A Contract Repair Station Inspector was informed that he overlooked the correct thickness of a repair doubler installed at the skinlap seam between fuselage frames 13/14 on the left side of a customer A319 aircraft. Inspector noted that fatigue from a long humid night and stress from being the only Inspector to cover an aircraft undergoing a Heavy C-check were contributors.

Narrative

I am a Quality Control Inspector for an aircraft Contract Repair Station. An A319 aircraft from Air Carrier X was having a structural repair to a skinlap seam between frames 13 and 14 left side. When called to review the repair parts and the repair layout and fit; I reviewed the non-routine [paperwork] for the mechanic's entries. Mechanic stated [that] fabricated doubler from material 2024T3 [was] .080 [thousandths of an inch thick] and filler from material 2024T3 [was] .071 [thousandths of an inch]; which I checked against company material issue tags and part numbers (P/N). During inspection of repair rivet layout pattern and damage cutout; I discovered that the [fuselage skin] cutout [minimum] radius was incorrect according to Structural Repair Manual (SRM) 53-11-11; figure 218.After notifying the sheet metal crew what needed to be done; they took the majority of the night correcting it. After three inspections before the end of the shift; the [fuselage skin cutout] repair radius was finally corrected. I reviewed the cutout radius; instructed Mechanic to Cleco [(hold together)] all repair parts in place for fit and pattern line up. I was satisfied and gave the Mechanic the 'OK' to treat and [paint with] fluid resistant primer; then install repair [doubler]. Now; it has been brought to my attention that I overlooked the correct thickness of the repair doubler material; which should have been 0.090 [thousandths of an inch] instead of 0.080 [thousandths] thickness.This has taught me a valuable lesson; to never let my guard down to make sure that all pages of task from [maintenance] manuals are present; and; if I feel the need of additional eyes to triple check behind myself to ensure that all work was done according to the manuals; to ensure the safety of the flying public. Air Carrier X returned their A319 aircraft to our Repair Station in ZZZ for rework of the repair. I believe that the human factors that contributed to this event were fatigue from a long humid night and stress from being only one Inspector to cover an aircraft undergoing a Heavy C-check when the work load is intense.