Quote:
Originally Posted by
WAH 
Quote:
Originally Posted by AAIB
The investigation has so far revealed that the MGB had suffered from a major failure within the epicyclic module. This is supported by HUMS data; however, this is not yet fully understood.
So HUMS done exactly what it was supposed to be doing in respects to alerting the engineer that there was something abnormal.
I read that part of the AAIB report to mean that the HUMS data from the time of the accident supports their determination that the failure was within the epicyclic module.
The daily inspections were initiated not due to HUMS indications but:
Quote:
Originally Posted by
AAIB
As the result of the discovery of a particle on the main rotor gearbox epicyclic module magnetic chip detector
Furthermore, while the HUMS data were under close monitoring:
Quote:
Originally Posted by
AAIB
No further abnormalities were identified during this period.
I'd say your eagerness to hang the operator and manufacturer HUMS guys out to dry is not warranted by the evidence.
That does not make sense as you are assuming that 1 second the gearbox was fine, and then a second later it comes to a catastrophic collapse without anything causing it. How do you suspect this would have happened? A crack in a gear or a missing tooth will have developed over x amount of time, it does not just appear instantaneous and then cause catastrophic failure. This crack or whatever it was (i do not know) will have been under close monitoring HUMS wise. (Hums on epicyclic was put under close monitoring, that is factual)
You have got it the wrong way round, what would have happened is the aircraft would have landed on the 25th March and the engineer would have downloaded the days flight. An exceedance would have been generated and then reported to BOND HUMS dept. Bond hums dept would then have given advice on what to do or referred it back to EC for their input. The advice given would then have been to carry out frequent mag probe checks along with putting the AC under close monitoring. (This is standard procedure)
Are you suggesting they found chips on the detector out of the blue, i.e during a scheduled maintenance check? They then checked the HUMS to find that it was over threshold and then put it on close monitor? That is back to front, any engineer who is familiar with HUMS will tell you that. Basically HUMS would not go under close monitoring unless there was a reason to do so, i.e it had breached a threshold. You could not possibly close monitor every single component and relevant indicator in the MGB just because there was debris found on the mag pickup probe. It's far too big a job, there are hundreds of different indicators that you could potentially be looking at.
Im not out to hang anyone out to dry, that is unfair as i do not have all the facts, nor have i seen the trend graphs from BOND so it is impossible to make that judgement. I did state however that there are 16 families in grieving and if it does prove that the prior HUMS warnings was pointing to the impending failure then questions are going to need to be asked.
On the other hand, if there were no prior warnings on HUMS in the week or so before the accident then you would have to ask questions as to why and then hope the manufacturer would develop the HUMS system to make sure something like this never happened again.