Manufacturing And Assembly Buildings
Everything about an aircraft manufacturing and assembly building must be driven by the manufacturing process, including process flow, process rate, and process requirements. The building must fully support the process, in addition to “keeping the weather out.” The manufacturing process must be well understood at a macro level by the facility planning and engineering team to ensure that an appropriate building concept is developed that is integrated with manufacturing needs.
In addition, individual manufacturing areas within the building must be understood on a finite level to ensure that the facility and infrastructure supports manufacturing efficiently. Following are key considerations related to an assembly building that must be evaluated during planning to establish an appropriate building overall design:
• Manufacturing process type and style — The manufacturing process type and style may include flow line, fixed position assembly, parallel assembly, subassembly shops, and fishbone assembly, all of which will determine the building’s size and layout. Different manufacturing process flows will likely be used for different components or steps within the overall process.
• Assembly rate and work-in-process — The assembly rate and work-in-process determine the total building size. The building’s designers and engineers will need to know how many aircraft will be built — in a week, a month, or a year (the rate). Also, how many units will be in production at one time and in how many assembly positions.
• Methods of assembling components — Methods of assembling components may include bonding, riveting, fasteners, or even welding. These methods determine the necessary support utilities and potential hazards to assembly workers, defining which safety features will need to be incorporated into the building design.
• Sizes of components — Sizes of major components including wings, vertical stabilizers, engines, main body, and wing joint components are critical. These determine the overall size of the facility necessary to accommodate the various components, as well as the types of doors, their speed, and staging space requirements.
The manufacturing process must be well understood at a macro level by the facility planning and engineering team to ensure that an appropriate building concept is developed that is integrated with manufacturing needs. • Manufacturing tooling, fixtures, and jigs — Manufacturing tooling, fixtures, and jigs are directly related to the manufacturing process, space requirements, and utilities. Determining how components move into the tooling or whether the tooling moves to meet components are critical issues. If tooling is “parked” out of the way during certain processes or if there are aircraft moves, this means that additional space is required.
• Materials conveyance — Materials conveyance includes getting the components into the building and moving them around inside. Components may arrive via aircraft, ship, train, or truck. Specialized fixtures are often used to transfer components into the assembly building. Once inside, material conveyance may involve true vertical lift cranes, under-hung cranes, transfer bridge cranes, multiple hoist cranes, fixed jib crane assembly stations, wire guided vehicles, air bearing jigs on floors, carts, tugs, forklifts, and man lifts. The selected systems impact the overall building height, structural support requirements, floor quality, floor flatness, floor joint types, and floor finishes.
• Aircraft materials — Since aluminum has a high coefficient of expansion, stable temperatures are critical for accurate assembly and tolerances. Space may need to be provided to acclimatize components or parts received from outside or other buildings prior to assembly. In addition, exposure to direct sunlight is usually prohibited due to thermal issues. Composite components may also require critical humidity and ventilation control. Composite materials, when machined, can create hazardous dust and fibers. Composites, when bonded, often need solvents for cleaning and adhesives that can have strong odors or generate hazardous fumes. Raw composite materials are often stored in freezers to extend their expiration date. Corrosion control coatings on metals, such as alodine and chromium, are often considered hazardous, but may be necessary to apply or for touch up at assemblies, joints, or fasteners.
• Manufacturing utilities — Most aircraft manufacturing has a high reliance on clean, dry compressed air as a primary utility. Therefore, providing redundancy, reliability, maintainability, and distribution and access flexibility for compressed air is critical. 400Hz aircraft power is often a critical test requirement. It needs to be close to the aircraft due to voltage loss. Also, exhaust air for fumes or heat processes is often necessary.
Additional utility considerations are as follows:
- Critical lighting levels and color are needed for some processes and inspections.
- Vacuum is necessary for composite materials assembly and bonding. Housekeeping vacuums for chip collection and cleanup are often required.
- Fuel test agents are often piped to critical testing locations during component or assembly testing. Keep in mind, fuel test agents are combustible oils with special requirements, as well. Code officials and insurance underwriters need to understand the fire-related issues with these materials.
- Hydraulic systems provide aircraft power to function flaps, wings, doors, and landing gear. Hydraulic systems need to be filled, drained, and may operate at high pressures.
Care must be taken for personnel safety, avoiding leaks or spills and to ensure over-pressurization or damage does not occur to the aircraft.
- High-volume, low-pressure compressed air is used for pneumatic testing, such as fuselage pressure testing.
- Aircraft grounding is important. Static electricity can damage sensitive electronic components.
- In an automated assembly factory, data communication is often necessary everywhere on the shop floor, including at the aircraft and all jigs and fixtures. High speed and wireless networks enable critical data to be available or sent directly from the shop floor.
• Foreign object debris (FOD) — No building materials, condensation, water, manufacturing waste, fasteners, or other objects can fall on or into the aircraft during assembly. All potential sources of FOD must be well thought out and mitigated. Broken light bulbs, fireproofing fibers, paint chips, and other building-related foreign debris need to be prevented from entering the manufacturing process.
• Exiting — Aircraft manufacturing facilities are often large buildings. Exit distances can often exceed code requirements. Exit egress from jigs or tooling platforms and around aircraft and materials must be well thought out. When exit distances become a problem, exit tunnels under the manufacturing floor can be used to create an exit path or an area of refuge. Emergency lighting is also a challenge in these large facilities. Designated marked exit paths are usually used.
• Noise — Some riveting systems are extremely loud and are a personnel safety issue. These manufacturing processes are often enclosed and isolated to prevent exposure to personnel and to limit hearing protection requirements within the overall assembly space. Often, components requiring these types of riveting are preassembled in controlled facilities outside the assembly building. Sometimes, these types of noisy or hazardous operations can be scheduled during off hours.
• Fire protection — Typically, an aircraft assembly facility houses only unfueled aircraft. This limits the fire protection requirements, and wet sprinkler systems can be used. Early Suppression Fast Response (ESFR) sprinklers are often used. High Expansion Foam (HEF) is also an option. Aqueous Film-Forming Foam (AFFF) is now rarely used in assembly facilities, due to the potential environmental issues and requirements relating to disposal. It is important to note that the facility is a manufacturing facility — per code, it is not an aircraft hangar. The aircraft is not able to fly and is, therefore, not yet an airplane. This is a critical code and hazard distinction in selecting the appropriate fire protection and addressing other code requirements.
Additional special attention must be understood and given to the unique requirements of final finish buildings. These types of facilities include paint and paint preparation, as well as final assembly, delivery center, and test facilities. Read about these considerations, including manufacturing process, environmental conditions, stripping, fire protection, and more, at theaustin.com/market-insights.