Wartime Aircraft Service Life

I hadn’t considered ‘Chobert’ rivets; I’m too used to the automotive world and, seeing them only from the outside, they looked like pop-rivets to me.

One of the reasons I noticed them in the first place was that they looked out of place with the otherwise flush and / or blind rivets that usually populate aircraft fuselages; I also wondered if they’d ‘whistle’ as the slipstream passed over them!

Now pop-rivets usually end-up blind, but Chobert rivets, if I remember, are never ‘blind’?

Amazing responses most interesting data many thanks to all the contributors

I think they look a bit more like Chobert rivets rather than Pop rivets. I believe Choberts were mounted on a long mandrel & were therefore quicker to install unless they needed plugging to either get full strength or for sealing purposes.
No idea what aircraft they are on!

In relation to notional costs, the cost of components is well documented in the Air Ministry (Ministry of Supply) contract books. I have seen the cost for Lancaster’s, new and for repair services with in one of these books. I can not state which book exactly it was, as it was 10 years ago.
I was looking for information on other subjects.

The PRO reference was Supp 4/323 for the contact book I was looking in. Anyone interested should look for the contract book starting with A, somewhere with in this series.

The term Major Service may be post WW2, but it was normal for wartime aircraft to spend a restricted time on one particular squadron before returning to a Maintenance Unit for strip-down and major overhaul. Fabric coverings (Control surfaces, Hurricane rear fuselages, Swordfish..) would need regular recovering. Obviously this time could be shortened by whatever damage was experienced. There are many stories of the increasingly poor condition of aircraft after one or more of these cycles, from official Russian complaints about pre-used aircraft to the “clipped, cropped and clapped” epithet applied (not entirely fairly) to the Spitfire LF Mk.V.

I think however that engine overhaul times are a red herring – engines could be and were replaced on the squadron. There need be no connection with the airframe overhaul times.

I recall going through the list of serials of P-40s operating with 112 Sq in the Desert, and discovering that the average life of these aircraft on the unit was one month. This is including combat losses, of course, and recycled aircraft will have spent some time with other units later. On the other hand, the official replenishment rate of Halifaxes in the desert was one per month, leading to considerable problems with serviceability.

(Vega #7: author has misremembered: 150 flight hours is nicely a piston return sortie, Down Under-UK. More likely 500 hr. Done at 390MU/Seletar, where FEAF Shacks were handled).

The notion of a Major Service is post-WW2, even post 1st.post-war equipment generation: obsolescence meant, say, Hunter F.2 displaced by Hunter 5 and either reduced to produce or put to Ground Instruction.

That average of 100 hr. p.Wimpey is further complicated by reduction in assumed attrition rates: many new builds went straight to Storage Units, whence they were scrapped.

Notional costs were of no significance to the User: we simply do not know what wartime kit “cost” because no system existed (until about 1965!!) to bring to one piece of paper all Unit average procurement costs for every item Embodied in an end-item. Avro (might) know how many £ they received per Lancaster flown away, but neither they nor anyone else knew the cost of the radio…or engines, because that kit was procured in glob-Lots by MAP for free issue to various places, as MU spares, or for Embodiment in new build.

Users were only interested in Servicability Rates: can I declare all/some/none Operational tomorrow. When one a/c became a persistent Servicability pain, Unit would yell for exchange from an MU. Whether then it was “overhauled” depended on stock of Servicable current-mod. standard examples. Maybe best to extract engines/radios, whatever is scarce this week, and junk the carcase. The Repair Organisation was exactly that, not a Heavy Maintenance Organisation.

Same for tanks…most everything. That is why, when civil-potential types were put up for tender, your engineer would hunt out a low-mileage example.

Gentlemen, I salute your phenomenal knowledge and understanding. I have been trying to explain some of the basic elements of the operation of Bomber Command to young people in lay terms. (‘Of sons and skies’) I was shocked at what a veteran RAF engineer told me about his responsibilities and circumstances, and felt a duty to convey this to a new generation in a way they would find accessible. A fascinating task, the results of which seem so shallow next to your expertise.

I looked up the 200 Lancaster I in serial range R5482 – R5763 for aircraft with notably higher hours:

R5483 – 450 hours
R5485 – 542 hours
R5547 – 502 hours
R5547 – 506 hours
R5572 – 424 hours
R5573 – 477 hours
R5614 – 440 hours
R5625 – 535 hours
R5665 – 487 hours
R5672 – 695 hours
R5677 – 512 hours (67 operations)
R5687 – 518 hours
R5734 – 529 hours
R5736 – 513 hours
R5739 – 810 hours
R5740 – 416 hours
R5744 – 526 hours

This serial range also includes sixteen Lancasters that were scrapped in 1946-1948 (hours not recorded) and sixteen that became M-serial instructional airframes at Technical Training Schools (hours not recorded) after retirement from operational flying due to high hours or being damaged in accidents.

I photographed this rivet-work on a wartime bomber a few weeks ago (anybody guess which bomber?) because I was surprised to see pop-rivets being used on the outside of a fuselage.

Does anybody else remember the BBC documentary from years ago with William Woollard (I think?) relating the story of how an early Spitfire was tested to see if flush rivets were required on all external surfaces to maintain performance or whether ordinary domed rivets could be used instead; the story goes that split-peas were progressively glued over selections of flush rivets and the aircraft was flown to gauge its loss of performance.

Re #2 and “built (…) at a budget price (and with ‘semi-skilled’ labour in many cases).”

I’m sure I saw a wartime photograph on here a few years back, of a pilot leaning out of a cockpit window of a Lancaster or similar. The fit and finish of the rivet work around the window was somewhat erratic. Definitely an element of ‘close enough’ about the whole thing. Speaking of which, this is the closest match I can find:

However I’m not sure this is the exact photo.

Presumably the difference between nine and seven Lancasters lost is that seven failed to return, but ED490 and one other were written off back at base, or at least somewhere in this country.

Yes, you’re right, Lancaster R5894 crashed into high-tension cables within 3 miles of returning to Scampton.

Six Halifaxes are recorded in ‘Bomber Command Losses 1943’ and they have a slightly less depressing record of survival for shot-down crews; four crew members surviving as POW (plus one evading capture) in total from three different aircraft. Of the four Stirlings lost twelve crew members survived to become POW (one evading capture for nine months!) from three different aircraft. A further Stirling was lost in a crash on returning to the United Kingdom but thankfully without loss to the crew.

One night in a very long war for Bomber Command.

To clarify, I wasn’t directly linking engine-life to airframe-life in my earlier post. What I was suggesting was that engine-life was probably the main factor in designating an aircraft as ‘war weary’; aircraft that were slower, slower to climb or that could climb to a lower ceiling that ‘factory fresh’ aircraft.

I remember reading an account by one pilot (possibly Donald Bennett of the Pathfinder Force?) who flew Lancaster ‘S-Sugar’ when it already had many operations to its credit; if I recall correctly he didn’t particularly enjoy the experience and claimed that the aircraft ‘crabbed’ all the way to the target and all the way back!

Linking air-frame overhaul life to engine life is probably unlikely as engines were subject to life extensions as operational knowledge was acquired and reliability improvements made. According to one of the Rolls-Royce Heritage Trust booklets, Merlin’s fitted to fighters went from 240 to 300 hrs, twins up to 360. Bombers 300 hrs extended to 420 on the Merlin 24 but the earlier marks stayed at 360. Transport wartime Merlin’s reached 480 to 500 hours.

Richard

Early photos of R5868 show the line of small windows along the fuselage that it no longer possesses, so it’s obviously had a major amount of work. Plus the port outer wing was replaced earlier after a mid air with another Lanc.

There is a photo in Lancaster At War 3 of R5868 on rebuild minus the nose section. I understand rebuilds were done on the basis of the sections being bolted together as available and only the nose would keep the original identity, since that’s where the data plate was/is. In wartime, getting an aircraft back on the line ASAP was more important than worrying about which bits were original. There is a photo of a rebuild in progress showing the serial number chalked on the side of a nose section awaiting the remainder of the fuselage.

Presumably the difference between nine and seven Lancasters lost is that seven failed to return, but ED490 and one other were written off back at base, or at least somewhere in this country.

I wondered what Bomber Command were up to ‘last night’ 1/2 March in 1943?

There was major operation to Berlin involving 302 aircraft: 156 Lancasters, 86 Halifaxes and 60 Stirlings. ‘Only’ 5.6% of the force was lost: 7 Lancasters, 6 Halifaxes and 4 Stirlings (note the very different loss-rates for the different types).

Although the raid was something of a failure, with the Pathfinder H2S marking scattered and no concentration of bombing, the raid caused considerable damage (more than any other raid on Berlin up to that point); twenty-two acres of workshops at the Tempelhof railway repair works were burnt-out, 20 factories were badly damaged and 875 other building (mostly houses) were destroyed. (From ‘The Bomber Command War Diaries’.) Surprisingly, perhaps, ‘only’ 191 people were killed, given the tonnage of bombs dropped, and an indication of the Bomber Command policy of ‘de-housing’ when bombing ‘area’ targets.

I looked-up the take-off times for the lost bombers and most seemed to be between about 18:30 and 19:00; the only returning bomber (combat-damaged and crashing) that I have a time for came down near the East Anglian coast at 02:45 so I’m guessing the average time in the air for the operation would have been about 7 to 7.5 hours. The total ‘hours’ for the raid therefore would have been about 2250 hours and would only result in the need for four base-service overhauls (even if all of the bombers had had long service careers before this, which they wouldn’t)!

I also looked-up the total hours for the lost Lancaster bombers (I don’t have figured for the Halifaxes or Stirlings):

Lancaster III ED490 – 9 Squadron (21/01/1943) – 7 Operations: 42 hours

Lancaster I W4829 – 44 Squadron (??/12/1942)

Lancaster III ED423 -50 Squadron (20/12/1942)

Lancaster III ED592 – 50 Squadron – 38 hours

Lancaster I R5894 – 57 Squadron

Lancaster I W4920 – 61 Squadron – 8 hours

Lancaster I W4825 – 97 Squadron

Lancaster I W4361 – 103 Squadron (??/11/1942) – 194 hours

Lancaster I W4880 – 103 Squadron (??/02/1943) – 35 hours

I make that nine, not seven, Lancasters?

Only four men, all injured in a crash-landing returning to base at Waddington in Lancaster ED490, survived from any of these lost Lancasters; in every other Lancaster the whole crew was killed.

So did Lancasters have a similar at base service requirement?

Actually, I was wrong about the ‘base-service’ interval for the Lancaster; it was only 500 hours.

Apart from this base-service all other maintenance would be carried out on the Bomber Command stations themselves. There would often only be a single large hangar capable of taking two bombers; all other routine servicing would be done in the open, whatever the weather!

According to ‘Lancaster at War’ AVRO had there own base workshops at Brace-Bridge Heath and Langar. Base-servicing was also done at the LMS railway workshops at Derby.

I don’t know whether it is still in place, but when NX611 “Just Jane” was parked up at Blackpool, there was a data plate attached to a bulkhead in the cockpit with a serial number from an altogether different aeroplane. TW*** comes to mind but it was a long time ago.

There used to be this Heinkel He 111H-23 on display at RAF Hendon which is a later wartime model that got simplified in many details. Some parts considered not vital were even left out to ease production.

Actually, I think the nose section retained the serial number identity on Bomber Command aircraft, particularly if there were significant unofficial emblems painted on it. Ironic considering the official serial number was only ever displayed on the rear fuselage.