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.
The examination of the MGB is continuing in conjunction with detailed analysis of the HUMS and other recorded information.
So HUMS done exactly what it was supposed to be doing in respects to alerting the engineer that there was something abnormal. Let's not beat around the bush here, if this is the case, then it is not the system at fault but the user. Surely?
So that is where the attention should be focused.
Someone said before that all 3 Aberdeen bases have dedicated HUMS departments, if this is the case, what were these guys doing about it?
If they had reported it to EC and their advice back was 25FH close monitoring and chip det inspections then the buck surely lies with EC. However, if the fault had not been reported to EC, then someone at Bond is clearly in a world of sh*t.
Flytest....
You are incorrect, the strongest
reccomendation EC/Hums engineer can make is to ground that particular aircraft and replace the gearbox. It has happened before so why not in this case? I know components are changed all the time in relation to hums data and advice given by the Hums dept and manufacturer so why not in this case? They have mountains of data from other operators all over the world so they have data trends from the whole fleet of their aircraft to analyse. If 1 steps out of line against the others it should be thoroughly investigated.
All gears and bearings within the MGB are monitored by HUMS and it is clear to see by the release of this report that HUMS did pick this up. I suspect this release is to make sure all other AOC around the world checks their HUMS MGB data.
Now with a HUMS alert, it is unlikely that the manufacturer would advise a MGB replacement but it is possible. However, taking that aside, i see the advice given here was to close monitor for 25FH and check the chip detectors? A pretty basic and standard action, well what good is that going to do if their is a crack developing down 1 of the gears?
Why did the HUMS guys/EC not ask for a boroscope inspection of the internal gearing? Why did they not take a SOAP (oil) sample from the GB for further analysis? There is far more they can do than just the basic 25FH close monitor and chip det inspection.
Hums did exactly what it was supposed to do, it appears the advice given by EC/Hums dept was not good enough however.
I read that Norwegian article a few pages back, some scary similarities to that.
16 people are dead here and HUMS picked up on it beforehand. No matter what way you look at it, there was prior warning.
There is clearly nothing wrong with the HUMS system. I suspect the press will have a field day with that above fact if i am being brutally honest.
Very scary stuff. Its a great pity to see HUMS fail to spot this one coming. The procedure of finding a small metal particle on a chip detector then putting the component onto "close monitoring" is totally standard, but in this case not good enough.
Perhaps it will be a large crack such as was found in the bevel gear of a CHC 332L some years ago, totally un-spotted by HUMS. Since cracks don't release much debris (to be picked up by a chip detector etc) we rely on HUMS, but really HUMS has not evolved much since inception in 1990 or so. We need to get the Neural Network concept being trialled by GE, into service asap.
HUMS was a great invention and step forward, but for the last 20 years the industry has been resting on its HUMS laurels. Not good enough!
As above, HUMS
did pick this up. It is incorrect to state that the system did not otherwise this investigation would not be focusing centrally around HUMS. It was the advice given that was not satisfactory. An internal boroscope inspection would undoubtedly have found a crack in a gear or a missing tooth to big to be picked up by the mag probe. If the trend is saying there is something wrong then it should be treated as such. I hope to god that this particular problem was reported to EC beforehand by Bond HUMS