Trent 800 >> Trent 900
The ongoing discussion about rules and regulations applied or questioned by the one or the other member of this circle are, what I would like to call an additional battlefield to take care off. I admit that my imagination stretches far enough to understand the expressed uncomfortable feelings about institutions, operating like state administrations, but responsible for so sensitive items like certification of aircraft engines. However, to be honest, one must concede that no one within these official bodies is intentionally wrong doing. Thought that needed to be said ones at a time.
Since Bolty McBolt brought up the comparison of Trent 800 and Trent 900 engines, this has drawn my special interest. I looked for a way to compare the engines as far as possible visually. That worked by using those RR issued brochures of the Trent 800 and 900 engines cutaways.
Provided RR has not set up these two pictures at different scales and keeping in mind the relative non precise method of measuring parts on a 26 " screen I found these differences between the two engines.
All length measurements show greater values at the T 800 for IPC, HPC, combustion chamber, etc. than on the T 900. The more it surprises me that the distance between the ball bearing Nr. 1 and Nr. 3 and especially Nr. 2 and Nr. 3 are shorter than those found in the T 900.
In connection with these findings a question to the engineers:
Is the tendency to flutter of a longer rotating cylindrical body - HPC-module - compared to a shorter, more compact desighn to be expected on a lower level ? With other words, could one expect to have a longer cylindrical body accelerated to comparable rotating speeds to run smoother and with lesser vibrations ??
What influence- if at all - does that greater distance between bearing Nr.2 and Nr. 3 have on the stiffness of the supporting structure between these two important bearings ??
What also is very obvious in that comparison of engines is the fact that the construction of the diaphragm / plenum chamber in front of the IPT disk is completely different, as is the desighn of the bearing chamber. Also there is no sealing diaphragm between the rear of the IPT disk and the plenum inside the LPT.
So, as Bolty McBolt has mentioned, why in gods name was that T 900 developed and used on the A 380, having a well desighned, functioning, more powerful and line proven engine in the inventory ??
Last edited by Annex14; 9th Jan 2011 at 11:15.