Technical report | Retrogression and Re-Ageing In-Service Demonstrator Reliability Trials: Stage III Component Test Report

Abstract

Retrogression and Re-ageing (RRA) technology is a two stage heat treatment of 7075-T6 aluminium alloy used to improve corrosion resistance while retaining MIL-HDBK-5J structural properties. This report assesses the compliance of the reliability trials, conducted at Boeing Australia Component Repairs (BACR) in August 2010, with the requirements of the compliance matrix in the Stage III Design Development Plan and, by extension, the Stage III Process Specification for RRA. All properties described by items in the compliance matrix received recommended ratings of either 'Compliant' or 'Non-Compliant (Acceptable)'. Of the 15 items in the compliance matrix only four were rated 'Non-Compliant (Acceptable)'. The trials demonstrated that the RRA process as defined in the Stage III Process Specification can be reliabily applied to an aircraft component in an industrial environment with a reliability exceeding 95%.

Execuitve Summary

Retrogression and Re-ageing (RRA) technology is a two stage heat treatment of 7075-T6 aluminium alloy used to improve corrosion resistance while retaining MIL-HDBK-5J structural properties.

The certification and acceptance of the RRA technology for application to Australian Defence Force (ADF) aircraft has been undertaken in sequential stages. The first stage was the qualification of the RRA technology under laboratory conditions. The second stage consisted primarily of an industrial trial of the technology on a real aircraft component. The third and final stage deals with the practical issues of transitioning RRA onto ADF aircraft.

Three industrial trials intended to test the reliability of the RRA heat treatment were on a C-130 Hercules component at Boeing Australia Component Repairs (BACR) on August 2010. This report assesses the compliance of these industrial trials with the requirements of the compliance matrix in the Stage III Design Development Plan and, by extension, the Stage III Process Specification for RRA. The Stage III Process Specification proved to be sufficient to conduct an industrial heat treatment satisfying the great majority of the compliance items from the compliance matrices. Of the 15 items in these matrices 11 were given recommended ratings of 'Compliant' while the remaining four received recommended ratings of 'Non-Compliant (Acceptable)'. The trials demonstrated that the RRA process as defined in the Stage III Process Specification had a reliability in excess of 95%.

This report concludes with a set of recommendations for updating the Process Specification. These will be incorporated into a fourth revision of the Process Specification.