Not so many years ago, before war brought the need for thousands of airplanes every month, a factory manager could give worker Joe Doakes a few parts and tell him to see that they got on a certain ship perhaps the only plane in the plant. And Joe would see that the parts were put on the plane.
But current demand for more aircraft in a month than the entire industry formerly produced in a decade has wiped out the personal touch in airplane building.
Today, emphasis is on mass production which means controlled material flow and proper planning of assembly operations. Briefly, mass production is the timing of the flow of materials and parts so that a worker gets a specific piece at the split second he needs it for his particular operation. But this function doesn't stop with one worker it is carried through the entire plant. The timing must be perfected from station to station.
The Army Air Forces ordered immediate conversion of a number of B-24 components to transports in order to speed important men and material to the lighting fronts. Our first C-87 left the plant late in the summer more than 30 days ahead of schedule and carried Wendell Willkie on his epic globe-girdling flight.
Most aircraft plants, like Topsy, have "just growed," spreading out as additions were needed to meet a rapidly expanding war program. Several years ago, however, Consolidated Vultee, drawing on its 20 years of experience in construction of large aircraft, drew up plans for a completely new type of plant based on efficiency alone. Result is the Fort Worth plant, built by The Austin Co as the largest windowless factory and probably the largest self-contained aircraft manufacturing plant in the world.
Because of this very size, though, one of the most important layout factors considered was the distance a part must travel while not in work. The time required for material or a part to reach one operation from another we call "dead time." The plant's 117 acres of concrete working space have thus been laid out to provide a minimum of material travel and, consequently, a maximum labor output going into the finished product through substitution of working for travel space. Wherever possible, workers' benches are so arranged that parts may be handed from one to another.
This type of planning has made it possible to keep the p1ant's two assembly lines continuously moving, producing not only B-24 Liberator bombers, but C-87 Liberator Express cargo planes. In addition, part of one of the lines has inaugurated assembly line modification of B-24s.
When the plant was first occupied in Mar 1942, there was no parts building; that was destined to come later. There was, however, one order: "Get into production."
Little more than a month later, utilizing parts and subassemblies from our San Diego plant to test the planning and feasibility of the assembly line, the first B-24 was rolled from the building and flown more than 100 days ahead of schedule. It was soon apparent that our Fort Worth assembly could readily outstrip its originally intended function, which was assembly of bombers from parts to be supplied by a plant located at considerable distance in a northern state. So a parts manufacturing building was ordered.
Meanwhile, however, parts machinery began to arrive, to be set up and put in operation in a section of the assembly building so that production could begin and the all-important job of training thousands of workers could get under way for this new job.
By the year's end, long assembly lines were ready for continuous motion, instead of the intermittent operating method often employed. Fifteen days after the start of 1943, the majority of the parts machinery was moved into the new parts plant, and through pre-arranged scheduling not a day was lost in the use of machinery.
Material flow has, in many instances, decidedly reduced the distance a piece of aluminum travels from initial raw stock to final part of a finished B-24 reduced the distance from 10 or 12 mi, the "travel" in some plants, to less than 1 mi, all despite the enormity of the Fort Worth plant.
Basically the flow of material is this: Raw stock enters one end of the building and goes out the other as part of a completed aircraft. This procedure, of course, is often broken down into several operations, so that the raw stock may be temporarily stored adjacent to its particular department, then flow across the plant through processing into finished parts stock adjacent to its assembly station then into the growing aircraft moving along the assembly lines. Other units, such as A & N stores, or government furnished equipment, move into separate storage areas near one end of the parts plant.
As aluminum sheet, for example, is received by the parts plant on one of three depressed railroad tracks reaching far into the building, it is distributed along the raw stock storage area directly behind fabricating departments for which it is destined, such as sheet metal, draw bench, tube bending, welding, and machine shop. Then, after uncrating and inspection, it is stored in racks near cutting machines of these departments.
Flow of material through a department such as sheet metal and drop hammer is broken into a number of different paths. Nearly all aluminum first travels to shears. Then it may go to a skin-contour-forming stretch press that reduces the old operating time from 30 to 40 min to a flat 60 sec. Some material moves from shears to blanking, punch, or roll presses or to drop hammer. Flowing in many different channels, these parts are processed through drilling centers, burring centers, brakes, etc all eventually winding up, of course, in the inspection area. Occasionally sheet metal will be processed through other fabrication departments, frequently to return for an operation.
Because of the countless thousands of parts required and the great variation in processing, the flow necessarily is by "lot" production to production centers, rather than "line" or "mass" production from machine to machine.
Since a combination of fabricated parts and purchased parts is used to make up the greater part of the airplane, the two receiving stores and the manufacturing departments are located together as a production aid. Fundamentally, these store rooms are centralized control stations from which parts are dispatched to stock racks at the assembly line stations throughout minor and major subassembly departments. Some of the parts move from finished parts stores directly to the spares department, where they are boxed and shipped out to various Army maintenance depots in the war zones.
Parts flowing to minor assemblies are stored in racks along, aisles in the departments in which they are to be used. Bulkheads, belt frames, bomb bay side panels all move to specific areas. Fixed equipment in the B-24 is made up in metal bench; electrical harness in electrical bench; upholstery and covering in the upholstery department. Some minor subassemblies are built primarily as bench work on the mezzanines, later to be incorporated into major subassemblies, while others move directly into installation points along the assembly lines.
Major assemblies, such as wing center sections, nose and tail fuselages, wing outer panels, and control surfaces are assembled from thousands of small detail parts in larger steel fixtures. The fixtures remain stationary and workers move from jig to jig. The procedure is reversed on the continuously moving assembly line, where the movement from "lot" to "mass" production finds the major assemblies moving and the workers and materials in fixed positions.
To cut production hours, each part is made as nearly complete as possible before the major assembly leaves its department. Such time-saving is especially noticeable in the nose fuselage operations, where a much greater percentage of wiring and other intricate interior installations, formerly done in final assembly, now are completed in the primary assembly.
Further innovations crop up in the wing bucks, where skin and stringer panel fixtures have supplemented the original jigs in an ever-improving tooling program. Complete stringer and bulkhead assemblies made up in subassembly fixtures are dropped into the wing fixture.
These mating jigs, unlike the spider-like arrangement common to such fixtures, tend to give more rigidity as well as to leave more unimpaired working space about the wing and fuselage areas.
Just as the moving horizontal conveyor line has eliminated the necessity of transporting the wing center section to the mating fixture, the proximity of nose and tail assembly departments to the jig eliminates much travel and handling. The overhead cranes quickly and smoothly drop nose and tail fuselages into fixed positions in the jig, where these assemblies are held by straps. All chances of variation are eliminated.
With mating of the nose fuselage, center section, and aft fuselage completed, the overhead crane lifts the mated craft from the fixture and places it on a carriage for its trip down one of the long assembly lines. The 28-ton planes move down these lines at 45° angles, thus allowing the noses and tails to nest together, thereby gaining space for one extra ship out of every three put on the line. Experience with the big craft has taught that such an arrangement more nearly utilizes every available foot of space in the building and puts three ships in work where normally only two would be.
An improved and simplified cantilever carriage design, plus attached scaffolding, aids the workers in reaching every part of the airplane, and the continuous movement of the assembly lines is so smooth that workers inside the ships have no sensation of motion. Carriages are painted white, not only to reflect light, but for cleanliness. Most new employees apparently are impressed not only with the tremendous production activity, but also with the constant state of cleanliness in the air-conditioned, fluorescently-lighted structure, which also incorporates white cement flooring. The latter augments both light reflection and cleanliness.
Carriage conveyors on the assembly line are valuable for many reasons, one being the elimination of the possibility of line stoppage through a shortage of any part of the landing gear, since the ship is not propelled along on its own wheels. Carriage operations allow for testing at stations of the retractable landing gear, with its complicated hydraulic system, as well as of landing flaps and other appurtenances, thus eliminating the need for a later jack-up and test.
The carriages, coupled by telescoping tow-bars not unlike those on railroad cars, are pulled steadily, by compound-geared electric motors, toward the 200-ft-wide doors at the end of the assembly building. These carriages are complete with air and electric connections so that workers may plug rivet guns and air lines directly into outlets in the moving carriages. Tracks are made of thin cold-rolled steel bars, bolted flush to the floor to enable trucks and other rolling stock to move across them without having to take long detours. Eight stations from the end of the line, a trigger arrangement on the telescoping connecting bar between carriages is released so that the bar lengthens to permit areas between the carriages at this point to increase from 50 to nearly 65 ft, partly opening up the nesting pattern to allow for outer panel installations.
Complete coverage on installation of all large parts on the ships and on the line by the "upside down" railroad also plays a major role in continuous movement of the line. Wing outer panels are brought from their assembly area near the installation stations and added to the Liberator without a halt in the line. Similarly, the tail assembly (completed in a nearby place to the extent that only four bolts are needed to attach it to the craft) is dropped into place. Power plants are installed from a 90° bridge over the planes. Armament, including gun turrets, then moves into place from a nearby assembly area. The bombardier's glass enclosure is left off the B-24 until the last moments in order to expedite movement of workers in and out of the fuselage.
Assuming greater importance as the size and weight of subassemblies grow is the just-mentioned "upside down" railroad. An overhead monorail crane system networking the millions of square feet of the plant's ceiling, it is used, for example, to lift center wing sections from the bucks and place them in a horizontal position on a moving conveyor line in which they are supported at each end on wheels. Wing installations then continue as the center section moves to the bomb bay fixtures where bomb bay side panels and cat-walk are installed. Further down the flat line, the wing moves into place on a self-leveling and aligning mating fixture.
Finally, the power-operated, overhead-lift, 200-ft-wide doors go up, and a complete B-24 moves from the line and out into the yard, where the concrete slopes just enough to aid the ship in rolling from its carriage as the landing gear oleo struts are inflated.
After an engine run, the Liberator goes to one of two large compass roses for compass swinging and calibration and testing of its complicated radio equipment.
From there it moves to the four-ship hangar, where it receives flight inspection. Shakedown flights are accomplished by experienced crews who take each Liberator to its operating ceiling and thoroughly test all functions for several hours.
Experience gained from Consolidated's other operations is reflected in the entire Fort Worth setup. Even the storage problem connected with the quantity production of four-engine aircraft of this size is complex.
As a hypothetical case, say our production is 300 Liberator bombers and transports per month. This means we must have on hand each month 1,200 engines, 1,200 propellers, and 3,600 .50-cal machine guns, plus turrets, armament, radio instruments, and countless thousands of "gadgets." All component parts in a ship the size of the Liberator are of necessity bulky.
To meet the heavy call for planes, controlled production planning is an absolute necessity. Nothing less can accomplish the maximum fluid production the aircraft industry is delivering to whip the Axis.
This article was originally published in the July, 1943, issue of Aviation magazine, vol 42, no 7, pp 146-151, 321, 323, 325.
The original article includes 14 photos and 1 diagram.
Photos are not credited but are certainly from Consolidated Vultee.