Breaking from the variants that came before it, the Boeing 747-8 is exclusively powered by the General Electric GEnx-2B turbofan, a close relative of the GE engine powering the popular Boeing 787 Dreamliner. To make the 747-8 economically feasible, especially important after what turned out to be disappointing sales, Boeing leaned on its 787 program and General Electric (now GE Aerospace).

In the past, it was normal for aircraft types to be developed with two or three engine options. However, the drive to produce bespoke engines optimized for a particular aircraft type has helped to change the economics of that. It is now too expensive for original equipment manufacturers and for planemakers (like Boeing and Airbus) to develop multiple engine options for most of their modern aircraft types.

The Boeing 747-400 Came With Three Engine Options

The Boeing 747-8 was the final version of the 747 family. Its predecessor, the Boeing 747-400, came with three engine options, depending on the sub-variant. The 747-400 and 747-400F came with the options of the Pratt & Whitney PW4000, GE CF6, and the Rolls-Royce RB211, while the 747-400ER had the options of the PW4000 and CF6. Boeing’s records show that it delivered a total of 694 747-400 family aircraft.

Of these, 132 were delivered with Rolls-Royce RB211 engines, 235 were delivered with PW4000 engines, and 336 were delivered with CF6 engines, making the General Electric engine the most popular. The CF6 engine has become the world’s most popular widebody engine ever developed, and it remains in production for the remaining Boeing 767-300F freighters on order.

By comparison, Boeing would only go on to deliver 155 examples of its 747-8 aircraft. This was too small to support the costs of having three engine options. In retrospect, this was only just enough to support one engine that already had most of its development costs paid for by another airliner program.

A Shrinking Market Size

By the time the Boeing 747-8 program launched in the 2000s, the market was very different from that of the 1980s when the 747-400 was developed. Boeing had expected to sell around 300 to 400 updated jumbo jets, which included around 200 to 250 freighters. This was a time when Airbus was building the even larger A380 that would compete with it. Boeing knew the very large aircraft market was shrinking in favor of more efficient twinjets​​​​, but still overestimated the market size for its 747-8.

Similar forces that doomed the clean-sheet Airbus A380 also worked against the 747-8. In the end, Airbus only sold 251 examples, not enough to recoup the $25 billion it had spent on developing the jet, and Boeing only sold 155 747-8s: 48 passenger versions and 107 freighters. A significant share of the passenger aircraft were business jets and VIP transports, with the number of commercial passenger examples just 35, spread across three airlines (Lufthansa, Air China, and Korean Air).

As a passenger aircraft, the 747-8 failed, but Boeing was able to break even on the whole, even if the program was commercially disappointing. However, it’s unclear what would happen to its thin profit margin if its financially disastrous contract to deliver the next generation 747-8 ‘Air Force One’ VC-25Bs is included. With the benefit of hindsight, Rolls-Royce is likely very happy it didn’t spend billions on developing a Trent engine for the 747-8.

The GEnx-2B As The Obvious Choice

By the 2000s, only GE and Rolls-Royce were realistically able to offer Boeing engines with the required thrust it wanted for its updated 747. This would be an issue that would continue to impact Pratt & Whitney, contributing to the company being sidelined in the A330neo, A350, 777X, and 787 programs. This has effectively pushed PW out of the widebody engine market, although KC-46A tankers (based on the 767) are still delivered with PW4000 engines.

At the time, the GEnx-2B was already being developed for the 787, which offered a lower developmental risk, cost sharing, and faster certification. Rolls-Royce could have developed a version of its Trent family for the 747-8, but this didn’t make economic sense. While the 747-400 had sold well, it was known that the 747-8 market would be much smaller, so the number of engines Rolls-Royce realistically could have sold while competing with GE would not have covered the costs of development.

In 2011, Boeing announced it had successfully completed the first engine runs for the 747-8. It stated that « the GEnx-2B engine is optimized for the 747-8. The new engine contributes to a reduction in fuel burn, emissions and noise, which gives customers the lowest operating costs and best economics of any large passenger airplane while providing enhanced environmental performance. »

The Exploding Costs Of Aircraft Engines

The costs of developing engines for modern commercial airliners have exploded dramatically. In the 1970s-1990s, new large turbofans were expensive, but, today, those costs are around five times to an order of magnitude greater. It is just dramatically more difficult to achieve the required NOx reductions, noise reductions, pass certification requirements, and achieve lower fuel burns.

Today, OEMs will often refuse to develop an engine unless they are granted exclusivity, and they are confident in the airliner program’s prospects for sufficient sales. Despite the small production run, General Electric was able to emerge from the 747-8 profitably, even if it was disappointing overall.

GE spent around $10 billion developing the GEnx family, using the core architecture of the GEnx-1B it developed for the 787, and the incremental costs for the 747-8’s GEnx-2B variant were likely around $1-2 billion. Also working in favor of OEMs is that the 747 (and A380) is a quadjet, meaning they get to sell four engines (plus spares) for every aircraft sold, so 155 sales would have amounted to around 650 to 700 engines when spares are factored in. GE reported having sold over 400 engines by 2008.

Why Do Few Modern Airliners Have Multiple Engine Options?

In the past, it was normal for aircraft to have multiple engine options, but now, it’s the exception, so it’s perhaps better to ask why modern airliners might still have multiple engine options. Airbus expected to sell over 1,200 A380s, but, in fact, it only sold 251 with two engine options. Rolls-Royce was able to just approach break-even with its Trent 900, having spent $3–4 billion on development. It delivered a total of 374 engines, plus spares, or around 60% of the A380s’ engines.

The Engine Alliance GP7200 was unsuccessful with only 270 engines and was unable to recoup its $2.5-$3 billion investment. Rolls-Royce won the contract to develop the Trent 1000 as an engine choice for the world’s most popular modern widebody, the 787. After initially claiming a third of the engine market share, it has collapsed due to durability issues, and the engine has become a financial loss for Rolls-Royce. Industry experts expect the Trent 1000 to go out of production after 2030.

The Airbus A320neo family is optionally powered by the CFM International LEAP and the PW GTF. What sets the A320 program apart is its massive size. It is the most popular aircraft in the world, and its many thousands of sales make it large enough to support two bespoke engines. The 737 MAX market size is also large enough, but the aircraft is limited by its old 1960s design, making it extra difficult to fit GTF engines.

Most Modern Aircraft Are Exclusively Powered

The Boeing 747-8 was built at a time of soaring aero engine development costs and at a time when the 747 was already an aging jet, and its sales heyday was already known to be behind it. At the same time, Pratt & Whitney was struggling to come up with workable solutions that would see its PW4000 family of engines upgraded for next-generation aircraft. Ultimately, Pratt & Whitney was pushed out of the widebody engine market.

It is normal for makers to try to limit production costs and risks on airliner update programs, as they are often more willing to invest in next-generation clean-sheet aircraft. The 747-8, 777X, and A330neo are all updates to older aircraft that are seen as worthwhile to update, but as having relatively limited future market potential. It would have been strange had Boeing developed the 747-8 with two engine choices, and stranger still if the OEMs had agreed to invest in it under those conditions.

In the past, most commercial airliners had multiple engine options, but, today, the Boeing 737 MAX, 777X, 767-300F, Airbus A350, and A330neo are all exclusively powered by a single engine type. The Boeing 787 is optionally powered, but it’s possible that after 2030, it will be functionally exclusively powered as a new production aircraft. Time will tell if Airbus and Boeing will develop the replacements for their respective A320 and 737 families with exclusive engines or not.