Without efficient maintenance, the vaunted German aces would never have gotten off the ground.
The Messerschmitt Me-110C-5 circled the airstrip once, came in for a smooth landing on the desert sand and taxied to what passed for a flight line, trailing a huge cloud of dust. Cutting the engines, its pilot and gunner climbed down and sheltered under the wing from the blazing sun. The pilot informed the ground crew that the Me-110’s radio had quit working during his mission reconnoitering British army units in the Libyan Desert, and would require immediate attention.
The aircraft mechanic, carrying his tool kit, pulled on gloves to prevent burning his hands on the hot metal, then opened a panel in the fuselage just behind the rear gunner’s position. He took a look at the radio set and knew immediately what he needed to do. The mechanic could tell this at a glance because the manufacturers had assembled the electronic equipment with color-coded screws, the color indicating whether or not the part could be removed and disassembled in the field. It was but one small example of how German maintenance procedures saved valuable time and ensured aircrews had equipment they could depend on.
From its inception as an independent branch of the German armed forces on March 9, 1935, the Luftwaffe adopted and followed a thorough plan of organization, with two distinct lines of command: operational and administrative, the latter including maintenance and supply. As a result, flying units could train and operate virtually unencumbered by administrative and supply concerns. The administration and supply branch similarly benefited by having a well-trained group of officers and men whose practical experience was used to best advantage, and who were kept in their specialized field of expertise. That system was one of the main reasons the Luftwaffe was so successful during the first two years of World War II, when it was operating mainly from established bases in the Reich.
The German air arm was divided into Luftflotten (air fleets) on a territorial basis. A Luftflotte was both an operational and administrative command, though both functions were exercised through a separate chain of command. This procedure was maintained down through most subordinate commands, including the Fliegerkorps (air corps), which had one to three administrative and supply Luftgau (air zones). All commands from Geschwader (wing) down to the Gruppe (group) were entirely devoted to either operations or administration and supply. A Staffel (squadron), the basic operational unit within the Gruppe, usually had its own mobile shops for minor maintenance and repair.
Operational airfield commands were assigned to permanent air bases to provide aircraft maintenance, supply, billeting and defense. At an established base, about 150 men and three technical officers manned a Werft, the actual aircraft maintenance section. Civilian engineers were also often employed by major workshops. The work performed was confined to major repairs and other jobs that were beyond the capacity of squadron personnel, who handled all servicing and most minor repairs. Each Werft was divided into three sections: repair, test and supply. In a Werft of 150 men, the division was usually 105, 10 and 35, respectively, including engine mechanics, metalsmiths, structural technicians, electricians, instrument specialists, etc. Werft personnel were typically equipped with proper tools and equipment and worked in well-lighted hangars and shops. The most experienced, capable men were normally assigned to the Werften in preference to the squadrons.
The basic organization and segregation of operational and administrative functions gave the Luftwaffe the mobility and efficiency that proved so successful during the first stages of the war. The later superiority of the Allied air forces can largely be attributed to operational success and superior strategy, tactics and numbers rather than to any German organizational weakness.
No one was ever awarded the Knight’s Cross for greasing an airplane. But maintenance was a job of great importance, made more difficult as the war progressed. The exigencies of combat operations outside Germany often necessitated the repair and even overhaul of aircraft, engines and equipment at airfields behind the lines, frequently under adverse conditions.
In the vastness of North Africa and the Soviet Union, the Luftwaffe, like the Wehrmacht, was frequently on the move. Ground crews as well as airmen worked long hours and usually lived in tents in the sun, heat and dust of the desert, and the cold, snow and mud of Russia. Converted buses were often used as offices and mobile workshops. In addition to watching out for air attacks, ground personnel in Russia and the Balkans had to be constantly on alert to defend against attack by armed partisan bands.
An incident in early July 1944 illustrates the hazardous conditions German ground personnel dealt with on the Russian Front. After the Red Army launched a major offensive against Army Group Center during the battle for Belorussia, orders were received to evacuate a forward airfield and relocate its squadron to a base farther west. Lieutenant Karl Stein had flown several ground attack missions that day, and his ground crew fueled and armed his Focke-Wulf Fw-190F for one last sortie before heading west. His crew was loading their tools and equipment on trucks when the cry went up: “Russian tanks on the other side of the field!” The crew drove away in the nick of time as shells whistled overhead, while Stein took off to bomb and strafe the advancing T-34s before heading for his new base.
Under normal conditions, every Staffel had one man assigned to lubricate each plane daily using a portable greasing machine. When possible, aircraft were also washed daily. In the desert, where washing was usually impossible, the windscreens were cleaned before each flight and special attention was given to dust filters, lubrication and gun cleaning. Lines for oil, fuel, hydraulic fluid and oxygen were color-coded for ease of identification.
Spark plugs were changed during every 25-hour engine check. Each Werft had a small shop for cleaning and checking plugs before reinstallation. At the front, of course, squadron ground crews usually performed that chore.
The Germans learned a lot about aircraft operations in extremely cold weather from their experiences in Russia, Finland and northern Norway. Oil dilution was standard practice under such conditions. The Luftwaffe handbook for cold-weather operations contained easy-to-follow dilution tables for various types of engines. Squadron maintenance personnel typically changed an airplane’s oil on each 25-hour engine check. Where possible, waste oil was shipped to refineries for filtering and reconditioning.
Starting engines in cold weather was simplified at major air bases by internal combustion preheaters, although their use was curtailed during the latter part of the war due to fuel shortages. Maintenance personnel sometimes employed electrical heaters, though these proved impractical because of the need for dispersal of aircraft and difficulties in providing sources of electricity. In Russia the Germans sometimes resorted to using a dangerous method employed by the Soviet air force: They simply built a fire under the engine. The Russians often just stacked up some logs, while the Germans usually built fires in old oil or fuel drums.
Very little radio or radar repair was performed in the field, either by operating or service units. Squadron personnel could make minor repairs such as tube changes, but faulty units were typically replaced. Mounting design, requiring the removal of just a few screws and two or three connections, helped facilitate replacement. Defective units were then returned to the manufacturer or depot for repair and reconditioning. To overcome the difficulty and time necessary for shipment of defective equipment back from forward areas, specially equipped trucks served as mobile radio and radar shops. Manned by trained technicians, they were used extensively in forward areas.
As might be expected, the Luftwaffe’s spare parts program was well organized and efficient. There were three types of storage depots: those located in the Luftgau areas, which were completely stocked with parts; smaller stores called Luftparks; and depots on air bases with stocks based on the type of aircraft assigned there. All repair and service facilities requisitioned parts through channels. Strict adherence to this protocol gave the Luftwaffe complete, accurate spare parts consumption records, reducing waste and simultaneously ensuring adequate stocks. There appears to have been less “scrounging” in the Luftwaffe than in the U.S. Army Air Forces.
The Germans carried out an extensive aircraft modification program, especially when it appeared the war was going to continue for some time. Manufacturers normally incorporated changes and improvements on the production line, but many modifications were made in the field. Factory conversion kits with instructions were provided to the Werften, where the upgrades were made whenever possible. Approximately three-quarters of the modifications were structural, and as many as 300 changes were made to some aircraft in service for years.
A major modification could sometimes result in an aircraft designation change. For example, the Fw-190F-16/U1 variant resulted from a conversion kit that added wing racks for two fuel tanks or 250-kilogram bombs; the Fw-190F-3/R3 modification saw two 30mm MK 103 cannons installed under the wing; and the addition of a gun camera in the left wing of an Me-109G-10 changed its designation to Me-109G-10/R5. Similar modification kits were used by the USAAF.
All maintenance and repair units used standard Luftwaffe instructions, handbooks, pamphlets and forms. There were forms for routine maintenance and repair and for reporting defective or unsatisfactory materiel, and separate forms for aircraft, engines, propellers, accessories and equipment such as oxygen and armament. Publications prepared by the Air Ministry were supplemented by up-to-date pamphlets on maintaining and repairing aircraft, engines and equipment.
One aspect of German maintenance that stood out above all others to ensure efficient work in the field was the control and direction of design. Whenever possible, new equipment was designed to utilize parts already in service. This was particularly true with standard fittings, hoses, studs, gaskets, nuts, bolts, rivets, etc.—in fact, with all standard maintenance supplies—but the effort extended beyond small parts. New engines used the same accessories as engines already in service, unless the accessory was totally inadequate, and accessories were often interchangeable among engines produced by different manufacturers. Accessibility and ease of inspection and adjustment were also considered. Part numbers were standardized, with different manufacturers using identical numbers for the same parts.
In general, the policy on equipment requiring highly specialized maintenance was to change out whole units. If equipment was to undergo only limited maintenance and repair work in the field, the manufacturers allowed for easy removal and installation. In addition to using color-coded screws in electronic equipment, manufacturers attached sealed safety wires to complex components on engines and equipment not intended to be serviced or repaired in the field.
Performance was occasionally sacrificed to some extent to simplify upkeep. By using a limited number of standard tubes in radio equipment, for instance, the Germans simplified supply and repair problems, even though it meant a reduction in operating efficiency.
The Germans had an excellent training program for ground personnel. Whenever possible, field assignments took advantage of trainees’ civilian experience and education. At the beginning of the war, the training course for aircraft mechanics lasted 12 months and covered work on a number of operational aircraft and engines. The course included theoretical instruction, and after an examination the student began training in two-month intervals on engines and troubleshooting. Trainees worked in an engine factory, an airframe factory and an accessory or propeller plant. Then it was back to the school, followed by an exam. Men who failed the course at any stage were assigned to an aircraft service unit rather than a repair unit. The course was shortened to six months during the war, but the caliber of maintenance personnel generally remained high.
As in other air forces, some German pilots and aircrews developed close personal relationships with their ground crews, on whom their lives depended. Günther Rall, who ended the war with 275 victories, often spoke of his high regard for his personal mechanic. In April 1944, they sheltered in a cave near an airstrip west of Sevastopol. The Soviets were on the verge of recapturing the city, and when orders were received for his squadron to evacuate, Rall was determined not leave his loyal mechanic behind to face capture. Somehow he managed to squeeze him in behind the pilot seat of his Me-109G, and together they flew across the Black Sea to safety at a German airfield in Romania.
In summary, there were three major advantages to the German aircraft maintenance program. First, its sound organizational structure, which separated operational functions from administrative and supply functions, permitting each to carry out its mission unencumbered by unnecessary details. Second, the thorough and practical training given to maintenance personnel. Third, the constant effort on the part of designers and manufacturers to incorporate features that simplified and sped up repair and replacement in the field.
There were a few drawbacks to the German methods. The Luftwaffe relied mainly on civilian contractors for overhauls. Air forces should have a maintenance and repair organization capable of every type of repair or overhaul function. There was no direct liaison between the German Air Ministry and operational units, and communication was entirely by mail or report, resulting in a lack of coordination and loss of time in handling difficulties that arose.
Luftwaffe aircrews fought valiantly for their country, and earned an enviable reputation in the annals of air combat. But their accomplishments would have been impossible without sound maintenance methods and the men who put them into practice.
C.G. Sweeting is a U.S. Air Force veteran and former curator at the National Air and Space Museum. While there are no specific references on German wartime aircraft maintenance, to read about U.S. practices see the 1944 book AAF: The Official Guide to the Army Air Forces.
Originally published in the September 2011 issue of Aviation History. To subscribe, click here.