The following information was taken from the Industrial heating Forum at the MTI website. It is a topic of discussion and is subject to interpretation and clarification.
You may adopt AMS 2750E in its entirety, in lieu of BAC-5621. This is applicable to Boeing Commercial. Currently, Boeing Military has not adopted AMS-2750E yet. One thing to be aware of is that if you are processing to Boeing specifications, such as BAC-5602, BAC-5617, etc., you will still need to meet the instrumentation types and furnace classification to the Boeing Process specifications. The PSD will help you to determine between AMS-2750 and BAC-5621 equivalent instrumentation types.
Be advised that when you do convert to use of AMS 2750E in lieu of BAC 5621, you need to make sure all your pyrometry procedures, work instructions, heat treat furnace classifications are clearly defined. There is a difference in instrumentations types that you need to assure you reconcile.
When converting use AMS 2750E for TUS sensors, locations, failed sensors, Intervals for TUS’s and SAT’s, extended intervals, calibration of field test instruments, thermocouple sensors replace/recalibrations, thermocouple number of usages…EVERYTHING. ISC’s replaced with SAT’s and instrument calibrations, allowance to use resident SAT sensors.
Essentially you can wipe out BAC5621 with the exception of Class and Type requirements called out in processing specs, i.e BAC5602 solution and age requires Furnace Class II, Instrument Type B in BAC5621 is equivalent to Class 2, Type C. PSD 6-42 has all this nicely documented to guide you.