Why Boeing Chose Dual Engines for the 757: A Look at RB211 and PW2000

Why Boeing Chose Dual Engines for the 757: A Look at RB211 and PW2000

In commercial aviation, different aircraft programs adopt varying approaches to engine selection. For example, the Boeing 737, formerly the most successful jet-powered airliner, has consistently featured a single engine type at any given time, transitioning from Pratt & Whitney to the CFM56 in the 1980s. In contrast, the Airbus A320, which has since surpassed the 737 in popularity, has always offered two engine options.

The Boeing 757‘s Unique Engine Options

Among aviation enthusiasts, the Boeing 757 stands out as a unique narrowbody aircraft because of its remarkable power and performance. Despite its capabilities, the aircraft’s sales were comparatively low, with only 1,050 units produced, fewer than many widebody programs. Notably, the 757 was offered with two different engine types: the Rolls-Royce RB211 and the Pratt & Whitney PW2000. There are specific reasons why Boeing made this decision.

Benefits of Offering Engine Choices

• Customers have options to configure the airplane to better match their operational needs. For instance, an engine with superior climb efficiency may suit airlines with shorter flight routes, while those minimizing fuel consumption during cruising may appeal to long-haul carriers.
• Competition among different engine models can lead to reduced pricing.
• Engine choices offer greater fleet commonality for airlines. United Airlines, for example, used Pratt & Whitney engines across most of its fleet and selected the PW2000 for its 757s. Similarly, British Airways used Rolls-Royce engines extensively across its fleet.

Offering multiple engine options broadens the market appeal and helps manufacturers penetrate new markets. A customer like United Airlines may have been hesitant to order a 757 had it only been available with the RB211, and vice versa for Rolls-Royce customers. Engine manufacturers can also use this opportunity to enter markets that might have otherwise been closed.

Drawbacks of Dual-Sourcing Engines

While multiple engine choices provide distinct advantages to airlines, they add costs and complexity for manufacturers. This complexity has resulted in a more recent trend toward sole-sourcing. For example, Boeing’s 777X uses General Electric engines exclusively, and Airbus’s A330neo uses solely Rolls-Royce engines.

The development of the Boeing 757 required certification with both the PW2000 and RB211 engines, thus increasing costs. Different engine models necessitate manufacturers to adapt aircraft and systems, often resulting in reduced profit margins due to heightened pricing competition.

While offering multiple engines can protect aircraft from model-specific issues, as seen with the 787’s Rolls-Royce problems, it has not been enough to deter manufacturers from preferring sole-sourcing. The Boeing 777 and Airbus A330 transitioned from three engine options to one in subsequent generations.

Boeing 757: The Decision for Multiple Engines

Boeing envisioned the 757 as a successor to the successful Boeing 727. By the late 1970s, the development timing allowed the 757 to use high-bypass turbofans, which were more powerful and efficient than the engines used by its predecessor. The RB211 engine, developed by Rolls-Royce and initially used on the Lockheed L-1011 TriStar, was further improved and selected by launch customers British Airways and Eastern Airlines, making it the first Boeing airliner outfitted with foreign engines.

Pratt & Whitney’s PW2000 was chosen for the 757, adapted from the engine developed for the McDonnell Douglas YC-15 demonstrator. This decision was confirmed when Delta Airlines placed its initial order for 60 aircraft. General Electric proposed a CF6 derivative, but lack of airline interest led to its cancellation.

Market Competition: PW2000 Versus RB211

Initially, it was common for aircraft developers to add an engine choice due to customer requests. Despite development and certification costs, sufficient demand justified incorporating the PW2000 and RB211 into the 757, reflecting the period’s standards.

The RB211 gained significant recognition with a major American Airlines order in 1988, bolstering its market presence. In the U.S., the engine was favored by Continental Airlines and Eastern Airlines, with existing operators like Icelandair equipping their fleets with the RB211.

While United Airlines and Delta favored aircraft with PW2000 engines, the RB211 ultimately dominated the market, thanks to refinements and releases like the 535E4 variant, known for its reliability and low noise profile.

The PW2000 was limited to the Boeing 757 in commercial use, though McDonnell Douglas later used its military variant, the F117, on the C-17 Globemaster III. It entered service in 1985, slightly trailing the RB211, but faced reliability issues early on and remained less popular.

Conclusion

The Boeing 757’s dual-engine options were born from customer demand, with companies like General Electric lacking sufficient interest to justify a competing engine. Despite the PW2000’s initial problems, Rolls-Royce improved the RB211, making it the leading choice. Today, advancements in certification and costs lead manufacturers toward limiting engine options, but multi-choice offerings were a more common practice during the 757’s development.

Boeing 757

• Launch Customer(s): Eastern Airlines, British Airways
• First Delivery: December 22, 1982
• Last Delivery: November 28, 2005
• Number Delivered: 1,050