EC 175
Joined: Feb 2009
Posts: 22
Likes: 0
From: amongst the clouds
The report provides a bit more context https://www.gov.uk/aaib-reports/aaib...-ec175b-g-emeb
Since the LAGB had successfully run on a test cell for 12 hours without any deterioration detected in the alternator pinion bearings, with a 10 kVA alternator installed, it is likely that the installation of the 10 kVA alternator by the operator directly influenced the F1 bearing failure that occurred after 18 minutes of the post-maintenance ground run.
Examination of the failed F1 bearing and alternator pinion revealed that they had been subjected to a compressive axial load during the ground run. This axial load was greater than the ability of the F1 roller bearing to withstand it, leading to the bearing overheating and causing the PEEK bearing cage to melt, which was then extruded from the bearing. The overheating also caused significant wear of the bearing rollers, releasing bearing debris into the MGB oil system and causing discolouration of the MGB oil.
Testing conducted by the manufacturer showed that an excessive quantity of grease within the alternator shaft link cavity can create a significant compressive axial load on the alternator pinion when the alternator is clamped to the LAGB. This is due to compression of the excess grease and air within the sealed shaft link cavity acting as a hydraulic piston. This loading case was unintended and had not been anticipated when the LAGB components and associated AMM maintenance procedures were developed.
The method of attaching the alternator to the LAGB used by the operator’s LAE meant that the compression of the grease and air within the shaft link cavity was up to four times greater than would have been the case if the method specified in the AMM had been followed.
The manufacturer stated that the reason for filling the alternator pinion cavity with sufficient grease to cause it to overflow was to ensure that grease remained within the alternator pinion splined area during the in-service period between overhauls, to ensure lubrication of the splines.
This large quantity of grease, combined with the sealed design of the alternator shaft link cavity once the alternator driveshaft was inserted, created a latent condition in which an unwanted axial load could be introduced into the alternator pinion and F1 roller bearing..
Examination of the failed F1 bearing and alternator pinion revealed that they had been subjected to a compressive axial load during the ground run. This axial load was greater than the ability of the F1 roller bearing to withstand it, leading to the bearing overheating and causing the PEEK bearing cage to melt, which was then extruded from the bearing. The overheating also caused significant wear of the bearing rollers, releasing bearing debris into the MGB oil system and causing discolouration of the MGB oil.
Testing conducted by the manufacturer showed that an excessive quantity of grease within the alternator shaft link cavity can create a significant compressive axial load on the alternator pinion when the alternator is clamped to the LAGB. This is due to compression of the excess grease and air within the sealed shaft link cavity acting as a hydraulic piston. This loading case was unintended and had not been anticipated when the LAGB components and associated AMM maintenance procedures were developed.
The method of attaching the alternator to the LAGB used by the operator’s LAE meant that the compression of the grease and air within the shaft link cavity was up to four times greater than would have been the case if the method specified in the AMM had been followed.
The manufacturer stated that the reason for filling the alternator pinion cavity with sufficient grease to cause it to overflow was to ensure that grease remained within the alternator pinion splined area during the in-service period between overhauls, to ensure lubrication of the splines.
This large quantity of grease, combined with the sealed design of the alternator shaft link cavity once the alternator driveshaft was inserted, created a latent condition in which an unwanted axial load could be introduced into the alternator pinion and F1 roller bearing..
Joined: Apr 2005
Posts: 280
Likes: 20
From: OZ
It’s disappointing that the OEMs are still producing machines that are vulnerable to common maintenance procedures. (Ti studs that need lube, a prayer, and calming music played while torquing. Over greasing causing catastrophic failure.)
It’s the equivalent of having a door handle that snaps off if you try turning it the wrong way. (And mentioning it once during the type endorsement.)
It’s the equivalent of having a door handle that snaps off if you try turning it the wrong way. (And mentioning it once during the type endorsement.)
Joined: Apr 2005
Posts: 280
Likes: 20
From: OZ
Not sure this is aimed at me.
There is nothing unfounded about Ti Studs failing or catastrophic gearbox failures.
Nothing trivial about the multiple fatalities from both either.
But we are drifting off topic - this one failed on the ground, and it sounds like a tiny design change (vent) or specific, non intuitive, maintenance instructions will be a permanent solution.
There is nothing unfounded about Ti Studs failing or catastrophic gearbox failures.
Nothing trivial about the multiple fatalities from both either.
But we are drifting off topic - this one failed on the ground, and it sounds like a tiny design change (vent) or specific, non intuitive, maintenance instructions will be a permanent solution.
Joined: Nov 2006
Posts: 1,951
Likes: 90
From: After all, what’s more important than proving to someone on the internet that they’re wrong? - Manson
G-EMEB?
Apparently, it had another incident offshore recently and while wheeling to one side of the deck to let another machine arrive with a maintenance crew the RH Main gear went through the deck.
Picture links on Helihub.
Apparently, it had another incident offshore recently and while wheeling to one side of the deck to let another machine arrive with a maintenance crew the RH Main gear went through the deck.
Picture links on Helihub.
Joined: Oct 1999
Posts: 1,444
Likes: 21
From: Beyond the black stump!
From the AAIB report.
Did we just go back 50 years in time?
The helicopter was undergoing scheduled maintenance to replace the main gear box (MGB), which had reached its overhaul life of 800 flying hours.
Joined: May 2017
Posts: 30
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From: wah gwaan
Cyclic
Further than that I think. Airbus previously EC previously Aérospatiale don't have a great history building quality MGBs which are durable and long lasting.
Did we just go back 50 years in time?
Joined: Jun 2014
Aviation Qualifications: Spotter
Posts: 3,896
Likes: 86
From: Netherlands
I recall the short TBOH was already rumored just after EC225 disaster in Norway.
I did not believed it then because NHV was also operating 1 or 2 EC175 in Ghana at that moment.
It was then also rumored that Airbus had at least 1 dedicated mechanic stationed at NHV (Den Helder) but makes sense now.
Airbus support must have improved apparently.
I did not believed it then because NHV was also operating 1 or 2 EC175 in Ghana at that moment.
It was then also rumored that Airbus had at least 1 dedicated mechanic stationed at NHV (Den Helder) but makes sense now.
Airbus support must have improved apparently.
Joined: Oct 1999
Posts: 1,444
Likes: 21
From: Beyond the black stump!
There is a very interesting little snippet in the Helihub article today about the CHC/Babcock transaction. https://helihub.com/2021/09/27/compe...on-of-babcock/
12 months of corrosion remedial work provides for an enormous workscope, and if the activities are limited to airframe corrosion remediation, there must be virtually nothing left unaffected on this airframe at this stage. Does anyone have any additional insight into what is happening with this machine, or the background to how an almost new helicopter could require such extensive action if it hadn't been ditched in the sea?
Anyone?
Of the UK fleet, one AW139 has been stored for 8 months and one H175 was recently ferried to Airbus for corrosion remedial works which will likely see it out of service for 12 months. Additionally one S92 is still being worked on after suffering a nose wheel collapse in June, and the total includes another S92 pulled out of storage on 10th September. Read more at https://helihub.com/2021/09/27/compe...on-of-babcock/
Anyone?
Joined: Dec 2007
Posts: 36
Likes: 0
From: Scotland
There is a very interesting little snippet in the Helihub article today about the CHC/Babcock transaction. https://helihub.com/2021/09/27/compe...on-of-babcock/
12 months of corrosion remedial work provides for an enormous workscope, and if the activities are limited to airframe corrosion remediation, there must be virtually nothing left unaffected on this airframe at this stage. Does anyone have any additional insight into what is happening with this machine, or the background to how an almost new helicopter could require such extensive action if it hadn't been ditched in the sea?
Anyone?
12 months of corrosion remedial work provides for an enormous workscope, and if the activities are limited to airframe corrosion remediation, there must be virtually nothing left unaffected on this airframe at this stage. Does anyone have any additional insight into what is happening with this machine, or the background to how an almost new helicopter could require such extensive action if it hadn't been ditched in the sea?
Anyone?
Joined: Oct 1999
Aviation Qualifications: ATPL
Posts: 7,371
Likes: 926
From: Den Haag
There is a very interesting little snippet in the Helihub article today about the CHC/Babcock transaction. https://helihub.com/2021/09/27/compe...on-of-babcock/
12 months of corrosion remedial work provides for an enormous workscope, and if the activities are limited to airframe corrosion remediation, there must be virtually nothing left unaffected on this airframe at this stage. Does anyone have any additional insight into what is happening with this machine, or the background to how an almost new helicopter could require such extensive action if it hadn't been ditched in the sea?
Anyone?
12 months of corrosion remedial work provides for an enormous workscope, and if the activities are limited to airframe corrosion remediation, there must be virtually nothing left unaffected on this airframe at this stage. Does anyone have any additional insight into what is happening with this machine, or the background to how an almost new helicopter could require such extensive action if it hadn't been ditched in the sea?
Anyone?
Joined: Oct 1999
Aviation Qualifications: ATPL
Posts: 7,371
Likes: 926
From: Den Haag
Joined: Feb 2009
Posts: 22
Likes: 0
From: amongst the clouds
There is a very interesting little snippet in the Helihub article today about the CHC/Babcock transaction. https://helihub.com/2021/09/27/compe...on-of-babcock/
12 months of corrosion remedial work provides for an enormous workscope, and if the activities are limited to airframe corrosion remediation, there must be virtually nothing left unaffected on this airframe at this stage. Does anyone have any additional insight into what is happening with this machine, or the background to how an almost new helicopter could require such extensive action if it hadn't been ditched in the sea?
Anyone?
12 months of corrosion remedial work provides for an enormous workscope, and if the activities are limited to airframe corrosion remediation, there must be virtually nothing left unaffected on this airframe at this stage. Does anyone have any additional insight into what is happening with this machine, or the background to how an almost new helicopter could require such extensive action if it hadn't been ditched in the sea?
Anyone?
Joined: Sep 2006
Posts: 876
Likes: 0
From: Inside the Industry
The first three H175s delivered to Babcock did not have the necessary corrosion protection applied during the build process. All three machines were scheduled to go to Albacete in Spain to have remedial works carried out by Airbus, which takes approx 12 months. MCSE was the first to be completed. I believe MCSG has recently arrived in Albacete for the same treatment.
Joined: Aug 2000
Posts: 497
Likes: 31
From: A very long way North