Air of Authority - A History of RAF Organisation

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The Preparation, Storage and Issue of Aircraft by No 41 Group

The following is extracted from Chapter 6, AP3397 'Maintenance' (AHB - 1954)

The Types of Units, their Disposition and Development from May 1940 to May 1945

On 20 May 1940 the technical control of No 41 Group passed to the Ministry of Aircraft Production.  At that time there were some twenty-one Air Storage Units (ASUs) in operation and these were mainly located in the west and West Midlands.  They normally consisted of five or more groups of from nine to fourteen hangars, dispersed adjacent to an aerodrome which, in the majority of cases, was shared with some other non-operational flying unit.   Additionally each unit had a number of dispersals or air storage parks, situated within towing distance of the airfield, which, together with one or more satellite aerodromes, were used for the open-air storage of aircraft.  The opening of No 44 Maintenance Unit, Edzell, and No 51 Maintenance Unit, Lichfield, brought the total number of ASUs operating on 1 August 1940 to twenty-three.

There was only one satellite aerodrome open on 1 December 1940, namely, Slade Farm, but a decision was made on that date to disperse operational aircraft on satellites where these were available.  Instructions were therefore issued to air storage units with affiliated satellites to use them for this purpose, providing that the landing strip was serviceable and a minimum of ten aircraft could be so dispersed.  Unserviceable satellites were to be made serviceable as soon as possible, with the aid of civilian contractors, but tracks and buildings were to be kept to a minimum, wind indicators being of the smoke type.  Provisional approval was obtained on 22 February 1941 for establishments at both Service and civilian manned satellites, based on an 'opening up' figure of twenty-five aircraft.  It was also decided that satellites should be filled to capacity directly the weather improved.  It was hoped that by 1 April 1941 twelve of the fifty projected satellites would be open, but this proved to be too optimistic and only Slade Farm, Middle Farm, Berrow, Hornby Hall and Aberffraw were actually functioning on that date.  Further satellite aerodromes continued to come into operation as the year progressed, eleven being opened during May, four in June, seven in July and three in August, bringing the total number to thirty.

The number of air storage units was reduced to twenty-two on 15 July 1942 when No 37 Maintenance Unit was closed down owing to the handing over of RAF Station, Burtonwood, to the United States Army Air Force.  The aircraft held there were withdrawn to other ASUs, the technical equipment being returned to store and the personnel posted elsewhere.

The air storage units were grouped, for administrative purposes, into three regions, Northern, Midland, and Southern.  On 21 April 1941 a Wing Headquarters was formed in each region, the Commanding Officer of each being responsible for the administration of the ASUs in that region.  This normally consisted of ensuring that orders from Group HQ and other higher authorities were fully implemented.  They also formed a reserve headquarters in the event of Group HQ being temporarily put out of action by enemy attack.  These Wing HQs were disbanded on 21 November 1942 as it proved impracticable to find employment for more than five officers without duplicating the work of Group HQ.  There continued to be a need for the short-range supervision of units within the three regions so each Wing HQ was replaced by five regional staff officers who were located at the regional Air Transport Auxiliary ferry pools at Kirkbride, Hawarden and Aston Down.  The houses occupied by the Wing HQ were, however, retained under caretakers in case a future emergency should necessitate decentralisation.

In September 1944 there were still twenty-three storage units in operation with thirty-two satellite landing grounds and eight purgatory storage units attached to them.  These remained comparatively unaltered until the end of the war in Europe when a redisposition became necessary to meet the changed situation.

The Supply of Aircraft by No 41 Group during the Battle of Britain2

On 1 August 1940 the Group consisted of eleven partly developed Air Storage Units (ASUs) that had been in existence since before the war.  Ten of these were civilian manned and each unit had an establishment of 9 officers and about 630 other grade personnel.  A further ten units were in process of forming and were sufficiently developed to take some share of the load, although buildings and other works were completed to only a fraction of the final scale.  The shortage of personnel at most of the eleven original units had been made up during May and June by attaching some 800 airmen to the civilian manned units, but by August 1940 many of the same personnel had been transferred to RAF formations.

From the beginning of the war until June 1941 the Group fitted all 'service fit' equipment on new aircraft, so that during the Battle of Britain, they had to fit such items as guns, sights, firing mechanisms, most of the wireless equipment as well as making them operationally serviceable.

The ferry organisation for the delivery of aircraft at this time was under No 41 Group (later controlled by MAP) and consisted of the Air Transport Auxiliary (ATA) formed in April 1940 to ferry aircraft overseas.  In the period of the Battle of Britain the ATA were primarily responsible for ferrying from factories to the ASUs and the Service pilots from the ASUs the user units, but this division was by no means rigidly adhered to.  The organisation had a hard but exciting time during the period of the battle.  The rapid increase to nearly 4,000 aircraft movements a month in August 1940 was beyond their capacity and the Group had to call on the operational Commands to collect a proportion of their own aircraft.  The fighter squadrons frequently moved at short notice from the station quoted the day before and extra trips were incurred in finding them.  This added to the difficulties of transporting ferry pilots back to their base and of Group HQ in keeping track of them to allot their next task.  The aircraft were armed for delivery during this period but ferry pilots were instructed to evade combat unless this was unavoidable, and in consequence there is no record of this occurring, as was the case with deliveries to France before the evacuation.

The difficulties of the Group were greatly reduced by being able to start the battle with a good reserve of fighter aircraft, a substantial proportion of which were ready and complete to operational standards.  The supply of equipment, although still not in step with the supply of aircraft, had improved considerably and the controlling organisation at Group HQ had behind them the experience of high-speed supply to the Continent during May and June 1940.

It had been the rule to prepare aircraft to operational standards according to the rate of input, but with the start of the battle, with its high wastage rate, preparation at the rate of input was not enough.  The lag had to be overtaken and aircraft prepared much faster than they were being received.  The units therefore had to work seven days a week and for as many hours daily as they could.  A good deal of time was lost in the early stages due to air raid warnings, and there were twenty-two actual attacks on No 41 Group units, resulting in a small number of casualties, damage to hangars and to some 54 aircraft.  There was a shortage of armourers and of ground equipment and ASUs had to obtain a good deal of assistance from neighbouring flying training schools.  Exceptional efforts were necessary in order to obtain the aircraft equipment quickly.

The urgent need for the aircraft, enhanced on occasions by Fighter Command pilots standing by waiting to fly them away, formed an incentive which had a remarkable effect on the spirit of the personnel,  Service and civilian alike, and spurred them on to overcome difficulties, work long hours and turn out aircraft faster than they had ever done before.

In the first week of August 1940 the Group had a reserve of 5,300 aircraft of all types and the average monthly turnover for the previous three months had been 1,640 received and prepared, 1,420 issued.  During August/September the turnover rose to 1,790 received and 1,970 issued, the increase consisting mainly of Hurricanes and Spitfires, the two fighters most used during the battle.  On 8 August the total reserve of these two types was 572, of which 290 were complete to operational standard and ready for issue.

The demands and issues of single-seater fighters during the next four weeks was at the average rate of 212 a week, whilst receipts averaged 143 a week.  The reserve fell to the lowest point on 13 September with 173 Hurricanes and 81 Spitfires, of which 93 were complete and ready.  In the following four weeks demands and issues averaged 147 a week whilst receipts averaged 150.  The increase in deliveries from factories, and especially from the repair organisation, was very noticeable after the first week or two of the battle.  The reserve of aircraft of these two types rose slowly but steadily from 13 September, but it was not until the end of November that the commencing figures were reached.

With a reserve of aircraft, which at no stage of the battle was ever exhausted, there was no difficulty or delay in meeting demands as they were received.  These demands mostly came in between dusk and midnight and were dealt with at the same time as the night staff were completing the 'daily aircraft states' from the telephonic returns from air storage units.  The allotments to user units were made at once and signalled to all concerned.

At times during the first four weeks of the battle the demand rose to between 50 and 70 fighter aircraft a day.  This was three times the rate of input of new or repaired aircraft and it was calculated that at that rate of consumption the reserves of aircraft would have been exhausted in 10 days.  Fortunately this rate of demand was never sustained for more than three consecutive days and therefore the reserve was never exhausted.

Organisation of the Ferry Pools - November 1940

Diagram 11

The No 41 Group Headquarters Organisation for Planning the Preparation of Aircraft

Increased production from the aircraft factories and increased demands from the Service necessitated a system of planning in order to make the best use of available storage and preparation capacity, and also to ensure that all requirements were satisfied as speedily as possible.  A memorandum on the organisation of staff duties to implement the planning was issued on 17 October 1942 and planning on these lines was introduced in the following November.  The system underwent several detailed modifications during the next few months before taking shape in its final workable form in February 1943, as follows: -

Extent of Planning

The planning fell into two distinct phases: first phase planning, which comprised one comprehensive plan drawn up to cover the preparation of all types of aircraft over a definite period of time, and second phase planning, which consisted of a series of additions to and deletions from the first phase plan in order to meet changing requirements within the period covered.  Both phases of planning detailed the quantity of aircraft which would be allocated to units from production and repair, together with the quantity of aircraft that were to be prepared by units to meet requirements.

Period of Operation

This was from the eighth of each month until the seventh of the succeeding month and this period was chosen for two reasons

(a) In order to obtain the full benefit of the Ministry of Aircraft Production (MAP) short-term forecast of aircraft available during the calendar month, which was not received until the fourth of the month.

(b) To allow for the time lag between the completion of an aircraft at the factory and its arrival in No 41 Group.  The period selected ensured that the input of aircraft to No 41 Group approximated to the output from the factory over the calendar month.

Planning Input First Phase

A conference was held on the fifth of each month under the Deputy Senior Maintenance Staff Officer and attended by the regional engineer and equipment staff officers, together with representatives from the allotments, engineer and equipment branches of HQ, No 41 Group.  The MAP forecast was presented, each type of aircraft was considered in turn and a distribution arranged among the holding units for that type.  The factors governing distribution were, broadly, the capacity available at any unit to store, disperse and prepare the aircraft and the necessity to maintain an even distribution among all units in order to facilitate provisioning and preserve the continuity of preparation.

The practical difficulties connected with the calculation of the best distribution were considerable as all allocations were dependent on so many different factors, with the overriding consideration that the time which could be allowed for forming the first phase plan was limited, as it had to be finished before the second phase plan could be started, and yet both plans had to be forwarded to units before the seventh of the month.  A wall chart was therefore used which showed present stocks and number of aircraft prepared during the previous month, by types, at each unit.  The proposed allocations were added to this chart as the conference proceeded so that the allocation of a specific type to a particular unit could always be made in relation to the distribution of all types within the group as a whole.  Detailed information was supplied by the regional officers.

Planning Preparation First Phase

The preparation plan was compiled as soon as the input plan was ready, and was based on allotment staff estimated requirements for that period.  This information was supplied on a special form which was subsequently returned to the allotments branch with the last column completed, thus presenting a picture of the extent to which requirements would be met.  The capacity of units to prepare aircraft was assessed from past records and expressed in index points as a theoretical average.

Four-engined aircraft 3 points
Twin-engined aircraft 2 points
Single-engined aircraft 

1 point

Trainer or commercial aircraft point

All tasks were allocated and the index points continuously recorded as a cumulative total against each unit, so as to ensure that the work was within the unit's capacity and was being evenly divided.  The details of the plan within these limits were worked out with the production teams concerned with each type, depending upon the amount of work to be done and the number and state of the aircraft available.

The tasks allocated under this system were notified to each unit as a 'primary target' with maximum priority.  Where this did not cover estimated requirements, the less important of these tasks were notified as a 'secondary target' and the preparation of these aircraft was not commenced until the capacity became available without interfering with the completion of the primary target.

During the month it was seldom necessary to make any alteration to the first phase input plan, except in so far as aircraft had to be diverted to meet the special requirements of the second phase preparation plan.

Planning Preparation Second Phase

New requirements and cancellation of existing commitments were constantly occurring and it was necessary for these to be added to or deleted from the targets as they arose.  The cancellations were straightforward and when they reduced primary targets aircraft were upgraded from the secondary targets to take their place.  New requirements, however, were dealt with by one of the following methods

(a) A direct addition to a primary target where this could be done without overloading.

(b) As an addition to the primary target and, in order to provide the necessary capacity, a corresponding reduction from primary to secondary targets of some other types required on lower priority.

(c) As an addition to the primary target with an instruction to the unit concerned to work overtime.

(d) As an addition to the secondary target.

The selection of the most suitable alternative was dependent upon the capacity available and the urgency of the requirement.

Planning Preparation

Standing Instructions. In order to provide for unforeseen requirements, and to ensure that the efforts of units were only directed towards the preparation of aircraft that were required, a standing instruction was issued detailing the quantities of each type to be held in Class I primary and Class I secondary.  The preparation of aircraft against this standing instruction was only undertaken on priority after both primary and secondary targets had been completed.

Summary of Method of Control

The control by HQ, No 41 Group of the flow of aircraft passing through its units may be summarised as follows: -

(a) First and second phase input plan.

(b) First and second phase preparation plan.

(c) Units planned their work to comply with

(i) The primary target.

(ii). The secondary target.

(iii) The standing preparation instructions.

Organisation of Staff Duties

There were two branches of the policy staff controlled on behalf of the AOC by the Senior Maintenance Staff Officer (SMSO) and the Staff Officer-in-Charge of Administration (SOA).

The SMSO laid down the policy for the preparation of aircraft, issuing instructions to the heads of the Services accordingly, who were responsible through their organisations for its execution.  Matters affecting those services which were the concern of the SOA were passed to him for action.

Organisation, HQ No 41 Group - June 1940

Diagram 12

The supply of aircraft was the operational function of the Group and the allotment staff therefore took the place normally occupied by the air staff (operations) in an operational group.  Part of this staff was responsible for the statistical side of planning and another for progress.

Planning Section

In order to assist the development of advance planning it was decided on 25 May 1943 to form a planning section within the allotments branch.  The aim of the new section was to collate and analyse available information and records for reference by all branches of No 41 Group, and thereby form a basis upon which could be planned the various functions of the Group.

Preparation Teams

There was an internal reorganisation within HQ, No 41 Group on 1 May 1944, when the existing 'production teams' were superseded by what were termed 'preparation teams.'  Five of these teams dealt with power-driven aircraft, each team specialising in certain types and makes, a sixth team dealt with all gliders.  Their function was to deal with the aircraft for which they were responsible from the time that they left the contractors' works or other sources of supply until, after preparation, they were ferried to their operating units.

The Reorganisation of HQ Responsibilities

On 27 May 1944 the title of the branch concerned with the supply aspect of aircraft was changed from 'Allotment' to 'Aircraft Supply,' the head of which was to be known as the Chief Aircraft Supply Officer (CASO).

At the same time Org 4, the department responsible for flying matters, was transferred to the maintenance staff, where it functioned as a separate branch under the senior maintenance staff officer.  Its responsibilities were

(i) Flight test procedure.

(ii) Aircraft handling notes - flying limitations, contractors' flight test schedules and notes.

(iii) Ferrying of gliders and all ferrying to and from satellite landing grounds (SLGs).

(iv) Suitability of maintenance units and SLGs for operation of types of aircraft.

(v) Organisation and flying discipline of aircrews.  Flying assessments.

(vi) Flying personnel facilities and maintenance units from an air aspect.

(vii) Supply of test pilots to meet the emergency requirement of industry and to test Category 'AC' aircraft in transit when required.

(viii) Advice to other branches on flying accidents and log book endorsements.

(ix) Training. (Flying and ground personnel for aircraft taxying employment.)

(x) Distribution of flying personnel.

All other aspects of flying and airfield control remained the responsibility of the senior organisation staff officer.

Organisation, HQ No 41 Group - May 1944

Diagram 13

Amendments to the Monthly Target Scheme

On 30 September 1943 it was decided in the light of experience to introduce certain amendments to the monthly target scheme, in order to give units more advanced information on future targets and thereby avoid the monthly break in production which was then occurring, and to allow the system to become more flexible in order to facilitate the rapid preparation at short notice of high priority requirements.  The procedure was therefore adopted of issuing the targets as usual on the seventh of each month but making the preparation period run from the fifteenth of one month to the fourteenth of the next month, thus enabling units to plan for at least one week ahead.  Owing to the impossibility of anticipating production for the last week of the new period, it was also decided to make future targets cumulative, in that arrears from one period were to be carried forward into the next.

The existing system of denoting priorities by primary and secondary targets was cancelled and all requirements were henceforward sent out as one target.  Unless otherwise stated the quantities of each type on the target were prepared on an even-flow basis over the whole period.

The monthly production reports from units were continued, but as the introduction of specialisation had robbed them of their comparative value publication of these figures was therefore discontinued.

The Technical Organisation of Units

The technical control at units was carried out by a chief technical officer through the medium of the appropriate specialist officers.

The Inspection and Servicing of Aircraft in Storage3

New or repaired aircraft were inspected on arrival by the Unit Inspection Department (UID*) and, except for those aircraft required for the monthly target, were then prepared for storage. Preference for storage under cover was given, where available, to aircraft of wooden, composite or fabric covered construction.

After the aircraft had been prepared for storage, routine maintenance inspections were carried out at intervals determined by the conditions under which they were stored.  Where this was at satellites, dispersal fields, or in super-robins, robins and blister hangars, the period of storage was divided into inspections for each trade at daily, weekly and four-weekly intervals.  On aircraft stored in proper hangars this monthly inspection was carried out only at three-monthly intervals, except for the inspection of guns and turrets which was normally carried out monthly.  A four-weekly inspection was always carried out on aircraft which were moved into hangars from dispersal, after which the hangar cycle of inspections was adopted.

All stored aircraft, with the exception of a list of certain types (mainly the metal aircraft), were passed at intervals to the UID who carried out the inspections applicable to a new arrival.  Rectification work and air test followed after which the aircraft were again prepared for storage as before. For aircraft stored in the open the interval was a minimum of three and a maximum of six months, but for aircraft stored in hangars this was extended to six and twelve months respectively.

*Each unit had what was designated as a Unit Inspection Department (UID) whose function was to carry out independent inspections of aircraft with the object of maintaining a recognised standard of preparation and issue The UID not only ensured that aircraft and equipment were issued to user units in the best possible condition but also formed a medium through which faults on production aircraft could be more readily detected and reported, thereby easing the work of the unit in the future.

Picketing In the Open

The general method of picketing aircraft in the open was of a temporary nature using concrete blocks and screw pickets, the number and disposition of which were in accordance with instructions laid down for each type of aircraft.  Where permanent concrete anchorages were available they were used, but no provision was made to extend them as it was considered that this type of picketing did not give the necessary flexibility required for a Group handling so many different types of aircraft.  All other normal picketing precautions, as applicable, were also employed, such as chocks, locking controls, covers, etc, etc.

Functional Tests of Aircraft Hydraulic Systems

In an amendment to No 41 Group Technical Staff Instructions on 30 May 1944 it was laid down that ground functional tests of hydraulic systems were to be carried out on all aircraft before flight if these systems had not been air or ground tested for a period exceeding two months.  They were also to be carried out if any work had been done which might affect the functioning of these services.

Where this could not be done in full due to lack of equipment on satellites or for any other reason, it was brought to the notice of the collecting pilot, who signed the Form 1860 accordingly.* It was left to his discretion as to whether he took the aircraft or not.  In all instances where the undercarriage system was unserviceable or there was no emergency system the pilot flew the aircraft with the undercarriage locked in the down position.

* Form 1860 was made out for every aircraft in stock and comprised a complete history of that aircraft whilst in No 41 Group.  It was divided into sections covering leading particulars, engines, inspection on receipt by UID and Equipment Section, modification record, STI record, routine maintenance, record of work carried out, preparation for functional tests, certificate of fitness for issue, daily inspection and final certificate.  This form was retained by the ASU on allotment.

Aero Engines - Protection from Corrosion by Inhibiting

Experience had shown that little more than seven days was sufficient to allow serious internal corrosion to develop in an engine which had not been run during that period, and on which anti-corrosion treatment had not been carried out.  The only alternative to anti-corrosion treatment would have been repeated engine running, and as the limit for oil priming was five days this would have meant an engine run at least every five days.  This repeated running would have meant an uneconomical use of man-power and waste of fuel, together with the heightened risk of engine starting failures.*

The policy was therefore to carry out anti-corrosive treatment on all engines which were likely to stand idle for a period exceeding seven days.  The maximum periods of protection given by inhibiting, beyond which re-inhibiting or recurrent engine running was necessary, were eight weeks for short-term inhibiting and six to twelve months for normal inhibiting, according to whether the storage was outdoors or in permanent hangars.  The period for American engines was six months under both conditions.

*E.g. 'Hydraulicing.' The mechanical failure of the engine normally caused' by cxe petrol or oil draining into the lower combustion chambers and creating a hydraulic Radial engines were particularly susceptible to this fault.

The Preparation of Aircraft at Units for Issue to the Service

The preparation of aircraft for issue to the Service consisted of restoring the aircraft to a fully serviceable condition, roughly the reverse procedure to that necessary when preparing them for storage, and at the same time making them operationally serviceable for the task which they were to perform.  Whilst every attempt was made to standardise equipment throughout the various Commands, nevertheless operational requirements necessitated a certain amount of variation, which from the units' production standpoint was very nearly as bad as increasing the number of aircraft types handled per unit.  A further commitment was that of incorporating such modifications as were essential to the safety of the aircraft and the rectification of routine faults.  The number of man-hours necessary to prepare an individual aircraft could vary considerably within a permutation of any of the above factors.

In the early stages of the war it was often necessary to issue aircraft deficient in certain items of equipment.  A shortage of modification kits was another source of delay, although where these were not essential they could be passed to No 43 Group working parties for retrospective fitting.

Most of the preparation work at units, both for storage and issue, was centralised in order to achieve the maximum possible efficiency.  Whilst it was not possible, for the reasons already given, to take full advantage of modern production-line methods, some degree of specialisation was possible, and where employed yielded rich dividends in the form of increased output.

The production plan at units for the preparation of aircraft was prepared at unit level, the controlling factor being the unit monthly target issued by HQ, No 41 Group.  This plan was essentially flexible in order to cover variations in requirements and to suit changing local conditions at individual units.  The plan for the following month was prepared during the week previous to the date on which it was due to come into effect, and by this means it was possible to preserve a certain degree of continuity from one month to the next.  This was not quite so necessary when the volume of work exceeded the units' capacity, and the practice was introduced of carrying forward the arrears of work from one month to the next.

All stages of the work during preparation were inspected by the personnel of the Unit Inspection Department, who were quite separate from production, and when completed the whole aircraft was inspected by them, both before and after air test.  This air test was carried out by the units' own test pilots, and if satisfactory the history sheet for that aircraft was then completed (Form 1860), loose equipment stowed, and the aircraft signalled as awaiting disposal instructions or, where these were already known, as awaiting collection.

Various complaints were received from time to time from the user formations that the aircraft they were receiving from No 41 Group were not functionally serviceable.  In an attempt to rectify this complaint units introduced a system of functional tests to be carried out on the ground during preparation and also during air test.  However, these tests were not entirely successful in eliminating the trouble and in fairness to No 41 Group allowance must be made for the fact that the aircraft being handled were mass produced in large numbers and, despite the relatively high standard for this type of work, needed a longer 'running-in' period before delivery to users than it was possible to give them.  This deficiency was further accentuated by the necessity for replacement aircraft to be used operationally almost as soon as they were received.

No 41 Group Modification Policy'

The modification policy of the Group confined the basic responsibility for the incorporation of modifications to Class I and Class II only.  No aircraft were issued for flying purposes with any Class I modifications outstanding, but in the case of Class II modifications this was sometimes permitted when the necessary parts were not available.  Modifications of a lower class were not incorporated except under specific instructions.

Command modifications were not normally embodied by No 41 Group units except under special arrangements with the Group HQ, and there was no obligation to remove such modifications, when fitted, before reissue.

The Distribution of Aircraft at No 41 Group Units

Before June 1942 the rule had been to distribute the quantities of each type of aircraft over a minimum of five units.  Representation to the Ministry of Aircraft Production on that date secured a reduction to a minimum of three units per type but, because of the limits then in operation on the numbers of one type in one hangar or dispersal area, and consequently at a unit, it had not been possible to take full advantage of the concession.  This particularly applied to a number of types with a high storage or turnover rate.  Through this, and the introduction of new types without withdrawing the old, the average number of types per unit rose in April 1943 to six operational, three non-operational and one glider.  Most of these types were of many Marks and varieties.

The number of modern types of aircraft per unit had become too high for a reasonable standard of efficiency and the AOC, No 41 Group, put forward to the Ministry of Aircraft Production the proposal that: -

'The distribution of each type of aircraft should be through the smallest number of units practicable and acceptable, the minimum number of all principal types being two per unit; the exception to this being where the numbers received would be insufficient to maintain a steady flow if passed through more than one unit.'

This it was stated would result in the majority of units handling an average of three types of aircraft, one large and one medium or small operational type, and one non-operational type or glider.  It would be necessary for one unit taking naval types and three units who dealt with American aircraft to handle more than this average, the units erecting gliders would remain unaltered.

The Ministry of Aircraft Production approved these proposals and on 3 June 1943 Air Ministry confirmed this approval in detail.

With the approach of the end of the war in Europe and the changing circumstances which accompanied it, it became necessary to modify further this policy by concentrating the preparation of aircraft at certain units only, leaving the remainder to deal with surplus aircraft and long-term storage.

Aircraft Received Complete from Contractors and Held Ready for Issue

By 16 September 1943 certain types of aircraft were being received from contractors to an equipment and modification standard which enabled them to be issued direct to users, where such vacancies existed in their establishments.  It was therefore decided to allot all such aircraft to units for temporary storage only so that they would be ready for reissue at once should requirements suddenly materialise.  Previously these aircraft had been prepared according to the full Directorate of Repair and Maintenance instructions for preparation, which in addition to placing them unserviceable also entailed duplication of much of the work already carried out at contractors.  On arrival they were therefore brought on charge in the normal way, given a between-flight inspection and any defects found or reported on the pilots' 'snag' report rectified.  Any missing equipment was replaced and the aircraft were then picketed out and given a daily inspection at least once every seven days.  If they had not flown for 72 hours before they were required for issue they were given an air test, and if this was satisfactory were reported as ready for issue.

The aircraft were normally held in this state for a maximum of 14 days, after which they were downgraded and prepared in the normal manner.  Where ample stocks were held it was the policy to replace wastage from aircraft held temporarily and to satisfy re-arming or increases in establishment from aircraft which had been prepared in the normal way.

Non-effective Aircraft

On the same date (September 1943) it was decided to introduce a class of aircraft to be known as Non-effective Aircraft (NEA) which comprised

(a) All those aircraft which were surplus to Command and formation requirements and which would normally be passed direct to repair units or contractors but for which no immediate repair capacity existed.

(b) Those aircraft from No 41 Group stock for which authority was held that they were either to be broken down or returned to contractor for repair, overhaul or major inspection.

Such aircraft were stored at No 41 Group units pending the availability of suitable capacity.

The Clearing of Aircraft from Contractors to Warehouse Storage (Purgatory)

It was agreed at a meeting held at HQ, No 41 Group on 23 September 1940 that the responsibility for aircraft in storage lay with the Ministry of Aircraft Production and not the contractor.  MAP would indicate to the RAF Purgatory Officer suitable storage premises which he then surveyed, and those suitable were requisitioned by the Lands Branch, any necessary alterations being the responsibility of the Purgatory Officer.

As aircraft became available for storage the AID at the contractors applied to Allotments who then allotted the aircraft to the appropriate ASU, a special endorsement being made if they were to be stored in warehouses.  In the latter case the contractor prepared the aircraft for purgatory storage, and this entailed removing the mainplanes, storing the covers within the aircraft together with the sparking plugs in a special container, and where aircraft were to be stored 'tails up' removing the compass and propeller, the former being suitably crated.  They were preserved so that they required no attention for the first month of storage but the aircraft had to be sufficiently accessible to permit maintenance after this period had expired.

The aircraft inventories and log books were passed to the ASU concerned, who retained them until such time as the aircraft were required.  If and when the aircraft were returned to the original or any other contractor for re-erection, an allotment was issued by the MU holding the aircraft on charge to the contractor undertaking re-erection and a copy of this was sent to the Special Accounts Section.

The Procedure for the Supply of Aircraft and the Organisation of the Ferry Pools

Allotments ex Contractors

(a) To Maintenance Units. The majority of aircraft ex contractors were allotted, in accordance with a Group stock holding policy, to MUs within the Group, where, if necessary, they were prepared to operational standard for subsequent issue.

(b) To Squadrons. Certain aircraft, which had been prepared to operational standards at contractors' works, were allotted direct to squadrons instead of via MUs.

Aircraft ex contractors were allotted, in advance of their actual readiness, on receipt of applications from the chief AID Inspector at the works.  Local Ferry Pilot Pools of the Air Transport Auxiliary received copies of the allotments and automatically arranged delivery of completed aircraft to either MUs or squadrons.

At 18.00 hours daily each MU rendered a return showing the state of readiness of its operational aircraft to the Allotments Branch of HQ, No 41 Group, where the information was consolidated and recorded.

Demands from the Commands

Every day, and/or as necessary, each Command notified its requirements of replacement aircraft to the Allotments Branch.  If this was by telephone it was confirmed by signal or postagram which stated such essential details as type and Mark of aircraft, quantity, unit for which aircraft was required and its location for delivery, and particulars of any unusual equipment or modification requirements.  In the absence of any notification to the contrary, demands were satisfied in the order in which they were received, multiple demands being tested in order of priority, and aircraft for squadrons and OTUs were assumed to be required operationally equipped.

Aircraft to meet requirements, except when allotted direct from contractors, were selected by the Allotments Branch from those notified as suitable and ready for issue and allotted to squadrons by immediate signal.  This signal was addressed to the maintenance unit holding the aircraft and repeated to Command, Group and squadron.  It contained all necessary allotment particulars and indicated intended ferrying arrangements.

The Ferrying to Squadrons

The following methods were employed to ferry aircraft to squadrons.

(a) Normal. Delivery by an ATA ferry pilot.

(b) Squadron to arrange collection (e.g. when insufficient ferry pilots were available), and collection under operational Command/Group arrangements on behalf of the squadron.

When the normal method was employed ferrying instructions were issued through Central Ferry Control, ATA, Andover, which worked in close liaison with the Allotments Branch.

The Emergency Advanced Headquarters

An advanced Headquarters was prepared at Cheltenham to accommodate both the Allotments Branch and Central Ferry Control in the event, of HQ, No 41 Group being put out of action.  Arrangements were made to send personnel from Andover to Cheltenham and even from HQ of Wings should the necessity arise.

In the event of both Andover and Cheltenham being out of action arrangements were made to decentralise the control to the three Wing Headquarters.


Both No 41 Group and ATA were included in Maintenance Command Emergency W/T Ground Station Organisation, which was intended to be used in the case of a major breakdown in the landline system.  Should the W/T also fail use was to be made of neighbouring unit facilities, Despatch Rider Letter Service, etc.

The Operation of Ferry Pilots from Maintenance Units'

It was decided on 20 January 1941 to place ferry pilots at certain maintenance units in order to gain experience in this method of ferrying to operational units.

The maintenance units which were chosen, their monthly output of operational types of aircraft and the allotment of ferry and taxi pilots were as shown below: -

MU No Place Operational Aircraft Ferry Pilots Taxi Pilots
S.E. T.E. Total S.E. T.E. Total
6 Brize Norton 36 20 56 3 2 5 1
8 Little Rissington 26 54 80 2 5 7 1
15 Wroughton 30 10 40 3 1 4 1
19 St. Athan 40 20 60 3 2 5 1
20 Aston Down 40 40 80 3 4 7 1
38 Llandow 6 16 22 1 1 2 1
Totals 178 160 338 15 15 30 6

S.E. = Single-engined    T.E. = Twin-engined   

It was hoped that by this method unit commanders would take a more active interest in the ferrying side of the work and that the delays and consequent friction between ferry pilots and units would disappear.  As it was the intention eventually to fuse the duties of test and ferry pilots at units they were expected to help each other out, and whilst it was permissible to ferry all types of aircraft the highest priority was reserved for operational types.

This scheme proved a success and in March 1941 it was extended to include other maintenance units.  At the same time it was decided to form ferry 'balance ' pools to cover emergencies, large batches of aircraft for packing, and the ferrying of special new aircraft, etc.  These ferry pools were located at Kemble, Hullavington and Dumfries, the first of these concentrating on the new large types of aircraft.  In order to obtain an economy of ferrying and flexibility a scheme was evolved whereby air storage units were grouped together for liaison.

The Standardisation of Equipment Procedure at Air Storage Units4

In November 1942 HQ, No 41 Group reviewed the establishments of air storage units with a view to conserving man-power and creating an ideal establishment based on the least possible personnel which could be employed, having regard to the highest standard of efficiency in relation to known estimates of production.  Every aspect of equipment procedure and administration was considered and certain personnel were allocated to each and every job.  Visits to units soon revealed that some employed more men on a particular job than did others and that unless some standard method was laid down an economic but fair basis could not be achieved.  A standardised procedure for units was therefore worked out. (See Diagram 14)

Revised establishment for ASUs

Diagram 14

This was the ideal establishment, but it was found after it had been compiled that the saving in the numbers of personnel was not sufficient to satisfy the requirements of the National Man-Power Board.  In view of this and bearing in mind that many units had been working much below their existing establishments, it was agreed to make a further 10 per cent reduction on the ideal establishment.  No reduction, however, was made in grades or trades which were less than ten in number.  Nevertheless, despite this cut the new establishments more nearly approximated to actual strengths than they did before.

The Organisation for Gilder Erection, Testing, Ferrying and Storage by No 41 Group

It was decided in April 1943 that No 41 Group would commence erection of Horsa gliders and the two units selected for this task were No 6 Maintenance Unit, Brize Norton, and No 9 MU, Cosford.  After erection the gliders were to be air tested and ferried either to the glider storage maintenance units or direct to the user units as required.

The following maintenance units were selected for the storage of Horsa gliders: -

No 5 MU, Kemble.

No 8 MU, Little Rissington.

No 15 MU, Wroughton.

No 19 MU, St. Athan.

No 20 MU, Aston Down.

No 27 MU; Shawbury.

No 29 MU, High Ercall.

No 38 MU, Llandow.

No 39 MU, Colerne.

No 48 MU, Hawarden.

No 51 MU, Lichfield.

The gliders were dismantled for storage and whilst in store all modifications not already carried out were incorporated by the storage unit.  On allotment they were reassembled for delivery by a glider assembly party established at each unit and then air tested.  The storage of Horsa components was allotted to Nos. 5, 6, 9, 15 and 29 Maintenance Units.

The Formation of No 53 Wing and the Aircraft Packing Unit

The control of the packing organisation, which hitherto had been carried out jointly by the Air Ministry and HQ, No 41 Group, was transferred to HQ, Maintenance Command and delegated to No 53 Wing on 27 March 1941.  The Wing consisted of a HQ, Service and civilian manned packing units, Service manned packed aircraft transit pools and twelve civilian contractors engaged in the packing of aircraft under the Air Ministry contracts.

The quantities and types of aircraft to be packed were determined by the Air Ministry, according to operational and training requirements.  This programme was then allocated to the various packing units by No 53 Wing, and where civilian contractors were involved the Air Ministry was requested to place covering contracts.  Aircraft which were to be packed for shipment overseas were flown into packing units or contractors' packing sites, either direct from production or from air storage units or operational stations, the cases into which the aircraft were to be packed being manufactured at the respective units.  The work of the packing units included the dismantling of the aircraft, removal of loose or delicate equipment, thorough anti-corrosion treatment of the whole aircraft, including engines, and finally the packing of the aircraft in such a manner as to ensure its complete protection against all foreseeable handling and climatic conditions.

If shipping space was available immediately the packed aircraft were transported by road straight to the port of embarkation, but normally this was not possible and they were delivered to the packed aircraft transit pools pending shipment, or dispersed locally at the packing unit or contractor.

Aircraft packed by No 53 Wing included both operational and training types.  They were shipped to the Dominions and Colonies, the Mediterranean, Middle East, Far East and the USSR.  Approximately 35,000 single and twin engined aircraft were packed for shipment by No 53 Wing during the course of the war.

The Output of Aircraft from No 41 Group

The stock of aircraft within No 41 Group on 30 September 1939 amounted to some 2,515 aircraft, a figure which by the end of May 1945 had reached a peak of 12,399.  During 1941 the number of aircraft received was 21,270, as compared with 22,310 prepared and issued, an increase over the figures for 1940 of almost exactly 50 per cent.  Receipts, which were 4,800 in the first quarter, rose to an average of 5,450 in each of the last three quarters, whilst issues exceeded receipts during the two middle quarters by 2,000 aircraft.

This heavy demand for aircraft still existed at the end of 1941, the last two months of which saw preparation delayed and output reduced below intake by bad weather, unserviceable aerodromes and shortage of production items such as engines, propellers and modification parts.  The aerodromes were actually in a worse condition than in the previous two winters owing to delays in the laying of runways.

Arrears of aircraft at the end of September and December 1941 represented 37 and 48 weeks' delivery for the two quarters respectively, as compared with 43 and 51 weeks for the same quarters of 1940.  This improvement was mainly due to increased supplies of operational equipment.

In 1942, 28,636 aircraft were received and 24,109 issued, an increase over the figures for 1941 of 33 per cent and 9 per cent respectively.  In consequence, the stock in the Group rose to 8,346, an increase of some 4,000 aircraft.  The production of certain types of aircraft was in excess of early requirements, and in order to avoid the wasteful employment of labour in maintaining all aircraft in a 'ready to issue' state it became necessary to depart from the existing policy and limit such complete preparation to the aircraft most likely to be required in the near future.

The turnover during 1943 was 28,356 aircraft received and 27,830 issued, which represented an increase of approximately 6 per cent over the previous year.  The direct delivery of aircraft from factories, to Commands at home and to packing depots for overseas, commenced in May 1943 and by the end of the year 8,315 machines had been delivered in this manner.  The stock in the Group rose to 9,000 aircraft by April, but fell away to 7,300 in October, rising again to 8,466 by the end of the year.  Whilst preparation during 1943 was relieved by the substantial increase in the numbers of aircraft delivered direct, this was more than counterbalanced by an increase in the number of special installations to be fitted and by a greater variation in operational equipment, mainly due to an increase in the numbers of aircraft despatched overseas.

At the beginning of 1944 a detailed examination of the arrears of aircraft required by No 44 Group for fly-out overseas indicated that, in order to supply the requisite number by the target dates it would be necessary to increase the working stock and reserve of aircraft within No 41 Group, so as to cover the time lost during ferrying between air storage units.  The arrears of fly-out aircraft at the end of December 1943 were 131, whilst those for January and February were 105 and 82 respectively, but March showed an improvement as all but 20 of the 355 aircraft required were delivered.

The number of aircraft ferried by the Air Transport Auxiliary during March 1944 was 7,569, whilst the number of gliders ferried by No 41 Group for that month was 217.  Ferrying continued at this high rate throughout the year reaching a peak in June when ATA ferried some 7,725 aircraft.

As from 'D' Day, 6 June 1944, an aircraft supply night staff was established at Group Headquarters in order to allot ready aircraft against Commands' demands during the night.  This enabled Central Ferry Control to notify the ATA pools immediately, and the ferrying of aircraft allotted could then commence early the next day.

The demands for aircraft to replace operational wastage during the first few days of the liberation of NW Europe were only 10 per cent over those for the previous three weeks, although this represented an increase of 30 per cent over the average for previous months.  The modesty of this increase may have been due, at least in part, to the fact that some of the units engaged were overborne on their aircraft establishments.  The heavier demands for the three weeks before 'D' Day were partly due to the policy of holding three reserve aircraft per squadron at AEAF Group Support Units.  The majority of aircraft demanded were available from the ready reserve which had been accumulated in the three months previous to 'D' Day, but due to a lag in production of certain types and a shortage of modification kits, the final reserve of ready aircraft available at air storage units did not conform at all closely to replacement requirements and in some cases was non-existent.  The preparation of aircraft that were not ready and could not be supplied at once to meet the nightly demands had therefore to be accelerated, and at the same time any delays due to allocation and delivery had, as far as possible, to be eliminated.

During the first two weeks after D ' Day, demands to replace wastage in the 2nd Tactical Air Force (2nd TAF) and the Air Defence of Great Britain (ADGB) remained at approximately the same average daily level, being largely met from ready stock.  At this date the cumulative inability was averaging about 20 aircraft, spread over some four different types, and this fortunately was not sufficient to cause a serious drain on the operational units' own reserves.  The actual rate of wastage did not vary very much from that previously estimated, and future rates of preparation were therefore assessed accordingly.

On 16 June 1944 the Chief Aircraft Supply Officer and the Director of Operations, ATA visited HQ, AEAF to discuss the ferrying of replacement aircraft for No 85 Group squadrons based on the Continent, No 85 Group having no Group Support Unit.  It was therefore agreed that ATA should ferry aircraft direct to No 85 Group airfields in either the British or American zones on the Continent, and this was continued throughout the year.

During the third week after the invasion the wastage remained at about the same level but the cumulative inability to meet demands from ready stock increased to an average of 25 due to a reduction in the availability of Spitfire VBs and VIIs, production of which had ceased.  It was therefore decided to re-arm a proportion of the squadrons as and when Command reserves fell to a point where it would be liable to lead to squadrons being below establishment.  By July 1944 demands to replace wastage were considerably reduced, and every demand was met as it was received.

Mention has already been made of the reduction in output caused by bad weather.  On 23 January 1942 severe winter conditions developed, over most of the country and lasted for the whole of the week.  This reduced movement by air to less than a quarter of the normal and the number of aircraft outstanding for ferrying rose to 951, including 505 from contractors (almost exactly the same figure as in the same week of 1941).  Hurricanes and Airacobras had to be moved by road from air storage units to packing depots in order to meet the monthly targets of aircraft required for shipment to the USSR and the Middle East.  The extent of road deliveries from factories was sufficient to keep the number of aircraft dispersed there to within satisfactory limits.  These conditions were repeated again on  February 1942, reducing movements by air and air testing to little more than half of the normal.  In the period of bad weather lasting from 1 to 5 November .1943 an 'open allotment scheme' was adopted for Lancaster aircraft.  Instead of allocating a particular aircraft to a particular unit, all the units and aircraft were pooled.  This enabled A V Roe Ltd to prepare the maximum number of aircraft for flight each morning, which ATA could then deliver to any of the 'weather free' units for which an allocation existed.

This page was last updated on 21/12/17

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