EC 225 Return to REAL Service

[Concentric]

Originally Posted by Satcomm

One thing that has struck me a bit odd is all the design questioning. All the load anaylsis, material anaylsis, cycle counts, bearing types, rotation counts, number of blades, number of suspension bars, weight reductions, power increases, and on and on ........All, over the top blabbering IMO ...... The L2 flew for how many years? About 18-19 years before that gearbox failed. I don't care who you are, after almost 20 years of operation of any mechcanical item, do you go straight into believing there is a design flaw or a structural integrity problem? Probably not! The next similar failure of the same component, 7 years later, 25-26 years after design and about 12 years into the 225 life .... Design problem? Again, probably not.

Which L2 are you referring to? G-REDL didn’t fly for 18-19 years (it was built 2004; crashed 2009). Its first MGB epicyclic module certainly didn’t either. From the AAIB report 2/2011:

“1.6.8 In June 2004 the epicyclic module (manufacturer’s serial number M2088) was removed for overhaul due to the presence of metallic particles being found on the magnetic chip detectors. The module had accumulated 844 flying hours since new. During this overhaul all the first and second stage planet gears were replaced with new units”.

Not a design issue? Halfway through its first year of service? Remind me what the designers originally set as the TBO and SLL for epicyclic components, and for MCD physical inspections? What are they now? There appears to be a huge variation in life expectancy on this planet gear component. Why? How long had the gearbox been in LN-OJF? If it is not a design issue, are you in effect saying the MGB is well designed but badly manufactured?

You may be right though, the planet gear issue may be a manufacturing problem more than a design error, although manufacturing parameters and limits have to be set by design engineers to keep the product within design assumptions otherwise the design and any certification thereof is simply invalid. But the architecture of the 225’s MGB is such that fracture in a single planet gear is enough to bring down the aircraft and that gear and failure mode is one of the hardest things in a helicopter to actively condition-monitor. That is where it has a very, very serious structural integrity problem. Not just the planet gear itself; that is just one of the 16 eggs in the basket, the basket itself (ring gear) being rather fragile and critical in retaining the mast.

How many other manufacturers have planet gears that fragment in flight? How many other AH helicopter models suffer that catastrophic failure? Not a design issue? I find that pill hard to swallow. Then again, no-one is forcing me to.