I enjoy this thread as it is filled with useful info.
To add to Turbine D input
Several things strike me: If there is any scale at all between the artistic renditions, the thrust ball bearings in the GP7200 look larger than those in the Trent 900
The GP7200 ball thrust bearing carries greater radial loads as well as thrust loads where the T900 has a large roller brg to carry the radial loads with the thrust loads transferred to location bearing adjacent the engine mount. Roller bearings typically have higher load capacity than ball bearings for a given size.
Both engines deliver the same thrust, both have the same fan diameter, both have 14 compressor stages, the GP7200 has 6 LPT stages verses 5 for the Trent 900. The GP7200 is slightly longer and weighs 956 lbs. more. It has been reported the GP7200 has a 1% better SFC than the Trent 900,
The GP7200 has had its fair share of problems, Fan balance issues that have cracked airframe structure and lowered engine mounted accesories life spans. This has generated huge manhour costs and extended ground times but to date has not exploded mid-air. GP7200 1 , RR nil
For those wondering why the Trent 800 couldn't be used, you can't just clip 5" off the fan without rebalancing the rest of the engine, especially if you are being pressed on SFC to meet aircraft range goals. So two things happened on both engines, incorporation of 3-D highly aerodynamic efficient swept fans, higher HP spool speeds, higher pressures and temperatures, all to generate thrust requirements and deliver good SFC.
I see your point except the T800 was a known off the shelf product, now very reliable with the thrust avail to do whats asked plus more. So why the T900 when it requires greater SFC to offset its greater weight before it offers any greater efficiency to the aircraft. So at a glance it does not add up unless huge future promises (SFC) were attached to the T900 model that could not be acheived from current models ?
...--------...Thust...Weight .Thrust to weight...Length.. Fan Dia..Serv Enrty
Trent 892 - 92,000...13,100....---....7.0 ......... 172 .... 110...... 1997
Trent 972 - 76,752...13,842....---....5.5 ......... 179 .... 116...... 2006
I do wonder if the counter-rotational feature (new to a commercial high by-pass engine) had any effects on bearings, frequencies or vibration in the Trent 900.
This is true but RR have been building a contra rotating core for the harrier since the 1960s so I would not call it new to RR and the location IP bearing that supports the fan location bearing turns in the same direction i.e. the ball race speeds have not been a marked increase. This bearing design has been a thorn in RR side since the conception of the RB211 but again is not new technology.
I suspect we will find out once the hype has died down and RR
PR machine have massaged and cajoled its customers to accept a modified core engine at a lowered price with the guarantees of increased efficiency ?? (read reliability)
The money will have to come from somewhere and I suspect it will be shared across RR EADS and customers all of whom have committed so much can not afford this to fail. Time will tell.