Fuselage rib 6 with strengthened connection

A LAME has note fretting of the rivets connecting RF-PLT-007 to RF-BKT-004 in one of a fleet of Sling 2s that have been in service a number of years, used in basic training. He attributed this to side loads. I have decided to strengthen this connection without changing the pattern of stresses within this structure, as follows

A ) Remaking RF-PLT-007-C-A-1 out of 1.03mm material (to match the thickness of RF-BKT-004-C-A-1) instead of the original 0.63mm. I will also increase the dimensions of this plate in the up-down direction to create 3x hole-centre to edge distance. I will leave the across dimension unchanged so that the part will continue to fit the slot in RF-RIB-601-C-A-

B ) A new folded doubler plate of 1mm material which sits on the forward-facing surface of RF-BKT-003-C-A-, connecting both rows of 4mm holes. This will augment the thin material (0.51mm) used in RF-BKT-003-C-A- in its connection to RF-RIB-601-C-A-, thus completing the beefing up of the load bearing role of the plate RF-PLT-007 

C ) Upsizing the 4mm holes in the revised RF-PLT-007-C-A- to 4.8mm which connect to RF-BKT-004-C-A-. 

Overall, the force concentration on the rivets connecting BKT-003 and BKT-004 will be reduced owing to the greater thickness of the new plate PLT-007 and the greater diameter of the rivets. Further, the introduction of the new folded plate ensures a continuous path of 1mm thick aluminium (at least) all the way from BKT-004 to RIB-601.