Modification Centers … An American Military Innovation

by Glenn Hotchkiss
Works Manager, Consolidated Aircraft Modification Center

Modification centers relieve back pressure built up on quantity production lines in form of engineering change orders made in light of combat experience. Consolidated center described here is typical of dozens of quickly built plants where "airplane tailors" are making parts and equipment with make-shift tools. to give our airmen "Tomorrow's Fighting Planes Today".

United Nations aircraft manufactured in the United States will not fail, as did those of the German Luftwaffe on the Russian front in the winter of 1941-42, because of the cold weather. Neither will the sand and heat of the desert, nor the sticky mud and humidity of the equatorial jungles put them out of action. Because every military plane, for whatever front, is sent, not from a factory, but from a modification center, where it has been specially equipped to meet the conditions under which it will operate.

As far as we know, the United States is the only nation in the war using the modification center plan. Dozens of them are either already in production or rapidly nearing completion in the United States and foreign countries. And it is their combined production, in the final analysis, that is the military aircraft production of the United States.

Undoubtedly much of the credit for the mechanical life and performance records made by US aircraft is attributable to the fact that each ship is weatherized and otherwise equipped for specific theaters of operation or special missions. What is done is, of course, a military secret. How it is done will be told, in part at least, in this article.

Chronologically, orders for modification are received from the several fronts by the Special Projects Branch, Production Division, of the Materiel Center, AAF, Wright Field. There they are studied and, if practicable, forwarded to the modification center handling the model or type of plane involved.

An order may include many changes, some of them of such nature they will always have to be made in the modification center, and others that will be made there only temporarily. We estimate that about 25 percent will always be what we now call "permanent" work, such as weatherization installations, and 75 percent will be of a "temporary" nature, so handled only until the parent plant can put them into production.

For the latter the Modification Center engineering department makes drawings that will put the change into production and also sends copies to the parent plant. There, if necessary, they are redrawn and steps are taken to incorporate the changes on the production line. The center will continue to fabricate and install the changes until they come through permanently from the parent plant. By that time, however, orders for still other changes will very likely have arrived and will be in progress. It is expected that this routine will continue throughout the war. And, of course, installation of weatherization and special mission equipment will always have to be done in the modification center.

When the engineering department has finished its sketches, to be followed later by drawings, the tooling and methods departments go into action. Tooling, of course, in most instances is of the "quick and rough" variety; its goal is to get into production fast, but generally for only small quantities. Small, that is, when compared to the production of the manufacturing plant.

As quickly as possible, usually a matter of a few hours, tools are made and methods of producing the new parts or equipment are put into operation. Production, as in the early days of the industry, is necessarily almost exclusively of the handmade kind — "quick and a bit rugged," as we describe it. In one instance recently we went back 18 yr for a method to make a part, producing it exactly as we did at that time by primitive methods long since abandoned.

At Consolidated Aircraft Corp's Tucson, AZ, modification center, deliveries are flown in by company ferry crews from the manufacturing plant. Dispersed about the landing field adjoining the center's hangars, planes await assignment. When that is arranged they are taxied to the reception ramp at the head of the modification line.

Before they enter the line itself, and while still outside the huge hangar buildings, fuel, alcohol, and oil are removed and engines are drained, cleaned, and treated to prevent corrosion.

In the first stations of the line, all loose equipment, particularly that inside the fuselage compartments, is removed, tagged, and shuttled in a. special box to a specified final station on the line, where it is reloaded when the same ship rolls through that station.

In one of the first stations, cowling racks made of plywood, with solid bottoms and ends, and slat sides 4 x 2 x 3 ft in size, are fastened to the upper surface of the outer wings, two to each ship. Cowlings and parts removed so modification can be done, are placed in these racks and remain on the ship throughout the trip down the line. Each rack is divided into three compartments and these are specified for certain uses. In this manner, uniformity is achieved —parts are always found in the same place when needed, and the possibility of damage due to improper piling and jamming in the racks is avoided.

As on the assembly line of the manufacturing plant, work on the modification line is broken down into its logical segments, each to be accomplished at a given station of the line. In setting up the line — in fact in practically all phases of the work, whether in fabrication, installation, or reassembly — we have drawn upon the methods of the parent plant for ideas and timing.

Because of that we have found that holding to approximately the same interval of time per station as that allotted in the parent plants best dovetails our production with that of the source plants. However, the work done requires only about one-third the time, and one-fortieth of the manhours, required to build the plane. And those ratios will no doubt be changed as other units of the center are occupied and our personnel acquires greater skill.

Throughout the departments, nucleus staffs were drawn from other Consolidated plants. Around these we added staffs drawn from the community near which the center is located. Naturally, much of this personnel, with the exception of a few skilled mechanics, machinists, electricians, and the like, was inexperienced. However, they are rapidly learning the techniques of their jobs, and we do not anticipate any difficulties from that direction in maintaining the steadily increasing production rate we have planned.

As in all other plants these days, the labor problem boils down to: How many jobs can women handle? So far we have found the percentage about the same as that of the producing plants. Along the assembly line we move the planes on their own wheels, by towing them (linked together by a single cable extending from nose wheel to nose wheel) with a tractor. Stations consist of fixed work stands arranged so the fuselages pass between them, and port and starboard wheels move through slots from which leaves in the floor of each stand have been removed. Because of the nature of the work, we can assign only about one-eighth as many workers as are used at average stations of the parent plant's assembly lines.

In the fabrication departments our workers have to be resourceful. A Jap fleet gathering at some distant harbor will not wait for us to figure out the most polished way to equip some bombers to go out and intercept it. Instead, it is our job to find a way to get the needed special equipment made and installed by the deadline set in the order. And we do it — often by forming parts on such machines as a 60-ton hydraulic press we bought from a wholesale automobile supply concern. With a die made of hard wood, and one accepted part as a pattern, we rush out the required number of parts.

Or, we out stock with tin snips, hand form it over maple blocks, and burr the pieces with disk-type knife sharpeners picked up at the ten cent store. Parts requiring machining are frequently produced on small bench and tool-room lathes.

Taken as a whole, the modification center staff has to be not only resourceful, but must include a large percentage of people who are all-around craftsmen. When a ship leaves here it has to be ready to carry out its military mission.

We look upon this modification center as an extension of the parent plants. Its work cannot be standardized, and its methods, equipment, and line arrangement will probably have to remain highly fluid. Gen Arnold has said that our current heavy bombers are the "last of the small bombers." Whenever those bigger ones start coming along we will be able to handle them, too, because our arrangements were designed with such probabilities in mind.

When we finish our work, a military service ferry crew takes over and flies each plane to its particular delivery point. There it may be flown across an ocean, perhaps immediately loaded with ammunition and bombs in readiness for an attack on enemy objectives. Whatever its mission, it is ready for it.

The only American planes that fight go from modification centers. No longer do our field commanders say, merely: "Please send us some planes." Instead they ask for ships of specified types, equipped to meet climatic and tactical conditions of their respective theaters. And it is up to the "airplane tailors" in the modification centers to produce specialized airplanes for this specialized war —"Tomorrow's Fighting Planes Today" — one jump ahead of the enemy.

This article was originally published in the April, 1943, issue of Aviation magazine, vol 42, no 4, pp 134-136, 329-330, 333.
The original article includes nine photos of activity in the modification center, all on B-24s.
Photos are not credited.

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