EC225 crash near Bergen, Norway April 2016

[Concentric]

Originally Posted by Brucci2000

This is my first post - thanks to everyone over the 73 pages for an informative read.

I'm interested in the latest revelation about the two types of second stage gears - it raises these questions:

1. Did the two types exist prior to the REDL accident and if so why was analysis of the differences not a feature of the AAIB investigation? Which type was REDL using?

2. If the second type post-dated the REDL accident, why was it introduced, and if it was a quiet response to internal AH findings with respect to REDL, why was the immediate retrofit of the second type not mandated?

You ask a couple of very good questions. I think it raises further questions too.

I do not mean this as criticism of the AAIB but if you look at their report on G-REDL, section 1.18.2 it states that:

“Data provided by the helicopter manufacturer indicated that between 2001 and 2009 there were nine recorded cases of planet gear spalling on the AS332 L2 (see Table 2)”

and then goes on to add that:

“The information provided by the manufacturer regarding the number of planet gear rejections due to spalling was incomplete. During the investigation anecdotal evidence was provided that indicated that overhaul facilities disposed of rejected gears without routing them for investigation”.

As the EC225 and AS332L2 are widely reported to share the same epicyclic gearbox module, isn’t it surprising that only data on L2 gears with spalling was considered relevant? Was the Type 2 gear introduced for the EC225 to use exclusively, therefore considered to not be relevant to the 2009 investigation? Something doesn’t add up here.