Manufacturing and Handling Techniques Used in the Assembly of Polished Commercial Aircraft 890925
The use of polished aluminum fuselage skins has been a standard on U.S. commercial jet transport aircraft for decades. Increasingly stringent environmental regulations for paint stripping combined with fuel and maintenance savings allows consideration of flying polished non-painted aircraft.
Boeing, McDonnell Douglas and Embraer currently manufacture commercial aircraft with polished alclad aluminum fuselages. Commercial airlines such as American Airlines, USAir, Eastern, Northwest and ASA fly non-painted fleets. These customers require the aircraft to be delivered with a polished appearance incorporating minimum fleet graphics.
The manufacturing of polished aircraft requires unique production and handling procedures to fabricate all exterior panels with identical color match and reflectivity. This paper compliments previous papers on the economic advantages of non-painted planes and transition procedures from painted to non-painted aircraft. (1)* The various procedures used to produce and protect the valuable skin material from the plant to delivery of the fully assembled aircraft will be fully explored.
THE COMPLEXITY OF PRODUCING an entire fuselage with aesthetically pleasing and uniform appearance is enormous. Airframe fabrication ranges from severly stretch-formed to substantially chem-milled parts, requiring special mill fabrication. Tailor made practices for the exterior aluminum skins allow for consistent manufacturing results while maintaining an extremely constant finish for the fuselage.
As an example, Northrop Corporation has produced the fuselage of the 747 since inception of the program. The improvements in handling and manufacturing of the aluminum skins have advanced through the years. Even the 747, with its massive fuselage resembles a mirror-like surface with color-matched and defect-free panels.
The integrity of the aluminum can only be sustained by careful manufacturing techniques. Implementation of these standards often raise the entire consciousness of quality needs for other components of the aircraft. The attention given to equipment, parts handling, techniques and awareness has helped reduce reject and rework levels while raising the quality of all parts produced.
The result to the fleet purchaser is an aircraft with unmatched quality. The overall economic savings by flying unpainted aircraft are ever increasing. The cost of jet fuel savings alone for a 747 is nearly $200,000/year with fuel at $.50/gallon (see Figure 1). Additional savings of faster maintenance schedules, elimination of strip/repaint cycles and ease of inspection also support the operation of a polished non-painted fleet. Specifically, painted surfaces tend to develop filiform corrosion. During Eastern Airlines conversion to unpainted aircraft, filiform corrosion was noticed on aircraft as new as three years old. Since conversion to unpainted aircraft, Eastern's rate of filiform corrosion has been reduced to near zero. (2)
The recent air worthiness directive's (AD) by the FAA, requiring stripping and eddy current testing of rivets for early model 737's, points out clearly the potential for increased inspection of the world's rapidly aging fleet.
The cost to strip the 100 737's involved in the inspection is nearly 60 million dollars. (3) The ability to eddy current test and inspect the affected areas is greatly facilatized by starting with a surface that does not require the initial stripping.