A664 and colpaz
I read and re-read this article and this part is still baffling to me. First it states the Trent 900's HP/IP support structure would be subject to "high severity" if the engines were to be operated at 540 psi at P30 on more than 75 flight cycles.
I assume 540 psi at P30 is a 72,000 pound non-derated take-off.
So then they say on November 12, 2010, Qantas, you must apply a minimum 8% derated take-off thrust to your 72,000 lb. engines.
So max derated thrust is now 66240 lbs.
But it goes on to say (gives some Tflex temperatures for both 72K and 70K engine ratings) or a minimum take-off fixed derate of 8% (72K) or 4% (70K) should be used.
Since Qantas doesn't have any 70K thrust engines, what is this saying? Does this apply to other operators who's fleets are comprised of 70K Trent 900 engines? The 70K derate of 4% = 67.2K
It does say "the thrust derate was made in order to reduce the engine pressure ratio in the P30 area of the engine and therefore increase the life of the oil transfer tubes within the HP/IP support structure"
It does not mention spline wear.
Turbine D