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9-1-10 Blanik News


Report of Gregg Heer and George Wacker
:

 Greg Heer, IA, who has worked on improving N125DW for many years, got a return call from Greg Davison of the FAA.  This is a summary of the points made during that discussion:

 Blanik L-13s are grounded until the factory adequately addresses the wing spar fatigue crack issues.  This could be accomplished by an inspection and/or modification program. 

 During the conversation, Mr. Davison, discussed the issues that concern him (no significance to the order of listing):

  • EASA AD 2010-160-E says "EASA now concludes that the inspection method (of Mandatory Bulletin No. L13/109a) might not be sufficient for detecting the crack which means that the unsafe condition might still be present even if the sailplane has passed the inspection required by EASA AD 2010-0122-E." Apparently cracks were discovered during the subsequent investigation of the failed spar that cannot be detected by the inspection detailed by the MB and previous AD.
  • The most likely place for cracks to begin (the outer surface of the spar cap) cannot be seen without removing the outer skin.
  • The design of a steel tapered spar cap sandwiched between two aluminum members and fastened by rivets.
  • The skin is fastened to the spar cap by drilling into the rivet heads holding the spar cap together and then rivets installed to hold the skin to the spar cap rivet heads which potentially further compromises the rivets holding the spar cap sandwich together.
  • Knowledge, or lack thereof, of the corrosion and fatigue characteristics of the materials involved.

Mr. Davison said that the reason a US DER may have trouble proposing a satisfactory solution is that the material details and characteristics are not known within the US. He also said two other things which will likely happen:

  • The FAA will likely issue a document which is intended to clarify some of the confusion.
  • A delegation of folks from the US may go to Europe to discuss these issues and what to do about them.  Participants and date of visit unknown.  

I'm willing to help in any way that I can but don't know what would be helpful at this moment.  It does appear that the FAA is waiting for the factory and EASA to come up with something.  Due to the concerns and unknowns listed above, the FAA will likely be looking to the factory and EASA to approve any proposals received in the US.

 Pass this along to anyone as I am interested if anyone else has received any information that would shed new light or open up a new avenue allowing us to resume flying more quickly.

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Members wishing to participate in a group discussion of the topic may send their email contact information to  feedback@ssa.org, subject line Blanik Wing Spar AD.  Please include a description of your role: owner, A&P or A.I., DER, or structures engineer or metallurgist.  SSA will create a group email listing from these respondents to facilitate communications.

Posted: 9/1/2010


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