《知識》CFM International：從 CFM56 到 LEAP，全球主要窄體客機引擎供應商 CFM International: From CFM56 to LEAP, a Leading Engine Supplier for Narrow-Body Aircraft

CFM International 是全球主要商用飛機引擎製造商之一，也是窄體客機市場最具影響力的引擎供應商。這家合資公司是由美國通用電氣航空 (GE Aviation) 和法國賽峰集團 (Safran) 於 1974 年共同成立，兩家公司各持有 50% 的股份。CFM 目前最重要的兩個引擎系列，就是 CFM56 與它的後繼產品 LEAP。

CFM56：奠定 CFM 地位的經典引擎

CFM56 是航空史上最成功的商用噴射引擎，目前已經累計生產超過 3 萬具，並廣泛使用在全球大量窄體客機上。通用電氣的歷史資料甚至將 CFM56 系列稱為航空史上最受歡迎的商用噴射引擎系列之一。

1981 年，波音選擇 CFM56-3 作為 737-300、737-400 和 737-500 的動力來源。到了 1990 年代，波音又選擇 CFM56-7 作為 737 Next Generation，也就是 737-600、737-700、737-800 和 737-900 的引擎。CFM 幾乎一路跟著 737 家族成長。

CFM56 的另一個重要客戶就是空中巴士。CFM56-5 系列被廣泛使用於 A318、A319、A320 和 A321，也就是我們今天非常熟悉的 A320ceo 家族。連廣體客機也曾使用 CFM56。例如，Airbus A340-200/300 就使用 CFM56-5C。

CFM 最重要的商業優勢是：同一個引擎系列，可以衍生出不同版本，服務不同的飛機。

LEAP：CFM56 的下一代產品

到了 2000 年代，CFM 開始開發新一代引擎，最後推出了 LEAP。在保留 CFM56 高可靠度與低維護成本優勢的同時，進一步降低燃油消耗。LEAP 於 2016 年開始投入商業服務，目前已經成為新一代窄體客機最重要的引擎之一。

LEAP 使用了許多新技術，其中碳纖維風扇葉片和 CMC 熱端零組件，是 LEAP 很重要的技術突破。LEAP 目前主要有三個版本：

• LEAP-1A，提供給空中巴士 A320neo 家族
• LEAP-1B，提供給波音 737 MAX 家族
• LEAP-1C，提供給中國商飛 C919

飛機製造商選擇「單一引擎供應」成為發展趨勢

早期的飛機製造商，針對同一種機型會提供兩種甚至三種引擎，讓航空公司有更多選擇。例如波音 787 可以選用 GE GEnx-1B 或是勞斯萊斯 Trent 1000。空中巴士 A380 可以選用勞斯萊斯Trent 900 或是 Engine Alliance GP7200 （通用電氣與普惠共同成立的 Engine Alliance 開發）。

但問題是每增加一種引擎，就增加一套整合、測試與認證工作。更多的引擎選擇代表飛機製造商會有更多開發與認證成本。

對於飛機製造商來說：

即使飛機機型相同，不同引擎仍會影響：引擎掛架、機翼結構、引擎整流罩、燃油系統、引擎控制系統、飛機軟體、維修與備件及飛行性能等。因此，引擎選擇其實是飛機製造商非常重要的工程決策。

對於航空公司來說：

原本擁有的飛機假設都是使用 CFM56 引擎。當後續新的飛機使用 LEAP 引擎，雖然是不同系列的引擎，但因為引擎製造商相同，就可以延續過去累積的維修、培訓、零件供應和工程經驗。航空公司不需要重新建立一整套完全不同的引擎維修體系。

CFM 最大的競爭對手：普惠（Pratt & Whitney）

在窄體客機市場，CFM 最大的直接競爭對手為美國雷神科技 (RTX) 旗下的普惠 (Pratt & Whitney)。目前空中巴士 A320neo 家族，可以選擇 CFM LEAP-1A 或是普惠 PW1100G 引擎。至於勞斯萊斯引擎，則主要集中在大型廣體客機市場，例如空中巴士 A350 使用勞斯萊斯 Trent XWB、空中巴士 A330neo 使用勞斯萊斯 Trent 7000。勞斯萊斯與 CFM 的直接競爭並不像 CFM 與普惠那麼集中在同一個窄體客機市場。延伸閱讀：《精選》全球最大航空引擎 - 英國勞斯萊斯 UltraFan 介紹

普惠 PW1100G 引擎採用 Geared Turbofan 技術，與 CFM LEAP 採用了不同的技術路線。LEAP 主要透過更大的風扇、先進材料與高效率核心提升燃油效率；PW1100G 則加入齒輪箱，讓大型風扇與低壓渦輪可以用不同轉速運轉，在高旁通比架構下進一步提升推進效率。延伸閱讀：《知識》飛機引擎運作原理及何謂「旁通比」？

CFM 下一步：開放式風扇（Open Fan）

CFM 下一代引擎技術的重點之一，是 RISE（Revolutionary Innovation for Sustainable Engines）計畫中的開放式風扇（Open Fan）。這項技術也常被稱為開放轉子（Open Rotor）。

現在的客機引擎，前面都有一個巨大的風扇，而風扇是被包覆在引擎內部。開放式風扇的概念則是把傳統風扇改放到引擎外部。如此一來，就可以使用更大的風扇，推動更多空氣，進一步提升推進效率。CFM 的目標，是希望開放式風扇技術相較於現今最先進的商用引擎，能帶來約 20% 以上的燃油效率改善。

以下是 CFM 開放式風扇的概念影片。看到開放式風扇，很多人第一眼可能會覺得：「這不就是螺旋槳引擎嗎？」因為兩者都有大型、外露的葉片。不過，開放式風扇本質上仍是延續了渦輪風扇引擎的設計，只是將風扇改為超大型的外顯方式設計，這樣可以推動更多空氣，希望在接近現代噴射客機的高速飛行下，也能進一步提升推進效率。

-

CFM International: From CFM56 to LEAP, a Leading Engine Supplier for Narrow-Body Aircraft

CFM International is one of the world's leading commercial aircraft engine manufacturers and one of the most influential engine suppliers in the narrow-body aircraft market.

CFM International is a joint venture between GE Aviation in the United States and Safran in France, founded in 1974. The two companies each own 50% of the company.

Today, CFM's two most important engine families are the CFM56 and its successor, the LEAP.

CFM56: The Engine That Built CFM's Success

The CFM56 is one of the most successful commercial jet engine families in aviation history, with more than 30,000 engines produced. It has been widely used on narrow-body aircraft around the world. GE's historical materials have even described the CFM56 as one of the most popular commercial jet engine families in aviation history.

In 1981, Boeing selected the CFM56-3 to power the 737-300, 737-400, and 737-500.

In the 1990s, Boeing selected the CFM56-7 for the 737 Next Generation family, including the 737-600, 737-700, 737-800, and 737-900.

In many ways, CFM grew alongside the Boeing 737 family.

Airbus also became an important CFM customer. The CFM56-5 series was widely used on the A318, A319, A320, and A321, better known as the A320ceo family.

The CFM56 was even used on wide-body aircraft. For example, the Airbus A340-200/300 was powered by the CFM56-5C.

One of CFM's biggest business advantages was that the same engine family could be developed into different versions for different aircraft.

LEAP: The Next Generation After CFM56

In the 2000s, CFM began developing a new-generation engine, which eventually became the LEAP.

The LEAP kept the CFM56's strong reputation for reliability and relatively low maintenance costs, while significantly improving fuel efficiency.

The LEAP entered commercial service in 2016 and has since become one of the most important engines for the new generation of narrow-body aircraft.

The LEAP uses many advanced technologies. Two of its most important innovations are carbon-fiber fan blades and CMC (ceramic matrix composite) components in the hot section of the engine.

There are currently three main versions of the LEAP: 

• LEAP-1A — for the Airbus A320neo family
• LEAP-1B — for the Boeing 737 MAX family
• LEAP-1C — for the COMAC C919

A Growing Trend: Single Engine Supplier for an Aircraft Family

In the past, aircraft manufacturers often offered two or even three engine options for the same aircraft model, giving airlines more choices.

For example, the Boeing 787 can be powered by either the GE GEnx-1B or the Rolls-Royce Trent 1000.

The Airbus A380 was available with either the Rolls-Royce Trent 900 or the Engine Alliance GP7200, developed by a joint venture between GE and Pratt & Whitney.

However, adding another engine option also means more integration, testing, and certification work.

More engine options mean higher development and certification costs for aircraft manufacturers.

For Aircraft Manufacturers
Even when the aircraft itself is the same, different engines can affect many parts of the aircraft, including: Engine mounts, Wing structure, Engine nacelles, Fuel systems, Engine control systems, Aircraft software, Maintenance and spare parts, and Flight performance. Because of this, choosing an engine is a very important engineering decision for an aircraft manufacturer.

For Airlines
Imagine an airline already operates a fleet powered by CFM56 engines. When the airline later purchases new aircraft powered by LEAP engines, the engines are from a different generation, but they are still made by the same manufacturer. This allows the airline to build on its existing experience in maintenance, training, spare parts, and engineering support. The airline does not need to build an entirely new engine maintenance system from scratch.

CFM's Biggest Competitor: Pratt & Whitney

In the narrow-body aircraft market, CFM's biggest direct competitor is Pratt & Whitney, which is part of RTX in the United States.

The Airbus A320neo family can be powered by either the CFM LEAP-1A or Pratt & Whitney's PW1100G.

Rolls-Royce, on the other hand, is more focused on the wide-body aircraft market. For example, the Airbus A350 uses the Rolls-Royce Trent XWB, while the Airbus A330neo uses the Rolls-Royce Trent 7000. As a result, Rolls-Royce and CFM are not as direct competitors as CFM and Pratt & Whitney, since their products are less concentrated in the same narrow-body market.

The Pratt & Whitney PW1100G uses Geared Turbofan technology, which takes a different approach from the CFM LEAP.

The LEAP improves fuel efficiency mainly through a larger fan, advanced materials, and a more efficient engine core.

The PW1100G uses a gearbox, allowing the large fan and the low-pressure turbine to operate at different speeds. This helps improve propulsive efficiency while using a high-bypass-ratio design.

CFM's Next Step: Open Fan

One of the key technologies CFM is developing for its next-generation engines is the Open Fan, part of the RISE (Revolutionary Innovation for Sustainable Engines) program. This technology is also commonly known as an Open Rotor.

Modern commercial jet engines have a large fan at the front, but the fan is enclosed inside the engine nacelle. The Open Fan concept moves the fan outside the engine nacelle. This allows the engine to use a much larger fan and move more air, potentially improving propulsive efficiency.

CFM's goal is for the Open Fan technology to deliver more than 20% better fuel efficiency compared with today's most advanced commercial aircraft engines.

When people first see an Open Fan engine, they may think: "Isn't this just a propeller engine?" It is an understandable comparison because both designs have large, exposed blades.

However, the Open Fan is still based on the principles of a turbofan engine. The main difference is that the fan is designed as a much larger, exposed fan system. The idea is to move more air and improve propulsive efficiency, while still allowing the aircraft to fly at speeds close to those of modern jet airliners.