B747 From United States, joined May 1999, 245 posts, RR: 6 Posted (2 years 2 months 1 week 1 day 13 hours ago) and read 3136 times:
Topic almost says it all, how are the CX RB211 pilots adapting to the SQ 744's that have been modified to Freighters handling the difference in the old SQ 744's PW4056 engines.
Has anyone heard any complaints, or do they seem satisfied?
N754PR From , joined Dec 1969, posts, RR: Reply 2, posted (2 years 2 months 1 week 1 day 11 hours ago) and read 2942 times:
I was going to say the same thing.... what are they going to notice??
As I spotter the only thing I notice apart from the bloody obvious is the amount of crap the PW engines produce over the RR. Some of them (not only CX) look more like 707's these days!!!
Lightsaber From United States, joined Jan 2005, 3850 posts, RR: 71 Reply 4, posted (2 years 2 months 1 week 1 day 6 hours ago) and read 2719 times:
Quoting Litz (Reply 3): As long as they push the levers forwards and the airplane moves, they're probably not going to notice a thing, other than possibly response time.
The pilots should also notice that a triple spool has better climb characteristics than a double spool. This is due to the fan "holding back" the low compressor during climb due to the high loading. Thus, a triple spool will maintain more of its pressure ratio than a double spool giving better cooling and power during the climb stage.
That said, the Pratt's burn a little less fuel, so its more than made up in cruise.
Good to have a post from ya, Lightsabre. Always look fwd to reading your stuff. Now, what specific models are we dealing with here since I have fuel burn data coming out the ying-yang.
BOE773 From , joined Dec 1969, posts, RR: Reply 8, posted (2 years 2 months 1 week 20 hours ago) and read 2453 times:
Quoting Lightsaber (Reply 4): The pilots should also notice that a triple spool has better climb characteristics than a double spool. This is due to the fan "holding back" the low compressor during climb due to the high loading. Thus, a triple spool will maintain more of its pressure ratio than a double spool giving better cooling and power during the climb stage.
Would you have data to back that up, Lightsabre?
The 4 RRs together will weigh 1828 lbs more than the Pratts, thus negating any improvement in ROC over the Pratts.
When you note, "the fan holding back", do you mean reduced fan RPM?
The hi loading of the LPC?
Ejazz From United Arab Emirates, joined May 2002, 680 posts, RR: 29 Reply 9, posted (2 years 2 months 1 week 19 hours ago) and read 2390 times:
BOE773
What APD or EPD are you taking into account for the PW engines? The PW 4000 engines on the B744, A310, B772 and B773 normally have one of the best fuel flow figures when brand new but deteriorate very quickly and much faster than the RR and GE. You therefore end up with a PW engine burning more fuel than the RR or GE after only a few months and this then continues for the remaining years of service. So over the life of the engine you can work out which is the more economical.
PW did urgently introduce a PIP (Performance Improvement Programme) on the 4000 series which did help but still today their Performance deterioration exceeds that of the RR and GE. Thats from figures sent by Boeing to Operators.
You cannot take the advertised engine fuel burn figures as these will only exist for a very limited time and will worsen as the engine wears.
BOE773 From , joined Dec 1969, posts, RR: Reply 11, posted (2 years 2 months 1 week 19 hours ago) and read 2352 times:
So we know that thermal erosion rate will negatively impact fuel burn.
Next question:
Which engine has the longer wearing metal?
I'd bank on it being a toss-up between Pratt & GE as being on the leading edge of metallurgy.
But then Pratt invented single crystal alloy for blades.
RB211-524H From Australia, joined Nov 1999, 42 posts, RR: 0 Reply 14, posted (2 years 2 months 1 week 17 hours ago) and read 2110 times:
That's gold AirWillie! LMAO - I could just imagine this old dimunitive Chinese man like u see in commercials except this one has a hunched back, walks with a cane that doubles as a blind 'poking stick' (I don't know the real term, sorry to blind ppls) sitting on a double decker bus with sunnies on and is a professional 'fortune teller'. You give him a coin and suddenly a PW engined CX744 flies overhead on its way out of HK and he tells you...'the pilot doing oookkkk'.
Lightsaber From United States, joined Jan 2005, 3850 posts, RR: 71 Reply 15, posted (2 years 2 months 1 week 4 hours ago) and read 1042 times:
Quoting BOE773 (Reply 8): Would you have data to back that up, Lightsabre?
The 4 RRs together will weigh 1828 lbs more than the Pratts, thus negating any improvement in ROC over the Pratts.
The weight is an issue. As to climb thrust data, alas what I have is under NDA.
Quoting BOE773 (Reply 8): When you note, "the fan holding back", do you mean reduced fan RPM?
More reduced low compressor RPM. The "mid compressor" on the RR will be able to balance out better than on a twin spool.
Quoting BOE773 (Reply 11): Which engine has the longer wearing metal?
I'd bank on it being a toss-up between Pratt & GE as being on the leading edge of metallurgy.
But then Pratt invented single crystal alloy for blades.
Its not just the metal, its also the cooling design. A single "hot spot" can cut 75% of a turbine's life away. The Pratt's are life limited by the 5th stage HPC compressor blades (due to engine surge) not the turbine! (Odd... a problem they're still trying to find a permanent fix on... The turbine should set the engine durability limit...) Pratt prides itself on its metals, but tends to push them a bit more than the compitition. While RR and GE tend to have better compressor efficiency and thus improved turbine cooling.
A triple spool, due to the natural "self balancing" will have improved cooling during climb. End of climb is actually the nastiest time for the turbine (its cooling starved) and thus the thermodynamic cycle can play an important role in turbine durability too.
LMP737 From United States, joined May 2002, 3589 posts, RR: 14 Reply 16, posted (2 years 2 months 6 days 3 hours ago) and read 887 times:
Quoting BOE773 (Reply 8): Would you have data to back that up, Lightsabre?
The 4 RRs together will weigh 1828 lbs more than the Pratts, thus negating any improvement in ROC over the Pratts.
When you note, "the fan holding back", do you mean reduced fan RPM?
The hi loading of the LPC?
It takes a lot gaul to question an engineer in the aerospace industry. Tell us BOE773, what exactly is your area of expertise?
Pratt is a no go for the 787.
Pratt & RR are a no go for the 747-800.
Pratt is a no go for the A350WBX, but there might be Pratt/GE 'alliance' engs
hung on the A350WBX-1000 if it ever gets launched.
Poor old Pratt.
They might hit paydirt with the next gen 37 if their geared fan 6000
is a success.
BOE773 From , joined Dec 1969, posts, RR: Reply 20, posted (2 years 2 months 6 days 1 hour ago) and read 793 times:
Even though the RRs pack a slightly higher punch, the ROC of the Pratt craft will be a tad higher than the RR since the four pack weigh 1828 lbs less than the RR and the BPR for the Pratts is higher as well.
Did you catch all that.
As for feel in the butt end on the seat.......naaw.
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