Does anyone know what the actual latest TBO is for the H225 MGB epicyclic module? All I seem to be able to find is that it has been reduced to“ less than half” what it was previously.
[Edit: See correction in post #1616]. At one time (2009) the TBO was 2000FH but under the Maturity Plan had a target of 3000FH.
So, what was previously measured in the thousands is now measured in hundreds.
That is obviously applicable to epicyclic modules fitted, or retrofitted, with the supposedly superior type B planet gear/bearing. I find it slightly odd that, given the possibility of subsurface fatigue cracking, only the TBO is reduced but there is no mention of any revised Service Life Limit? Has this also been reduced and if so, to what?
How exhaustive will overhauls of these gearboxes now be to guarantee them for the next TBO interval? Will each planet gear need to be radiographed or CT scanned for the smallest possible inclusion or micro-defect? Or would they only further examine a gear if it shows signs of spalling, since AH’s faith still appears to hang on that premise?
Who would meet the cost of these enhanced and more frequent inspections and the maintenance time necessary to remove the modules from the aircraft and refit them?
I am also curious as to AH’s ‘confidence’ in the effectiveness of the MCD devices fitted to their MGB system. Mandating inspections of the oil filter and all these MCDs at 10FH intervals seems to suggest that these elusive ‘spalling particles’ can miss MCDs at the epicyclic, at the MGB sump and at the oil cooler (I assume the filter is placed, logically, after the cooler?).
Last edited by Concentric; 20th Oct 2016 at 17:11.
Reason: Confused TBO with SLL.