Hi, Talking about B747 & engine power settings etc. I am not a qualified aeronautical engineer and this question might look stupid, but Would a B747 by any chance have two different variants of the same engine -"RB211-524H2-T-" and "RB211-524G2-T-. I have come across an issue related to engines and Navigation database software loading and related queries.
Not stupid at all!
I think that all four engines on a particular airframe have to be either 'G' or 'H'. When I was on the -400 there was a sticker on the instrument panel which said:
'This aircraft is 'G' rated' ;or
'This aircraft is 'H' rated.
The pilots had to check that the FMC IDENT page reflected the same engine rating.
My understanding is that all -400 on that fleet are now 'G' rated, so the sticker has probably been removed.
The '-T' suffix relates to the modification of the core to 'RR Trent' standards. The intermix of -T with non-T on the same airframe was permitted. There would be a note in the tech-log with words to the effect of, "No 2 engine has been modified with a Trent core. All procedures and limitations are the same but pilots may notice lower EGT and Fuel Flow when compared to engines Nos 1, 3 and 4".
Never heard or the holding technique involving retarding symmetrical engines and advancing the others. It sounds perfectly plausible from a technical standpoint but was never SOP.