Maintenance Developments

On the outbreak of war No 40 Group was commanded by Air Commodore R W Thomas and comprised the following equipment depots

In addition, the undermentioned sub-depots were used for storing various items of equipment

It had been decided before the war that No 1 Maintenance Unit, Kidbrooke, was situated in a vulnerable position and the majority of the stocks had been transferred elsewhere. On 3 September 1939 the other six major MUs were in process of being reorganised as universal equipment depots. Kidbrooke was in use as storage for repairable equipment. During the four weeks that followed, No 7 Maintenance Unit, Quedgeley, No 14 Maintenance Unit, Carlisle, and No 25 Maintenance Unit, Hartlebury, were in addition all engaged in packing and despatching equipment and MT vehicles for the units of the Advanced Air Striking Force for service on the Continent. These depots also equipped and despatched Nos. 1, 2, 4, 5 and 6 Air Stores Parks, Nos. 1 and 2 Supply and Transport Sections and part of No 21 Aircraft Depot for the maintenance of the Force. Altogether 43 units and 933 vehicles were moved to the Continent during the month.

In order to provide for the rapid supply of urgent equipment and stores to the Air Stores Parks on the Continent an Air Transport Service was organised on 7 September to operate between selected bases in the United Kingdom and in France. The aircraft for the service were supplied on a temporary charter by Imperial Airways, Ltd. and British Airways, Ltd. Initially two aircraft were made available; two weeks later a further three with three more in reserve were supplied and arrangements were made for additional machines to be provided if necessary. The aircraft were accommodated and maintained at the National Air Communications base at Whitchurch (Bristol) but operated from Brockworth (Gloucester) aerodrome where a RAF Collection Centre was established to deal with the receipt and despatch of consignments of stores between the United Kingdom and France. The aircraft were controlled by NAC Headquarters at Whitchurch, the tasks and destination of the aircraft being notified to that organisation by Maintenance Command Headquarters via Air Transport Officers established at Brockworth and on the Continent.. The Air Transport Service remained in being until 9 December 1939 when it dosed down and was replaced by the normal sea transport.

On 1 November 1939 the reorganisation of the equipment depots on a universal basis was still uncompleted, and on 2 November the Air Officer Commanding the Group called a conference which was attended by all his unit commanders to discuss the means whereby the dispersion of stocks in all vocabulary sections to five universal maintenance units could be speeded up with a view to commencing issues on 30 November. Various measures for improving the situation which existed were recommended and agreed upon, but it was not until 15 December that the machinery for implementing the universal supply system was completed. An additional UED - No 16 Maintenance Unit - was formed at Stafford on 1 December 1940.

At a further conference held on 9 and 10 January 1940 to discuss the ways and means of increasing the supply efficiency of the universal depots, the Group Commander stated that the degree of competence to be aimed at was: -

He expressed the view that these standards of efficiency could only be obtained by establishing immediately routine processes in the transportation sections and at the stocking sites of the depots, and providing adequate personnel to supervise and undertake the work. In the discussion that followed it was agreed by the depot commanders that by working to a standard it should be possible to bring about the degree of efficiency demanded and recommendations were made as to the establishments required and the changes in administrative procedure necessary to produce this result.

On 19 January 1940 a conference was held at Maintenance Command Headquarters to discuss the space required by No 40 Group for equipment storage. It was then stated by the Air Ministry representative that storage for nine months stocks of equipment was desirable and that for this 9½ million square feet was required. It was estimated that the existing universal equipment depots and other storage, including No 4 Maintenance Unit, Ruislip, but ex-eluding No 1 Maintenance Unit, Kidbrooke, would supply 8 million square feet, leaving 1 million to be found. It was agreed that one additional universal equipment depot at least was necessary; in the meantime no hirings could be given up and other hirings would be required whilst additional UEDs were being built. At the moment, the full 8 million square feet was not available as several storage sheds at Quedgeley and Heywood were not complete and no sheds at Stafford were in use. It was considered that the best way to provide the additional area would be to establish specialised depositories and to ensure that steps were taken to dispose of obsolete stocks. The existing and proposed hirings were reviewed but these did not appear to provide the accommodation required and it was the opinion of the meeting that it would be necessary to use Kidbrooke (when emptied of repairable equipment) and other hirings in the London area to act as specialised depositories to the universal equipment depots.

A review of the accommodation available for the storage of mechanical transport vehicles showed that it would be necessary to find space for 12,800 vehicles in addition to the normal reserves. These vehicles would be received at the rate of 1,000 per month commencing 1 February 1940. It was estimated that the storage available when the MT sites at Heywood and Stafford were completed would be

leaving accommodation for over 7,000 vehicles to be found. It was suggested that the Air Ministry should approach the Automobile Association with a view to obtaining particulars of civilian firms and municipalities which could undertake to store and maintain small quantities of vehicles for the Royal Air Force.

By March 1940 the shortage of storage space in the Group presented a major problem. Only two depots - Hartlebury and Carlisle - were virtually complete. Heywood and Quedgeley were still far from completion. Stafford would not be able to hold stocks for another six weeks and Milton was still in the throes of reorganisation. It was estimated that the shortage of storage space on the provisioning programme was 2,500,000 square feet. In the sub-depots there was acute congestion. At Wembley and Hammersmith this was due chiefly to overcrowding with anti-gas clothing. At Coventry and Newport the cause was the vast amount of barrack equipment with dues in requiring another 400,000 square feet. In addition, sites totalling 200,000 square feet had been misappropriated at the UEDs for the storage of furniture.

Various measures were adopted to relieve the position. Arrangements were made for units to hold three sets of anti-gas clothing per man, much repairable equipment, including furniture, was transferred to the Civilian Repair Organisation, and steps were taken to persuade building contractors to work overtime to complete the depots still in course of construction. In April 1940 it was decided to use part of the MT sites at Carlisle, Hartlebury, Heywood and Stafford, which had been earmarked for reserve vehicles, for the storage of other equipment. Arrangements were also made for galvanised items such as dustbins, barbed wire, etc., and material in drums such as oil, caustic soda and silicol to be stored in the open. Available empty bomb stores were used for equipment which required no heating. Obsolete stocks at Kidbrooke were disposed of and the vacant space used for new furniture of which large quantities were being received. Action was also taken to get rid of obsolete engine spares and engines in store at Ruislip to provide additional space. Storage for approximately 30,000 parachutes was found in the White City exhibition buildings at Shepherds Bush, which were also called upon to house some of the stocks of anti-gas clothing. To find accommodation for the reserve MT vehicles displaced from the UEDs it was decided to utilise vacant balloon hangars, other than those in inaccessible parts, and to obtain particulars of open air 'hard standings ' normally used for agricultural shows, etc., which could be employed pending the availability of other storage. The Society of Motor Traders was also approached with a view to arranging for the storage of vehicles at trade garages.

The Air Council's decision to disperse the stocks of RAF equipment amongst several universal holdings and issuing depots presented a number of administrative problems. The chief of these was perhaps the question of how to co-ordinate the requirements of the various stock holders, and how to ensure that fresh stock was not purchased for one depot at a time when surplus stock of the same equipment was available elsewhere, and when one particular depot could not satisfy a demand, the quickest method by which stock available at other depots could meet the requirement.

During 1938 the staff of the Headquarters of Maintenance Command devoted continuous thought to the devising of a system which would overcome the difficulties, and in the autumn of that year submitted to the Air Ministry details of a scheme which provided for each equipment maintenance unit to have within its organisation a 'Master Provision Office' responsible for certain sections of the vocabulary of RAF equipment, regardless of whether the stocks of these sections were held at the maintenance unit at which the MPO was located or at other maintenance units. The special responsibility vested in each Master Provisioning Officer consisted principally of :-

The scheme originally put forward was not approved by the Treasury, and the Air Officer Commanding Maintenance Command was advised to reconsider his proposals. Immediately the war started, however, the objections of the Treasury were withdrawn and on 26 October 1939, after a number of amendments had been incorporated, the system for master provisioning at equipment maintenance units was inaugurated.

The new system, although it was ultimately most successful, did not, of course, come into being without many teething troubles. Much confusion was caused at the outset by disagreements amongst members of the Air Ministry, Maintenance Command, No 40 Group and the UEDs regarding responsibffities. The master provisioning offices suffered from a lack of personnel sufficiently skilled to undertake the work required. There were complaints from the Commands regarding delays in obtaining replies from the MPOs and the lack of information given in the replies received.

Immediately after the outbreak of war, No 41 (Aircraft Storage) Group was given the task of impressing the large numbers of civilian aircraft which existed in various parts of Great Britain. These aircraft, many of which had been employed in civil schools, were required for the expansion of RAF flying training and for communication purposes. The aircraft were at first inspected and reported upon by RAF engineers from units adjacent to the aircraft, but as the numbers to be taken over increased, arrangements were made for the inspections to be carried out by technical personnel from No 43 (Repair) Group. Owing to the work and the large numbers of aircraft involved, however, it was decided at the end of November to form a section under a Wing Commander engineer at No 41 Group Headquarters to undertake the impressment of aircraft. Attached to this section were four pilots from each of the two Ferry Pilots Pools for the collection of aircraft impressed. In December, arrangements were made for the inspection of aircraft earmarked for impressment to be undertaken by the Air Registration Board working in conjunction with the Group impressment officers. The numbers of civil aircraft impressed for training and communication purposes during the period under review were

November 1939	67
December 1939	52
January 1940	82
February 1940	48
March 1940	74
April 1940	34

On 12 September 1939 the methods existing in the Royal Air Force for the supply and equipping of aircraft were changed in the following manner

*Although the document states this group, it was actually in existence in September 1939, not being formed until 1 September 1940.

The scheme introduced for the final equipping of aircraft by the aircraft storage units was not extended to training and Fleet Air Arm aircraft beyond the fitting of items which should have been installed by the manufacturer. Training Command, therefore, continued to collect their aircraft from the manufacturers and to fit the final equipment at stations. Aircraft not immediately required by training units were delivered to the ASUs by the Ferry Pilots Pool.

The new arrangement for operational aircraft did not work satisfactorily at first, and six weeks after No 41 Group had assumed the responsibility only a very few machines had been completed. The reason for this was the delay experienced by the aircraft storage units in obtaining the necessary equipment from the depots of No 41 Group, due partly to the fact that those depots were in process of being converted from specialist to universal supply units and did not know what the depots contained, and partly because the production of some items by civil manufacturers was behind schedule. The situation eventually became so serious that Headquarters, Maintenance Command, ordered No 40 Group to carry out an investigation to ascertain which items were and which were not available. During the enquiry copies of all the demands outstanding were taken to the various depots and it was finally discovered that there were over a hundred different items which could not be supplied. A list of these was then forwarded to the Director of Equipment for investigation by his production staff.

The next step taken to overcome the shortage was to ascertain the possibility of obtaining serviceable equipment from the salvage sections of the repair group, but it was decided that any items forthcoming would not be supplied direct to the aircraft storage units but would be issued via the equipment depots in the normal manner in order that demands could be regulated and the ASUs relieved of the responsibility of testing the equipment.

In November 1939 the supply of operational equipment improved but the availability from production was still 25 per cent short. At this stage it became apparent that provided the equipment was available, the time taken by the average ASU to equip a twin-engined bomber aircraft to operational standard was approximately 14 days while smaller types were taking seven days.

The operational aircraft completed by the aircraft storage units of No 41 Group included the requirements of other users besides those of the Royal Air Force. In September and October 1939 aircraft were supplied to the Rumanian Government. In December, aircraft were sent to Finland and Yugoslavia. In January 1940 aircraft were packed and sent by sea to South Africa, and further supplies were despatched by air to Finland. In February, March and April aircraft were prepared for both the Egyptian and the Canadian Governments. The ASUs were also called upon to undertake work additional to their normal activities. For instance, owing to delays in the production of certain types of aero-engines during the early months of the war, numbers of aircraft had to be delivered to the Group with 'slave' engines which were removed, returned to factories and used for ferrying other aircraft. Meanwhile, the airframes were stored until sufficient engines became available. Then again, certain aircraft stored as reserves for operational squadrons had become out of date during their period of inactivity and had to be modified to the latest standard before they could be issued. In the case of Blenheim bombers, action had been taken to provide armour for this type of aircraft employed on the Continent, the installation being carried out by manufacturers' working parties. Unfortunately, however, no action had been taken to modify the aircraft in storage, consequently those despatched by the ASUs to the Continent to replace wastage were unacceptable to the squadrons and were sent back to be armoured.

During the middle of November 1939 the Group was ordered by the Air Ministry to assume the responsibility of allotting from operational units all aircraft that were redundant to their requirements, whether serviceable or not. This, of course, meant another addition to the work of the Group and a further restriction of the valuable storage space which was already showing signs of being inadequate to meet requirements.

As previously stated, the planned storage capacity of the Group was approximately 9,600 aircraft contained in 24 storage units, but only nine units were functioning on the outbreak of war. Two more commenced to take in aircraft during September 1939. In that month the eleven units between them received a total of 739 aircraft and issued 694, the majority of which were for training and required little work to be performed on them. The total stock in the Group at the end of September was 2,515. On 14 September the Group was informed that the estimated war wastage of aircraft in the Metropolitan Air Force was approximately 620 per month and the ASUs must therefore be prepared to issue up to this number at short notice. During the weeks that followed, however, owing to the lack of air activity, there was little indication to show when this figure was likely to be reached, and issues to replace wastage were only slightly higher than they had been under peace conditions. This, coupled with the fact that the despatch of aircraft to units overseas had been stopped by the Air Ministry on the outbreak of war, resulted in an accumulation of aircraft in the ASUs at the rate of 400 a month. Under these conditions it was estimated that unless additional covered accommodation could be made available the Group would have to arrange for at least 1,000 aircraft to be stored in the open by 1 April 1940. Pending information on the storage programme it was decided to provide space in the open for 500 aircraft by the end of December 1939.

During October 1939, 833 aircraft were received and 369 issued. The stock held rose to 3,324. In December the twelfth aircraft storage unit was opened - No 23 Maintenance Unit, Aldergrove - but gave little relief as receipts during the month were 527, issues 309 and stock 3,572. Very few of the issues during these months were for the replacement of wastage and were mainly for the re-equipping of units with new types and for the formation of new units.

Bad weather during December 1939 and January 1940 caused the aerodrome landing [surfaces] of several storage units and the roads leading to them to become unserviceable for varying periods, with the result that not only were receipts and issues restricted but the preparation of aircraft at the end of January was reduced to 60 per cent of the normal due to employees being unable to reach their places of work and the transportation of equipment from the supply depots being impossible. In January 694 aircraft were received and 500 issued, including 284 operationally equipped, which was the utmost possible with the equipment available. The stock at the end of the month was 3,766. In addition, a large number of aircraft were awaiting collection from the manufacturers and a still larger number were awaiting test. An improvement in weather conditions in February enabled the preparation of aircraft to reach 90 per cent of normal. 728 aircraft were received and 507 issued, including 317 equipped operationally. The stock rose again to 3,990.

During February Nos 1 and 2 Ferry Pilots Pools were transferred from the control of the Air Ministry to No 41 Group, although they remained positioned as 'lodger' units at the Fighter Command stations at Hucknall and Filton respectively. Temporary arrangements were also made for the RAF Component Field Force to collect their own aircraft from the ASUs pending the formation of a Ferry Pilots Pool for the purpose of flying aircraft to the Continent. The second packing depot (No 52 Maintenance Unit) for despatching crated aircraft overseas was opened at Cardiff on 3 February 1940.

On 8 March 1940 the capacity of No 41 Group to meet the full war requirements in aircraft wastage was reviewed by Headquarters Maintenance Command. It was estimated that with the initial equipment of the operational units at home and on the Continent at approximately 2,000 aircraft, the wastage for the following two months at sustained effort was 800 per month or 190 per week. For periods of intensive effort this might be increased to 280 per week and at maximum effort to 370 per week. The capacity of the Group to prepare operational aircraft at that date was, however, only 400 a month, the limiting factors being the rate of supply of operational equipment, contractors' ability to modify aircraft and, to a lesser extent, the storage accommodation available. If output was to be improved it was necessary to increase the production of equipment, restrict modifications to those really essential and improve contractors' capacity for embodying such modifications. A 25 per cent increase in the supply of equipment was expected within the next few months which, of course, would greatly facilitate the preparation of aircraft. Even, however, if the number of aircraft issued by the ASUs approached the estimated sustained rate of 800 a month, a limiting factor would be applied by a shortage of the number of aircraft supplied by the manufacturers. According to the production programme the number of operational types forecast for June 1940 was 600 only. Therefore, a number of reserve aeroplanes would have to be used to meet the requirement. With a combination of new production and reserve aircraft it was calculated that the full sustained rate of 800 aircraft per month could be maintained for two months, followed by 650, 550 and 600 for the following three months, i.e. an average of 680 per month. In addition to operational aircraft the Group had also the task of issuing an approximately constant figure of 300 trainers per month to replace wastage and for issues overseas to Dominions, etc. In order to fulfil its commitments, the aim of the Group was to build up a reserve of prepared aircraft amounting to a month's wastage at sustained rates, an achievement which, however, was restricted by the Air Ministry policy of giving priority to meet expansion and re-arming.

As a means of utilising the available equipment to the utmost extent it was decided in March that the Group Headquarters would indicate periodically to the ASUs the types of aircraft in batches of about a hundred which were required in order of urgency. This enabled the ASUs to demand from No 40 Group supply depots and the depots to provide the equipment required in the correct sequence, thus avoiding many delays which had occurred in the past.

Further developments during March were the opening of the thirteenth ASU (No 48 Maintenance Unit, Hawarden) and the receipt of information that 1,270 American aircraft (Brewster, Douglas, Lockheed, Harvard and Hudson types), additional to the 400 Harvards and 250 Hudsons ordered at the outbreak of war, were being sent from the United States. This brought the number of types of aircraft on order for the Royal Air Force to 48 and the number of variations to be stored in the Group to 71.

The total number of aircraft equipped operationally during March (five weeks) was 513 or 102 per week, an increase of 45 per cent over the December/January figures. This improvement was largely due to an increase in the supply of equipment and, to a small extent, to the method introduced of controlling the hastening of outstanding demands in order of priority of requirements. The number of aircraft received during March was 1,101; issues were 620, including 44 equipped operationally. The stock at the end of the month was 4,480 of which 600 were picketed in the open.'

The arrival of April saw the opening of four more aircraft storage units, bringing the total to 17. The new units were

The number of aircraft equipped operationally by the Group during April was 448 of which 341 were issued and the remainder taken into storage towards building up the reserve of one month's wastage at sustained rates which the commitments of the Group necessitated. The reserve at the end of the month stood at 228 against the requirement of 800. Ten days later Germany invaded Holland and Belgium, the British Air Forces in France went into intensified action and incurred rates of aircraft wastage which for some days averaged four or five times the assessed rates for sustained effort. The total number of aircraft received by the Group during April was 1,001. Total issues were 772.

The Air Council Enquiry into the Shortage of Aircraft Operational Equipment, February 1940

The concern felt by the Commands and squadrons after the outbreak of war over the difficulty in obtaining aircraft fully equipped for operations came to a head on 13 February 1940 when the Air Officer Commanding-in-Chief, Bomber Command, drew the attention of the Deputy Chief of the Air Staff to the serious position that had arisen through the shortage of equipment items necessary for aircraft to be used operationally.

An investigation into the situation was made forthwith by the Air Member for Supply and Organisation and on 19 February 1940 a special meeting to discuss the matter was held under the chairmanship of the Secretary of State for Air which was attended by members of the Air Council and representatives of the various Commands.

The Secretary of State said that the meeting had been summoned to consider the position revealed by the latter from the AOC-in-C, Bomber Command, regarding inadequate supplies of operational equipment. A paper explaining the situation had been prepared and circulated to those present by the Air Member for Supply and Organisation and the matter was so urgent as to warrant immediate attention. Urgent consideration would need to be given to what steps could be taken to remedy the position as speedily as possible.

During March 1940 two reports were forwarded to the Secretary of State by the Director of Aircraft Equipment Production giving details of progress made, and on 2 April the former called a second meeting to review the position. On this occasion the Commands were not represented. Regarding the adequacy of the pool of aircraft equipment, which at the time of the last meeting consisted of six months' requirements for a programme of 2,250 aircraft per month, the Director of Equipment stated that orders for equipment had originally been restricted to items common to all types of aircraft with a margin in the case of other items of 20 per cent above the aircraft orders already released. He had now been authorised to order sets of equipment for all types of aircraft due for production under the programme up to 1 July 1942. He was also authorised to call for delivery twelve months in advance, i.e. by 1 July 1941. In the circumstances he was satisfied as to the adequacy of the pool and it was now possible to place bulk orders which would facilitate the planning of production.

After discussion the meeting was of the opinion that no further action regarding the adequacy of the pool could be taken at present other than to await the results of the regular conferences that were to be held by the Director General of Production.

On 3 September 1939 No 43 Group Headquarters assumed control of the three Service repair depots

These depots, particularly Nos 30 and 32, were in the formation stage only and were fully occupied in endeavouring to obtain a smooth working organisation. Insufficient quantities of equipment and tools were available and although the numbers of personnel were adequate there were surpluses and deficiencies by trades which required adjustments.

Throughout September both Henlow and St. Athan were called upon to mobilise maintenance units for service on the continent of Europe in accordance with the 'Western Plan. On the 18th of that month Henlow, Sealand and St. Athan assembled personnel and equipment for the formation of five Service and one civilian Salvage Centres to undertake the salvage and disposal of crashed aircraft in the United Kingdom. Sites for the location of these salvage centres had been reconnoitred previously and they moved to their stations described on the dates stated.

A seventh salvage centre was planned in October 1939 to cover the more westerly part of England but it was not until March 1940 that the centre which as named No 34 Maintenance Unit came into being at Monkmoor near Shrewsbury. No 50 Maintenance Unit at Cowley was civilian manned except for officer personnel.

On 27 September 1939, No 43 Group became responsible for the technical administration of 15 emergency W/T fitting parties, the functions of which were the repair of communications damaged by enemy action. These parties were located at RAF Works Depots situated at various stations. They were handicapped during the first three months of their existence by the lack of trained personnel, hutments and equipment but fortunately were not called on to undertake any repairs. While waiting to perform the work for which they had been formed the personnel of the parties were employed on important duties in connection with the installation of R/T at Radar stations in Fighter Command

On 1 November 1939 it was decided to fit all combatant aircraft operating m the United Kingdom with one or another of three different types of radio equipment, and arrangements were made for aircraft to be flown into No 32 Maintenance Unit, St. Athan, for the work to be done. Considerable difficulties were experienced owing to the state of the aerodrome at St. Athan which became very soft in wet weather. It became necessary, therefore, to form mobile fitting parties and detach them to operational units to fit the special installations into aircraft at their home stations.

The three repair depots continued to suffer throughout October and November 1939 from the lack of equipment and tools. A further drawback was the fact at large numbers of personnel were either untrained or were reservists who were out of practice in their trades and had no experience of modern RAF equipment. The following work was, however, carried out

During December small quantities of equipment and tools arrived at the depots and it was decided that all engine repair sections should concentrate on the repair of Bristol engines, but Nos. 30 and 32 Maintenance Units were unable to commence the work owing to the lack of tools and test rigs. No 13 Maintenance Unit commenced the repair of Pegasus engines but were compelled to despatch other types to civilian contractors. This depot also received seventy aircraft (Hart Variants, Hurricane, Moth and Lysander types) for repair but the work could not be undertaken owing to a lack of spares and trained personnel. Towards the end of the month arrangements were made to form mobile repair parties at all depots to effect repairs to damaged aircraft on site when the work was beyond the capacity of units but not sufficient to warrant transport of the aircraft to a depot or contractor. Ten such parties were operating by the end of 1939.

An improvement in the supply of equipment and tools during January 1940 caused a corresponding increase in activity at the repair depots, but engine overhauls at Nos. 30 and 32 Maintenance Units still could not be undertaken owing to the lack of suitable tools and test equipment. The allocation of repairable equipment to the depots and civil firms by the Civilian Repair Organisation commenced to function during January, but, as the work came from a variety of sources, allocation of tasks was difficult to control and co-ordinate. Meanwhile, all three depots continued to mobilise maintenance units for service on the Continent.

On 9 February 1940, No 43 Group assumed technical control of the workshops at No 1 Maintenance Unit, Kidbrooke, and No 4 Maintenance Unit, Ruislip. These maintenance units remained under the administrative control of No 40 Group, so that the repair group was only responsible for the input and output of work to and from the workshops. This increase in repair capacity and the allocation of considerable quantities of ancillary equipment for overhaul from the Civilian Repair Organisation resulted in the stimulation of the activities of the repair depots during February. Electrical and wireless equipment awaiting repair at No 1 Maintenance Unit was diverted to the depots at Henlow and Sealand and the manufacture of engine packing cases, of which 28,000 were required, was transferred from No 4 Maintenance Unit to the St. Athan depot as the former was only capable of an output of 50 per week. All depots were engaged upon the removal of engines from unserviceable aircraft. The engines were despatched either to Training Command for instructional purposes or to the makers for modification and reissue. It was not possible to repair the majority of airframes as the aircraft repair sections at Nos. 30 and 32 Maintenance Units were not yet functioning. Progress was, however, made on the repair of 46 airframes in the aeroplane repair section at No 13 Maintenance Unit

The mechanical transport repair sections at all depots were fully occupied during February but owing to the shortage of spares it was only possible to turn out a total of 13 vehicles. Lack of tools and special jigs also severely handicapped all the engine repair sections. Thirteen mobile repair parties completed repairs to crashed aircraft on site during the month.

The organisation of and the output from the depots improved during March and April and the majority of the sections were fully occupied in the repair of ancillary items although shortages of spares and equipment were still experienced. Closer co-operation was maintained with the Civilian Repair Organisation and considerable quantities of repairable equipment were received. By the middle of April 37 aircraft of seven different types were undergoing repair or complete overhaul at No 13 Maintenance Unit. The other depots were still engaged on the removal of engines, and the repair of complete airframes and engines had still not commenced. The output of repaired MT vehicles increased during March to 29, and owing to a betterment in the supply of spares the improvement was maintained during April.

The work of fitting special installations in aircraft by the mobile parties continued during the early months of 1940 and was speeded up considerably, although progress was at times retarded by delays in the supply of equipment. By the end of April a total of 1,062 operational aircraft had been fitted. The parties formed for the repair of communications were also not idle. Although by March they had only been called upon to carry out nine repairs a considerable amount of work was performed in fitting ground station transmitters and receivers at various units throughout the country.

The salvage sections continued to increase in efficiency during the end of 1939 and the beginning of 1940. When they commenced operations they were siderably handicapped by a shortage of trained personnel and transport vehicles. By the end of December the initial difficulties of the centres had been mastered, although none was as yet working to its full strength of ten mobile sections. The following is a summary of the salvage operations carried out from the outbreak of war to the end of April 1940.

Month	Crash reports received	Inspections carried out	Aircraft repairable on site	Aircraft repairable in factories	Aircraft fit only for strike-off	Aircraft dealt with by other units	Enemy aircraft salved
September 1939	122
October 1939	348	336	39	183	114
November 1939	328	345	25	94	186	86
December 1939	333	378	26	72	92	196
January 1940	419	420	47	80	110	161
February 1940	302	294	29	59	93	115
March 1940	550	533	54	75	170	172
April 1940	501	500	54	41	150	175	3

On 4 September 1939 Headquarters of No 42 Group moved from Andover to Burghfield Common near Reading. Only three of the Group's proposed five ammunition depots were in existence when the war commenced. They we No 2 Maintenance Unit, Altrincham, No 11 Maintenance Unit, Chilmark, at No 21 Maintenance Unit, Fauld. Prior to the outbreak of hostilities, the demands for the supply of ammunition and explosives were submitted by units in the United Kingdom to No 2 Maintenance Unit. This cumbersome centralised procedure was unavoidable on account of the disposition of stocks. Immediately after the outbreak of war, however, the completion of certain building programmes combined with dispersal and balancing of stocks on a universal basis, enabled decentralisation of supply to be effected and Nos 11 and 21 Maintenance Units to be made self-accounting. It was also decided to make the fourth ammunition depot (No 28 Maintenance Unit, Harpur Hill) which was under construction, similarly self-accounting in all respects as soon as it was formed. A Master Provisioning Office for ammunition and explosives on the lines of those introduced in the equipment depots of No 40 Group was established at No 21 Maintenance Unit, Fauld, for the maintenance of stock at all the ammunition depots.

On 5 September 1939 the first four of the proposed seven air ammunition parks were formed at the following places: -

In addition, a small arms ammunition sub-store was established at Ruislip. The air ammunition parks were all situated east of a line drawn approximately from Edinburgh to Southampton, i.e. in the neighbourhood of the operational stations based in the east of England. The ammunition depots were place west of the line in areas as remote as possible from enemy bombing. The RAF operational stations based upon the ammunition parks drew all their supplies therefrom. The parks in turn replenished their stocks from their parent ammunition depot.

It was also arranged to base a fifth ammunition park (No 95 MU to be formed at Lords Bridge) upon No 11 MU, Chilmark.

Many of the existing RAF operational stations were, of course, situated in locations beyond easy reach of the ammunition parks, and on 1 October 1939 these were based geographically upon one of the ammunition depots as follows: -

Demands for ammunition and explosives to meet the requirements of overseas Commands, the Continental contingent and special issues to contractors were dealt with in the first instance by the Master Provisioning Officer who instructed the maintenance unit holding the largest stocks at the time the demand was received to effect the supply.

Immediately the air ammunition parks were formed they also assumed the responsibility for supplying operational stations with breathing oxygen. Under peace conditions, RAF units obtained their oxygen requirements direct from the British Oxygen Company who delivered the oxygen in large-capacity, high-pressure transport cylinders, from which RAF units filled theft aircraft cylinders. Aircraft cylinders were of 750 litre capacity at a pressure of 1,800 lb. Transport cylinders were of 18,000 litre capacity at a pressure of 3,600 lb. and each was capable of filling 10 aircraft cylinders, an action which reduced the pressure in the transport cylinder to 1,800 lb. It was then necessary to return the half-filled cylinder to the filling station for 'topping up' to the 3,600 lb. pressure. On the outbreak of war there were 11 filling stations established for the supply of breathing oxygen to the Royal Air Force. These were situated at Southampton, Greenwich, Wembley, Witham, Coventry, Wolverhampton, Irby, Rotherham, Leeds, Hull and Stockton-on-Tees. On 4 September 1939 the oxygen supply arrangements were switched from direct supply between the contractor's filling station and the RAF operational station to supply from the contractor's filling station through the air ammunition park to the RAF station, or through the parent maintenance unit (ammunition depot) in the case of stations not served by ammunition parks. As regards the Continental expeditionary force it was intended that the supply of oxygen would be maintained by mobile plants but none of these plants was available when the war commenced and it became necessary to deliver cylinders to France by air from the British Oxygen Company's filling station at Southampton. Returning aircraft brought back the empty cylinders for replenishment.

On 9 September 1939 the air ammunition parks took over the supply of anti-aircraft shells to Army anti-aircraft units situated in the vicinity of the RAF units based on the parks. This additional duty plus that of the supply of oxygen had not been provided for when the war establishments of the air ammunition parks had been worked out, consequently the parks found themselves considerably handicapped when they commenced operations by an insufficiency of personnel, transport and other equipment. One of the major difficulties of the parks resulted from the fact that gravity rollers and tarpaulins in the required quantities were not obtainable on the outbreak of war.

The belting of small arms ammunition in the early days of the war was not carried out at the air ammunition parks but at No 2 Maintenance Unit, Altrincham. The methods used were at first somewhat elementary, hand-operated machines being employed which could only belt 300 rounds per hour. During September, however, a number of power-operated 'Plessey' machines, each capable of producing approximately 3,000 per hour with unskilled labour, were obtained. Eventually twelve of these machines were installed at each of the ammunition depots at Altrincham, Fauld and Chilmark respectively and at the ammunition sub-store at Ruislip.

The fifth air ammunition park (No 95 Maintenance Unit) was opened on 16 November 1939 at Lords Bridge, near Cambridge. On 15 December the fourth ammunition depot (No 28 Maintenance Unit) commenced to function at Harpur Hill. Additional storages were provided at Ridge for No 11 Maintenance Unit, Chilmark, and at Holywell for No 21 Maintenance Unit, Fauld. The possibility of opening an air ammunition park to feed the units in Scotland was explored.

A conference held on 8 March 1940 at Maintenance Command Headquarters to review the position as regards the supply of ammunition, explosives and liquid oxygen by the units of No 42 Group under sustained war conditions showed that the air ammunition parks were holding more than the stocks laid down, and that they were ready for their war task. S hould it be decided to form an AAP in Scotland it was considered that it could be ready for action in ten days. The new ammunition depot at Harpur Hill although functioning was not yet complete and consequently had not taken over the responsibility for supplying its ammunition parks (Nos. 91 and 92 Maintenance Units). The arrangements for the supply of breathing oxygen appeared to be satisfactory.

The arrangements made during peace for the supply of aviation petrol and oil underwent a complete change when the war commenced. On 5 September 1939 all the stocks in the United Kingdom were acquired by the Air Ministry and held in the Air Ministry depots and petroleum companies' storages; the companies at this juncture being merged into a Petroleum Board, an organisation which operated as agents for the Air Ministry. The Petroleum Board took over control of the existing commercial fuel depots, the RAF reserve and distributing depots, the RAF rail cars and the stocks of TEL. Strategic dispersal of bulk stocks was made by means of large tanker vessels berthed in outlying northern areas of the British Isles. The plan for the supply and distribution of aviation fuel to RAF stations in the United Kingdom during the period of hostilities was amplified to permit issues from certain commercial depots in addition to the Air Ministry aviation fuel reserve and distribution depots. All these depots were renamed 'Distribution Points' and each Command was allotted a number of these DPs from which the aviation fuel requirements of their stations were obtained. The procedure was for units to forward their demands for fuel direct to the distributing point but the accounting of issues to the Service was undertaken by Headquarters No 42 Group Central Accounts Office, which was notified by both the distributing point and the unit concerned of the demands and issues made. The checking and maintenance of stocks of aviation fuel and oil was carried out by checking officers detached from Headquarters No 42 Group who were each allotted a number of distributing points within defined geographical areas.

A review of the aviation petrol and oil position in the United Kingdom held on 6 February 1940 showed that the total Royal Air Force stocks of aviation fuels (all types) was 509,189 tons and the ultimate total to be built up was 800,000 tons. The total tankage available for the storage of aviation fuels was for 616,700 tons of which 254,500 was hired from the Petroleum Board, 50,563 was in underground tankage hired at Backford, Cheshire, and the balance in tankage belonging to the Air Ministry. It was anticipated that additional tankage under construction at Air Ministry fuel reserve depots would be completed by the end of March 1940. The stock of lubricating oil on 8 February 1940 was 34,219 tons. By the end of April, stocks had risen to 607,343 tons (186,460,647 gallons) of aviation fuel (all types) and 35,899 tons (8,974,872 gallons) of lubricating oil. The total weekly issues of aviation fuel and lubricating oil at this period, which included the requirements of Royal Air Force units, the Admiralty, flying training schools, national air communication units, the War Office and aircraft contractors and civilian firms, was: -

Week ending 25 April 1940	Aviation fuels (all types) 6,469 tons (1,929,443 gallons). Lubricating oil 212 tons (53,032 gallons)
Week ending 2 May 1940	Aviation fuels (all types) 5,044 tons (1,528,846 gallons) Lubricating oil 121 tons (30,304 gallons).

MT sites at five UEDs at 750 each	3,750
Wembley and Park Royal	1,600
Total	5,350