AW139 Accident rate discussion
BlenderPilot, accident rates can and are misleading at times depending on what data is used.
Linking accident rates to hours flown is one of the worst ways to view accident rate data when you consider that around 80% of all accidents happen during the takeoff and landing phases of flight.
Put the AW139 accidnet data in comparison to takeoffs and landings. Do the same with a commercial airliner. Yes, the helicopter will still be worse, but the airliner accident rate will have jumped closer.
If helicopters could do 12 hour legs with one takeoff and one landing, our accident rate would probably be pretty darn good too!
Linking accident rates to hours flown is one of the worst ways to view accident rate data when you consider that around 80% of all accidents happen during the takeoff and landing phases of flight.
Put the AW139 accidnet data in comparison to takeoffs and landings. Do the same with a commercial airliner. Yes, the helicopter will still be worse, but the airliner accident rate will have jumped closer.
If helicopters could do 12 hour legs with one takeoff and one landing, our accident rate would probably be pretty darn good too!
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Viewing the table featured, some rather uninformed comments in the cause column for the Gulf Helicopters incidences. unless you have information relating the events directly to flight crew mismanagement I would suggest you amend the table.*
Spinwing
Not sure what you are trying to sell, but tail rotor track and balance has nothing to do with the current issue on the 139. Currently the tail rotor blade is the focus of the investigation. The balance and pitch variations used even to the extreme of gross incompetence may have a long term impact on secondary airframe structure, but are just a flea speck on the loads seen on a hub or blade (they rotate so these adjustments are just very minor static load variations).
The Sultan
Not sure what you are trying to sell, but tail rotor track and balance has nothing to do with the current issue on the 139. Currently the tail rotor blade is the focus of the investigation. The balance and pitch variations used even to the extreme of gross incompetence may have a long term impact on secondary airframe structure, but are just a flea speck on the loads seen on a hub or blade (they rotate so these adjustments are just very minor static load variations).
The Sultan
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Brings back memories of the period a decade ago when A109s/A119s were slinging TRBs and TRGBs. AW must have thought they'd left that all behind when they switched to composite TRBs.
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AW139 ACCIDENTS
Friends,
I haven't heard any comment regarding AW139 fragile composite Tail Boom. In fact I am Helicopter Pilot at 30 years. But this helo is probably the only medium size with full composite Tail I have seen.
As everybody knows: Composite are very resistant at compression and expansion forces but very fragile at torsion forces - just forces suffered by a helicopter tail. I will bet that if Agusta should install cameras to screenning this helo flights.....I am sure they would have many "surprises"......
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Savoia,
nice job on the table/matrix.
Last week I was in Liege, Belgium. There was the 31250, owned by the Dutch police for a repair on the crosstube of the collective. It seems the crosstube was fitting wrongly in the factory (Vergiate).
The tube didn't fit in the brackets and was with excessief forces put in place. This concluded that lots of forces where needed to move the collective. The force needed where that high that the AP wasn't able to maintain altitude.
Something to keep in mind by the investigating of the South Korean Coast Guard 139. (31264)
nice job on the table/matrix.
Last week I was in Liege, Belgium. There was the 31250, owned by the Dutch police for a repair on the crosstube of the collective. It seems the crosstube was fitting wrongly in the factory (Vergiate).
The tube didn't fit in the brackets and was with excessief forces put in place. This concluded that lots of forces where needed to move the collective. The force needed where that high that the AP wasn't able to maintain altitude.
Something to keep in mind by the investigating of the South Korean Coast Guard 139. (31264)
Vandee, grazie. The purpose of the table is to assist those (such as myself) who know little or nothing about the 139's accident history.
I was cautioned by a number of respected Rotorheads that the table runs the risk of being an over-simplification of what is unquestionably an involved subject but, I hope that despite this, it will in some small way encourage more meaningful debate (for some) as a result of offering a snapshot of the basic facts.
Early next week there shall be some amendements to the comments surrounding both of the Gulf Helicopters incidents and which will reflect the input of those who are close to these events.
Regarding serial no. 31250, she's a tidy ship and your comments regarding the flight-control installation seem intriguing. Signore Anderozzi heads up AW's Liège team so the Dutch Police will be in good hands. Lets hope it was a one-off incident.
I was cautioned by a number of respected Rotorheads that the table runs the risk of being an over-simplification of what is unquestionably an involved subject but, I hope that despite this, it will in some small way encourage more meaningful debate (for some) as a result of offering a snapshot of the basic facts.
Early next week there shall be some amendements to the comments surrounding both of the Gulf Helicopters incidents and which will reflect the input of those who are close to these events.
Regarding serial no. 31250, she's a tidy ship and your comments regarding the flight-control installation seem intriguing. Signore Anderozzi heads up AW's Liège team so the Dutch Police will be in good hands. Lets hope it was a one-off incident.
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AW139 PR SEK Brazil´s accident up dating
Hello AW139 flyers,
Greetings from Brazil!
Regarding last information about AW139 crash in Brazil (Aug 19 2011)which came to me, I´d like to share with all of you that:
1-This last accident, is considering as TR Blade rupture (not officially confirmed yet). But, the last Agusta´s bolletin issued lead us to conclude something like that.
2-In our case, there was some blades, featuring cracks with less than 300h TT.
3-We are expecting further actions (by chance, more radical and effective actions beyond simple bulletins!) from Agusta and Authorities, but until now, nothing.
Greetings from Brazil!
Regarding last information about AW139 crash in Brazil (Aug 19 2011)which came to me, I´d like to share with all of you that:
1-This last accident, is considering as TR Blade rupture (not officially confirmed yet). But, the last Agusta´s bolletin issued lead us to conclude something like that.
2-In our case, there was some blades, featuring cracks with less than 300h TT.
3-We are expecting further actions (by chance, more radical and effective actions beyond simple bulletins!) from Agusta and Authorities, but until now, nothing.
Helicap, who told you that the 139 has a composite tailboom?
The tailboom is composite construction, not composite materials.
The tailboom is Aluminium skins (Aluminum for you Nth American types
) bonded to an Aluminium or Nomex paper core. Nothing new there, the B212/412 use the same construction methods in the forward sections of their tailbooms, and have similar debonding issues (greatly reduced with Alpine Aero ejectors fitted).
There are next to no composite materials used in the construction of the AW139 from the codkpit doors back. Forward of the cockpit doors it is Kevlar, behind the cockpit doors is nearly all Aluminium.
Hope that clarifies things for you.
The tailboom is composite construction, not composite materials.
The tailboom is Aluminium skins (Aluminum for you Nth American types
) bonded to an Aluminium or Nomex paper core. Nothing new there, the B212/412 use the same construction methods in the forward sections of their tailbooms, and have similar debonding issues (greatly reduced with Alpine Aero ejectors fitted).There are next to no composite materials used in the construction of the AW139 from the codkpit doors back. Forward of the cockpit doors it is Kevlar, behind the cockpit doors is nearly all Aluminium.
Hope that clarifies things for you.
Shell Management.
How can this happen? Shell having to ground a type which fully meets your hard won Shell FAR/JAR criteria? Just what sort of advice are your Aviation Advisers giving to your management? I think you should be auditing AW's manufacturing to tell them what they are doing wrong.
How can this happen? Shell having to ground a type which fully meets your hard won Shell FAR/JAR criteria? Just what sort of advice are your Aviation Advisers giving to your management? I think you should be auditing AW's manufacturing to tell them what they are doing wrong.
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failure issues
Industry Insider
You and others have criticised Shell Management for his comments, which relate predominantly to operational management issues where I have no expertise so I will not directly join in the criticism of SM.
However, failures may also be driven by issues other than operational matters, such as structural deficiencies.
I have been trying to do this for ages with no response from AW or EASA. The frustrating issue here is that with correct design and certification procedures, properly validated processes and produced with appropriate control of humidity and contamination can actually produce adhesive bonds which will NEVER fail under any load case. Hence, to address SM's operational concerns it is possible to design and produce bonds which will not be the locus of failure even where operational airworthiness is violated. No matter what the pilot does, the structure should always fail elsewhere in the structure AWAY from the bond.
Now this is a radical concept, because if you can be sure that the bond will NEVER fail in certification testing or in service, then certification test costs will be reduced substantially. Also the cost of ownership will be reduced because in-service NDI will not be looking for interfacial disbonds (where it's value is limited anyway) it will be limited to secondary damage assessment such as in-service impact damage. That will significantly reduce the cost of ownership for the operator.
This is not an academic position based on theoretical bovine excrement. Applying these principles in a practical repair environment we have reduced bond failures for repairs performed in a large field repair facility from 43% in 1992 to virtually zero since then. The same principles applied to production will produce similar levels of difference in performance for bonded structures at original production.
The reason this does not happen now is that there is no regulatory requirement to demonstrate long-term bond durability during certification, and current damage tolerance analysis metodologies do not manage critical bond failure modes.
With respect to the current case, there may be two issues:
1. Micro-voiding due to moisture absorption by the adhesive during the production process. This reduces the bond strength significantly in joint peel, honeycomb peel and shear. It is NOT detectable by NDI. It is NOT managed by damage tolerance analysis (as currently used by AW). It results in disbonds. Nooby says
Micro-voiding is exacerbated by exposure of Nomex to the same humid environment. This is the problem with the tail boom disbonds and it may be the same problem for the tail rotors.
2. Again referring to Nooby's comment, the second issue is the durability of bonds to aluminium/aluminum. These are highly susceptible to environmental degradation usually by hydration of the oxide layer to which the adhesive is bonded. Hydration leads to disbonding at the interface between the adhesive and the metal. The worry is that short term strength and fatigue tests, NDI and damage tolerance analysis as specified by FAA and EASA will not prevent these failures.
These issues are addressed in a recent paper. http://www.adhesionassociates.com/pa...d%20Joints.doc
I have also provided advice on management of micro-voiding previously on this or other AW 139 threads.
Now to short-circuit those who believe I have an anti-AW position, I assure you that I have also raised the same issues with another significant helicopter manufacturer and they dealt with me directly and resolved a number of issues at an effective charge out rate far less than a junior helicopter pilot's pay rate. My interest is in flight safety, not bashing particular manufacturers.
regards
Blakmax
You and others have criticised Shell Management for his comments, which relate predominantly to operational management issues where I have no expertise so I will not directly join in the criticism of SM.
However, failures may also be driven by issues other than operational matters, such as structural deficiencies.
I think you should be auditing AW's manufacturing to tell them what they are doing wrong.
Now this is a radical concept, because if you can be sure that the bond will NEVER fail in certification testing or in service, then certification test costs will be reduced substantially. Also the cost of ownership will be reduced because in-service NDI will not be looking for interfacial disbonds (where it's value is limited anyway) it will be limited to secondary damage assessment such as in-service impact damage. That will significantly reduce the cost of ownership for the operator.
This is not an academic position based on theoretical bovine excrement. Applying these principles in a practical repair environment we have reduced bond failures for repairs performed in a large field repair facility from 43% in 1992 to virtually zero since then. The same principles applied to production will produce similar levels of difference in performance for bonded structures at original production.
The reason this does not happen now is that there is no regulatory requirement to demonstrate long-term bond durability during certification, and current damage tolerance analysis metodologies do not manage critical bond failure modes.
With respect to the current case, there may be two issues:
1. Micro-voiding due to moisture absorption by the adhesive during the production process. This reduces the bond strength significantly in joint peel, honeycomb peel and shear. It is NOT detectable by NDI. It is NOT managed by damage tolerance analysis (as currently used by AW). It results in disbonds. Nooby says
The tailboom is Aluminium skins (Aluminum for you Nth American types 
) bonded to an Aluminium or Nomex paper core.
) bonded to an Aluminium or Nomex paper core.
2. Again referring to Nooby's comment, the second issue is the durability of bonds to aluminium/aluminum. These are highly susceptible to environmental degradation usually by hydration of the oxide layer to which the adhesive is bonded. Hydration leads to disbonding at the interface between the adhesive and the metal. The worry is that short term strength and fatigue tests, NDI and damage tolerance analysis as specified by FAA and EASA will not prevent these failures.
These issues are addressed in a recent paper. http://www.adhesionassociates.com/pa...d%20Joints.doc
I have also provided advice on management of micro-voiding previously on this or other AW 139 threads.
Now to short-circuit those who believe I have an anti-AW position, I assure you that I have also raised the same issues with another significant helicopter manufacturer and they dealt with me directly and resolved a number of issues at an effective charge out rate far less than a junior helicopter pilot's pay rate. My interest is in flight safety, not bashing particular manufacturers.
regards
Blakmax
Blackmax
If you were to audit AW manufacturing, I am sure the outcome would be most enlightening.
Alas my comments to SM were intended as a little tongue in cheek at his "expert" assertions on behalf of Shell whom he does not represent.
My point is that FAR/JAR 29 latest amendment is a worthy paper certification goal but there are other aircraft types (S-76) which while they may not fully comply, have a demonstrated safety record based on 6m flight hours.
I believe that these aircraft should not be ruled out of contracting for OGP companies based purely on a tick in a few boxes when the product certified to the latest paper standards is maybe not demonstrably safer, yet.
If you were to audit AW manufacturing, I am sure the outcome would be most enlightening.
Alas my comments to SM were intended as a little tongue in cheek at his "expert" assertions on behalf of Shell whom he does not represent.
My point is that FAR/JAR 29 latest amendment is a worthy paper certification goal but there are other aircraft types (S-76) which while they may not fully comply, have a demonstrated safety record based on 6m flight hours.
I believe that these aircraft should not be ruled out of contracting for OGP companies based purely on a tick in a few boxes when the product certified to the latest paper standards is maybe not demonstrably safer, yet.
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Mr. Shell Management
Originally Posted by Shell Management
I think you will find SAI pay very close attenion to AW and other OEMs, hence Shell took action before the OEM or the regulator.
I'm sure once the real experts have got to the bottom of the issue they'll let you know and hopefully they'll have them flying again in time to spare your blushes.
Fixed your leaky pipe yet?
Don't forget also that the list here is of hull losses.
There must be a proportionate amount of incidents that are NOT in the public domain.
There must be a proportionate amount of incidents that are NOT in the public domain.
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EMERGENCY AD - TAIL ROTOR
Emergency AD for AW139 Tail Rotor Blades, sounds scary. 
Emergency AD Issued for AW139 Tail Rotor Blades | Vertical - Helicopter News
Emergency AD Issued for AW139 Tail Rotor Blades | Vertical - Helicopter News
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The irish air corps have grounded their machines too.
Air Corps suspends some helicopter operations - RT News
Air Corps suspends some helicopter operations - RT News
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Shell Management - disappearing act
What ever happened to all those comments from Shell Management? Has he been moderated? I wonder if the real Shell Management would agree with many of his comments in other areas of Rotorheads?
Sorry for the thread creep, but couldn'r resist it!
Sorry for the thread creep, but couldn'r resist it!
My point is that FAR/JAR 29 latest amendment is a worthy paper certification goal but there are other aircraft types (S-76) which while they may not fully comply, have a demonstrated safety record based on 6m flight hours.
I believe that these aircraft should not be ruled out of contracting for OGP companies based purely on a tick in a few boxes when the product certified to the latest paper standards is maybe not demonstrably safer, yet.
I believe that these aircraft should not be ruled out of contracting for OGP companies based purely on a tick in a few boxes when the product certified to the latest paper standards is maybe not demonstrably safer, yet.
If you want to kick an aircraft off contract because it does not have the range or the payload, that's justified, but not allowing a 76 or 412 on a contract because it is not certified to the latest standard is absolute BS
We have all seen how these latest standard certified aircraft have tragically demonstrated they are not exempt from catastrophic failures. 6M flight hours (76) or in the case of the 212/412, 12M flight hours does mean somthing.
Right to the point ...
same approach can be extended to Mi8 types....
particularly last modernizations like Mi17 V5 or Mi171...
Total millions of flight hours means nothing if you ask your local CAA
On the other hand we see how FAR 29 can be used like chewing gummy
on example of S92 MGB issue...
We are over-regulated on one side, safety not yet accepted like culture rather like just popular SMS shortcut.
Only better relations/cooperation between regulators-industry-operators and vice versa, can lead us to some real life safety improvements.
In particular 139 cases, black clouds were visible more than year ago.... "Ostrich
engineering" was the only visible answer so far...
... same approach can be extended to Mi8 types....
particularly last modernizations like Mi17 V5 or Mi171...
Total millions of flight hours means nothing if you ask your local CAA
On the other hand we see how FAR 29 can be used like chewing gummy
on example of S92 MGB issue...
We are over-regulated on one side, safety not yet accepted like culture rather like just popular SMS shortcut.
Only better relations/cooperation between regulators-industry-operators and vice versa, can lead us to some real life safety improvements.
In particular 139 cases, black clouds were visible more than year ago.... "Ostrich
engineering" was the only visible answer so far...
Last edited by 9Aplus; 30th Aug 2011 at 09:08.