Turbine D - Bolty McBolt
Once again a very helpful explanation to a layman in jet engine technology.
Especially I like the comparison of GP 7200 and Trent 900. Within a glance it is clear that the construction of those elements that carry the dynamic loads are much lesser concentrated on one small area in the GP 7200 than in the Trent 900. Wether that has a real influence on the problems we have seen on the QF - Trent I only can imagine / assume. But if this problem exists for so many years - Bolty McBolt says since the beginning of the RB 211 - and the production of that type engines goes on with now and than a "big bang" one must ask the question wether there has been ever an in depth investigation towards possible harmonics???
I remember that there have been aircraft desighns that used a long driving shaft for the propeller. Few of these even had counterrotating props. Some of the types ran into kind of severe shaft failures - as far as I remember - caused by kind of harmonics or resonant frequencies ?? I may be corrected at this, too long ago. Doesn´t know if this is applicable in now a days desighn technologies. But what if, . . . . . the counterrotating HP component generates a harmonics that is transferred via bearings the different shafts to other parts of the engine ?? Is that thinkable ?? I must admit, my confidence in RR - engineers abilities exclude such a scenario.
Again I have to cry for help by the engineers !!
DERG
Is that yellow marking just a gag or is it true ??. I have seen some Harriers - must admit on fly by - but havn´t seen something like that. But I can imagine that it might have been indeed a measure of caution.
Jo