Engine Development. Part 4. Turbofans go mainstream.

Subscription Required

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.

Read more

Engine Development. Part 3. The early turbofans.

Subscription Required

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.

Read more

Engine Development. Part 2. The early jet engines.

Subscription Required

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.

Read more

Bjorn’s Corner: Sustainable Air Transport. Part 33. eVTOL batteries.

August 19, 2022, ©. Leeham News: This is a summary of article Part 33P, eVTOL batteries. This article discusses the trickiest system on an eVTOL, the battery system.

The battery system supplies the energy to the VTOL, and given today’s and tomorrow’s battery technology; it’s a tight resource that needs a lot of pampering.

Figure 1. We use graphs in the Pipistrel spare parts catalog to show the battery system of the Pipistrel Velis Electro. Source: Pipistrel and Leeham Co.

Read more

Engine Development, Part 1: Launch to Entry into Service

Subscription Required

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.

Read more

Pontifications: Rolls-Royce and the Next Boeing Airplane

April 18, 2022, © Leeham News: The aviation industry is waiting to see what Boeing will do when it comes to a new airplane.

By Scott Hamilton

The Next Boeing Airplane (NBA), whatever form it takes, will largely be driven by what advances in engines are available. Boeing CEO David Calhoun downplays the engine element. He’s said repeatedly that the next engine will only have about a 10% lower fuel consumption than today’s powerplants. He didn’t today’s name engines, but the benchmarks are now the Pratt & Whitney Geared Turbo Fan and CFM LEAP.

Calhoun places more emphasis on a moonshot in design and production advances to lower the cost of the airplane—with the theory the price paid by the customer will be lower as a result, providing a combined benefit of lower operating costs and lower capital costs.

PW agrees that by around 2030, the usual date (plus-or-minus a year or two) given for the NBA’s entry into service (EIS), it can get another 10% of improved fuel economy out of the GTF. CFM, on the other hand, is pressing ahead with what used to be called the Open Rotor concept. CFM now calls it an Open Fan. The company has a target EIS of 2035 and a fuel improvement of 20%. Emissions for the two engines would be reduced by roughly a corresponding amount vis-à-vis fuel burn.

Read more

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.

Read more

A Boeing 787-10 HGW, how good is it?

Subscription Required

By Bjorn Fehrm

Introduction

February 24, 2022, © Leeham News: The CEO of Boeing Commercial Aircraft (BCA), Stan Deal, said at the Singapore Air show the company worked on increased gross weight versions of both the 787-9 and -10.

Target is to get the 787-10 to the range of the aircraft it shall replace, the 777-200ER and -300ER. It means more than 7,000nm of range against the 6,400nm of today.

How many tonnes of increased Gross weight does this mean, and what would be the performance compared with the Airbus A350-900? We use our airliner performance model to find out.

Summary
  • The 787-10 can grow to a range of over 7,000nm with a modest increase of its gross weight.
  • It will be competitive with the A350-900 but for the longest routes in such a variant.

Read more

Engine OEMs pushing ahead for next airplane, even as Boeing pauses

Subscription Required

By Scott Hamilton

Nov. 1, 2021, © Leeham News: David Calhoun may not be anywhere near ready to launch the Next Boeing Airplane (NBA), but the engine makers are actively researching and developing engines to hang of whatever that NBA will be.

Calhoun, the CEO of Boeing, repeatedly said the NBA will be more about reducing production costs through advanced design and production methods. For some time, Calhoun said the next engines available on the assumed timeline—to about 2030—will have only 10% better economics than today’s engines.

And 10% isn’t enough for the airlines or the commensurate reduction in emissions.

CFM/GE Aviation/Safran are developing an “open fan” engine that will reduce fuel burn and emissions by 20%. A target date for entry into service is in the 2030 decade. The open fan builds on R&D of open rotors that have been underway since the era of the Boeing 727 and McDonnell Douglas MD-80.

Pratt & Whitney sees an evolution of its Geared Turbofan engine. The GTF was under development for 20 years before an operating engine made it onto the Bombardier C Series (now the Airbus 220), the Airbus A320, and United Aircraft MC-21. The GTF also was selected for the Mitsubishi MRJ90, which launched the GTF program. However, Mitsubishi pulled the plug on the MRJ/SpaceJet program last year. PW remains committed to the GTF for future engines.

Rolls-Royce is developing the Ultra Fan and Advanced engines. GE’s Open Fan and RR’s engines adopt geared turbofan technology pioneered by PW but add new technology.

LNA takes a look at the new engines for the NBA or any other competing airplane in a series of articles.

Read more

Pontifications: Engines drive timing of new Embraer TPNG

The first report appeared Oct. 18, 2021.

By Scott Hamilton

Oct. 25, 2021, © Leeham News: Embraer appears marching toward launching a new turboprop aircraft next year with a targeted 2027 entry into service.

The timing will be determined by the engine. Pratt & Whitney, GE Aviation and Rolls-Royce have development programs. PW and GE are farthest along. PW is thought to have the best chance of winning Embraer’s business. (Pratt & Whitney supplies the engines for the E2 jet. GE supplied the engines for the E1.)

In an interview at the IATA AGM Oct. 3-5 in Boston, Arjan Meijer, the president of Embraer Commercial Aviation, said the competition remains open today.

Read more