RAF aircraft periodic inspections

[CZ_RAF]

Hi all,

I am looking for any good source regarding aircraft periodic inspections and things around. Is there any online source please? I suppose it would be described is some maintenance manual but I was unable to find anything so far and if than the archives are closed at the moment. If there are dependencies on the type, I am interested in 311 Sq aircraft - Wellington & Liberator.

So far I was able to find out only that there were:
Minor Inspection after 30, 60, 90, 120 hrs
Major Inspection after 150, 180, 210, 240 hrs

1. Were there same for any type of aircraft? Or there were differences for example between fighter and bomber or depending on number of engines?
2. Where they were done? I suppose some of them were done at the squadron (all minor?) but for the others aircraft was flown to the MU (all major?) or there were some dependencies or exceptions etc?

I understand that this is very wide subject but I will be thankful for any additional information which may help to put the whole picture together.

TIA

Pavel

[David Duxbury]

Pavel,
Probably the sort of thing covered in a general way in some of the RAF Engineering publications, I think the series you would have to study would be AP 830. However "Periodicity" is the specific subject you are looking for, but this was always a moving feast so far as I can make out. I think most types of aircraft in normal service would tend to follow a basic overall plan (the figures you give in your post look pretty typical to me), although one of the most important was of course the "DI" (Daily Inspection), which I think was the responsibility of the captain (or somebody delegated by him). Come to think of it, that is still the civilian system, including largest airliners, but thinking harder, now almost certain that it was members of the ground-staff that did the DI's in the RAF; perhaps they still do, although much could be civilianised now. Often on first entry into military service, a new type might have a fairly low periodicity, particularly for the "Majors", but with experience built up by the type as a whole, the periods could be increasingly spaced out after, say, after 6 months in service by the type, or twelve months, but after 18 or 24 months service it might be extended again. The fact that many individual aircraft did not last that long in service was of no importance, it was the accumulated hours, and knowledge built up by careful study of all parts of the engine and airframe on each inspection, daily, minor and major, as well as operation of other equipment, that confidence in the design and manufacture of all the constituent parts could be built up. I would imagine that Minors would all be undertaken by squadron or station personnel and equipment, but Majors could be undertaken by more specialised entities, perhaps including MU's or civilian contractors, and I believe some major damage jobs such as major repairs, if considered well beyond capability of station Workshops) would be sent to contractors, including original manufacturers. However don't quote me on that, and any members reading this thread, with familiarity or deeper knowledge on this subject, please feel free to criticize any of my comments! Aero engines, of course were one of the most vital items of equipment fitted to aircraft, and had their own tables of "Periodicities", some perhaps in step with the airframe people for convenience, but others (obviously "Time Between Overhauls") would be entirely separate. There was started a series in the "RAF Narratives" volumes intended to cover the whole history of maintenance of aircraft and engines of the RAF in WW2, but I think only one actual volume was completed. However that single book is well worth a read, as the early development of the system which became more standardised later in the war is explained in some detail. Worth looking out for.
David D

[bvs]

Complicated subject (of course :) )
There would probably have been slightly different servicing periodicity for each different type of Aircraft and some of the servicing periods would have been extended a bit as the war progressed due to changing interpretations of the best/most efficient servicing regimes.
One way of finding out any 'type specific' servicing/inspection periodicity might be to look for any surviving copies of the particular Form 700 (Aircraft Servicing Form) - which in WW2 would be a wealth of aircraft type specific info.
The RAF Museum may have a couple of F700's but I know they are pretty rare beasts.

From this site -

F700 for Jean Battens Percival Gull
Even just the first page gives quite a bit of info...

https://collection.motat.org.nz/objects/105059

[CZ_RAF]

Thank you both, to seems to me like a good start!

Pavel

[Franek Grabowski]

i think the easiest way would be to contact present operators of the types, as they should have all the related paperwork and amendments.

[robstitt]

Hi Pavel:

A review of some Form 78s for 311 Sqn aircraft should give you an indication for where unit aircraft typically received their Major Inspections and at what point in their services lives. Scottish Aviation was designated as responsible for both the Liberator and the Fortress regarding design, modification and airworthiness issues and also carried out modifications, manufactured spare parts and later performed inspections and overhauls but there may have been other organizations that specialized in Liberator inspections.

In the case of case of the Fortress, their Major Inspections were due every 800 hours - there may have been a shorter interval early in their service. In practice, this meant that surviving early deliveries that had entered service in mid-1942 were turning up at Thornaby in Yorkshire for their Majors later in 1943 - I've not been able to identify a specific RAF unit there that would have done the work. Of course, many aircraft never built up enough hours to receive a Major Inspection.

Work was also performed by other organizations. Langford Lodge Air Depot in Northern Ireland for example performed a number of 300- and 360-hour checks on a handful of Fortresses which leads me to believe that backup capacity was identified and used when necessary. All this is separate from repairs which were sometimes conducted on-site by Maintenance units (MUs) or by Civil Repair Organizations (CROs) such as Marshall of Cambridge or the aircraft was patched up by an MU and ferried to a larger organization such as Scottish Aviation or, as in one case, Langford Lodge.

I would imagine Daily Inspections, especially on larger aircraft, were typically conducted by ground crews as these would have involved confirming the operation of various systems, beyond the ability of the pilot. His responsibility would be to conduct or delegate an external walkaround, looking for obvious fluid leaks, loose panels and fasteners, and so on.

Hope this helps.

Robert

[bvs]

Yes CZ/Rob - regardless of Aircraft type - Daily Inspections (DI's) were normally carried out by Ground Crew,this would apply across the whole RAF Fleet from Tiger Moth to Liberator.

In certain circumstances with a fairly simple a/c I would imagine that if an a/c was unexpectedly diverted then a DI might be carried out by a qualified Pilot - but I would also imagine that a Pilot would have to be officially certified/qualified to carry out and sign for such work.

[robstitt]

Worth remembering too that a daily inspection was just that, daily at the start of the day. Once done it was assumed that there was enough integrity in the design and systems that an aircraft would function throughout the day with cursory inspections before each flight unless there were reported snags or damage.

As far as I’m aware, all designated operational aircraft, from EFTS Tiger Moths to squadron Liberators, received an engine run as part of the daily inspection so they were ready to go.

A guess on my part but think it likely that aircraft with liquid-cooled engines required more tweaking for leaks than those with air-cooled engines, particularly with changes in ambient temperature. I know that RAF-surplus types with Merlins and Allison’s operated in Canada post-war suffered from chronic and sometimes destructive leaks, unlike American types with ‘round’ engines.

Robert

[CZ_RAF]

Franek - well in case of Liberator it may be helpful but there is no flying Wellington:) Anyway I would like to stick with the historical documents if possible.

Robert - thank you for both of your comments. It is good point with Form 78s!

Anyway many thanks to everyone, I have now enough to start digging.

Pavel

[bvs]

Hi Pavel
In the case of the Wellington I wonder if RAFM Cosford still have the original F700 for their a/c.