# Man hours to build aircraft



## Micdrow (Nov 3, 2007)

I ran across this chart of the actual man hours required for the manufacture of a complete airframe, subcontracted work and the installation of engines, propellers and equipment included. Numbers below are total man hours.


Does any body have any more aircraft that can be added to the list?


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## FLYBOYJ (Nov 3, 2007)

Great info! BTW the P-38 "B" was Lockheed B-1 plant where most of the P-38 assembly was done. Later in the war there was a final assembly line at plat B-6 located a few miles away. The building where this took place was demolished a few years ago and the tower for Burbank airport stands in its place.


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## evangilder (Nov 3, 2007)

Not much of the old Lockheed left over there anymore, sadly.


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## Micdrow (Nov 3, 2007)

Thanks Joe, to bad, I would think that the buildings of lockheed would have made a great WWII museum.


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## FLYBOYJ (Nov 3, 2007)

Agree, at least one of them - sadly I witnessed their closing in 1990. Lockheed was quick to make a buck because the land was so valuable but also very contaminated. Even the city saw their one time tax cow dying and emphasized on other businesses. Today a few buildings are still there. Everytime I pass through there it seem like a dream...


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## syscom3 (Nov 3, 2007)

I'm surprised at the high rate the C46 had. it wasnt that sophisticated an aircraft.

I surmise the C54 had such a high manpower total was its production rate was low.


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## evangilder (Nov 3, 2007)

Compared to a C-47, the C-46 is bigger and more complicated. The fuselage is the "figure 8" construction that has cargo areas below the floor, as well as above.


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## FLYBOYJ (Nov 3, 2007)

Agree Eric - both aircraft were big and might of been complicated to assemble.


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## Glider (Nov 4, 2007)

The one that I wasn't expecting was how close the P47 and the P38 were. I know the P47 was a big beast but with its two engines and unusual configeration, I thought the P38 would take much more time


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## ppopsie (Nov 5, 2007)

Chief designer of Mitsubishi A6M Zero Jiro Horikoshi wrote in his book "Zero Fighter" about the man hour needed to complete an A6M estimated at 10,000 during 1943-44 period, comparing this with one for a NA P-51 at 2700 during 1944-45. 

BTW I remember losing radio communication over Burbank airport in a C-152 on one Sunday afternoon in early 1982.


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## FLYBOYJ (Nov 6, 2007)

ppopsie said:


> BTW I remember losing radio communication over Burbank airport in a C-152 on one Sunday afternoon in early 1982.



Set the transponder to 7600 and fly to Whiteman!


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## ppopsie (Nov 6, 2007)

FLYBOYJ said:


> Set the transponder to 7600 and fly to Whiteman!



Thanks for a warm invitation to Whiteman but I landed at Chino. 7700 for one minute then 7600. Respond to Green signal gun from the tower by flickering the landing light on final R/W26 (then only one).

I was a student pilot and I think it was happened on my second solo XC. 
Happy landings+thanks.


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## FLYBOYJ (Nov 6, 2007)

ppopsie said:


> Thanks for a warm invitation to Whiteman but I landed at Chino. 7700 for one minute then 7600. Respond to Green signal gun from the tower by flickering the landing light on final R/W26 (then only one).
> 
> I was a student pilot and I think it was happened on my second solo XC.
> Happy landings+thanks.


 Very Cool! I used to live in the area and have flown into those airports many times. Back in the early 80s it was a bit simpler until the Cerritos 727/ Cherokee mid air happened. Flying in the LA basin these day is a bit of a challenge - I used to pride myself on going into John Wayne and only making 3 frequency changes!


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## Civettone (Nov 7, 2007)

Yesterday I read the Re.2005 needed more than 20,000 manhours to build. Compared to the 15,000 for the G.55. Apparently this was because the Re.2005 was an aircraft which needed complex machinery which was not available in Italy. It also made me wonder if this wouldn't turn into an advantage if produced by a more developed country like Germany. 
The Re.2005 reminds me a bit of the He 100 because of its extreme tight fuselage. Also given the Guidonia report which was posted some weeks ago, it seems the Re.2005 was at least as good as the G.55. Plus, it could carry a substantial bombload. 

Kris


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## drgondog (Dec 5, 2007)

The labor hours for the P-51 went from 12,000 hours in October in 1941 to 2,077 in August 1945... For P-51 and P-51D respectively

The cost to USAAF in 1942 was $58,698 in 1942 and $50,985 in 1945 including all GFE. The airframe cost less FGE was ~$22,000. The Packard-Rolls 1650 was ~$12000 plus $6000 royalty


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## Micdrow (Dec 5, 2007)

Wow thats a huge difference compared to a P-47, Thanks drgondog. I thought it would be alot closer.


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## Micdrow (Dec 5, 2007)

Then again if you think about it, it makes sense. I read some where that Germany was pumping out Bf-109's at a rate of one per hour at its peak but have found no offical data for production rate's.


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## GregP (Jul 14, 2013)

If that were true, maybe they wouldn't have run out of them ... then again, it could be that fuel, propeller, and pilot shortages made them in short supply.

Germany didn't have a fuel shortage, but the airfields did. Every transport for war materiel was being attacked frequenty and in numbers, so getting the fuel, props, and ammo to the places where the stuff was needed just wasn't happening. They also had a severe pilot shortage in the late war. Almost as bad as Japan later, though the cadre of "Experts" stayed relatively intact with regard to the Japanese situation.


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## davebender (Jul 14, 2013)

Directly related to fuel shortage. After 1941 fuel for German pilot training was cut in order to keep operational units supplied. That strategy works for awhile but eventually you end up with replacement pilots who have hardly any flight hours in high performance aircraft. 

What puzzles me is Japan had the same problem. Why didn't they shift pilot training to the East Indies? Locate training airfields next to oil refineries and you should have unlimited fuel for pilot training.


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## MiTasol (Oct 10, 2013)

About 15 years ago I had a Boeing report on the manhours to build any aircraft or component that showed that as the team gained experience the hours dropped.

From (probably faulty) memory the 17th unit took 1/3 the man-hours of the first. This would have been part of the significant drop in the man-hours of some of the listed aircraft. Better jigs so that parts fitted together without any further drilling of attaching parts would have been perfected in that time as well. Some aircraft had very few jig drilled parts early on and everything possible jig drilled with at least pilot holes later on.

Mi Tasol


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## daveT (Oct 11, 2013)

And don't forget that there were ongoing and constant modifications being made to the aircraft during production. Many of these were designed to make production easier. 

"The modifications HAD to work their way through the chain of command. first comes the idea,then next is the selling of the idea, along with possibly several alternate solutions...next, once a modification is settled on, a company has to be selected to test the feasibility of making the modification,...and a series of testing the modification, then the actual modification, has to be fitted into the production line... and this modification, rather than stopping the production line, was provided first to a Modification Center to bring up an aircraft to the latest configuration just prior to delivering the aircraft to a combat theater."


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## daveT (Oct 11, 2013)

British Numbers
As early as January 1940 when the first wartime program embodying the heavy bombers was settled, it was reckoned that ratios of weight to man-hours would, for the principal types, work out as follows:

1st number is Airframe structure weight in lbs, 
2nd number is Average man-hours in Thousands
3rd number is lb. structure weight per 1,000 man-hours

Fighters

Spitfire
2,055
15.2
135
Hurricane
2,468
10.3
240
Whirlwind
3,461
26.6
130
Tornado
3,600
15.5
233

BOMBERS

Battle
4,466
24
186
Whitley
9,557
52
184
Wellington
10,117
38
266
Manchester
15,650
52.1
300
Halifax
16,157
76
213
Stirling
26,630
75
314

The actual figures, especially those for man-hours, were modified in the course of the subsequent three years, but the basic relations between weight and man-hours remained the same, and the heavier aircraft continued to require much less manpower per pound of weight than the lighter ones.

ref link
HyperWar: British War Production [Chapter IV]


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## daveT (Oct 14, 2013)

80% rule of thumb.
Each time the number of produced units doubles, it only takes 80% of the time to produce.
So, the second airplane takes 80% of the time that the first one took, the forth airplane takes 80% of the time that the second one took,
the eighth airplane takes 80% of the time that the forth one took.…etc.
It's a logarithmic progression that naturally occurs with training and becoming familiar with the assembly process and tooling.


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## Alison90 (Apr 12, 2016)

Has anyone a table of manhours evolution for the principal planes along the war, and also the aircraft prices?


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## FLYBOYJ (Apr 12, 2016)

Alison90 said:


> Has anyone a table of manhours evolution for the principal planes along the war, and also the aircraft prices?


Look around the forum, it's posted somewhere


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## stona (Apr 13, 2016)

The total man hours to produce an aeroplane is a very crude guide to productivity without context.
What sort of man hours, how they are organised and payed are equally important. To touch on the first, the most significant task facing the British aircraft industry by the late 1930s and into the early war years was not the acquisition of skilled labour but the absorption of unskilled labour. The British did this very well over a period extending back to the mid 1930s. Between January and October 1942 output of aircraft rose by 50% whilst the labour force increased by just 16.5%. The use of unskilled labour forced different and more productive processes on the industry and these new manufacturing processes, designed for use by unskilled labour, resulted in productivity far higher than equivalent skilled processes.
The new factories commissioned by the Air Ministry in the late re-armament period were designed to utilise an extremely high proportion of unskilled workers and these to significantly increased productivity when they cam on line in 1941/42.
Much of the unskilled labour was made up of women. Across the industry in Britain the proportion of women in the work force increased from 9.5% in 1940 to 23% in 1941, in some works it was over 30% by the end of 1931.
These women (and many men) had never worked in any kind of industry before. It is an unfortunate geographic fact that in the 1930s many unemployed men with some experience working in engineering industries were located in the North of England and the Midlands, whereas the aircraft industry was largely in the South. People were not as mobile in the 1930s as they are today. These recruits to be trained for the 'repetition work' they would do, but the factories had to to be transformed too. Layouts were reorganised, factories were extensively rejigged and tooled and production was divided into operations that could be easily learned.
This is just a few of the factors reflected in the reduction in total man hours per unit produced. It is and was a complicated business. Productivity didn't increase just because a work force had somehow got used to making a particular product!
Cheers
Steve
Edit: I have a note I made from Mensforth's 'Aircraft Production' which says that the time taken to produce a bomber centre section went from 1014 hours at the start of production to 592 hours after one year and then to 230 hours after 17 months. Unfortunately I forgot to note which bomber! I suspect it is the Lancaster. The improvement is put down to factors above, the work force taking advantage of the piece work/bonus system of payement and the longer production run.


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## stona (Apr 13, 2016)

daveT said:


> And don't forget that there were ongoing and constant modifications being made to the aircraft during production. Many of these were designed to make production easier.



I know this is a very old comment but it is worth pointing out that the reverse is true. Modifications introduced on the production line, and they were many for any British type that was in production for any length of time, invariably led to a loss of production.
One government report identified the frequency with which aircraft were modified to meet service requirements (not to make production easier!) as the prime factor in the gap between the numbers of aircraft called for in the various production programmes and actual production.
Then there is the delicate balance of quality and quantity. Quality may have been sacrificed to quantity at mass production factories like Castle Bromwich or Ford's Manchester Merlin factory, but at design factories like Rolls Royce and Supermarine production schedules were often upset by the ongoing process of qualitative refinement.
Cheers
Steve


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## Alison90 (Apr 13, 2016)

FLYBOYJ said:


> Look around the forum, it's posted somewhere


Hi, FLYBOYJ and thanks. I'm new around here and what I'm looking for is a comprehensive, yet sumarized table in which one could find how many hours did take to produce the different models of, at least, the most emblematic WWII aircraft, and the evolution of total man hours along for each model along the war.

I would also know how much did each model cost, in US dollars. It is true that for most models there is some information in wikipedia, yet it is incomplete (it doesn't show the evolution of costs as the production for the model keeps going) and what is worse, it is given in the currency of the country, so no comparisons are feasible.

Maybe people who has been longer in this forum knows better where to find this kind of information.


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## Alison90 (Apr 13, 2016)

stona said:


> The total man hours to produce an aeroplane is a very crude guide to productivity without context.
> What sort of man hours, how they are organised and payed are equally important. To touch on the first, the most significant task facing the British aircraft industry by the late 1930s and into the early war years was not the acquisition of skilled labour but the absorption of unskilled labour. The British did this very well over a period extending back to the mid 1930s. Between January and October 1942 output of aircraft rose by 50% whilst the labour force increased by just 16.5%. The use of unskilled labour forced different and more productive processes on the industry and these new manufacturing processes, designed for use by unskilled labour, resulted in productivity far higher than equivalent skilled processes.
> The new factories commissioned by the Air Ministry in the late re-armament period were designed to utilise an extremely high proportion of unskilled workers and these to significantly increased productivity when they cam on line in 1941/42.
> Much of the unskilled labour was made up of women. Across the industry in Britain the proportion of women in the work force increased from 9.5% in 1940 to 23% in 1941, in some works it was over 30% by the end of 1931.
> ...



Hi ,stona, I was not aware of that kind of behaviour, but it doesn't surprise me. Skilled workers were always needed during the war, so it is reasonable that production engineers tend to divide the processes to make them accesible to untrained, unexperienced workers as well, although your facts are interesting.

Anyway, I think the total manhourss and cost for the different models of aircraft give a reasonable good idea of a ratio ("quality"/cost) that is not always in mind nowadays when judging these aircrafts.


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## stona (Apr 14, 2016)

Alison90 said:


> Anyway, I think the total manhourss and cost for the different models of aircraft give a reasonable good idea of a ratio ("quality"/cost) that is not always in mind nowadays when judging these aircrafts.



I agree that man hours give a measure of productivity, but it is most useful when comparing like for like, as, for example, in the man hours to produce the same air frame or aero engine in different plants.
There are many factors that can lead to misunderstanding of such a generalised figure when comparing different plants producing different products.

It is a very useful measure in some other contexts. Man hours was the measure used to divide processes between the different participating companies in the first shadow aero engine scheme. Austin, Standard, Rover, Humber and Daimler all got to produce components which required totals of between 676 and 729 man hours. Bristol then assembled and tested each engine (250 hours).

The Air Ministry was more concerned with costs. The first 500 engines produced by the shadow industry averaged £1,915 per engine. The first 987 produced by Bristol cost an average of just £1,486 and the Ministry wanted to know where that extra £429 (nearly 30%) went 

Cheers

Steve


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## Alison90 (Apr 17, 2016)

stona said:


> I agree that man hours give a measure of productivity, but it is most useful when comparing like for like, as, for example, in the man hours to produce the same air frame or aero engine in different plants.
> There are many factors that can lead to misunderstanding of such a generalised figure when comparing different plants producing different products.
> 
> It is a very useful measure in some other contexts. Man hours was the measure used to divide processes between the different participating companies in the first shadow aero engine scheme. Austin, Standard, Rover, Humber and Daimler all got to produce components which required totals of between 676 and 729 man hours. Bristol then assembled and tested each engine (250 hours).
> ...



Again, really useful information, Stona. Where did you get those numbers?


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## stona (Apr 17, 2016)

Alison90 said:


> Again, really useful information, Stona. Where did you get those numbers?


Most from Sebastian Ritchies book on industry and air power. I will post the title, ISBN etc when I get home in a couple of days (hopefully).


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## FLYBOYJ (Apr 17, 2016)

_"Corelli Barnett, in Audit of War, ruefully compares the 13,000 man-hours needed to make a Spitfire Mk V airframe with the 4,000 for an Me 109G. (The Spitfire also took two-and-a-half times as long to make as a Hurricane, though Barnett does not mention this.) He is correct that Willy Messerschmitt took production needs into account in his design. Mitchell took nothing except performance into account, and this was one of the consequences. Maybe he would have done better to do so, but the advantages of his design over the 109 have also to be considered. Even German engineers would have had trouble with the wing, which allowed every Spitfire pilot to outturn any 109 (Heinkel had rejected the elliptical wing after his experience with the He 70 because it was so difficult to manufacture in quantity.) Nonetheless, despite all the incompetence it could muster, British industry finally managed to make 22,000 Spitfires."

Building Spitfires, Slowly | Daily Planet | Air & Space Magazine_


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## stona (Apr 18, 2016)

Barnett, like most post war historians, has judged the British aircraft industry's wartime performance not on a proper and detailed assessment of its productivity, but simplistically by its failure to meet official production programmes. This leads to harsh and unjustified phrases like _'despite all the incompetence it could muster.'_
There is no quantitative evidence that the British industry was less efficient than its German counterpart.
In 1940 Britain produced more aircraft than any other country in the world.
British output, expressed in terms of structure weight, was significantly higher than German output between 1941 and 1944.
In 1941 Britain outproduced Germany by 71% in terms of complete aircraft and by 28% in terms of structure weight. It also produced 63% more aero engines than Germany whilst employing fewer resources of labour and aluminium.
In 1942 Britain produced nearly 50% more aircraft than Germany and 40% more airframe structure weight. The percentages change, but the trend is the same throughout the war. The German industry was also employing more labour by 1941 than the British did throughout the war.
The MAP calculated that per capita output had increased fourfold between 1936 and 1944, despite major quantitative sacrifices in 1943 and 1944,justified by the Air Ministry on the grounds that an improvement in the quality of aircraft should be put ahead of increasing quantity.
Comparing British production with US production, another stick used to beat the British aircraft industry, is unfair. The Americans had production targets many times higher than the British. The scale of the American programmes justified a level of fixed investment that dwarfed that undertaken by the European powers. The higher level of production also reduced production costs. It also allowed American factories to be very much bigger than their British counterparts. This degree of concentration was impossible in Britain, because unlike in the US, there was a risk to German bombing.
There are many other factors which should be taken into account, but lazy historians, trotting out the old cliches, as late as the mid 1980s in Barnett's case, should not be.
Cheers
Steve

I'll add here a summary by Ritchie, a rather different type of historian who has spent much time looking at the actual figures (and there are a lot of them!) to draw his conclusions.

_"In fact the achievements of the British aircraft economy in the Second World War did not stem purely from the work of a handful of brilliant engineers and administrators. Rather, they were the result of consistent and methodical plans for wartime production first proposed in the 1920s and finally implemented during the rearmament and early wartime years, and of sustained effort and innovation on the part of the leading firms. Indeed, this was one of the few instances in Britain's industrial history when it has been recognised that successful manufacturing operations require careful long-term planning, and close cooperation between the state and private enterprise.
It is true that the plans did not always work as expected, chiefly because the impact of rapid technological change on production was impossible to predict. Yet by the end of 1941, as the War Potential Programme came to an end and the new bomber programme was launched, the aircraft industry had been organised into a number of groups geared to the development and production of the most important airframes and ancillary products. The groups' effectiveness lay in their productive capacity and in their ability to respond flexibly to changing service requirements. The maintenance of this balance between the quantity and quality of military aircraft - notoriously more complex and technologically advanced than any other product of the armaments industry - was the single most outstanding accomplishment of the British war economy."_


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## Alison90 (Apr 20, 2016)

stona said:


> Most from Sebastian Ritchies book on industry and air power. I will post the title, ISBN etc when I get home in a couple of days (hopefully).



Thanks a lot, I would only need title and a place where to buy them or download them. Do you know any other interesting books about production of the german, soviet or american aircraft?


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## parsifal (Apr 20, 2016)

Rule of thumb, the bigger the production run, the less expensive and quicker to produce.

if I can uplift a commercial analogy, the first ring pull can of coke cost about $6m (USD) and 5 years to produce. How may billions of cans since then. For small production runs, R&D costs and manufacturing glitches are big ticket costs in the production, both time and money.

Tiger tanks in 1942 were averaging well over 700000 man hours to produce and about 700000 RM in production costs. By the end of the production run in late 1944, this was down to about 200000 man hours and well under 200000 RM per copy.

There are no exceptions to these basic rules of production. There are a few added complications. Changes made in the line, such as the germans were so fond of doing are not beneficial to output. they are greatly harmful actually. Frittering around the edges with your design wrecks your output. Lesson for the day....get your design finalised, then get your production systems organised then go hell for leather to get as many as you can made accepting minor imperfections until it becomes absolutely essential to change things. the Americans were masters at this, the germans never learnt that most basic of wartime production lesson. Wartime production 101. The Russians were even more rigid in organising their production in this way.

Another complication....if your design has components that are cutting edge technology, untested and untried, you are in for a bumpy ride in their production. There will be problems and there will be recalls, you can bet on that. Moreover, if you are honest and include those componentry development costs in the overall cost of the unit being built, such cute technology will cost a bomb. Lesson 102 for the day, keep your technology as simple as you can, and if possible use off the shelf technology over some new fangled you beaut new design. Existing and well tested componentry has known reliability characteristics and will generally cost a fraction of the new design in a wartime environment.

Rule 103, be aware of the technical difficulties of production and the limits of your workforce. if you have a design requiring high skill levels, or use of scarce raw materials, or vast amount of factory space that you don't have, you should forget it. again, the germans pretty much for various designs struck out in all three of these areas. in a word, their wartime organisation of their aero industry was atrocious. Again the best people at this were the Americans and the Russians. American aero industry really lacked for nothing, but it also needs to be said that that was no accident. Russians were probably the best at organising scarce resources and skill sets to churn their designs out like hot cakes


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## stona (Apr 21, 2016)

*'Industry and Air Power - the expansion of British aircraft production 1935-1941' *Sebastian Ritchie ISBN 0-7146-4343-2.
This is one of the 'Studies in Air Power' series edited by Sebastian Cox and is available at a sensible price. I am unaware of an electronic version. It is reasonably up to date, first published in 1996.
For a more general over view* 'The Strategic Air War Against Germany 1939-1945'* which is the official report of the British Bombing Survey Unit has some useful statistics. Unfortunately this is a difficult book to find at a sensible price.

For the Germans the best reference is *'German Aircraft Industry and Production 1933-1945' *by Ferenc Vajda and Peter Dancey. ISBN 1-85310-864-2. It's a similar vintage, published in 1998. I see this book go for silly prices these days, but you might be lucky and find one at a reasonable cost.

Cheers

Steve


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## MiTasol (Aug 23, 2016)

Good one Steve, two books I was not aware were worth getting.

I have just purchased *'Industry and Air Power - the expansion of British aircraft production' *through bookfinder.com and priced *'The Strategic Air War Against Germany 1939-1945'* from the same sources - new costs from US$234 to US$1193!!!. Used from US$63.65 to US$221.20. All bookfinder prices include postage to my US address so depending on where you live prices will vary. 

The review of *'The Strategic Air War Against Germany 1939-1945'* from Caliver Books in the UK turned me off though so I would appreciate your further input on its value. To quote _Used. 260p 64 Illustrations Pbk. Mint. Compared to its American equivalent, this is not a particularly impressive monument to 70,000 RAF and Allied lives. However, it does present a short view of the strategic bombing offensive, and serves as a valuable summary of the main events. With 12 A3 pull-out tables. (RAF MUSEUM HENDON). _ EndQuote I am guessing that the review may be by the RAFM.

I already have *'German Aircraft Industry and Production 1933-1945' *and agree it is a very worthwhile reference. Bookfinder list it for 
US$46.50 new and US$22 used, again including postage.

I find the books by two MAP staff to be good value as they went to the USA and Germany early post war so their comparisons of the relative merits of German and US production were made with the benefit of vast experience in the field. They also describe the frustrations with the processes - a factor that those looking at the problem from a distance cannot do.

*Planning in Practice*, Ely Devons (1950 - pre ISBN) BookFinder.com: Search Results 
Drafted into the British war effort between 1940 and 1945 Devons became the Director General of Planning, Programmes and Statistics with the Ministry of Aircraft Production. The first chapter summarizes the problems at MAP - these can be likened to herding cats.







*Planning in Wartime: Aircraft Production in Britain, Germany and the USA, *Sir Alec Cairncross (1991 ISBN 0333538404). BookFinder.com: Search Results Cairncross was born the seventh of eight children of an ironmonger, won a scholarship to Glasgow University, where he specialised in economics. He then went to Trinity College, Cambridge. During World War II, most of his work was in the Ministry of Aircraft Production, where he rose to become Director of Programmes.


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## MiTasol (Aug 24, 2016)

parsifal said:


> There are no exceptions to these basic rules of production. There are a few added complications. Changes made in the line, such as the Germans were so fond of doing are not beneficial to output. they are greatly harmful actually. Frittering around the edges with your design wrecks your output. Lesson for the day....get your design finalised, then get your production systems organised then go hell for leather to get as many as you can made accepting minor imperfections until it becomes absolutely essential to change things. the Americans were masters at this



While I agree with most of your para above one of the more recent reviews of the Ford Willow Run program (I cannot find the link again *YET *but it has some great photos of B-24s with major sections removed) considered the consequential costs and manhours of Fords "build every one the same" ethos that you reiterate above.

The financial costs and manhour costs to convert the finished Willow Run B-24s to combat ready aircraft was often substantial and occasionally reached (from memory of the above article) close to 50% of the "factory door" costs. Add to this the several months delay between departing Willow Run and departing the modifications centre for the combat theatre and there is a strong case for more significant changes to take place in the production run. Yes - it would have slowed production but the costs of all the modification centres and manhours wasted dismantling the "finished" aircraft would surely have been greater than the cost of having a second major plant compensate for the production lost by introducing the major changes earlier like Consolidated did at its two factories. Building and outfitting a nose/tail (or other major section) just to fly the aircraft to a mod centre and then remove that nose/tail/section to install a different one containing a different configuration and scrapping the original parts fitted is a massive drain on both physical and manpower resources.
Furthermore, logistically and planning wise shipping all the turrets and other major components to few locations instead of many locations has cost and production scheduling benefits
Significantly Consolidated/Douglas/NAA built aircraft were apparently built for similar costs to the Ford aircraft but they only went to mod centres to be equipped to meet climatic and tactical conditions of their respective theaters or for modifications that were essentially multiple prototypes to prove and evaluate improvements planned for incorporation on the production line at the earliest possible time. Often Consolidated used their mod centres to create the drawings and tooling for the main factory aircraft which is why I have called some Mod Centre aircraft essentially multiple prototypes. When San Diego and Ft Worth inserted the change into their production line the drawings, tooling and production systems had already been organised and fully documented thus minimising the production disruption.

To indicate the amount of waste I quote Consolidated B-24 Liberator
_By March of 1944, Ford was producing one B-24H every 100 minutes, seven days a week. ... By mid-1944, the San Diego and Willow Run plants were capable of delivering more than enough B-24s and the Douglas at Tulsa and North American at Dallas lines were terminated. Fort Worth continued to build B-24Js until the end of the year. *On January 1, 1945, there was a pool of over 900 aircraft in storage waiting for modifications at mod centers*. *By VJ-Day, this was reduced, but still over 400 aircraft were awaiting modifications when the war ended.* _I would expect the majority of these will have be Willow Run aircraft needing major modifications and a far lower number Convair aircraft needing operating theatre modifications.

As an aside - Willow Run is often incorrectly credited with producing over half of all B-24 aircraft. The correct figures are
Consolidated San Diego, *6,725*
Consolidated Fort Worth, *2,743*
Douglas Tulsa, *964*
Ford Willow Run, *6,792 * 
North American Dallas/Grand Prairie, *966 *
making just 37% produced at Willow Run.

Mi


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## stona (Aug 24, 2016)

MiTasol said:


> The review of *'The Strategic Air War Against Germany 1939-1945'* from Caliver Books in the UK turned me off though so I would appreciate your further input on its value. To quote _Used. 260p 64 Illustrations Pbk. Mint. Compared to its American equivalent, this is not a particularly impressive monument to 70,000 RAF and Allied lives. However, it does present a short view of the strategic bombing offensive, and serves as a valuable summary of the main events. With 12 A3 pull-out tables. (RAF MUSEUM HENDON). _ EndQuote I am guessing that the review may be by the RAFM.



That review is a little harsh, there is plenty of useful information in the book. I do however agree that it is a pale imitation of the mammoth USSBS.
I would find it hard to justify paying $200+ for it and it certainly isn't worth the higher prices quoted! You could easily buy all four volumes of Webster and Frankland for less and get most of the statistical data, and some.
Cheers
Steve


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## MiTasol (Aug 25, 2016)

Thanks Steve
I got lucky recently and a family member got me *Air Bombardment: The Story of Its Development *by Robert Saundby and *Strategic Air Offensive Against Germany 1939-1945 Vol 1 *at a flea market for $10 for the pair. I have to wait for her visit at xmas to get them though. I was waiting to see the Webster & Frankland book to decide if it was worth getting the balance of the set as I find the USSBS series rather hard work. Having just read your suggestion I tracked down a five page review in _The Journal of Modern History_ and ordered book 3 new ($37) and book 4 used ($54). Book three will have to wait for a more realistic price.


Mi


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## GregP (Jul 21, 2020)

Reference post #23.

You might want to look up manufacturing learning curves. The "80% rule" you mention is really a 20% learning curve. There are many learning curves and they usually go ... in real life ... from 5% to 30%. There is also an eventual bottom to the learning curve ... a number that is the minimum value if everyone knows their jobs perfectly.


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