San Antonio Air Depot

With rapid Air Corps expansion a new and greater responsibility is being placed on its airplane and engine overhaul bases

An air corps is only as good as its maintenance system. If fighting planes are to accomplish their missions, if engines are to purr smoothly on difficult flights, the maintenance organization on the ground must be efficient and trained to a state of perfection.

In the system of maintenance used by our Air Corps, great reliance is placed upon the four depots located at Harrisburg, Dayton, Sacramento and San Antonio. These are the major overhaul stations where engines, propellers, accessories and even the planes themselves are sent for complete overhaul. Daily and monthly checks are made at the flying fields, but only the depots are equipped to do such complex jobs as tearing down and rebuilding engines or making major structural repairs in large bombers.

Largest of US depots is at Duncan Field, San Antonio. Its 1,900 trained mechanics are the guardians of equipment for some 1,000 airplanes. In the course of a month as many as 250 engines, 15,000 spark plugs, 350 starters and hundreds of other items will flow through the depot for complete disassembly, rebuilding and testing. Then they are sent back to the tactical squadrons or training centers for installation.

In addition to this overhaul and rebuilding of removable parts of the airplane, a vast amount of fabrication work is done at Duncan. A visitor to the depot, catching a glimpse of a line of Republic ships, as shown on the opposite page, may conclude he is in an airplane factory. The sheetmetal shop with its hydraulic press, forming equipment and the busy rat-tat of rivet guns, and the huge machine shop are especially reminiscent of manufacturing plants.

Work in the huge 6-acre building which houses the overhaul shops is under the direction of Col Clements McMullen, Station Engineering Officer, and R H Van Horn, who is Shop Superintendent. While the commanding officer and his assistant engineers are Air Corps officers, the Shop Superintendent and the balance of the personnel are civilians who have qualified for their jobs through federal civil service examinations. Civilian employees have doubled in the past eight months due to the increased volume of work flowing through the depot. The engine overhaul shop is now operating two shifts per day, and the machine shop and sheetmetal departments have so much work they are running on three shifts.

Work at any Air Corps depot is complicated because of the many different kinds of airplanes and engines being serviced. In a commercial airline shop there are seldom more than two kinds of engines to be overhauled. At Duncan Field in February there were more than 15 different types of engines sent through the shops. As the photographs indicate, everything from Link Trainers to Flying Fortresses may come in for repairs or alterations. Both the pilots and the mechanics at Air Corps flying fields have great confidence in the work of the depots — a confidence that over the years has been justified.

Bathtubs for the B-17s

Duncan Field is more than a maintenance base — it is a small aircraft factory. It has the skilled workmen and equipment to build or rebuild almost any kind of airplane. The early versions of the famous Boeing B-17 are now four years old. To bring them up to the perfection of the B-17D series now coming off the Boeing assembly lines, mechanics at this base are making a number of changes, some of which are shown here.


The blister on the fuselage roof is being removed and a new cover is being streamlined into the forward section. Side blisters are coming off to be replaced with flush windows. Greatest change is the addition of the bathtub, shown in these photographs.

This article was originally published in the April, 1941, issue of Aviation magazine, vol 40, no 4, pp 38-41.
The PDF of this article [ PDF, 14.6 MiB ] includes numerous captioned photos of facilities and activities at the San Antonio facilities, including the B-17 upgrades.
All photos credited to Aviation magazine.