Reduction of Man-Hours In Aircraft Production

By I M Laddon
Executive Vice-President, Consolidated Vultee Aircraft Corp

How Consolidated Vultee's rule-of-thumb for fabricating efficiency has grown info science for saving priceless time in manufacture of long range Liberator bombers.

One of the outstanding factors in America's swiftly growing aircraft production to meet the United Nations' wartime demands has been the sharp reduction in man-hours per plane fabricated. Among the greatest such time slashes are those which have been accomplished at the two San Diego plants of Consolidated Vultee Aircraft Corp, where the B-24 Liberator bombers, PBY-5 Catalina and PB2Y Coronado patrol bombers are fabricated.

During the past year, the over-all efficiency increase in both plants has been more than 200 percent, and the curve is still rising. Calculating from Sept, 1941, when the Liberator conveyor line was first established, the increase is even greater.

Despite a tremendous labor turnover clue to selective service demands, plus the complication of hiring and training thousands of unskilled women, the company today is producing 2.5 planes for every one produced in Apr 1942, while employment of production workers has increased but 10 percent. Employment of women has risen from less than 1 per- cent in Dec 1941, to more than 43 percent at this writing, a great majority of the women being hired to replace men going into the armed forces.

These figures give an indication of the great savings in man-hours per unit produced, but in discussing specific reductions on the Liberator, for example, it is essential to have a basis of comparison. This basis may well be the production methods used to fill what we now consider comparatively small orders prior to the vast prewar production increase which started rolling in 1939-40.

Under the pre-war production system, if an order for say 60 planes (a big order in those days) was received, groups of workers would concentrate on the various parts needed for the components and produce 60 units. As fast as these components were made they were stored in a central stockroom, there to remain until all the parts for certain subassemblies had been completed. They then would be withdrawn and the 60 subassemblies fabricated. And as the 60 subassemblies were finished they, in turn, would be assembled into the completed unit until the 60 had been constructed, tested, and delivered.

This system was economical in filling small orders, as it saved setup time and parts fabrication cost. Once a job was started, the 60 units were completed in sequence; if ten units per ship were needed, then 600 would he produced. .

Under this method there can he set forth a thumb rule for increased production efficiency, which is in reality the lowering of man-hours on each unit or group of units. This rule is based on the learning curve which, in turn, is based on the simple fact that the more times a human being, or group of human beings, does a job, the better they do it individually and together.

The thumb rule is that when a manufacturer doubled the number of units produced, he reduced man-hours for the entire quantity by 20 percent. To apply this mathematically, let us say that for the first 100 units of airplanes produced, the man-hours involved in each amounted to 100,000. With the manufacture of the next 100 units of the same aircraft, the man-hours for the full 200 units should drop to 80,000 hr., which means that the second 100 units were produced at a cost of 60,000 man-hours.

With 400 units completed it is found that the entire 400 were produced at a cost of 64,000 man-hours per unit, with the last 200 costing but 48,000 man-hours per unit. Carrying the thumb rule on to 800 units, the overall average per unit drops to 51,200 man-hours, with the units from 400 to 800 costing only 38,400 man-hours per unit. From 800 to 1,600 units, the overall cost per unit drops to 40,960 man-hours for the 1,600 units produced. Units from 800 to 1,600 — the last 800 produced — cost but 30,750 man-hours per unit.

Application of this thumb rule to the manufacture of Liberators shows that Consolidated has beaten "par" by about 50 percent. Improved manufacturing methods have given the company the difference between par and the production "eagles" which have been scored.

What, then, are some of the methods which have made possible this progress in reducing man-hours? Let us consider this question:

With the inception of today's large orders, which have brought huge and originally unanticipated expansions, several problems arise if attempts are made to adhere to the old methods. For instance, plant stockrooms would be hopelessly inadequate to hold the millions of finished parts. At the start of Liberator production, all available warehouse facilities in San Diego were leased. Had the old methods been retained these facilities would not only have been filled but would have overflowed to hamper production. Even under present construction practices, new warehouses are constantly being built.

This parts storage problem brought about the necessity for establishment of a flow of raw materials through fabrication processes into subassembly lines and also the flow of subassemblies into the final assembly line. At each point in the process of manufacture, the right number of fabricated parts must reach the right place at the right time, and the entire flow must be in a direct line to the last operation before testing the completed aircraft. The first step was to get each fabricating and subassembly department in the plants scheduled to produce parts and components at the same rate that the aircraft were coming off the final assembly line. This resulted in abolishing the central finished parts stockroom and installation of stock bins along all subassembly and assembly lines. It was found that this made a large cut in the number of man-hours required to move stock in and out of the old type central stockroom. Not only was there a definite saving in the labor required to shift stock, but it was possible to avoid tying up raw and fabricated materials. In general, the small stock bins carry only an eight to ten days' supply.

This system of handling stock, pioneered by Consolidated Vultee, differs from other methods currently employed by many fabricators in the industry and is to some extent responsible for the company's success in cutting down man-hours on the Liberator.

When the assembly line first came under consideration, there arose the problem of whether the line should be moving or whether it should stand still. There were two obvious possibilities: To leave the airplanes in process of fabrication static and move the assembly crews from one plane to the next, or to move the airplanes and permit the crews to be stationed. Careful investigation resulted in a decision to mechanize all assembly lines. The flow of stock into the moving lines was obviously simpler than the flow of stock into a stationary line, due to the fact that stock, crews, and tools were prepositioned at a planned work area. With a stationary line, these three elements had to move rather than the airplane.

This brings us to another cause for the lowering of man-hours consumed in Liberator manufacture — a cause which was the outcome of a combination of chance and headwork. The building in which the Liberator final assembly line was to be set up was found to have bays which were too narrow to permit the line to operate with the 110-ft. wings at 90° to the direction of flow.

The result was that the planes were turned to a 45°. angle. This gave plenty of space for all operations attendant to assembly and left ample space for the station stock bins and access thereto. In addition, the production line was figuratively 50% longer. That is, 33-1/3% more stations could be put on the line with the planes at a 45° angle than could be at a 90° angle-to-production flow. So well did the Liberator 45° angle final assembly line operate that it was installed at Fort Worth even though the nearly-mile-long building was wide enough to accommodate the plane at a 90° angle.

During the past year considerable conservation of man-hours has been brought about by establishing predetermined operating department controls inaugurated by Harry Woodhead, president of the company. Based on the comparison of standards to actual performance, these indicate the efficiency of operation and act as a measure of each and every department's status in the efficient use of the production facilities and manpower at its command.

Once standards have been established, the next step is to check the performance of a department against them. From this check, which is a yardstick to measure every department, comes management's control of operations. The data gives management and the department heads a forecast of what can and must be done in sufficient time to make necessary corrections and plan their action accordingly.

Under operating control, not only is management advised weekly of the operations of the entire organization, but in addition supervisory personnel benefits from increased efficiency through a method termed the Foremen's Cost Conversion Bonus System. Based on comparative efficiency on a month-to-month basis, the improvement of performance in a department results in a bonus to foremen within that department. Each month a "bogey" is established, based on performance during the previous month, and this in turn becomes the "bogey" for the current month. To receive a bonus, the foremen must improve on the previous month's performance.

Those who share in the bonus are graded not only on improvement in performance, which is in actuality the lowering of man-hours per unit produced, but on housekeeping, safety record — both as to frequency and severity of accidents — and on the meeting of schedules, which has a direct effect on the subassembly and final assembly lines. Failure of one department may cause "starvation" on any of these.

In addition, foremen are graded on the performance of all other departments, which means that inter-department cooperation is promoted. If one department is doing an excellent individual job but is not cooperating with other departments, the efficiency of the entire organization suffers. General performance, and therefore production, is lowered. On the other hand, if departments are cooperating the general production standard is raised.

It has become increasingly imperative that the company's methods and conditions be constantly improved so that conservation of man-hours can be applied to the ever-increasing production schedule. The operating controls have proved eminently successful, not only as a production yardstick but in making supervisory personnel man-hour conscious and has done more than any other factor to step up the tempo of production.

Another element in saving man-hours has been the institution and operation of the supervisory Cost Improvement Proposal Plan. This phase of production engineering went into effect last August. Since then more than 4,500,000 man-hours per year have been saved as the result of actual installation of labor-saving methods and devices. Another phase of engineering for production is the Employee Suggestion System which has been in operation for some time but which was specially promoted with a concerted drive about ten months ago. Under this system, workers have been paid more than $30,000 in war bonds, stamps, and cash for suggestions which to date have resulted in savings of more than 700,000 man-hours.

Among the other ways man-hours have been saved are:

  1. Long, complicated assembly operations which formerly had to he done by craftsmen who required several years of apprenticeship are broken down into small subassemblies which can be accomplished by "green" hands, including women totally inexperienced in any kind of factory procedure.
  2. Increase in skill in tooling design methods, which has resulted in better tooling.
  3. Better assembly fixtures developed over a period from the time the first Liberator came off the line up to the present time.
  4. Better installation fixtures developed over the same period of time.

One example of the thousands of problems which have been licked was this: When Consolidated saw that hundreds of airplanes must be fabricated in place of tens in the latter part of 1940, the then seemingly astronomical goal of four planes per day was set. One of the problems which the company faced was that of making the fuselage nose installations fast enough. At that time, 6,000 man-hours were assumed to be required for each unit, and, at the same time, it was impossible to work effectively more than six people inside the assembled nose. On this basis, with six persons working on two 10-hr shifts, a total of 120 hr per day, it would require 50 working days to complete the job. In order to produce four planes a day it would be necessary to have installations under way in 200 fuselage noses at all times, requiring a line for this subassembly alone that would stretch over three-quarters of a mile.

The answer to this problem was found in opening up the fuselage nose, eliminating the cramped quarters, and permitting more man-hours to be applied simultaneously. Four cleavage lines were decided upon. These lines — two extending horizontally in the upper half of the assembly and two extending horizontally in the lower half — were not riveted. Once the nose was properly mated, it was disassembled, which made it possible to install equipment on all the separate panels and flight deck. The nose was then reassembled, ready as a complete component, to go to the final assembly line.

The reason for building the fuselage nose as an assembly and later disassembling into the flight deck and other segments, was the time required to tool separately each segment of the nose. Separate tooling for each fuselage segment would undoubtedly save man-hours required in fuselage fabrication and eventually the company will have tooling of this type.

The step outlined above in cutting man-hours is only one of an almost incalculable number put in effect in the manufacture of the Liberators. As forecast, further methods and tooling are now being devised, more and more subassembly lines are being established, and it is anticipated that during 1943 many millions more man-hours per year will be saved.

Any attempt to credit any one specific person is out of the question. The production record is not due to the genius any individual or group of individuals but is based entirely on the fact that everyone within the organization is cooperating on the job of turning out aircraft as fast as possible under such handicaps as lack of trained personnel, labor turnover, continual expansion to meet constantly increased production schedules, and lack of production facilities due to wartime shortages.

This article was originally published in the May, 1943, issue of Aviation magazine, vol 42, no 5, pp 170-171, 173, 356, 359-360.
The original article includes 5 photos of the B-24 production lines.
Photos are not credited.

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