Reader Response draft #1

The CFM56 is a family of high-bypass turbofan aircraft engines produced by CFM International, a 50/50 joint company between Safran Aircraft Engines and GE Aerospace (CFM International, 2024). As the widely known Airbus and Boeing companies continuously develop different aircraft models over the years, the CFM company would also have to address the needs and challenges of each plane model. The CFM company has produced several variants in its engine family to cater to the needs of such airplanes including the military. Each of the variants is a better, more updated version of its predecessor. According to the CFMI (2003, pg 26) training manual, the CFM56 variants include the CFM56-2 series, CFM56-3 series, CFM56-5A, 5B and 5C series, and the CFM56-7B series. A high-bypass turbofan engine has a large amount of air passing through the core of the engine instead of through the engine's combustion chamber, hence the name, high-bypass. This makes the engine more efficient than its low-bypass counterpart as it consumes less fuel, producing fewer emissions, making it a preferred choice for commercial airlines (One Monroe Aerospace, 2023). According to CFM International (2024), the CFM56 has accumulated over 1 billion flight hours, over 33000 engines delivered, and serving over 600 operators, the CFM56 has established itself as the benchmark for single-aisle commercial jet engines. Its success is attributed to its outstanding reliability and performance. The engine also achieves a 94% utilization rate and a dispatch reliability rate of 99.96%. This means that the CFM56 encounters one delay or cancellation for every 2500 flights (Levingston, 2019).

I feel that the CFM56 has proven itself to be a cornerstone in modern aviation history. Even though it is not the most advanced engine that is available today, it has built an excellent reputation based on its reliability, versatility, and longevity.


The main components of the CFM56 comprise the fan, compressor, combustor, turbine and nozzle. All of these components work hand in hand with one another to ensure that the engine is running operationally. Located at the front of the engine, the fan is the most important component because it is responsible for generating thrust. 


The fan is typically made of titanium alloy and it is used to suck in large amounts of air. The air subsequently moves through 2 parts of the engine. Part of the air passes through the engine’s core for combustion. The rest of the air called “bypass air”, passes around the core through a duct. This bypass air cools the engine, provides extra thrust and reduces noise by enveloping the exhaust air that is exiting the engine (Cutler, 2022). The amount of air that passes through the core or becomes bypass air will be in a bypass ratio. The bypass ratio compares the mass flow rate of air bypassing the engine core to the mass flow rate of air entering the engine core (Waqar, 2021). The variants of the CFM56 have bypass ratios that range from 5:1 to 6:1. For example, a bypass ratio of 5:1 means that 5kg of air passes through the core of the engine, and 1kg of air becomes bypass air.


After the fan, the CFM56 compressor comprises the Low-Pressure-Compressor (LPC) and the High-Pressure-Compressor (HPC). To summarise, the compressor consists of stages of small rotating fan blades that compress the air. As the air progresses through the compressor, each successive set of blades is slightly smaller, increasing the energy and compression of the air (Cutler, 2022). 


As the compressed enters the combustor, it is mixed with fuel and ignited. While the idea sounds simple, it is actually a complex process. The burner needs to maintain stable combustion of the air-fuel mixture while the air flows past it at high speeds (Waqar, 2021).


After passing through the combustor, the air moves through the turbine. It consists of small fan blades that are similar to the compressor that extract energy from the hot, fast-moving air which in turn, spins the turbine and the shaft that connects to the fan and compressor. This becomes a cycle that allows the fan to suck in more air for combustion (Cutler, 2022).


The nozzle is the final part of the turbofan engine. It generates thrust by expelling high-speed exhaust gases which propel the aircraft forward by demonstrating Newton’s third law. Some variants of the CFM56 include a mixed-nozzle. A mixed nozzle mixes bypass air with hot exhaust that can reduce engine noise (Waqar, 2021).


In conclusion, the CFM56 is a key engine in aviation history. While not the most advanced, it is known for its reliability, versatility, and long service life. Its consistent performance has made it a trusted choice in the industry.



[References] // used so far


CFM International (2024). CFM56 - CFM International Jet Engines CFM International https://www.cfmaeroengines.com/engines/cfm56/ 


Chelsey Levingston (2019, June 4). 1 Billion Flight Hours: “World-class experience” builds 15,000th CFM56-7B engine https://www.geaerospace.com/news/articles/manufacturing-paris-airshow-people-product/1-billion-flight-hours-world-class-experience 


One Monroe Aerospace. (2023, December 1). Low vs High Bypass Turbofan Engines: What’s the Difference? https://monroeaerospace.com/blog/low-vs-high-bypass-turbofan-engines-whats-the-difference/ 


CFM International CFM56 - Wikipedia (n.d) https://en.wikipedia.org/wiki/CFM_International_CFM56#cite_note-cfmstory-2 


CFMI (2003). TRAINING MANUAL CFM56-ALL BORESCOPE INSPECTION 

https://www.manualslib.com/manual/1589534/Cfm-Cfm56-Series.html#manual 


Cutler (2022, July 28). How Does A Turbofan Engine Work?

https://www.boldmethod.com/learn-to-fly/aircraft-systems/how-does-a-jet-engine-turbofan-system-work-the-basic-steps/ 


Waqar (2021). What Is A Turbofan Engine | How does a Turbofan work? https://mechanicalboost.com/turbofan/

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