In this article we would like to share with you our experience in the engine re-certification options our team used during their operational and maintenance experience of Boeing 737 Classics.
Option 1 - engine in as removed conditions
When your CFM 56–3 engine is in as removed conditions there is an easiest option to make Full Video Borescope inspection and if serviceable to issue 8130–3/EASA Form 1/NAA Form 1. Afterwards you may legally install the engine on wing.
Options 2 - 90/180/365 days preservation overdue
If 90 or 180 days on-wing preservation or 365 days ESM preservation is overdue to any reason owner/operator shall make a service request to CFMi representative to get a legal way of engine re-certification. As per our practice if this preservation was not significantly overdue and the engine storage and wrapping conditions are fine, you might require to make engine #4 bearing inspection on corrosion, VBSI and to make MPA run after installation on wing. This work package will include mentioned above steps and will take 5-6 days.
Option 3 - 365 days preservation overdue significantly or the engine is not preserved at all
With reference to Option 2 in this case you might do CFMi service request any way. CFMi reply might significantly vary depending on the conditions of physical engine storage: friendly (in hangar, previously stored, wrapped) or not friendly (on wing, with out covers, sandy or humid area).
CFM most likely will advise you a shop visit that might include the following WS:
2. Gain access to engine bearings #1, 2, 3, 4 & 5 & AGB/TGB for inspection
3. Engine Oil Circuit flushing
Overhaul per CMM of the following oil components:
Perform ESM 72–00–00 Test 002 & and Test 003
Option 3 may be called a Partial Performance Restoration as the engine inspection might give a positive result on the EGT of your engine after the inspection is completed.
To avoid additional expenses our team strongly recommends you to keep an eye on proper preservation and storage of your engines both on-wing or on-stand. This may save you and your company from shop visit expenses and keep the engine ready to fly. As well as you might consider that SV engine is an asset that you may sell/lease in any time and unpreserved engine cost will equal to sheet metal.