Elevator inspection port skin doubler

The 4mm rivnuts are typically spec'd with a minimum grip range of 0.5mm. Since the elevator skin is 0.4mm thick, the strength (against torque) of the grip will be marginal at best. It was decided to manufacture a doubler from 1.02mm 6061-T6. This will increase the rivnut grip to 1.4mm which is about midway in the specified grip range of 0.5mm - 2.5mm.

These plates will also be made for the six inspection ports in the wings.