RB211 747

[YOUNGBUCK]

Hi Guys,

Just out of interest, is anyone able to tell me about the technology differences between RR RB211 on 747-200 & 747-400 (524 - 524-g).

cheers,

[Dave Therhino]

The most obvious differences between the -524G and earlier -524 variants were wide chord fan blades and a full authority digital engine control. Higher thrust and higher bypass ratio as well.

[TURIN]

Common nozzle exhaust on the 524G/H too.

[Dave Therhino]

Forgot about that. That actually IS the most obvious difference!

[tdracer]

a full authority digital engine control.
Sorry to be a little anal here, but the RB211-524G/H was not FADEC - it was a "Full Authority Fuel Control" - FAFC. In one of those 'what were they thinking' decisions, Rolls kept the archaic fluidic (basically pneumatic) guide vane and bleed controls that dated all the way back to the L1011 installation. They were very troublesome systems on all marks of the RB211 - including the G/H.
The RB211-524G/H had a major upgrade in the early 1990s - the "-T" (i.e. an engine so modified became a RB211-524G-T or H-T. Vague memory says the -T was an upgraded HP turbine, good for ~1% fuel burn.

The wide-cord fan blades on the RB211-524G/H were a significant efficiency improvement, but the hollow titanium construction was susceptible to fan flutter issues when operated statically over a specific fan rpm range. We needed to update the FAFC software to implement a 'keep out' zone when the airspeed was less than 35 knots.

[esscee]

The "T" for some of the G/H engines meant that those engines used some of the Trent 700 core/hot section, saved some weight and gained a small power increase.