AW139 lost tail taxying DOH
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Gulf advised to replace tailboom?????
Heard today that after reported tail strike some months ago that the operator was advised by the OEM to replace the tail boom but elected not to do so? Some fairings replaced and boom inspected but not replaced?
Any intel confirming/denying this rumor?
Any intel confirming/denying this rumor?
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possibly been discussed before, but was the subject aircraft taxied while the nose gear was locked?
this would put a boatload of strain on the tailboom during taxi, just a theory
dr
this would put a boatload of strain on the tailboom during taxi, just a theory
dr
Heard of possible steps from FAA to ground 139 fleet in the US - any news??
Ain't gonna happen!
Not until it kills enough folks to force the FAA into doing something out of public embarrassment!
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Just finished up repairs on our ships
Wish me luck 
I think that Agusta is focusing more attention on the tail strike rather than the delam.
FYI our delamination was on the top right side where the exhaust typically hits. You can hear the void by just tapping with your finger. Not very scientific but the change in pitch was obvious even without the expensive little hammer.
Maybe a AS350 B3 Type heat shield is in order...of course that's all we need, more aft weight. (sarcasm
I think that Agusta is focusing more attention on the tail strike rather than the delam.
FYI our delamination was on the top right side where the exhaust typically hits. You can hear the void by just tapping with your finger. Not very scientific but the change in pitch was obvious even without the expensive little hammer.
Maybe a AS350 B3 Type heat shield is in order...of course that's all we need, more aft weight. (sarcasm
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heat shield is not the answer
Agreed Bandit19 this may have occurred where the exhaust hits, but my examination of photographs of other (typical?) disbonds is that the disbond problem is almost certainly caused by a weak bond due to microvoiding in the adhesive due to process issues. The real solution is to eliminate the microvoiding so that the adhesive actually achieves the potential strength of the bond which was used for the original testing and design. Heat shields etc. are only first-aid for a more serious weak bond condition which, with all due respect to AW's statement of 23 September 2009, can not be modelled by FEA or simulated by artificial disbonds in structural tests.
The evidence I have seen from sample disbonds from other aircraft has irrefutable characteristics of production related microvoiding, which results in a severe loss of structural strength of sandwich structures such as those in AW tail booms. Such a degradation in bond strength can not be modelled by FEA as localised nodal seprations. Tests which use localised teflon inserts as artificial disbonds also fail to correctly represent the true situation.
Reference data indicates that such extensive microvoiding as displayed in the AW139 samples I have seen represents approximately a 50% bond strength loss. Arnott, D.R., Wilson, A.R., Pearce, P.J., Mathys, G., Kindermann, M.R., Camilleri, A., DAVIS, M.J., Swan, G., Void Development in Aerospace Film Adhesives During Vacuum Bag Cure, Int. Aerospace Congress, Sydney, 25-28 Feb. 1997.
Admittedly, the data I have seen relates to shear and peel strength of overlap joints, but I would suggest that the reduced bond area for core bonds would make such defects even more susceptible to such a magnitude of strength loss.
The only way AW can even remotely represent this condition is to reduce their allowable adhesive properties by 50% and then see what their FEA model predicts.
I sincerely hope that AW examines the components thay have retrieved with a view to recognising the presence of microvoids in the fillet bonds between the core and the adhesive, and then to recognise the significance of those microvoids to strength loss in adhesive bonds. They should then address the causes of such microvoiding, and my previous postings have listed some of the production variables they should examine.
Regards
blakmax
The evidence I have seen from sample disbonds from other aircraft has irrefutable characteristics of production related microvoiding, which results in a severe loss of structural strength of sandwich structures such as those in AW tail booms. Such a degradation in bond strength can not be modelled by FEA as localised nodal seprations. Tests which use localised teflon inserts as artificial disbonds also fail to correctly represent the true situation.
Reference data indicates that such extensive microvoiding as displayed in the AW139 samples I have seen represents approximately a 50% bond strength loss. Arnott, D.R., Wilson, A.R., Pearce, P.J., Mathys, G., Kindermann, M.R., Camilleri, A., DAVIS, M.J., Swan, G., Void Development in Aerospace Film Adhesives During Vacuum Bag Cure, Int. Aerospace Congress, Sydney, 25-28 Feb. 1997.
Admittedly, the data I have seen relates to shear and peel strength of overlap joints, but I would suggest that the reduced bond area for core bonds would make such defects even more susceptible to such a magnitude of strength loss.
The only way AW can even remotely represent this condition is to reduce their allowable adhesive properties by 50% and then see what their FEA model predicts.
I sincerely hope that AW examines the components thay have retrieved with a view to recognising the presence of microvoids in the fillet bonds between the core and the adhesive, and then to recognise the significance of those microvoids to strength loss in adhesive bonds. They should then address the causes of such microvoiding, and my previous postings have listed some of the production variables they should examine.
Regards
blakmax
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Disbonding Found on dutch AW
Found disbonding on tailboom Dutch reg. AW in Den Helder, this A/C present also a damage near to VOR Antenne, damage is like a bubble, Agusta sent a compleet new tailboom in for replacement.
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New AD issued
EASA issued a new AD yesterday mandating a new BT. Daily visual inspection required on the right hand side of the tail boom, 25 hr tapping check RH side in certain areas and the 50 hr tapping check on the complete forward section of tail boom.
A common area of debonding is aft of the upper RH longeron, can be only 1 inch wide but can extend back 24 inches or further. I think AW will be increasing production of tail assemblies as this problem will not go away.
A common area of debonding is aft of the upper RH longeron, can be only 1 inch wide but can extend back 24 inches or further. I think AW will be increasing production of tail assemblies as this problem will not go away.
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this problem will not go away
I am surprised that the inspections are limited only to one zone. It may be that this is the critical location for this specific load case, but the causes of micro-voiding are such that the problem may be in every bonded part. In which case some other region may become critical under other load cases.
I am also surprised that there are not weight and manouver restrictions in the AD. Published data I have already referenced indicates a 50% strength loss in overlap joints with micro-voiding. While I don't have hard data, I would not be surprised to see at least an equivalent loss of strength for micro-voided sandwich structure, especially if the adhesive sees out of plane tension. The level of strength loss may even be higher. Now aircraft are designed not to fail at Design Ultimate Load, which is 1.5 times Design Limit Load, the maximum load the aircraft is expected to see once in its lifetime. If the strength is degraded by 50%, then failure may occur at 75% of DLL which means that the structure may be critical within the flight envelope under high loads.
These conclusions are backed up by the known occurrences of disbonds, and there is at least one case I am aware of which occurred on the OTHER side of the boom. While in a number of cases the disbonds appear to be self-arresting and repairable there is always the risk that the disbonds will not arrest as may (in the absence of the final report I stress may) have occurred in the Doha incident.
I also urge users to inspect the repairs for disbonding. The surface preparation processes described to me for repair have a known history of poor bond durability, so I expect that the repairs themselves will eventually disbond. AW really must address this issue. To repair a disbond with a procedure which will itself disbond is just asking for trouble.
Regards
blakmax
More chuffing tap testing - what a high-tech answer
Don,t worry Crab the Cojo does all the tap testing 
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I contend that to maintain flight safety it may be prudent to manage the reduced strength by flight and weight restrictions to prevent bond failures, rather than inspecting for disbonds after they occur hoping that they are captured before they reach critical size and limiting the inspections to specific locations.
The real solution is to correct the production deficiencies and re-issue the components.
The real solution is to correct the production deficiencies and re-issue the components.
One might surmise that the OEM will not voluntarily place flight and weight restrictions on the aircraft without what they believe to be proof. A prudent operator would probably make this surmise.
If the OEM believe that inspection and repair are sufficient to maintain current operating limits, they will do that, as inspection and repair are far quicker and have less impact on the top line than revamping the production and quality processes and thereafter reissuing components.
However, if the OEM believes that regulatory authorities and/or customers will begin to restrict the operating envelope, that in turn reduces the value of the aircraft.
Only when the OEM sees that a correction of production deficiencies translates directly into positive impacts upon the bottom line will they do anything about it.
Essentially, one might conclude that your message needs to get out effectively to someone in a production decision-making capacity or higher at Agusta.
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confusing message
Sorry Um Lifting. Most people would not have seen this message before I deleted it. I embedded two images in the text by inserting the web page link and could see them on the editing screen, but they reverted to a text web address on the thread page. Any ideas where I am going wrong in posting the images?
By the way I have tried addressing my comments to AW at several levels through several chanels including EASA and have not had any response. At present I suspect it is what I term "ostrich engineering"...bury your head in the sand and maybe it will go away.
Regards
blakmax
By the way I have tried addressing my comments to AW at several levels through several chanels including EASA and have not had any response. At present I suspect it is what I term "ostrich engineering"...bury your head in the sand and maybe it will go away.
Regards
blakmax
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WichiTech Digital Tap Hammer?
We are considering purchasing one of the units in order to perform inspections on composite panels, blades, etc.
Does anyone have experiance with this unit, or similar type equipment??
All replys welcome.
RD3 Tap Hammer
Does anyone have experiance with this unit, or similar type equipment??
All replys welcome.
RD3 Tap Hammer
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Down under technologies
G'day Cattletruck
Sorry but I am not familiar with the bonding processes on the Collins subs. I am aware that the Defence Science and Technology Organisation was involved in the early 1990s with some large bonded composite patches on cracked ship superstructure and that was very successful. I am unaware of any disbonds on these repairs, but that is mainly because I am no longer in the system. The patches were 4m x 1 m and the surface preparation was done using mops! My guess is that they may have taken note of the process used for that project.
My suspicion is that the other sub users suffer from the same problem as the aircraft industry; you use only the recommended procedures provided by the OEM even when there is irrefutable evidence that these processes are manifestly deficient. The AW approved scuff sand and solvent contamination process used to repair AW139 disbonds is a classic example. Everyone who knows anything about adhesive bonding has known for decades that this process may produ ce some short term strength but will without doubt result in later disbonding. The OEM is reluctant to introduce a more effective process because it may require a higher level of skills which may not be available in Blogslovia, and besides to admit the current process is deficient may leave the OEM open to litigation. Unfortunately, if the current repair process does lead to a loss of life, they again may be open to litigation anyway.
We Aussies do have a history of technological innovation. We claim the "black box" as an Aussie invention, and many of the scatter factors for full scale fatigue tests were generated down here. To some extent, we are driven by being a small nation which must maximise the useful life of the assets we have, and do that at minimum cost. (Our F-111s will go out of servide next year after over thirty years service.)
The composite patching technology I was involved in was spawned from the need to gain experience with the composite materials which were gradually entering military service. The problem was that they were expensive, so we focussed on using small amounts of materials on applications which gave high returns for the costs. It has been estimated that we saved over US$100 million by being the only C-130E user in the world not to change the wing planks because we extended their life using composite patches from 1975 to withdrawal. It was only in the 1990's that the USAF finally saw the benefits and saved billions adopting (and extending) this technology for repairs to C-141. The late entry has been attributed by some to the attitude of "Not invented in the USA, can't be good" and there may be an element of truth in it.
In my personal case, I am still trying to convince the FAA (and any other regulator who will listen) that the current regulations for certifying bonded structures are inadequate because it is possible to make a bonded structure which meets current certification requirements yet has a potential to fail in service. (see Davis, M.J. DEFICIENCIES IN REGULATIONS FOR CERTIFICATION AND CONTINUING AIRWORTHINESS OF BONDED STRUCTURES, International Aerospace Congress, Sydney, 25-27 February 1997
I can send a copy if requested)
There are two basic failure modes for adhesive bonds; cohesion failure where the adhesive fractures and adhesion failure where the adhesive disbonds at the interface between the adhesive and the adherend. Current regulations do not adequately address adhesion failures, or address them in a manner which is open to misinterpretation. Now helicopters have a lot of adhesive bonding in primary structure (blades for example) and I have seen interfacial failures in such structures.
I sometime do feel that there is an element of
Regards
blakmax
Sorry but I am not familiar with the bonding processes on the Collins subs. I am aware that the Defence Science and Technology Organisation was involved in the early 1990s with some large bonded composite patches on cracked ship superstructure and that was very successful. I am unaware of any disbonds on these repairs, but that is mainly because I am no longer in the system. The patches were 4m x 1 m and the surface preparation was done using mops! My guess is that they may have taken note of the process used for that project.
My suspicion is that the other sub users suffer from the same problem as the aircraft industry; you use only the recommended procedures provided by the OEM even when there is irrefutable evidence that these processes are manifestly deficient. The AW approved scuff sand and solvent contamination process used to repair AW139 disbonds is a classic example. Everyone who knows anything about adhesive bonding has known for decades that this process may produ ce some short term strength but will without doubt result in later disbonding. The OEM is reluctant to introduce a more effective process because it may require a higher level of skills which may not be available in Blogslovia, and besides to admit the current process is deficient may leave the OEM open to litigation. Unfortunately, if the current repair process does lead to a loss of life, they again may be open to litigation anyway.
We Aussies do have a history of technological innovation. We claim the "black box" as an Aussie invention, and many of the scatter factors for full scale fatigue tests were generated down here. To some extent, we are driven by being a small nation which must maximise the useful life of the assets we have, and do that at minimum cost. (Our F-111s will go out of servide next year after over thirty years service.)
The composite patching technology I was involved in was spawned from the need to gain experience with the composite materials which were gradually entering military service. The problem was that they were expensive, so we focussed on using small amounts of materials on applications which gave high returns for the costs. It has been estimated that we saved over US$100 million by being the only C-130E user in the world not to change the wing planks because we extended their life using composite patches from 1975 to withdrawal. It was only in the 1990's that the USAF finally saw the benefits and saved billions adopting (and extending) this technology for repairs to C-141. The late entry has been attributed by some to the attitude of "Not invented in the USA, can't be good" and there may be an element of truth in it.
In my personal case, I am still trying to convince the FAA (and any other regulator who will listen) that the current regulations for certifying bonded structures are inadequate because it is possible to make a bonded structure which meets current certification requirements yet has a potential to fail in service. (see Davis, M.J. DEFICIENCIES IN REGULATIONS FOR CERTIFICATION AND CONTINUING AIRWORTHINESS OF BONDED STRUCTURES, International Aerospace Congress, Sydney, 25-27 February 1997
I can send a copy if requested)
There are two basic failure modes for adhesive bonds; cohesion failure where the adhesive fractures and adhesion failure where the adhesive disbonds at the interface between the adhesive and the adherend. Current regulations do not adequately address adhesion failures, or address them in a manner which is open to misinterpretation. Now helicopters have a lot of adhesive bonding in primary structure (blades for example) and I have seen interfacial failures in such structures.
I sometime do feel that there is an element of
yet another case of Australia being considered a technological and cultural backwash
blakmax
More tails to be tested
The Qatar Armed Forces take delivery of their first AW139
The Qatar Armed Forces take delivery of their first AW139
News
The Qatar Armed Forces take delivery of their first AW139
November 25, 2009
AgustaWestland has announced that the Qatar Armed Forces has taken delivery of its first AW139 medium twin helicopter during an official ceremony held yesterday at AgustaWestland’s Vergiate plant in Italy, in the presence of Qatar Armed Forces Chief of Staff General Hamad Bin Ali Al Attiyah and Qatar Emiri Air Force Chief of Staff General Mubarak Al-Khayarin.
The aircraft will be operated by the Qatar Emiri Air Force supporting various government agencies to perform a range of roles including utility, troop transport, search and rescue, border patrol, special forces operations, law enforcement and homeland security.
A contract for 18 units was signed in August 2008 which also included crew training and an initial spares package. The Qatar Armed Forces becomes the third operator of military-configured AW139 helicopters following the Irish Air Corps and UAE Armed Forces.
Giuseppe Orsi, Chief Executive Officer, AgustaWestland said “It gives us great pleasure to celebrate the handover of the first AW139 to such an important customer ahead of the planned delivery schedule. The military configured AW139 has been developed to meet the Qatar Armed Forces’ demanding requirements and I am confident it will exceed their operational expectations in service.“
Designed to be easily and quickly converted between roles, the AW139 is perfectly suited for military and public security applications. The AW139 cabin can be configured to carry 8 to 15 troops in its spacious eight cubic metre cabin. Large sliding cabin doors allow both troops and equipment to be loaded and unloaded easily and quickly.
The AW139 sets new standards of performance in its class for military applications with a maximum cruise speed of 165 knots (306 km/h) and a maximum range in excess of 570 nm (1060 km) with auxiliary fuel. The aircraft has outstanding one engine inoperative capabilities even in the hot an high environmental conditions.
The advanced integrated cockpit with state-of-the-art technology minimises pilot workload allowing the crew to concentrate on mission objectives. For military missions the AW139 features dedicated equipment to meet a range of general and specialist roles.
Around 440 orders have been placed by over 120 customers from almost 50 countries to date, making it the benchmark helicopter in the medium twin category for a number of tasks. Designed with inherent multi-role capability and flexibility of operation, the AW139 can perform many roles including law enforcement, search and rescue, emergency medical service, offshore transport, VIP/corporate transport and military utility missions.
The Qatar Armed Forces take delivery of their first AW139
November 25, 2009
AgustaWestland has announced that the Qatar Armed Forces has taken delivery of its first AW139 medium twin helicopter during an official ceremony held yesterday at AgustaWestland’s Vergiate plant in Italy, in the presence of Qatar Armed Forces Chief of Staff General Hamad Bin Ali Al Attiyah and Qatar Emiri Air Force Chief of Staff General Mubarak Al-Khayarin.
The aircraft will be operated by the Qatar Emiri Air Force supporting various government agencies to perform a range of roles including utility, troop transport, search and rescue, border patrol, special forces operations, law enforcement and homeland security.
A contract for 18 units was signed in August 2008 which also included crew training and an initial spares package. The Qatar Armed Forces becomes the third operator of military-configured AW139 helicopters following the Irish Air Corps and UAE Armed Forces.
Giuseppe Orsi, Chief Executive Officer, AgustaWestland said “It gives us great pleasure to celebrate the handover of the first AW139 to such an important customer ahead of the planned delivery schedule. The military configured AW139 has been developed to meet the Qatar Armed Forces’ demanding requirements and I am confident it will exceed their operational expectations in service.“
Designed to be easily and quickly converted between roles, the AW139 is perfectly suited for military and public security applications. The AW139 cabin can be configured to carry 8 to 15 troops in its spacious eight cubic metre cabin. Large sliding cabin doors allow both troops and equipment to be loaded and unloaded easily and quickly.
The AW139 sets new standards of performance in its class for military applications with a maximum cruise speed of 165 knots (306 km/h) and a maximum range in excess of 570 nm (1060 km) with auxiliary fuel. The aircraft has outstanding one engine inoperative capabilities even in the hot an high environmental conditions.
The advanced integrated cockpit with state-of-the-art technology minimises pilot workload allowing the crew to concentrate on mission objectives. For military missions the AW139 features dedicated equipment to meet a range of general and specialist roles.
Around 440 orders have been placed by over 120 customers from almost 50 countries to date, making it the benchmark helicopter in the medium twin category for a number of tasks. Designed with inherent multi-role capability and flexibility of operation, the AW139 can perform many roles including law enforcement, search and rescue, emergency medical service, offshore transport, VIP/corporate transport and military utility missions.