The Evolution of Composite Patch Repair Technology at CTAS in Meeting the Challenges of the C141-B Drop-In-Repair Program for WRALC

This paper describes the unique experience gained by Chrysler Technologies Airborne Systems, Inc. (CTAS) in the development of composite patch repair techniques through an internally funded research and development program (IRAD) prior to the award of the C141-B Drop-In-Repair (DIR) Contract and subsequently in supporting the various activities of fulfilling the contractual requirements after the contract award, for Warner-Robins Air Logistics Center (WRALC) during August 1993 through October 1994. The mobility of the U.S. Air Force was threatened when more than 65% of the C141-B aircraft fleet faced grounding due to the discovery of cracking riser weep holes in the lower in-board wing structure, severely restricting the service life of the aircraft from reaching 45000 SLA-II equivalent flight hours. WRALC had decided to repair most of the weep holes (limited to a maximum of fifteen holes per wing), using Boron/epoxy composite patch doublers, as a near-term remedial measure, in lieu of full wing plank replacement. This option of using Boron/epoxy patches to repair cracked weep holes was attractive to WRALC due to reduced downtime anticipated for the repairs. This paper elaborates the details of CTAS's IRAD work in collaboration with Texas A&M University, in the use of Boron and Graphite/epoxy patch repairs, including the patch design, surface preparation technique, and analytical and experimental data, obtained prior to the award of the C141-B DIR contract. Although the overall C141-B DIR Program involved other repair and maintenance work, CTAS was able to respond to the challenges of the program on short notice, due to the groundwork laid with the composite patch repair technology through the IRAD Program. Also, this paper describes the quality assessment of the manufactured and the installed Boron/epoxy patches through the non-destructive inspection (NDI) data acquired for the patches before and after installation on the aircraft.