I noted that Graham gave the load limit on the rudder cable as 1080 lb. In
the US all cable sizes quoted for aircraft use are in inches; the 3/32" cable
is rated at 920 lb in the FAA's AC43.13-1A which is the only reference I have
seen on acceptable aircraft construction practices. Is this difference in
strength due to mm cable vs inch cable?
AC43.13-1A gives the specification on 18-2-G Nicopress sleeves as a change in
length from 7/16 to 1/2 inch rather than the diameter after compression with
a tested strength of 1180 lbs (greater than the cable!). Since the 3mm cable
is slightly larger than 3/32", what should the length of the sleeve be after
compression with the cable supplied? I have measured it at .530 to .540 but
the sleeves measure about .010 long prior to compression. Seems like this
info should be included in the manual for us first time builders.
And, the same reference specifies that zinc plated sleeves are required with
stainless cable while copper sleeves should be used with carbon steel cables.
Is this important?
Also, one of my project advisors has suggested using two Nicopress sleeves
instead of one on all cable ends in the rudder system, based on failures
reported in amateur built aircraft. His position is that it is cheap
insurance from both a cost and weight standpoint. Comments?
In another area, the DAR who will do the final inspection on completion
visited recently for an informal in-process inspection. He was generally
impressed with the quality of the kit but suggested two changes for safety
reasons. First, he said that any bolt subject to rotation in use should not
use self-locking nuts -- he noted that the bolt connecting TS05 to the trim
bellcrank was subject to rotation and should be pinned. Second, he said that
the roll pins which secure the LG08's should have two turns of safety wire
through them.
Finally, in the US rod ends need an inspection hole drilled to allow
verification of sufficient thread engagement by poking a wire into this hole.
The rod ends supplied did not have inspection holes so drilling was needed.
Is this required in the UK also?
I knew that building an airplane would be a learning experience, but the
depth of my ignorance has exceeded all expectations. Every day brings many
more questions than answers. It is truly humbling.
Regards, John A044 Newtown, CT
|