and all their luggage.

Boeing planned to introduce this aircraft by the 1990s and would bring the world ever more connected with new routes and impressive aircraft performance. Boeing was targeting British Airways, Cathay Pacific, Japan Airlines, Qantas, Lufthansa, All Nippon Airways, and Singapore International Airlines, as a launch customer.

This plane would have been the 7478 of the 90s!

Let's start with the engines. The engines were loud, and despite efforts by general electric and others, airports and airlines were not convinced that they would be able to make it quieter than a jet engine. Plus a new engine type would insert lots of unknowns into the design and development of the aircraft such as maintenance issues, spare parts and more. Ultimately, GE and other designers of the engine type decided to not go ahead with the production of the engine, and this was a major reason why the aircraft never went ahead.

Boeing would then reevaluate the design to include one with other engines, the normal turbojets, but there were some other issues.

This plane was created in mind for long haul routes, for operators like Qantas and Singapore. But these two carriers don't make a market for a new longhaul type they would only at max order 1020 each, leaving Boeing holding a massive development bill. Boeing had tried to enter this market before with the Boeing 747SP, a longrange version of the 747100. They only sold 45 of them, to carriers like Iran Air and Pan Am which by this time, we're not in the market for any new jumbo jet aircraft. In fact, no one needed it, the market was saturated by hundreds of 747400s, and there were plenty of twinjet designs like the 767 and A300 slowly encroaching on the market.

In 1985, the ETOPS rules were relaxed, allowing twinjet aircraft to fly over oceans. Airlines could now fly smaller equipment (767 or A300/A310) and sell all the seats or fly two daily round trips they would have struggled to sell the same on the 747500. With ETOPS expanded yet again in 1988, the need for a high capacity quad jet to fly longrange simply vanished. Airlines could still use it to fly Australia to South America but this market was limited indeed.

With no market for the type, and no engine, Boeing decided to pass on the easy to make and sell, 747500, and instead proceed to build the later 747X design. Which, as I mentioned, you can see on the channel right here, right now.