Leeham News and Analysis
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Engine Development. Part 5. The Turbofans go High Bypass
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By Bjorn Fehrm
Introduction
September 15, 2022, © Leeham News: Last week, we looked at how Pratt & Whitney’s JT8D turbofan came to dominate short-haul airliners while the JT3D had the long-range market.
The introduction of the widebody jets in the 1970s with Boeing 747, Douglas DC-10, and Lockheed Tristar brought GE and Rolls-Royce into the market. It was the start of the high bypass turbofans.
Figure 1. The roll-out of the Boeing 747-100 on September 30, 1968.
Summary
- The military TF39 for Lockheed C-5 Galaxy military transport set the benchmark for the new generation of high bypass turbofans with its 8-to-1 bypass ratio.
- Pratt & Whitney, GE, and Rolls-Royce developed civil engines along the lines of the TF39 for the new generation widebodies.
Engine Development. Part 4. Turbofans go mainstream.
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By Bjorn Fehrm
Introduction
September 8, 2022, © Leeham News: Last week, we analyzed the change from turbojets to turbofans for civil air transport. The jet engine was developed for high-speed military fighters and was not ideal for subsonic airliner use.
We also dwelled on why the three major engine OEMs came to different solutions for the first-generation turbofans. Now we look at the engine that made turbofans mainstream, the Pratt & Whitney JT8.
Figure 1. The Boeing 727-100 with Pratt & Whitney JT8 engines. Source: Wikipedia.
Summary
- The JT8 competed with the more developed Rolls-Royce Spey to engine the first US domestic jet airliner, the Boeing 727.
- After it captured the Boeing 727, it went on to engine all US short and median haul jets of the 1960s.
Engine Development. Part 3. The early turbofans.
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By Bjorn Fehrm
Introduction
September 1, 2022, © Leeham News: Last week, we looked at the motivation to change from propeller engines to jet engines as higher cruising speeds were sought for airliners.
We learned the straight jet engine, while good for military jets, wasn’t well suited for civil airliners. It was noisy and fuel-thirsty. It was why the subsequent engine development, the turbofan, was quickly accepted by the airlines.
Figure 1. A Boeing 707 with Pratt & Whitney JT3D turbofan engines. Source: Wikipedia.
Summary
- The first turbofans from Rolls-Royce, Pratt & Whitney, and GE had different designs.
- The advantages of the turbofan over the straight jet were quickly recognized. The turbofan has been the choice for airliners since the late 1950s.
Engine Development. Part 2. The early jet engines.
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By Bjorn Fehrm
Introduction
August 25, 2022, © Leeham News: Last week, we started a series about jet engine development for our air transport aircraft. The jet engine came to replace the piston and gas turbine propeller engines when airplanes sought higher cruising speeds.
In the second part of the series, we look at why the jet engines were developed and their advantages and disadvantages compared to what they replaced.
De Havilland Comet, the first jet airliner. Source; Wikipedia.
Summary
- When the propeller engine came to its speed limits, the straight jet engine was the answer.
- While it helped with speed, it created other problems.
Engine Development, Part 1: Launch to Entry into Service
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By Vincent Valery
Introduction
Pratt & Whitney Geared Turbofan
Aug 18, 2022, © Leeham News: LNA analyzed the evolution of commercial aircraft development timelines last month. The time between a program launch and entry into service significantly increased over time, including for derivatives.
The increase in development time is primarily the result of more complex and safer airplanes. Introducing new materials, notably a more extensive use of composites, also explain longer development timelines.
LNA now starts a new series on the topic of commercial aircraft jet engines. The goal is to go through significant innovations from the beginning of the jet age.
This first article analyses whether engine development time between launch and entry into service increased significantly over time.
Summary
- Military development led to the first commercial jet engines;
- The divergence between military and commercial programs;
- Pushing the envelope of the same fundamental engine architecture;
- Harder to identify development timeline evolution.
P&W, Collins Aerospace launch hybrid-electric demonstrator
By Scott Hamilton
July 18, 2022 (BST), © Leeham News: Pratt & Whitney and sister company Collins Aerospace announced the launch of a hybrid-electric technology demonstrator, it was announced today at the Farnborough Air Show. This program is for future advanced air mobility vehicles.
Collins and Pratt & Whitney Canada, the turboprop engine unit, also announced the completion of the preliminary design of a 1MW motor for the demonstrator. A De Havilland Canada Dash 8-100 will be the platform for the commercial hybrid-electric application.
Pontifications: Next new mainline jet likely will be conventionally powered
By Scott Hamilton
May 9, 2022, © Leeham News: Pratt & Whitney thinks a hybrid-electric propulsion system might be ready for installation on the next new airplane from Boeing or Airbus by 2031. But more likely is that the new airplane, whatever design it is, will more likely be powered by a conventional engine that is capable of running on 100% Sustainable Aviation Fuel (SAF).
Graham Webb, the chief sustainability officer at Pratt & Whitney, said PW is “obviously investing in our Geared TurboFan. That’s our bread and butter. We are working to infuse a large number of technologies, including ceramic matrix composites, and aerodynamic improvements to the turbines and the compressor. We’re working on improving the cooling optimization and sealing, and the traditional core efficiency suite of technologies to enable us to get to the higher overall temperatures we need for the next generation cycles.
“We’ve already completed a suite of work with the FAA and our clean aviation program that enabled us to expand the bypass ratio of our Geared TurboFan engine further from where we are till now. We’re going to use that technology to grow the engine. We’ll put a different fan-drive gear system technology as a result of that expansion. That’s kind of like the traditional engine efficiency piece,” Webb said at the Aviation Week’s MRO Americas event in Dallas. LNA spoke with Webb on the sidelines of the huge event, attended by more than 13,000 people.
Under the FAA CLEEN Phase I program, PW developed ultra-high bypass ratio technologies beyond the current 12:1 present in today’s GTF engines. These technologies are ready for deployment for a future new aircraft. The specific bypass ratio of this new engine will be optimized to each installation on the new airframe configurations being developed by the airframers, a spokesperson added.
Pontifications: The soup du jour
March 14, 2022, © Leeham News: You might call it the soup du jour.
By Scott Hamilton
EcoAviation is all over the place at aviation conferences these days. It was a key topic at last October’s Annual General Meeting of the International Air Transport Association (IATA). Likewise at last month’s annual conference of the Pacific Northwest Aerospace Alliance (PNAA). EcoAviation also was an element of the Speed News conference in Los Angeles early this month and at another event the following week. Investor Day events now routinely include ecoAviation discussion.
This is all well and good, but at last, some key members of the industry are putting caution and realism to the pie-in-the-sky stuff that is sucking up investment like the Dot Com era a few decades ago. Only a few ideas and technologies will be successful.
HOTR: Collins Aerospace sustainability
Feb. 22, 2022, © Leeham News: The headlines and debate over ecoAviation focus on the airframe and engine manufacturers, for good reason. But the aerospace supply chain is mindful of its ESG (Environmental, Social, and Governance) issues as well.
Pratt & Whitney makes the engines that emit emissions and burn fuel. It works to reduce fuel burn and emissions. PW also is exploring electric, hybrid and hydrogen alternatives. Sister company Collins Aerospace works to find solutions to reduce emissions in other areas.
“We play a big role in sustainability,” says LeAnn Ridgeway, Vice President, Sustainability. Collins purchased FlightAware, which is perhaps best know for flight tracking in competition with FlightRadar24. But FlightAware provides route planning and ADS-B services, among others.
For next new airplane, Pratt appears to trail CFM for next new engine
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By Scott Hamilton
Feb. 21, 2022, © Leeham News: As Boeing ponders whether to launch a new airplane program and industry consensus seems to be that this must happen in 2023 or 2024, Pratt & Whitney seems to face a dilemma.
Pratt & Whitney Geared Turbo Fan engine. Credit: Pratt & Whitney.
Convinced that the Geared Turbo Fan technology is the path to future engines, nevertheless, public statements indicate that by 2035, the GTF in the conventional form will fall short of the Open Fan being developed jointly by GE Aviation and Safran. GE and Safran are 50-50 partners in CFM International, which will sell the engine.
Rick Deurloo, the chief commercial officer for PW, told LNA last October that by 2031 (at the time, 10 years in the future), the GTF will have a 10% improvement in fuel burn and emissions compared with today’s GTF. PW will have a 1% improvement by 2024.
GE’s Travis Harper, who is the program manager for the Open Fan “RISE” engine under development, told LNA earlier this month that the RISE will reduce fuel consumption and emissions by 20% and be ready for entry into service by 2035.
If the goals outlined by Deurloo and Harper are taken at face value and achieved, this means the GTF will be up to 10% short of CFM’s engine ready for EIS four years later.
This was the question LNA put to other representatives of GE and PW at the Pacific Northwest Aerospace Alliance conference Feb. 10.