Today we are all looking for the possibilities to optimize cost of operations and minimize expenses trying to get business and provide a service to other industries for cargo/passenger transportation from point A to point B. Doing engine condition monitoring and providing engine support to our customers operating Boeing 737 Classic in different parts of the world and flying B737 in a different configuration we see very different engine deterioration rate.
Basically we have the following picture on 737–300/400/500:
For -300 basic option is CFM 56–3B1 or -3B2 operated at 20,1k lb
For -400 basic option is CFM 56–3B2 or CFM56–3C1 operated at 22,1k lb
For -400F or high gross weight is CFM 56–3C1 operated at 23,5k lb
For -500 basic option is CFM 56–3B1 operated at 18,5k lb
We see that the market is mainly proposing CFM 56–3C1 options after PR or partial PR, which means that there is a possibility for a shop to get any customer operating Classic aircraft.
But is it relevant for operator to use -3C1 configuration as the only available option?
CFM56–3 engines do not have rating plugs, that is why thrust of an engine model is changed in the following 3 ways:
2. Throttle box on MEC has a throttle lever mechanical stop
3. Engine conversion
Rerate permits to extend engine on wing life, to optimize LLP management and minimize parts degradation (temperature).
When you need to extend engine on wing life you can recover performance and to continue to use engine when EGTM=0 or less at higher thrust. Example for a CFM56- 3C1, there’s an increase of the EGTm as follow when an engine rerate:
Also you might consider that Rerate/conversion allows engines Intermix as per specific Boeing recommendations.
Engine model conversion required to get a possibility to install the engine on the aircraft where TCDS or intermix SB do not allow use available model. Model conversion is done by hardware replacement. The full procedure is prescribed in relevant SB.
Conversion of 3B1 or 3B2 to 3C1 requires minimum of 11°C EGTM as well as it will require to do check of P/Ns or replacement of the following parts: MEC, PMC, VSV actuator, HPTCCV Timer & Electrovalve, VSV F/B Coupling, VSV Mount Bracket, VSV F/B Cable.
Our team can perform conversion in our maintenance locations in US, Ukraine and UAE, as well as we can do it on-site for you. To convert your -3B1 to -3C1 in our shops it will take 2 days and only 28 m/h. And to re-rate -3C1 to -3B1 or -3B2 can be done in 20 m/h only. We propose our partners to make evaluation of their operational demand and to give our advise on the best option for their operations to make it safe and cost effective.