Development of the "component breakdown" method of assembly to its currently high and steadily increasing efficiency is said to be the aviation industry's major contribution to U.S. Manufacturing techniques. It is to that growing pool of industrial knowledge that the Vega Aircraft Corp contributes this brief description of the methods it has evolved for assembly of Flying Fortress bombers, from pre-assembled, structural, and skin-panel component breakdowns.
When the government asked Vega and Douglas to join with Boeing in the manufacture of Fortresses, design, materials, standards, and quantities were fixed, but methods were left to the individual concerns. The system developed at Vega might be described as a blend of the manufacturing philosophies of both Boeing and Douglas with numerous additions that are strictly our own.
Methods for manufacturing the B-17 had, of course, been developed by Boeing, its designer, and many months of valuable time were saved when this information was immediately made available to us. But some of those methods differed from practices already well established in the Vega and Douglas plants. These companies, therefore, began at once to evolve systems better suited to their respective plant buildings, equipment, and personnel experience.
The result is identical bombers assembled by three widely differing methods.
The Vega method, for example, has an inner wing installation line similar to that of Douglas and a final assembly line comparable to that of Boeing. But those words "similar" and "comparable" should not be interpreted to mean "identical", because there are numerous instances wherein these systems differ considerably.
Where Douglas and Vega both use an overhead carrier for the inner wing sections after they leave the mating or master jig, the jigs themselves are quite different; neither is the same as that used by Boeing. Where Boeing uses several short, 4-station final assembly lines, Vega uses two 3-station lines which are even shorter. Of these, neither is like those used by Douglas.
If each of these manufacturing philosophies Boeing, Douglas and Vega could be accurately labeled with a single word, the words would be "stationary", "progressing", and "breakdown," respectively. The Boeing system, which is termed "multiline", is based on jig assembly of large sections which are then completely equipped with installations before being joined to other sections. And the Douglas method starts sections in jigs but, after being tied together, they are attached to carriers for a steadily progressing trip through numerous stations of long assembly and installation lines.
Our Vega method is described as "a pre-assembled, skinned section breakdown system." It is used in manufacture of both Flying Fortress and Ventura bombers. By this method we assemble skinned panels of the exterior sections and interior structures as components, which are then equipped with as many installations as possible before being joined to other components.
In describing the method it is advisable to point out that all three companies make parts for each other, all three follow identical methods in many instances, and all three rely upon subcontractors for a large number of items. No attempt will be made here to identify sources or to describe methods that are used by all three companies. Rather, this article will briefly cover only those methods and systems created or adapted by Vega.
The pre-assembled component breakdown system of assembling airplanes has long been our manufacturing philosophy, but participation in the "BDV" Flying Fortress program has undoubtedly extended it considerably. Plant space has been at such a premium that it has been absolutely imperative that we make use of every foot of it to the fullest. This has been done by creation of large balcony areas, and these in turn have facilitated establishment of small lines for pre-assembly of components and skin panels.
Roughly, the system assembles components and panels on balconies and lowers them to the main floor for joining on the final assembly lines. Carried to the extreme found necessary here, this erection of balconies has virtually created a building-within-a-building and has made it possible to so increase our production volume that the government has several times "upped" the quotas originally allotted to us.
Let us begin on consideration of Vega variations in Fortress manufacture in the wing department. Here, at the starting point of inner wing assembly, the method is "strictly Vega" in that neither Boeing nor Douglas uses it.
First step in inner wing assembly comprises joining of the engine nacelles to the virtually bare, main or leading edge spar sections. With a spar truss placed on its side in a specially designed jig, two pre-assembled nacelles are seated vertically on it, critical points are established, and the assembly is firmly riveted in place. To save jig time, the final riveting and initial pick-up work are done after removal from the mating jig, while the joined assembly is mounted in a stationary holding fixture. With that work completed, the assembly is transferred to a dolly where additional pick-up of non-critical parts and equipment is accomplished. From the dolly, the leading edge section is transferred to the three-story master jig, where the inner wing section is assembled while in a vertical position, nacelles down.
Three other sections of the inner wings are also pre-assembled in jigs where critical points are established. They are then moved moved to holding fixtures for pick-up work and preliminary installations prior to transfer to the master jig.
Section No 2, containing spaces for feeder tanks, supercharger door, and landing gear well, is placed on the leading edge section and joined. Next the No 3 section, containing the main fuel tank space, is placed and joined. Both of these sections are connected by workers using a second floor level of the master jigs. The No 4 section, or the trailing edge, on which considerable assembly has previously been done in the master jig, is the last to be attached. Using the third floor level of the jig, workers have completed assembly of this section after it was joined to the balance of the inner wing section. This work is now being shifted to other jigs and hereafter only the actual joining operations will be done in the master jig. Plans for the jig were obtained from Boeing, but removal of assembly work formerly done on the third level is a Vega variation.
After the inner wing sections are joined in the master jig, they are removed by crane to hydraulic jack-equipped handling fixtures which are used to shuttle them to the first stations of overhead carrier lines. this fixture, too, is a Vega development.
Inner wing final assembly lines one for port and one for starboard sections are similar to lines used by Douglas in that there are two of them side-by-side and they are of the overhead type that carry sections over a series of working platforms. They differ in that sections are carried leading-edge-forward, instead of the reverse as at Douglas; only installation work is done in Douglas' 14 stations. There is no paint booth on the line, and camouflaging is not done until the ship is completed.
A new feature of the work stands beneath these lines is inclusion of indirect or reflected light. Floor areas of the lines are painted white and kept clean. Fluorescent lights hang low below the assemblies with reflectors in the normal position so light is thrown down to the white floor. I what would otherwise be dark working areas, shadowless, even illumination "just like daylight" is the result. Workmen say they like it, and their production indicates that is true.
An example of pre-assembled component breakdown is the assembly of pilot's floor, sidewalls, and the No 3 bulkhead being riveted together, with the only thing in sight identifying the section as part of an airplane being the two control columns already in place. To this structure are later added pre-assembled skin sections, seen awaiting use in nearby storage. All lines where these operations are performed are located on a balcony from which the assembled section will be lowered to the main floor, where it will be joined to other fuselage sections.
In assembling pre-assembled skin panels, the circumferential stiffeners, stringers, and skin are riveted together very rapidly on an Erco One-Shot riveting machine, which we rebuilt so large panels could be worked in it. Clecoed together in jigs before reaching the Erco unit, the panels are attached to a counterweighted holding fixture so that a girl operator can move them arc-wise over a higher-than-usual mandrel post.
The fuselage nose section, made up of four pre-assembled skin panels two sides, top and bottom are tied together in a hydraulically controlled vertical jig we call the "tepee" because of its Indian tepee shape. A 10-ft high jig, this "tepee" has two levels, where work goes on both inside and outside simultaneously. After removal from this jig, the nose section is mounted on a carrier that runs on angle iron inverted V rails through four pick-up and four installation stations. With places for workers both inside and on stands of varying levels outside, the section moves quickly through the line and is ready for lowering to the main floor when it emerges from the eighth station.
Similarly, the radio operator's compartment is assembled (station 5-6) from pre-assembled skin sections, the work being done in a vertical jig of Vega design. Critical points are established in the base and through a frame in the upward end, which is attached to an overhead tram with an electric crane motor rigged so that women may readily load and unload it. After removal from the jig, the section is transferred to a wooden platform where pick-up and installation work is completed.
The several balcony pre-assembly departments, overhead storage of parts in racks suspended from roof supports make possible full utilization of building space and more compact arrangement of the floor equipment. Overhead racks provide stock storage which in many instances is closer to point-of-use than would be possible with floor level racks.
The aft fuselage sections, like other sections of this aircraft, are started in assembly (stations 7-11) in a bank of stationary jigs, but in order not to tie up the jigs too long, they are removed as soon as possible by traveler crane and placed on castered, cradle-type dollies where pick-up assembly and installation work continues. In another Vega variation, now also being followed by Boeing, the rudder and fin assemblies are attached before the aft section is lifted from the mating jig. When the sections leave the jig they move through six stations of the pick-up and installation line, traveling sidewise.
Mention of the adoption by Boeing of the above Vega method brings up another phase of the "BDV" Fortress program that is, the constant exchange of ideas and developments between Boeing, Douglas, and Vega. All three participants are constantly working out new production methods designed to expedite production and improve the ships. As quickly as anything new is proven, full information is immediately supplied to each of the other companies, and where found to be applicable it is adopted or adapted by them.
The fuselage fore section assembly method followed by Vega is similar to that used by Boeing, with the exception of the breakdown of structures and skin panels to a greater extent than Boeing. From pre-assembled structures and panels, four sections are built up, complete with installations, on short assembly and installation lines located on a balcony. These are then transported by travel crane to the main floor mating jigs where they are joined. When that is completed they are placed on carriers of a fore section final assembly line, where they move sidewise through 13 structure pick-up stations, then move forward and finally reverse direction to pass through 12 stations of installation pick-up lines.
After the fore section is assembled and equipped, the pilot's cockpit enclosure and the aft gun emplacement are added. When this is done, the section is ready for mating with the aft section. Fore and aft section, now complete, enter a joining station, then proceed forward to a position between hydraulic jacks, permanently installed in the floor, on which the inner wing sections have been mounted. In this station the completed fuselage and inner wing sections are joined.
Upon completion of joining operations, the plane is raised and the landing gear is lowered. On its own wheels, the new Fortress now proceeds to the next station to pick up the nose cone and other minor items. Four of these lines operate simultaneously, but after pickup is completed, the four lines are reduced to two final assembly lines where the outer wing panels are attached in the first of three final assembly stations. Remaining clean-up is accomplished in the second station; inspection and correction of final inspection "squawks" in the third station. The ship, now "off the line", proceeds to the camouflage shop, located in a separate building.
Throughout the plant, floors of two-level jigs and other low-ceilinged working areas are painted white to reflect light. Jigs, too, are white with movable parts in blue.
Through pre-assembly we have utilized plant space efficiently; and by getting a product as large as a Fortress "out the door" as quickly as possible after the ship is completely assembled and requires maximum floor space, we have held plant-space overhead to a minimum.
By pre-assembly of even the skin sections, we have reduced the time spent on large components in jigs and on assembly lines. And, perhaps even more important, we have broken down otherwise complicated assembly jobs to the point where most of them can be successfully handled by more-or-less inexperienced workers, a majority of them women.
That the method is getting gratifying results is best attested by the fact that production next month will quadruple that of Jan, 1943, yet in the first month of this year we were in full operation on the Fortress contract.
Later this year, and in 1944, production is expected to continue to climb, to reach a daily volume that was not thought possible when the "BDV" orders were originally placed. Some of the future increase in volume will be accomplished by further application of the pre-assembled skin panel and structural component method and by continual smoothing up of the system. The latter will include further shifting of departmental arrangements, a process now in progress which will not be completed until equipment being made is installed.
Fleets of Flying Fortresses, regularly darkening the skies over enemy targets, loose bombs which furnish violent evidence that the "rugged individualism" of US businesses does not prevent their cooperating as in the Boeing, Douglas, and Vega instance in defense of this country and the world. And as those identical Fortresses wing toward their objectives, they furnish living proof that the ingenuity and individuality of US industry is rewriting an old saying into a more modern version: "There are only two ways to skin a cat, but there are three ways to build a Flying Fortress."
This article was originally published in the July, 1943 issue of Aviation magazine, vol 42, no 7, pp 136-138, 143-145, 318-319, 321.
The PDF of this article [ PDF, 14.4 MiB ] includes fifteen captioned detail photos of various stages of manufacturing, including one flight shot of a B-17F seen from 12 o'clock, looking through the greenhouse into the bomb/nav compartment, and a diagram of the production flow.
Photos are not credited, but are certainly from Lockheed-Vega.