AW139 lost tail taxying DOH
Join Date: Jun 2008
Location: Canada
Age: 67
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
Yes Victoria there is a Desk, but is there someone there?
Anyone who has tried to contact Agusta for help should know that nobody would have picked up the call anyway.....
Anytime I've tried to call anyone at Agusta I have never been successful and sad part is that there isn't even voice mail....
Anytime I've tried to call anyone at Agusta I have never been successful and sad part is that there isn't even voice mail....
....For those that do not know, Fuselages AND tailbooms are manufactured in Poland ......
there.
Concerning tail booms, Bell 412 booms are in production there for long time now.
Anyone who has tried to contact Agusta for help should know that nobody would have picked up the call anyway.....
Therefore your claim is bit unfair.... even to me, who stand besides and wonder
what is going on with that tail booms.
Was on 139 test ride on 2008. for approx 45 min, for me that was one of the best experience in helicopter world.
Guest
Posts: n/a
"The INTRODUCER"
What's the significance of the seven?
Anyone able to shed light on the common factor in the seven aircraft identified in today's EASA AD as requiring inspection within 5hr rather than the 25hr for the rest of the fleet? Serial numbers: 31006, 31020, 31022, 31042, 31136, 31157 and 31248.
Join Date: Aug 2009
Location: France
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
I don’t wish to repeat any findings already posted but had news that a operator had found de-bonding detected by the tap test and visual inspection on the compressively loaded side wall of the boom., at about the location seen as the failure point on the photographs back in this thread.
As blkmax has now given us all a understanding of the issues related to design and manufacture and the strength degrade that bonding failure can cause, would it now be the time to strengthen our understanding of repair techniques to these structures. Would repair be an option? In these cases,? I feel not, however, if you could enlighten us blakmax I certainly would be keen to have your views.
As blkmax has now given us all a understanding of the issues related to design and manufacture and the strength degrade that bonding failure can cause, would it now be the time to strengthen our understanding of repair techniques to these structures. Would repair be an option? In these cases,? I feel not, however, if you could enlighten us blakmax I certainly would be keen to have your views.
PZL Swidnik is manufacturing ONLY the fuselages for the AW139. Information about the tailboom production is 
.
AW139 tailbooms (and some parts of AW101 fuselage) will probably be produced now, that AW will became the owner of the factory.
Arrakis
.AW139 tailbooms (and some parts of AW101 fuselage) will probably be produced now, that AW will became the owner of the factory.
Arrakis
Join Date: Jul 2008
Location: Australia
Posts: 372
Likes: 0
Received 0 Likes
on
0 Posts
Repair of adhesion fillet bond failure
Hi OldTimer. Thanks for the information that is is a compression loaded area because that adds to the suggestion that adhesion fillet bond failure may have played a part. For the skin to separate there needs to be an out of plane force and that would come from compression buckling of the weakly bonded skin. Once the disbond exceeded a critical size, the structure would be susceptible to collapse by overall buckling. (In deference to previous comments, this is only a suggested failure mechanism which is consistent with features observed in other bond failures in this region together with the stated loading mechanism. Examination of the part by a person competent in adhesive bond forensics will be required to confirm the cause of failure.)
I'd also express some concern that if the processing is to blame, and if that process has been used elsewhere, then there is a reasonable probability that the problem is not just limited to the disbond area; it just means that the structure has not seen loads that would result in the skin separating in other areas. The real solution is to eliminate the causes during manufacture rather than chasing damage which has a high potential to continue to occure in other locations.
Firstly let me state that I do not have design loads, and in any repair to critical structure, validation by FEM and/or testing is appropriate.
The first step is to verify the failure mechanism. Adhesion fillet bond failure is characterised by an absence of adhesive on the core. If adhesion fillet bond failure is confirmed, then an inspection of the core itself is essential, because fillet bond failure is often coupled with another core defect known as weak node bond failure, where the core cells separate at the sites where the cells walls were bonded together in the process of manufacturing the core. This inspection is best performed using a Mark 1 eyeball and a magnifying glass. Any sign of node bond failure necessitates complete removal of the core. Repair is the same as for aluminium core below.
Now for the manner of repair. If I were to repair adhesion fillet bond failure, the first thing to do is to remove the skin surrounding the disbond until the adhesive actually fractured, in contrast to the fillet bond separating from the core. For nomex core dry the core using a vacuum bag and heater blankets for at least six hours at a temperature of 85C +/- 5C. Bond an insert repair over the core and then bond a splice repair between the insert and surrounding skin.
For aluminium core, the story is less friendly. Because the core surface at the fillet bond zone has hydrated to enable adhesion failure to occur, it is prudent to remove all core in the area where the adhesion fillet bond failure has occurred. Fabricate a replacement core insert and bond that in place after preparing the skin at the bottom of the cut-out. Use a film adhesive to bond the core to the face sheet and a foaming adhesive to splice the core to the insert. Sand the core to the OML shape and bond a repair patch over the core and adjacent skin.
Now if the failure is between the skin and the adhesive, then it is a different matter. If the adhesive has a glossy appearance and has no visible reproduction of the surface of the metal, then it is probable that there was a pressurisation or fit up problem and the adhesive was never in contact with the skin. If the defect is limited to a specific area (verified by removing skin until the adhesive fractures from the core) then an insert repair may be possible.
If the skin shows signs that it has been in contact with the skin (the surface is not as glossy and there is replication of the surface of the metal) then there is a problem with the surface preparation method due either to contamination or the use of an ineffective process which does not prevent hydration. No repair is possible.
If I haven't bored everyone to death, I could discuss how to heat the structure because most aircraft SRMs contain heating methods that even Walt Disney would not be able to make people believe.
Regards
Blakmax
I'd also express some concern that if the processing is to blame, and if that process has been used elsewhere, then there is a reasonable probability that the problem is not just limited to the disbond area; it just means that the structure has not seen loads that would result in the skin separating in other areas. The real solution is to eliminate the causes during manufacture rather than chasing damage which has a high potential to continue to occure in other locations.
Firstly let me state that I do not have design loads, and in any repair to critical structure, validation by FEM and/or testing is appropriate.
The first step is to verify the failure mechanism. Adhesion fillet bond failure is characterised by an absence of adhesive on the core. If adhesion fillet bond failure is confirmed, then an inspection of the core itself is essential, because fillet bond failure is often coupled with another core defect known as weak node bond failure, where the core cells separate at the sites where the cells walls were bonded together in the process of manufacturing the core. This inspection is best performed using a Mark 1 eyeball and a magnifying glass. Any sign of node bond failure necessitates complete removal of the core. Repair is the same as for aluminium core below.
Now for the manner of repair. If I were to repair adhesion fillet bond failure, the first thing to do is to remove the skin surrounding the disbond until the adhesive actually fractured, in contrast to the fillet bond separating from the core. For nomex core dry the core using a vacuum bag and heater blankets for at least six hours at a temperature of 85C +/- 5C. Bond an insert repair over the core and then bond a splice repair between the insert and surrounding skin.
For aluminium core, the story is less friendly. Because the core surface at the fillet bond zone has hydrated to enable adhesion failure to occur, it is prudent to remove all core in the area where the adhesion fillet bond failure has occurred. Fabricate a replacement core insert and bond that in place after preparing the skin at the bottom of the cut-out. Use a film adhesive to bond the core to the face sheet and a foaming adhesive to splice the core to the insert. Sand the core to the OML shape and bond a repair patch over the core and adjacent skin.
Now if the failure is between the skin and the adhesive, then it is a different matter. If the adhesive has a glossy appearance and has no visible reproduction of the surface of the metal, then it is probable that there was a pressurisation or fit up problem and the adhesive was never in contact with the skin. If the defect is limited to a specific area (verified by removing skin until the adhesive fractures from the core) then an insert repair may be possible.
If the skin shows signs that it has been in contact with the skin (the surface is not as glossy and there is replication of the surface of the metal) then there is a problem with the surface preparation method due either to contamination or the use of an ineffective process which does not prevent hydration. No repair is possible.
If I haven't bored everyone to death, I could discuss how to heat the structure because most aircraft SRMs contain heating methods that even Walt Disney would not be able to make people believe.
Regards
Blakmax
Now I see why the S-92 uses tin and rivets!
212,
Too bad that the 92 guys did not spend a little more time on the transmission lube system.
I am sure Agusta will take care of the issue and not wait a year to see what happens next.
The Sultan
Too bad that the 92 guys did not spend a little more time on the transmission lube system.
I am sure Agusta will take care of the issue and not wait a year to see what happens next.
The Sultan
Just like they did for the the A109E tail boom and the AW101 TR Hub cracking. Come to think of it, the 101's MGB reliability isn't anything to brag about either.
Join Date: Oct 2001
Location: In the gutter..........
Posts: 114
Likes: 0
Received 4 Likes
on
1 Post
From the Sultan.
You might well know all about that?
Didn't Bell play a significant part in the design of the problem parts? Maybe the Sultan actually designed it?
I am sure Agusta will take care of the issue and not wait a year to see what happens next.
Didn't Bell play a significant part in the design of the problem parts? Maybe the Sultan actually designed it?
I was told that another problem is that traditional Non Destructive Testing Techniques don't work on composites so finding voids in the structure or identifying cracks is much more difficult. Any gurus know what techniques are being used nowadays?
Arrakis
PS. What about other AW helicopters tailbooms?
Join Date: Jul 2008
Location: Australia
Posts: 372
Likes: 0
Received 0 Likes
on
0 Posts
NDI
I was told that another problem is that traditional Non Destructive Testing Techniques don't work on composites so finding voids in the structure or identifying cracks is much more difficult. Any gurus know what techniques are being used nowadays?
Remember that NDI is only capable of finding air gaps. It can not find weak bonds which are still in contact but which have a high potential for subsequent failure. I once asked an over-confident technician to tell me where a sample I had just made actually had good bonds. He easily found the deliberate void in the centre and then confidently told me the rest of the sample was well bonded. Pity it was joined together using double sided tape! NDI is effective at finding bad bonds. It can not give total assurance of good bonds.
Regards
Blakmax
So my statement is true then - eddy currents and visual inspections (traditional NDT) don't work but modern techniques (thermography and ultrasound) do
Join Date: Jul 2008
Location: Australia
Posts: 372
Likes: 0
Received 0 Likes
on
0 Posts
visual and eddy currents
Yes Crabby, these are a waste of time. Eddy currents require a conductive medium and while carbon composites do set up eddy currents, the nature of damage in composites (delamination, fibre fracture, intra-ply splitting, fibre pull-out) does not lend itself to detection by that method.
Visual is only of any value when the defect is excessively large so that the skin distorts. Composites are linear elastic to failure and therefore they tend to spring back into place. In sandwich structure visual may be of assistance only if the core is crushed sufficiently to prevent the skin springing back.
The most rediculous visual inspection prize goes to a certain brand of helicopter which issued an AD requiring visual inspection for disbonds before every flight. Now, a dark disbond on a black blade viewed against a bright sky? What chance?
Regards
Blakmax
Visual is only of any value when the defect is excessively large so that the skin distorts. Composites are linear elastic to failure and therefore they tend to spring back into place. In sandwich structure visual may be of assistance only if the core is crushed sufficiently to prevent the skin springing back.
The most rediculous visual inspection prize goes to a certain brand of helicopter which issued an AD requiring visual inspection for disbonds before every flight. Now, a dark disbond on a black blade viewed against a bright sky? What chance?
Regards
Blakmax