AW139 lost tail taxying DOH
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The nuances of the english language were never one of my strong points so I'll try and continue the original thread.
We have recieved the latest and greatest Tailboom Assy from Agusta which is identified by an additional data plate the size of a postage stamp along side the original with BT 139-159 engraved in it.
Fingers crossed this new Assy with the aluminium or for those on minimum wages aluminum core and improved production standards has solved the disbonding issue and we can all, especially our pax and drivers, can get back to operating what is really a good machine in absolute confidence. Anyway I will keep everyone posted as to it's serviceability. No news is good news.
Blakmax I'm still waiting to hear your recommended surface prep for metal to metal bonding for those of us in the field. Generally we use bond sheet for our repair doublers and fillers. Bond sheet for those who are unaware is aluminium or stainless sheet with a layer of film adhesive already bonded in place and covered with a layer of peel ply. It is available in different gauges. The benefit of using it in the field is you simply cut your repair parts to size remove the peel ply lightly abrade, do an M.E.K. wipe, air dry and install. However the surface prep for the original structure I'm afraid is still abrade and M.E.K.wipe. There seems to be a few options available from Deoxidines to Pasagels, none of which are mentioned in the SRM's I currently use, what I would like to know is, what is the most user friendly.
We have recieved the latest and greatest Tailboom Assy from Agusta which is identified by an additional data plate the size of a postage stamp along side the original with BT 139-159 engraved in it.
Fingers crossed this new Assy with the aluminium or for those on minimum wages aluminum core and improved production standards has solved the disbonding issue and we can all, especially our pax and drivers, can get back to operating what is really a good machine in absolute confidence. Anyway I will keep everyone posted as to it's serviceability. No news is good news.
Blakmax I'm still waiting to hear your recommended surface prep for metal to metal bonding for those of us in the field. Generally we use bond sheet for our repair doublers and fillers. Bond sheet for those who are unaware is aluminium or stainless sheet with a layer of film adhesive already bonded in place and covered with a layer of peel ply. It is available in different gauges. The benefit of using it in the field is you simply cut your repair parts to size remove the peel ply lightly abrade, do an M.E.K. wipe, air dry and install. However the surface prep for the original structure I'm afraid is still abrade and M.E.K.wipe. There seems to be a few options available from Deoxidines to Pasagels, none of which are mentioned in the SRM's I currently use, what I would like to know is, what is the most user friendly.
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Dont all answer my last at once!!
any news, is everyone waiting on a new super improved TB or are others rocking and rolling but with extreme tap tap sounds at every walk-a-round.
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Acceptable surface preparations
Hi Skin King
Firstly, let me shudder again. I am concerned about the concept of a peel ply based on my experience with peel plies on composite patches. For those who don't know about peel plies, these are a sacrificial layer incorporated onto the surface which is removed just prior to bonding. The concept is that the peel ply protects the surface from contamination and removal leaves a "clean" surface. These are often used in production bonds as well. As already stated, a clean surface is a necessary but not sufficient condition for adhesion.
For fibre composite laminates, the problem is to make the bond to the peel ply weaker than the bond between the plies, otherwise the act of removing the peel ply risks pulling the first ply off the composite. With composites, my expereince is that the peel ply manufacturers use one of two processes; they either coat the surface of the peel ply with a release product such as silicone, or they heat-set the fibres of the peel ply which results in a glazed surface which inhibits adhesion to the laminate, thus making it easier to remove the peel ply. See Hart-Smith, L.J., Redmond, G, DAVIS, M.J., The Curse of the Nylon Peel Ply, 41st. Int SAMPE Symp. and Exhib., Anaheim, 25-28 Mar 1996.
Both of these methods produce their own problems. Irrespective of whatever the peel ply manufacturer may claim, coated peel plies DO transfer the release material to the surface and as a consequence you end up with a layer of contamination on the surface. Abrasion simply spreads that material and it is often not solvent soluble. So coated plies are not appropriate. The glazed surface of the fibres in heat-set plies result in a cast replicate of the glazed surface and that surface is also resistant to adhesion. There is some hope that abrasion of heat-set peel plies may provide an adequate bond.
Now I am not aware of the type of peel ply used in this case, but if it is the coated variety, you have problems.
As far as preparation processes for repair, there really are only three which are effective in providing bond durability.
1. Phoshoric acid anodising (PAA) using either the PANTA process or PACS process, but these won't be suitable for the Sand Box area, because they are ineffective if the structure is above 85F (29C). It is also messy and not suited to full depth core repairs.
2. The grit-blast and silane GBS process which uses a polymer coupling agent, and
3. Boeing's Bo-jel process which uses the same coupling agent as GBS with a few additional ingredients.
Of these the last two are far easier to apply. Bo-jel requires a primer but RAAF has used GBS without a primer for seventeen years without corrosion or bond failures.
Acid etching using Pasajel has been found not to produce adequate bond durability, even with primers, unless the structure is heated to between 140 and 180 F (60-80C) during application. The material does contain hexavalent chromates which are acknowledge carcinogens, so I would not advocate reaching past heat lamps to apply the stuff. The risk of accidental brushing producing a carcinogenic vapour puts me right off. Boeing's hydrofluoric acid etch procedure is also off my list for OHS reasons apart from its poor durability performance. Alodine is a corrosion passivation process and as such the passive nature of the surface may mean that the chemical reactions necessary to generate bond durability may not occur. I've seen mixed results for this process.
If you don't use one of the three processes I have listed, then there is a high risk of disbonding. If you simply apply a bond primer without generating a chemically active surface then that will not work, despite the assurances of the salesman.
Whatever the answer is, it really is time that OEMs took their heads out of the sand and faced the undeniable fact that scuff sand and solvent contaminate processes do not produce sound structures and hence have no place in SRMs or any other authorised repairs.
Regards
Blakmax
Firstly, let me shudder again. I am concerned about the concept of a peel ply based on my experience with peel plies on composite patches. For those who don't know about peel plies, these are a sacrificial layer incorporated onto the surface which is removed just prior to bonding. The concept is that the peel ply protects the surface from contamination and removal leaves a "clean" surface. These are often used in production bonds as well. As already stated, a clean surface is a necessary but not sufficient condition for adhesion.
For fibre composite laminates, the problem is to make the bond to the peel ply weaker than the bond between the plies, otherwise the act of removing the peel ply risks pulling the first ply off the composite. With composites, my expereince is that the peel ply manufacturers use one of two processes; they either coat the surface of the peel ply with a release product such as silicone, or they heat-set the fibres of the peel ply which results in a glazed surface which inhibits adhesion to the laminate, thus making it easier to remove the peel ply. See Hart-Smith, L.J., Redmond, G, DAVIS, M.J., The Curse of the Nylon Peel Ply, 41st. Int SAMPE Symp. and Exhib., Anaheim, 25-28 Mar 1996.
Both of these methods produce their own problems. Irrespective of whatever the peel ply manufacturer may claim, coated peel plies DO transfer the release material to the surface and as a consequence you end up with a layer of contamination on the surface. Abrasion simply spreads that material and it is often not solvent soluble. So coated plies are not appropriate. The glazed surface of the fibres in heat-set plies result in a cast replicate of the glazed surface and that surface is also resistant to adhesion. There is some hope that abrasion of heat-set peel plies may provide an adequate bond.
Now I am not aware of the type of peel ply used in this case, but if it is the coated variety, you have problems.
As far as preparation processes for repair, there really are only three which are effective in providing bond durability.
1. Phoshoric acid anodising (PAA) using either the PANTA process or PACS process, but these won't be suitable for the Sand Box area, because they are ineffective if the structure is above 85F (29C). It is also messy and not suited to full depth core repairs.
2. The grit-blast and silane GBS process which uses a polymer coupling agent, and
3. Boeing's Bo-jel process which uses the same coupling agent as GBS with a few additional ingredients.
Of these the last two are far easier to apply. Bo-jel requires a primer but RAAF has used GBS without a primer for seventeen years without corrosion or bond failures.
Acid etching using Pasajel has been found not to produce adequate bond durability, even with primers, unless the structure is heated to between 140 and 180 F (60-80C) during application. The material does contain hexavalent chromates which are acknowledge carcinogens, so I would not advocate reaching past heat lamps to apply the stuff. The risk of accidental brushing producing a carcinogenic vapour puts me right off. Boeing's hydrofluoric acid etch procedure is also off my list for OHS reasons apart from its poor durability performance. Alodine is a corrosion passivation process and as such the passive nature of the surface may mean that the chemical reactions necessary to generate bond durability may not occur. I've seen mixed results for this process.
If you don't use one of the three processes I have listed, then there is a high risk of disbonding. If you simply apply a bond primer without generating a chemically active surface then that will not work, despite the assurances of the salesman.
Whatever the answer is, it really is time that OEMs took their heads out of the sand and faced the undeniable fact that scuff sand and solvent contaminate processes do not produce sound structures and hence have no place in SRMs or any other authorised repairs.
Regards
Blakmax
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Sources?
GBS - where can one obtain the silane compound?
Bo-Jel - could not find any sourcing, or even citation on the web.
The repair standard YOU wrote for the RAAF - lots of citations, no sourcing info for that either.
Any thoughts on the Ac-130 Sol-gel product? AC TECH Products - Surface Pre-Treatment It appears to be Boegel-EPII under license.
Bo-Jel - could not find any sourcing, or even citation on the web.
The repair standard YOU wrote for the RAAF - lots of citations, no sourcing info for that either.
Any thoughts on the Ac-130 Sol-gel product? AC TECH Products - Surface Pre-Treatment It appears to be Boegel-EPII under license.
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response to karmarepair
Hi Karmarepair (Crikey, I hope you weren't offended by my "bad karma" comment on the Tech Log stream on 787 composites!)
You wrote
It is sold as Dow Corning Z6040.
You are correct. I believe that I may have incorrectly spelt Boegel and that product is I believe licensed to the manifacturers of AC130. The procedures are available from that source or from the updated Boeing manuals.
That is because they are RAAF documents. I used to work for RAAF. I now work as a consultant and the knowledge I now market was used to write those documents. You could request the publications from ASI-DGTA, RAAF Williams, Laverton, Victoria 3027 Australia if you wish, or you can send me a Private Message to ask my company to assist.
BUT it is not a simple process of slappping these products on the surface. The mixing ratio, time before use, pot life, processes before and after application, allowable process gaps, curing temperatures and times etc. are all important.
I believe I have done a service to the industry and to flight safety to educate people in the deficiencies in adhesive bonding technologies through PPRuNe. But please realise that while I am prepare to educate on the basic principles of bonding, I simply can not afford to give away all of the process details because these are the source of my current income. Besides, if you simply read the process specifications, you do not get the complete package of quality management, materials selection, process validation, materials handling and management, bonded repair design, testing and inspection procedures etc. etc. which are all fundamental aspects of the technology.
Regards
blakmax
You wrote
GBS - where can one obtain the silane compound?
Bo-Jel - could not find any sourcing, or even citation on the web.
Any thoughts on the Ac-130 Sol-gel product? AC TECH Products - Surface Pre-Treatment It appears to be Boegel-EPII under license.
Any thoughts on the Ac-130 Sol-gel product? AC TECH Products - Surface Pre-Treatment It appears to be Boegel-EPII under license.
The repair standard YOU wrote for the RAAF - lots of citations, no sourcing info for that either.
BUT it is not a simple process of slappping these products on the surface. The mixing ratio, time before use, pot life, processes before and after application, allowable process gaps, curing temperatures and times etc. are all important.
I believe I have done a service to the industry and to flight safety to educate people in the deficiencies in adhesive bonding technologies through PPRuNe. But please realise that while I am prepare to educate on the basic principles of bonding, I simply can not afford to give away all of the process details because these are the source of my current income. Besides, if you simply read the process specifications, you do not get the complete package of quality management, materials selection, process validation, materials handling and management, bonded repair design, testing and inspection procedures etc. etc. which are all fundamental aspects of the technology.
Regards
blakmax
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JC
Skin King,
Can you offer your expert opinion on the latest / upgraded tail boom assy you recieved from Agusta?
Were there any significant differences other than the aluminum vs nomex honeycomb panels?
Thanks much for keeping us updated!
Can you offer your expert opinion on the latest / upgraded tail boom assy you recieved from Agusta?
Were there any significant differences other than the aluminum vs nomex honeycomb panels?
Thanks much for keeping us updated!
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JC, there are no obvious visual differences between the old and new type booms. The only real way to tell is by the additional itsy bitsy data plate attached to the top of the Tailboom near where the two of the side panels are joined and usually directly under the tail rotor driveshaft.
Having said that the side panels for my part actually look at lot smoother. That is to say they don't appear to have the dips and hollows where the longerons are fitted or the tell tail perpendicular bulge of the internal doubler strip just aft of the longerons. I have also been reassured that the manufacturing process and Q.C. of the new side panels has been improved, but then again, no actual details of this has been issued by Agusta at this stage and more than likely never will.
I'm also optimistic that we can persuade Agusta to either sell, loan, lease or give us a tailboom jig in order to carry out BT 139-159 not only for ourselves but for other operators as well. This would alleviate a heck of a lot of downtime for everyone waiting on booms to come from Agusta.
In my humble opinion it is only a matter of time before a mandatory BT or AD comes out giving all Tailbooms currently in service a finite time before the side panels are to be changed to the new type. God willing.
As a footnote, another of our Tailbooms went U/S yesterday bringing the total now to a nice even dozen. Trust me they are not cheaper by the dozen.
I probably have very little to add to this thread now and would just like to finish off by saying that working collectively as an industry where safety is foremost we will solve this problem. In the meantime keep vigilant in our preflights.
Having said that the side panels for my part actually look at lot smoother. That is to say they don't appear to have the dips and hollows where the longerons are fitted or the tell tail perpendicular bulge of the internal doubler strip just aft of the longerons. I have also been reassured that the manufacturing process and Q.C. of the new side panels has been improved, but then again, no actual details of this has been issued by Agusta at this stage and more than likely never will.
I'm also optimistic that we can persuade Agusta to either sell, loan, lease or give us a tailboom jig in order to carry out BT 139-159 not only for ourselves but for other operators as well. This would alleviate a heck of a lot of downtime for everyone waiting on booms to come from Agusta.
In my humble opinion it is only a matter of time before a mandatory BT or AD comes out giving all Tailbooms currently in service a finite time before the side panels are to be changed to the new type. God willing.
As a footnote, another of our Tailbooms went U/S yesterday bringing the total now to a nice even dozen. Trust me they are not cheaper by the dozen.
I probably have very little to add to this thread now and would just like to finish off by saying that working collectively as an industry where safety is foremost we will solve this problem. In the meantime keep vigilant in our preflights.
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Monnett and Schreder set homebuilt bonding back decades
Crikey, I hope you weren't offended by my "bad karma" comment on the Tech Log stream on 787 composites!
Not at all, my handle is a riff on "Zen and the Art Of Motorcycle Maintenance", and not on conventional Buddhist teachings.RE the RAAF Repair Standard, etc - I understand all your points. I'm trying to educate myself - it's not clear I'll ever use any of this fascinating information. But if my employer ever needs an expert in aluminum bonding or advanced composite repairs, I know who will be on the short list.
In this thread in another forum:
Conclusions on Aluminum Adhesive Bonding Tests
an enthusiastic amateur, watched over by some cooler heads, is attempting to work out methods for using room temperature cure adhesives to bond primary structures for a homebuilt. I noticed in the literature I was able to find that the "Australian Method" improved bonding performance. of room temperature paste adhesives. I think GESchwarz is on the wrong track, and has come to the wrong conclusion RE a solvent wipe over an abraded surface, and some silanes might begin to set him right. He doesn't seem to have heard of the ASTM wedge test...
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Homebuilt technology
Hi Karma
I had a look at that web site and you are correct. Yet another forum for blakmax to raid. This group are candidates for the Darwin Award (for the person who removed themselves from the gene pool in a spectactularly stupid way.)
Thanks for keeping me on the contact list and I really do hope that some day you get to use my advice. Adhesive bonding is a truly effective and remarkable technology that is getting a bad name from people who do not understand the basics of the technology.
Like Skin King, I don't know how much more I can contribute to this stream. I am trying to make contact with AW and once that happens, obviously that involvement will need to be confidential. I just hope that they don't assume that the new aluminium core boom fixes all their problems and ignore me. There are other issues in the samples I have seen that will not be fixed by one change. They also really MUST do something about their repair surface preparation because the one they currently specify without any doubt will result in disbonds.
Regards
blakmax
I had a look at that web site and you are correct. Yet another forum for blakmax to raid. This group are candidates for the Darwin Award (for the person who removed themselves from the gene pool in a spectactularly stupid way.)
Thanks for keeping me on the contact list and I really do hope that some day you get to use my advice. Adhesive bonding is a truly effective and remarkable technology that is getting a bad name from people who do not understand the basics of the technology.
Like Skin King, I don't know how much more I can contribute to this stream. I am trying to make contact with AW and once that happens, obviously that involvement will need to be confidential. I just hope that they don't assume that the new aluminium core boom fixes all their problems and ignore me. There are other issues in the samples I have seen that will not be fixed by one change. They also really MUST do something about their repair surface preparation because the one they currently specify without any doubt will result in disbonds.
Regards
blakmax
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Another AD
Hi Blakmax
I see that FAA have issued AD 2009-19-51-E, but ignores all the warnings you have given us recently. The debond must be no more than 0.5 sq in. One would hope that AW have given the correct repair info (that meets your requirements, rather than a fuzzy OEM process)
NOT good for the soul ~ VFR
I see that FAA have issued AD 2009-19-51-E, but ignores all the warnings you have given us recently. The debond must be no more than 0.5 sq in. One would hope that AW have given the correct repair info (that meets your requirements, rather than a fuzzy OEM process)
NOT good for the soul ~ VFR
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AD
Hi VFR. I have read the AD and it is basically a reaction to the failure. They had to do something to inspect the structures. The rejection criteria are standard which I think was based on MIL A 83377 which has been around since Adam wore shorts.
The AD is not the place to address the causes of the failure. What will be of great interest is the actions taken by AW to correct the deficiencies. As a bare minimum they must do something to stop the adhesive and core absorbing so much moisture. There area number of other issues which need to be investigated. The second thing they must do as a priority is to amend their repair practices. That is essential.
Regards
blakmax
The AD is not the place to address the causes of the failure. What will be of great interest is the actions taken by AW to correct the deficiencies. As a bare minimum they must do something to stop the adhesive and core absorbing so much moisture. There area number of other issues which need to be investigated. The second thing they must do as a priority is to amend their repair practices. That is essential.
Regards
blakmax
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Original pics
First off: Blakmax & others - many thanks for a truly informative post and for raising awareness levels on a very technical issue
Rest assured, all the drivers (regardless of type flown) at said company where the tailboom departed, have been watching this thread with keen interest.
If anybody has original, high quality picture files (not thumbs or uploads) taken on the day (on the ramp or in the hangar), please PM me.
Thanks
LF
Rest assured, all the drivers (regardless of type flown) at said company where the tailboom departed, have been watching this thread with keen interest.
If anybody has original, high quality picture files (not thumbs or uploads) taken on the day (on the ramp or in the hangar), please PM me.
Thanks
LF
Last edited by logicfree; 18th Sep 2009 at 08:45. Reason: Typo
Thread Starter
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First off: Blakmax & others - many thanks for a truly informative post and for raising awareness levels on a very technical issue
Rest assured, some of the SLF, have been watching this thread with keen interest.
and overall, am hugely impressed by the dedication generally shown by all.
The foibles of manufacturing processes . . , well, it's good that we constantly strive to be better.
One of the partner groups aviation reps has blamed me for the pictures as if 
"tis not a perfect world, but there do seem to be a few good people in it.
Rest assured, some of the SLF, have been watching this thread with keen interest.
and overall, am hugely impressed by the dedication generally shown by all.
The foibles of manufacturing processes . . , well, it's good that we constantly strive to be better.
One of the partner groups aviation reps has blamed me for the pictures
as if "tis not a perfect world, but there do seem to be a few good people in it.
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Blessed we are indeed
Airwave, we are just very grateful that the big 'ol Middle Eastern "rug & broom" didn't manage to swing into action to foil public awareness of the incident.
Bless the camera phone (yes, the same ones that the clients don't want us taking offshore) otherwise all the heads would still be blissfully in the sand.....
For those who may not have seen it yet: Emergency AD: Agusta S.p.A. (Agusta) Model AB139 and AW139
The EASA 198-E mentions 25 hr insp amongst others; still no warm & fuzzy feelings.....tap tap tap
Heard of possible steps from FAA to ground 139 fleet in the US - any news??
Bless the camera phone (yes, the same ones that the clients don't want us taking offshore) otherwise all the heads would still be blissfully in the sand.....
For those who may not have seen it yet: Emergency AD: Agusta S.p.A. (Agusta) Model AB139 and AW139
The EASA 198-E mentions 25 hr insp amongst others; still no warm & fuzzy feelings.....tap tap tap
Heard of possible steps from FAA to ground 139 fleet in the US - any news??
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Can't access web site
LF, I can't access that web site. My browser just sits there for ages until I give up. I have had this problem before and found that if it is a ".gov" site, we foreigners can not access the site because of homeland security exclusions to .gov sites. Seems a bit stupid that a safety of flight directive can not be accesses outside the US. Does anyone have info here? Am I wrong or is this just another BGF (Bill Gates Factor) with Vista?
If someone could mail me the AD I would appreciate it.
Regards
blakmax
If someone could mail me the AD I would appreciate it.
Regards
blakmax
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Approved repair procedures
Thanks Hedge36. I could access that site.
In reading the EAD, I noted :
Now the big question: Does the FAA consider scuff-sand and solvent cleaning (the current SRM method) an "FAA approved" procedure? If so, where is the evidence that this process produces "a sound structure" as per the FARs? If the FAA means another (more effective and reliable) process then what is that process and why isn't it in the aircraft SRM instead of a process which has been known for decades to produce bonds with extremely low durability.
Why didn't the EAD also mandate inspection of bonded repairs to the boom?
Regards
blakmax
In reading the EAD, I noted :
Before further flight, repair the tailboom using FAA-approved data and procedures
Why didn't the EAD also mandate inspection of bonded repairs to the boom?
Regards
blakmax
blakmax, I've been following this thread sporadically and find the entire discussion fascinating - even though it's outside my areas of responsibility or expertise. If there are any other documents you need access to please don't hesitate to PM me and I'll gladly throw them on my server for you.