Producibility Elements Highlighted:
Understand Current Process Capabilities (Company and supplier)
Implement a Risk Management Program
The Lockheed Martin Tactical Aircraft Systems (LMTAS) composite part design team for the F-22 aircraft planned to use new part materials, configurations, and tooling materials. However, LMTAS had no experience or historical database to determine if the capability existed to successfully fabricate these concepts within program cost and schedule constraints. This situation highlighted the need for development of composite manufacturing processes before entering the F-22 Engineering and Manufacturing Development phase of the program.
The team determined that a producibility test program was required to address these issues. For the test program to succeed, it had to provide proven materials for parts and tools; a proven engineering and tool design philosophy; part designs that would be producible with the baseline materials, processes, and tooling families; and proven manufacturing capabilities established for benchmarking. Consequently, a multi-disciplined Risk Reduction Team was created and the following test guidelines established:
- Design components were to meet actual airframe requirements.
- Production readiness and producibility on key part family candidates were to be demonstrated on key part family candidates. Key parts were to be established as program "pilot" proof articles.
- Baseline manufacturing processes, composite materials, tooling family, and quality methods were to be demonstrated and validated.
- The team's efforts were to be coordinated with the engineering Structural Development Test plan and Effects of Defects plan.
- Issues of engineering, manufacturing, and quality risk were to be resolved to support the Engineering and Manufacturing Development schedule.
- Accept/reject criteria for Quality Assurance/Inspection were to be determined.
- Drawing specifications, check procedures, and incremental release procedures for engineering and manufacturing data to support concurrent design concepts were to be established.
- Process Specifications, Material Specifications, Variability Reduction Procedures, and Quality Assurance processes were to be proof-loaded.
- Standardized Work Instructions and visual aids by part family were to be established.
- Risk reduction tools were to be fabricated using contracted F-22 tooling vendors.
- Components were to be fabricated and inspected with production equipment and procedures.
- Lessons learned were to be documented.
- Production capacity and facilities were to be verified.
The Risk Reduction Team reviewed the preliminary structural layouts and decided that composite parts could be segregated into five primary families of components: highly contoured inlet duct skins; fuel floors/shear webs; medium contoured outer mold line skins; thermoplastic weapons bay doors skins (outer mold line); and thermoset weapons bay inner mold line door skin (honeycomb panel inner skin).
From these families, three representative composite parts were selected and fabricated: an inlet duct skin, a fuel floor, and an outer mold line skin. These articles were judged to be among the most difficult of their part families. The Risk Reduction Program used the production drawings, planning, material requirements planning, tooling, and inspection systems planned for the F-22.
Statistical process control data was collected and used as a baseline for the division process capabilities for these types of parts. These capabilities were used to establish the tolerance guidelines in the production drawings. This activity resulted in a yield rate of 98% on composite part production during the Engineering and Manufacturing Development phase of the F-22 program. This yield rate, one of the highest in the aerospace industry, is usually not achieved until much later in a program.