Observers and technical personnel sent over by the United States to assist the Royal Air Force in the various theatres of war should have valuable information on wartime repair and maintenance for the United States Air Corps.
Britain has organized this work with great detail. Use is made of every part of a crashed plane. Over there they have learned much from experience and, of course, they have had the handling of American as well as British types. The organization for the repair of the equipment of Royal Air Force units based in Britain is controlled technically from a directorate in the British Ministry of Aircraft Production. Executive action is controlled jointly by a Royal Air Force group in the Maintenance Command and a Civilian Repair Organization.
Royal Air Force Service Repair Depots and the Salvage Organization, with its many units geographically spaced throughout the country, are contained within the Royal Air Force Group.
Salvage Units are equipped with specialist transport which includes mobile workshops and cranes, light utility vans for the transport of personnel, trucks for equipment and the 60’ long girder trailers colloquially known as "Queen Marys" on which complete fuselages and wings may be transported to appropriate repair centers.
A Civilian Repair Organization, which has been brought into being since the outbreak of war, coordinates the activities of the many civil firms whose services have been enlisted to deal with the vastly increased volume of repair work on airframes, airframe components and parts, instruments and other technical equipment.
This organization is also used to assist in maintenance when the volume of work arising due to periodic inspections, is beyond the the capacity of squadron and station technical personnel. The increased volume of repair work on engines, propellers, and other accessories, is being dealt with largely by daughter or fringe firms, who are associated with the main engine and propeller manufacturers.
Before the war, airplane maintenance undertaken by service personnel attached to squadrons and stations included a considerable amount of repair work, in addition to the routine "maintenance inspections," adjustments, replacements, and the like necessary to keep their aircraft in an airworthy condition. Since the war began, however, maintenance has become a more serious and specialized job. This has involved some reorganization in the duties undertaken by squadron and station technical personnel, and the majority of the repair work is now dealt with by the repair organization. Each station from which many squadrons may operate, however, has an engineer officer with a staff of mechanics and workshop equipment sufficient to cope with the maintenance of and minor repairs to all the aircraft at that station, in other than very exceptional circumstances.
The method and technique employed is comparable in essentials with that used on commercial airlines before the war, but is amplified, and, of course, greatly speeded up to include the maintenance of purely operational equipment as well as the basic engine and airframe routines. Time between overhauls have also been extended owing to the necessity of keeping aircraft in the air for the greatest possible time, consistent with reliability.
The most recent organization used by fighter units for the maintenance of their aircraft is known as "Echelon," and it is designed to avoid the movement of all "material" above an absolute minimum when the squadron moves its personnel from one station to another. Thus during such a move, merely the personnel, certain specified equipment and transport are moved, and the actual aircraft with all its kit and maintenance personnel which is termed the “Echelon" remains at the station and continues to maintain the aircraft, although a new operating squadron may have taken over this aircraft. This essentially is a similar scheme to that used by the Germans, and has the advantage of continuous maintenance and the minimum of transport difficulties consequent upon any squadron movements. This organization is standard to all operational aerodromes whatever their geographical or strategic location.
In the matter of periodic servicing and inspection, changes have been made, due to the stress of wartime conditions.
Before the war, a system of graduated maintenance operations and inspections was in force for performance after every 20 and 40 hours flying with major inspection normally at 120 hours. Now, however, minor inspections are made after every 30 hours flying with the major inspection normally at 240 hours.
Commands have latitude to increase the intervals between minor and major inspections, and to vary the inspections and operations in accordance with experience of the particular type with which they are concerned. The general principle, however, that maintenance must be organized in a series of graduated operations designed to ensure progressive repair and replacement is adhered to.
A definite life between complete overhauls is fixed for each type of engine, in the first place by the Ministry of Aircraft Production, but, after experience with the type, commands are empowered to vary this interval. A life between complete overhauls is not fixed nowadays for the airframe. As a result of a major inspection, the airframe is either certified as fit for a further period of flying, or is handed over to the repair organization for complete overhaul.
The equipment used by the maintenance personnel is standardized at all Royal Air Force aerodromes, whether front line fighter and bomber stations, or merely reserve training or communication fields. Each fitter and rigger is issued with a standard kit of tools, and there is, in addition, a "flight kit" comprising more elaborate and special tools, also an "engine kit" which includes all tools and devices peculiar to the power unit of the particular aircraft to be serviced.
In the case of crashed aircraft, the damage done is summarized in a report and is then classified and placed in one of the specified "categories." These cover crashes which can be repaired in the field, those which must be transported to a repair center (or, perhaps flown to a repair center after a temporary repair on the site) and those which are beyond economical repair. Those beyond repair are returned to particular units in the repair organization where all components, parts and materials that can be used again are carefully saved, the remainder being reduced to produce. There is also a scheme by which operational aircraft damaged by enemy action but still airworthy, can be flown in to repair centers for quick repair.
Operational and training stations are, therefore, relieved of all responsibility for complete overhauls and major repairs to equipment. These are dealt with by the repair organization, the work is fed in to repair capacity, service and civilian, which is widely dispersed throughout Great Britain. Specialist work demanding great skill has to be catered for, and special equipment has to be set up at centers dealing with engines, propellers, armament and the many types of aircraft instruments.
For some types of equipment, Royal Air Force resources at Service Repair Depots afford the main capacity, and at the same time, facilities for practical training repair and maintenance.
Engine Repair Depots are sometimes operated by civilian firms under contract, these firms having been experienced in peacetime in engine production, repair, or some associated activity. The Civilian Repair Organization has also established many centers for aircraft repair and other work of a specialist nature by adapting factories and premises used for entirely different activities in peacetime.
The maintenance and repair of US planes raised many difficulties in the early stages of their arrival in Britain. This was bound to arise, due to the haste with which orders had been placed, transfer orders accepted, and reception organized. Descriptive technical literature and information on accepted inspectional and maintenance routines for these types was difficult to obtain.
The installation arrangements on American types were designed mainly to meet peacetime requirements. Conduits, control runs, etc. were tidily built in, and were accessible for maintenance and inspection only by removal of various panels. British operational aircraft look untidy in comparison conduits, control runs being draped, it almost seems, haphazardly around the ship but that apparent untidiness is the result of long standing operational experience and spells accessibility, which means a saving of many hours when aircraft are grounded for maintenance attention. Thus, although US aircraft are certainly no more complicated in essentials than are the British types, the impression of complication may be given by the number of inspection panels which have to be removed to get at parts of the aircraft. In peacetime, these parts might need examination only at comparatively long intervals, but during active service, they must be readily accessible at all times.
The training of British personnel in the servicing of US aircraft is quite an easy job now that information and personal advice is available, and no more difficulties should be encountered. Apart from the excellent workmanship and design of US airframes which are too well known to need praise here, the individual items which have received most praise and most criticism are, respectively, flying controls and engines.
Without exception, pilots are enthusiastic about the lightness and positiveness of the controls on American aircraft, large or small. The trouble with the engines is more difficult to analyze. In the earlier cases, boost control gave trouble; British pilots, experienced as they were to automatic control of boost with throttle opening, neglected to watch the boost pressure, and on occasions, took off with full boost at ground level which did the motors no good at all. With American liquid-cooled engines, a lot of trouble was encountered in accessory drives which might be put down to the usual "teething" troubles of a type new to American manufacturers, but, of which the British have had long experience. American radial air-cooled types in commercial aircraft have, of course, proved themselves second to none, and any trouble they may have experienced in service in the Royal Air Force are probably due to the enforced necessity of maintaining full power over long periods for obvious reasons. These troubles are, of course, not confined to American types.
Another problem which is gradually being cleared up is that of adequate provision of American aircraft spares, which, during the early stages of deliveries, arrived in unbalanced and irregular batches.
At that time many perfectly good machines were grounded through lack of some component which had to be replaced owing to wear or to enemy action. In some cases, grounding was due to lack of special tool kits required for particular engines, and again in the early stages due to lack of transport organization and other causes there were instances of a "single tool kit" for the Allison engines of Tomahawks being passed from aircraft to aircraft, and sometimes even loaned by one station to another.
Without having detailed and up-to-date information on the maintenance methods of the US Air Corps, it would be reasonable to assume that they operated as did the Royal Air Force in peacetime on the basis of thoroughness rather than that of speed. The British plan may well be of assistance now that the organization faces up to the demands of active service.
This article was originally published in the March, 1942, issue of Aviation magazine, vol 41, no 3, pp 122-123, 125.