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<< Lancair Builders' Mail List >>
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Marv -
I know this subject has been beaten pretty hard, but please allow me to
say a final few words...
First, both the main gear and its backup structure receive a lot of shock
with the rubber "doughnut" installation (I won't even call them shock
absorbers). Installing either of the new style shock absorbers is certain to
alleviate the shock transmitted throughout the gear system, including the
secondary attach point. Therefore, I consider this part of the fix.
Second, installing the new full-width attach block that I recommend requires
extra work, i.e. you have to use a hammer and chisel to break out the
existing attach block that was installed as part of the fastbuild work. I
had an early fastbuild kit (April 1989) with some poor fastbuild
workmanship. The later fastbuild workmanship was dramatically improved. The
secondary attach block in newer kits is,therefore, more likely to last
longer, maybe forever. A word of caution before one decides to break out the
existing block is that good fiberglass skills are required in the fitting
and installation of a completely new block, especially in such a difficult
to access area. For those who don't have confidence in their fiberglass
skill, it may be preferable to simply do as the SB requires and simply add
the brace.
Bill Rumburg
N403WR (Sonic bOOm)
[While I (and undoubtedly others) can see the logic and benefit to your
'alternative' to the SB, I think it needs mentioning here that this is
a builder-suggested modification which doesn't carry the factory's
blessing at this point. I am pretty sure that if a builder who holds the
repairman's certificate for the aircraft which he is servicing decides
to install yours (or another) modified version of the attachment point
referenced in this SB he can probably do so as he is signing off his own
work and takes full responsibility for it. I don't know what effect this
might have on one's insurance should that part fail and it was discovered
that the SB hadn't been performed as specified. Additionally, anyone
who needs to have the SB applied to their aircraft for them and for it to
then be signed off by an A&P will probably have to do it the factory way
without question, as the only documentation for the modification that
currently exists in this regard is, in fact, the factory's SB. Considering
the amount of discussion this subject has received over the past week or
so, I didn't want there to be any confusion about the direction it was
initially headed.
Additionally, the stresses which seem to be causing the problem to this
secondary attachment structure appear to be related to gear side loads
and not the rubber donuts as you suggest. Severe side loads may be
imposed regardless of what type of shock absorbing mechanism is incorporated
into the gear leg, and are caused more by the gear leg's geometry than
any of its individual components.
Just my humble $0.02. <Marv> ]
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LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
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