Reader Response #3

The CFM56 series of high-bypass turbofan aircraft engines is manufactured by CFM International (Global Engine Maintenance, 2019), a 50-50 collaboration between GE Aerospace and Safran Aircraft Engines (MTU Aero Engine, n.d). With more than 30,000 units supplied to about 500 clients globally, it is the most dominant engine used on aircraft (CFM International, 2017, as cited by Mwanalushi, 2021). Among the series, the CFM56-7 is the latest engine developed (CFM International, 1995). According to CFM International (n.d), it is the sole engine “for the Boeing Next-Generation single-aisle airliner”, with over 15,000 CFM56-7 produced to power Boeing-737 aircraft, earning its title as “the most popular engine-aircraft combination in commercial aviation history”. The engine has also accumulated 25 million flight hours in just six years of commercial operations, setting yet another record for having “the fastest accumulation of flight hours in commercial aviation history” (CFM International, 2024). The CFM56-7 features a “three-dimensional aero design, a high-efficiency wide chord fan, advanced electronic engine control, and active clearance control systems”, offering substantial cost advantages from a significant cutback in fuel consumption and maintenance expenses (CFM International, 1997).

While the CFM56-7 has earned its reputation for its merits in efficiency and cost-effectiveness, it has been surpassed by newer models like the LEAP-1B in terms of performance.

Firstly, regarding efficiency, the CFM56-7’s specific fuel consumption is estimated to be 8 percent less than the CFM56-3 (CFM International, 1996). OpenAI (2024) described specific fuel consumption as the “amount of fuel consumed by the engine for producing a certain amount of thrust or power over a specific period”. This means the CFM56-7 uses lesser fuel to provide the same amount of thrust compared to its old version. Furthermore, each percent reduction in fuel consumption can yield annual savings of as much as $15,000 per aircraft (CFM International, 1996). As a result, it can be inferred that the CFM56-7 is more efficient and economical than its predecessor.

In addition, it was reported in 1996 by CFM International that the maintenance cost for the CFM56-7 is expected to be 15 percent lower than the CFM56-3 at the same thrust. An article by Aircraft Commerce (2003) states that a “performance restoration” for the CFM56-7 is estimated between $875,000 and $900,000 while a complete overhaul costs about $1.1 to $1.2 million. On the other hand, the “performance restoration” on CFM56-3 costs from $860,000 to $910,000, and the overhaul costs $1.4 to $1.5 million (Aircraft Commerce, 2006). Therefore, it is evident that conducting maintenance on the CFM56-7 is much cheaper than the CFM56-3.

Despite its edge over its predecessor, the CFM56-7 has shortcomings when compared to its successor, the LEAP-1B, which is developed with an identical design to the CFM56 series (Memon, 2023) by CFM International (GE Aerospace, n.d). In terms of thrust performance, the LEAP-1B can produce 23,000 to 28,000 pounds of thrust (Memon & Walker, 2024) while the CFM56-7 can only produce 18,500 to 26,300 pounds of thrust (CFM International, 1996). Since “in level flight, when thrust is increased, the aircraft speeds up and the lift increases” (Federal Aviation Administration, n.d), the LEAP engine will provide better velocity and lift under the same conditions than the CFM56-7.

The bypass ratio is another area where the LEAP-1B surpassed the CFM56-7.  The LEAP-1B engine has an outstanding bypass ratio of 9:1 (Memon & Walker, 2024) while the bypass ratio of the lowest-thrust-rated version of the CFM56-7 is 5:1 (Aircraft-Commerce, 2008). An article by Monroe Aerospace (2023) states that “high-bypass turbofans are typically more efficient than their low-bypass counterparts” as they utilize lesser fuel and produce lower amounts of gas emissions. Having said that, we can say that the LEAP-1B is more fuel-efficient while producing significantly lesser discharge than its older counterpart.

In conclusion, the CFM-56 engine series is highly regarded in the aviation industry and has significantly contributed to the aerospace industry with its capabilities and cost benefits. As aviation technology advances, it serves as the foundation for improvement present in the LEAP series. 

 

 

References

Aircraft Commerce. (2006). CFM56-3 maintenance analysis & budget. https://www.aircraft-commerce.com/sample_article_folder/maintenance_engineering_1_sample.pdf

Aircraft Commerce. (2008). Aircraft-Commerce. https://www.aircraft-commerce.com/wp-content/uploads/aircraft-commerce-docs/Aircraft%20guides/CFM56-7B/ISSUE58_CFM56_7B_SPECS.pdf

Aircraft Commerce. (2023). Maintenance cost analysis: JT8D-200, CFM56-5B/-7 & V.2500. https://www.aircraft-commerce.com/wp-content/uploads/aircraft-commerce-docs1/Maintenance/2003/ISSUE%2028-MTCE-B.pdf

CFM International. (n.d). CFM56 - CFM international jet engines. https://www.cfmaeroengines.com/engines/cfm56/

CFM International. (1995, May 22). CFM56 engines continue to lead the industry; new CFM56-7 begins ground testing on schedule. https://www.cfmaeroengines.com/press-articles/cfm56-engines-continue-to-lead-the-industry-new-cfm56-7-begins-ground-testing-on-schedule/

CFM International. (1996, December 7). CFM56-7: An in-depth look at the new industry leader. https://www.cfmaeroengines.com/press-articles/cfm56-7-an-in-depth-look-at-the-new-industry-leader/

CFM International. (1997, October 14). Thy places $280 million CFM56-7 order. https://www.cfmaeroengines.com/press-articles/thy-places-280-million-cfm56-7-order/

CFM International. (2024, February 24). CFM56-7B fleet achieves 25 million engine flight hours. https://www.cfmaeroengines.com/press-articles/cfm56-7b-fleet-achieves-25-million-engine-flight-hours/

Federal Aviation Administration. (n.d.). Chapter 5 - Aerodynamics of Flight. https://www.faa.gov/sites/faa.gov/files/07_phak_ch5_0.pdf

GE Aerospace. (n.d.). CFM LEAPEngine family. https://www.geaerospace.com/commercial/aircraft-engines/cfm-leap

Global Engine Maintenance. (2019, July 27).  CFM56-7B. https://global-engine.com/cfm56-7b/

Memon, Dr. O. (2023, February 24). The engine of the future: How does the CFM leap differ from the CFM-56?. Simple Flying. https://simpleflying.com/cfm-leap-engine-advantages/

Memon, Dr. O., & Walker, S. (2024, September 6). How CFM LEAP engines enhance the performance of the Boeing 737 MAX. Simple Flying. https://simpleflying.com/cfm-leap-engines-enhance-performace-boeing-737-max/

Monroe Aerospace. (2023, December 1). Low vs high bypass turbofan engines: What’s the difference? One Monroe Aerospace. https://monroeaerospace.com/blog/low-vs-high-bypass-turbofan-engines-whats-the-difference/?srsltid=AfmBOop4ZGcr6mZWW-cdLG1awlbSfKTi7qs2SL1JhmxJk_VVpLrinqqk

MTU Aero Engines. (n.d.). CFM56: Powering the Airbus A320 family and the Boeing 737. https://www.mtu.de/engines/commercial-aircraft-engines/narrowbody-and-regional-jets/cfm56-2/-5b/-7/

Mwanalushi, K. (2021, March 29). Turning turbines: Why CFM56 is the reigning engine of choice. Aviation Business News. https://www.aviationbusinessnews.com/low-cost/cfm56-aviation-aircraft-engine/

OpenAI. (2024, October 5). ChatGPT (October 2024 version) [Large language model] https://chat.openai.com/