The cumulative use of the OEI/LOW-2 min” is 10 min, with several incursions, for a maximum of 2 min per flight.
OEI LOW red LED will flash in the NG indicator when these 2 minutes are reached, and has to be reset before next flight.
The cumulative use of the OEI/HI-30” is 30”, with several incursions, or not, depending of the engine standard and MOD applied – See below.
From Turbomeca Engine maintenance Manual (Nov 2013):
- When cumulative use of OEI - Low reach 10 min : Removal and Overhaul of module 3, module 4 and DECU.
- BEFORE TU 6 or TU 14 : When OEI – Hi has been used : Removal and Overhaul of module 3, module 4 and DECU.
- AFTER TU6 or TU14 : When OEI – Hi has been used : Removal and Overhaul of DECU.
- AFTER TU6 or TU14 : When cumulative use of OEI – Hi reach 30 sec : Removal and Overhaul of module 3, module 4 and DECU.
- TU 6 : New material for free turbine envelope.
- TU 14 : Increase of the free turbine casing envelope.
From certification regulation, the 30 sec rating must be demonstrated 3 times on the same engines/same flight, but the RFM won’t mention it as being the limitation pilots could cope with….Just nice to know….
https://www.faa.gov/regulations_poli...cumentID/74478
Similar reg should exists in EASA regs, but no time to go through CS-Engine.
OEI HI and LOW cumulative use can be checked in the F.A.U display (Mode Memory – Digit G and J. To be checked in your RFM – Section 8.4 as there are plenty of different software version).