RB211
 

Cathays 747-400 are operating RB211-524H (apart from those ex-SIA 400s )engine which have logged more than 80 million flying hours, RR stated that the RB211 has lowest mature feul burn, lowest maintenance costs, so the question is why is the RB211 engine shorter than most other engines in its thrust class? And how it affect the engine's performance?

the Rolls Royce RB211 is triple-spooled. basically it means the engine has 3 different pressure systems, which is comprised of the compressor and the turbine. the three pressure systems (high pressure, intermediate pressure and low pressure) systems are independent of each other (they have independent shafts) and are free to rotate at their own optimum speed (the N1 fan must rotate slower than the internal compressors). as a result, the efficiency of the engine increases.

that answers part of the question. for the other part my understanding is that it is a short engine comparitively because each compressor has less stages to it

A shorter engine is also advantageous as there is less flexing through the shafts.

I think you will find the RR engines on the 744 are actually RB211 524 H/T. They are hybrids. The hybrid if memory serves me correct is an improved intermediate compressor stage, which results in slightly less fuel burn than the straight G or H models, but don't quote me on that.

The T means that it has been incorporated some of the RR Trent Engine technology. I believe that the G/box has also been modified as well.

thank you guys.
So does it mean RR are producing best engines for 400s? But it seems PW are providing longer range for their engines

That's a hard one to answer. You'd probably have to look at other issues such as time on wing without change. I know RR set a milestone many years back with one of their RB211 engines, for longest running time without the need to service any major parts. Perhaps someone could shed light on this?

I believe the 211's are heavier than the PW or CF6, which isn't always favourable for overall fuel burn, but it does have one big advantage with reducing wing flex.

CX's fleet has always been powered with Rolls Royce engines. this has been the case since the Lockheed L-1011, B747-200 and B747-300 aircraft were still serving pax routes with Cathay, all of which were powered by RB211s (albeit different variations of the engine). it is only natural that when the -400 came out back in the late 1980s, the management chose the "Rollers" instead of the other available options.

on an unrelated note, when the A330s, A340s and B777s joined the fleet, cathay always chose Rolls Royce engines when they could. their intentions were to keep the entire fleet running with engines made of a similar principle, so as to keep the maintenance cost down. it would be costly in terms of time and money to train engineers to deal with different types of turbofan engines.

so why ex-SIA 400's
 

So they keep alone well their original idea well until one day they got ex-SIA 400's.Actually my another question here is why they pick those ex-SIA 400's? giving money to SIA let them try on A380 ?!:cool:

beats me. i don't think that they chose those 747s just because they used to fly for SQ, but don't quote me on that!

I heard that they might not be as happy with some of the RR engines as they portray? I suspect it might be a little bit of a gimmick for lack of a better word. Does anyone have any insight? Maybe it's just a rumour, maybe not, i don't know.
What's clear though is that there are a few very good engine manufacturers, so I'd be suprised if the RR was outstanding in all areas, there's probably a trade off as with everything else in this business...

They probably chose SIA's ex fleet of 400's as they are generally young. Average fleet age was something like 7 or 8 years ( but that is over their entire fleet). Also SIA are very strict with their maintenance program, so CX could be rest assured they were getting good quality second hand aircraft.

Also it's very hard to source a RR specific 400 as only 3 other airlines fly them i.e BA, Air New Zealand and Qantas. At that time none of these aircraft were up for sale/lease.

Actually the ex SIA 400 have been in a terrible shape. Only now they start not breaking down all the time.
The only reason CX bought them was because they have been cheap.

cx252,

another major reason why the RB211 is shorter than other 2 spool engines is because of the arrangement of bearings supporting the 3 spool shafts. With GE/PW engines each compressor and turbine section has to have a roughly equal sized bearing module supporting each rotor at each end. Whereas the RB has a more substantial bearing system located inside the IP/HP compressor transition duct, the heart of the engine, called the IGB (internal gearbox). This takes more of the thrust loads for the compressors and turbines and therefore the other supporting bearings and cases can be shorter/smaller.

(and contrary to any GE/PW blurb, you'll find that the RB211 is about 300kg lighter than the competition)

Dakotablue/el Commandante,

one major reason could have been because when CX chose the new 747-400ERF the only choice of engine was a PW, the 4062 model. They probably got some sweet deals with P+W along the line, therefore owning some older 4056 powered a/c was an advantage. Consider the poor old PW asia sales rep who had been coming to CX for the last many years and always left with the sound of "nice brochures, don't call us we'll call you...." ringing in his ears. And, yes, as ever SIA are always cheap.....


holdmetight,

it could be a little more simple than you suggest:

John Swire & Sons Ltd.
Swire House
59 Buckingham Gate
London SW1E 6AJ
England


RR London Offices:
65 Buckingham Gate
London SW1E 6AT
England

Rumour has it that Swires of the day and RR chairmen were quite often seen drinking in the same London 'club'. Oh and perhaps the British government may have helped keep things on british order books......

coolbanana

RR took the HP Compressor/Combustion/HP Turbine module of the Trent 700/800, known within the overhaul business as the 04 module, and shoe-horned it into RB211-524(G rated as they were with CX). The only other small modfication was to the rear of the IGB (see above).

Hoping this clears some things up,

N1 Vibes

N1 Vibes
 

thank you very much for your information, all clear now. Cheers.:ok:
So in conclusion that RB211 more advance designed in general.

N1 Vibes, good post!:ok:

I'm just trying to make sure I haven't missed anything here. on the 747's engine wise we have the rb 211-524 and the pw4062. Am I missing any??

Don't forget the CF6-80C2 - It has a significant market share on the 744. It's also about 50 cm. shorter than earlier CF6-50s due to shortened combustor and removal of one bearing sump.

ash79

on the -400 we have the rb211-524h-t, the pw4062 and the pw4056 (a few pounds less thrust than the 4062, but essentially the same).

barit1

youre right the cf6-80 is a variant on the -400, but cx only have the CF6 on the classic 747f, soon to retire, the cf6-50e2. though we do have the cf6-80 on the a300-600, the -a5f.

regards,

n1 vibes