The first and last commercial bombers

In my article about the commercial bomber concept, I began my discussion of the idea that airliners could be turned into bombers in 1918, with the report of the Civil Aerial Transport Committee. But it turns out that it appeared some years earlier, though in a far more fragmentary and undeveloped form than in the interwar period. And it involved airships, not aeroplanes.

In December 1912, the Admiralty received a joint report from the military and naval attachés in Berlin about the wartime disposition and employment of Germany's airship fleet. They suggested that the German government was paying subsidies to airship manufacturers so that their civilian production would be built to the minimum standard required for military service. So, in the next war,

the naval and military authorities will thus have at their disposal not only the Government aircraft, but also a number of dirigible airships belonging to private firms fully manned and equipped and ready for instant service[.]1

The attachés estimated that this would yield a German fleet of between 21 and 23 airships, though as it's unclear how many of these were civilian it's equally unclear how much of a difference their inclusion would make. But generally speaking, they increased the aerial threat to Britain:

A number of vessels in this formidable array of airships would be capable of sailing from Germany to Sheerness, Woolwich, or any other desired point in England and return without the necessity of an intermediate descent to the earth.2

The commercial bomber idea also appeared in the press. 'C. C. T.' (i.e. C. C. Turner) , writing in the Observer at the end of March 1913, also attempted to estimate the size of the German air fleet in the event of war. He came up with 13 government-owned airships, and

In addition, there are in Germany privately-owned airships:--

First-class... 2
Second-class... 83

So his total came to 23 airships, which corresponds well with the (presumably confidential) estimate provided by the attachés. This could be because they were working from the same information, or perhaps Turner got his figures from the Admiralty. The basic rhetorical function of the commercial bomber is much the same here as it was later, to inflate the size of the enemy air fleet and make it seem more threatening, the better to demonstrate 'the fatal complacency and ignorance permitted, and even fostered, in this country'.4 However, in the 1920s and 1930s, the commercial bomber idea was useful only so long as Germany had no air force, and more or less disappeared with the creation of the Luftwaffe (or so I argue). Here, it is being claimed that it is Britain which effectively has no aerial force to speak of, since it is credited with only 2 airships '(on order)'.5 So piling on even more German airships hardly seems necessary. Perhaps the point is to increase the German lead over France, which has 10 airships attributed to it '(these are less powerful than Germany's').6

If Turner got his information from the Admiralty, he might also have taken the idea that civilian airships could be used for military purposes from the same source. But perhaps it was obvious enough: military airships and civilian airships were in fact more or less identical at this time. Schwaben, a DELAG airliner which first flew in June 1911, was built to the same plan as two military Zeppelins, Ersatz ZII and ZIII. Two other DELAG Zeppelins, Viktoria Luise and Hansa, were indeed pressed into military service in August 1914 after a rudimentary refit. Though they were mainly used for training, it seems that Hansa, at least, flew combat missions over France and the Baltic. And Sachsen, the last DELAG Zeppelin to be built before the war, raided Antwerp on the night of 25 September 1914. So as well as being the first commercial bombers in theory, airships might have been the first, and even the only, commercial bombers in practice.


  1. The National Archives [TNA], AIR 1/657/17/122/563; quoted in Neville Jones, The Origins of Strategic Bombing: A Study of the Development of British Air Strategic Thought and Practice upto 1918 (London: William Kimber, 1973), 39. 

  2. TNA, AIR 1/657/17/122/563; quoted in Alfred Gollin, The Impact of Air Power on the British People and their Government, 1909-14 (Stanford: Stanford University Press, 1989), 231. 

  3. Observer, 30 March 1913, 11. 'First-class' means Zeppelins and Schütte-Lanzes

  4. Ibid. 

  5. Ibid. 

  6. Ibid. 

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25 thoughts on “The first and last commercial bombers

  1. Idle question: what was the public level of discussion of armed\converted merchant ships as commerce raiders in this period? I know they got used in WWI, but I'm not sure how much preparation/awareness there was of the concept before then.

    This would seem to tie in quite closely to the idea of "convertible" airships...

  2. TF Smith

    That's an interesting question - "guerre de course" was an old concept, of course, and the French had popularized it with the idea of fast steam cruisers throughout the second half of the 19th Century (aimed at the British), but those were commissioned warships built as such.

    The German concept of the disguised merchant raider seems to have been somewhat unexpected to the RN, given the time it took to hunt them down...but the British were also concerned about the "classic" idea of cruiser warfare by the Germans, as witness the response to the German Pacific squadrons - in which, of course, the RAN made its bones at Cocos Island (Sydney vs. Emden).

    I remember seeing what I think can only have been Emden's ship's crest in the wardroom aboard Castlemain in the 1980s - dunno if it is still there.

    Best,

  3. Post author

    It definitely is the same sort of thing (I thought I had mentioned arming merchantmen in a footnote to my article, but it seems not. Oh well). The Admiralty, at least, was aware of the German plans to arm fast liners at the outbreak of war, which is why they did the same thing (but for defence, not offence) with Lusitania and Mauretania: in fact they were built with government subsidies and designed with a view to future naval use in exactly the same way that the attachés' report alleged that German civilian airships were. (Matthew Seligmann's The Royal Navy and the German Threat, 1901-1914 (2012) is apparently very good on this, though I haven't yet seen it.) As for public discussions, a quick check of Google Books and BNA doesn't show much evidence of this before 1914, though the terminology may have changed. Converted merchantmen were used in the Russo-Japanese War and the American Civil War, for example, so the idea was around. Given how scarce discussions of Zeppelin commercial bombers are (the above is virtually all I have found, though I'm sure I read at least one other and forgot to note the reference), it's impossible to know whether the two concepts were related, though you'd have to think so, especially given that the Admiralty was evidently interested in the aerial version as well as the naval version.

    I've speculated that the guerre de course that TF mentions has a similar sort of relationship to the knock-out blow theory. The whole question of naval influences on early thinking about aerial warfare is an interesting one, which coincidentally will come up in another post in the near future...

  4. The way of considering the airship here is much more naval than aeronautical, and there may be a combination of wargame type error (invulnerability, weather capability, performance) crossed with air as 'new-naval' ('sailing') which relates to the idea 'bigger is essentially better' (or more powerful - in warships) which aviation was to soon discover it generally wasn't.

  5. The German concept of the disguised merchant raider seems to have been somewhat unexpected to the RN, given the time it took to hunt them down

    surely not, as we actually prepared ships pre-war, even during construction, as potential armed merchant cruisers. That said, it's fairly clear that the commercial-bomber idea originates from the practice of converting merchant ships.

    Didn't the Germans use Ju52/M3 as bombers in Spain, btw?

  6. Alex, yes, Junkers Ju 52/3ms were, and they did an effective job as both freight/transports and as bombers. Technically speaking (as against Brett's writing about perceptions) the transport bomber was viable in the 1920s to early 1930s, and there were a few used in W.W.II, but like all transports they were generally vulnerable to enemy fighters, and as bombers likewise, while dedicated bombers were (simplistically) either faster or better defended, lacking design compromise. I'm thinking particularly of the Bristol Bombays the RAF used in early N Africa as both bombers and transports. Ad-hoc transport bombers, like Count von Rosen's DC-2 'bomber' for the Finns were also notable, but exceptions.

    In the interwar era, such multi role capability was attractive financially too...

  7. Post author

    JDK:

    Yes, and there was a lot of talk of Zeppelins as dreadnoughts of the air (by a nice coincidence they were about the same length), against which Britain had only cruisers or worse, destroyers. Thinking of aerial warfare in naval terms was not completely silly: for example, it was grasped early on that just as with the sea (but not the land), it's not possible to occupy the air: the best that can be hoped for is air superiority. But like all analogies it can be pushed too far and that was easily done when there was little practical experience of aerial warfare to go on.

    Alex:

    You need to read my article (which you can do for free), and/or my previous comment! But here I will just stress that the commercial bomber concept is not just that civilian aircraft can be used in combat roles, as happened in Spain (though as I understand it, the Ju 52/3ms there were militarised versions, not ordinary civilian models) and elsewhere. It's also that actually existing civilian aircraft already in service with airlines can be refitted for combat very simply and quickly (and in secret, if need be) and hey presto, it's an instant bomber force. This caused great headaches for would-be disarmers in the 1920s and 1930s, because you could disarm every single air force in the world and there was still the possibility that some aggressive power could covertly and suddenly convert its airliners into commercial bombers and launch a knock-blow against its neighbours. So then they got into convoluted responses like suggesting the international control of civil aviation (e.g. 'World Airways') to prevent any power having access to airliners, or an international air force to be held in reserve against such an eventuality. German before 1935 was the poster child for this problem: it had no force but suspicious minds could always point to its strong, subsidised civil aviation industry (so different to Britain's!) as evidence that it was still a danger. And they did (see my article). So what's novel here is that this is one of very few cases where airliners in regular service were handed over to the military, turned into bombers, and used as such. The Greek Ju G.24s in 1935 I discuss in my article are still a possibility, and then there's South Africa's Ju 86s might count here, though I think they were explicitly purchased as dual role machines (i.e. not ad hoc or even planned-for conversions). That's starting to split hairs, though.

  8. Brett said:
    "... the Ju 52/3ms there were militarised versions, not ordinary civilian models..."
    That is correct. Strictly speaking military transports capable of being used as defensively armed bombers with some fitting changes.

    "It's also that actually existing civilian aircraft already in service with airlines can be refitted for combat very simply and quickly (and in secret, if need be) and hey presto, it's an instant bomber force."

    Despite the worries (or perhaps because of!) that was a little harder to do with genuine civilian aircraft, and I believe the ultimate lack of benefit in civil to military convertible types (or need, in the face of more straightforward options) meant they weren't developed further in the end.

    "... then there's South Africa's Ju 86s might count here, though I think they were explicitly purchased as dual role machines (i.e. not ad hoc or even planned-for conversions)."

    My refs indicate that 17 were bought by South African Airways as straight airliners, (Ju 86Z) while one military Ju 86K was also delivered. See: http://www.saairforce.co.za/the-airforce/aircraft/175/ju-86-k-3-z

  9. Post author

    Despite the worries (or perhaps because of!) that was a little harder to do with genuine civilian aircraft, and I believe the ultimate lack of benefit in civil to military convertible types (or need, in the face of more straightforward options) meant they weren't developed further in the end.

    Certainly conversion wasn't as anywhere near efficient as P. R. C. Groves and others claimed; commercial bombers were only ever of marginal usefulness. I think it was also about numbers. Take Luft Hansa's Ju 52s. There were about 80 of them (according to Wikipedia), enough for a couple of gruppen. But in September 1939, the Luftwaffe had about 1200 bombers (including some militarised Ju 52s). So using the civilian Ju 52s as bombers would not have added substantially to German airpower. Many were indeed impressed into military service, but they were sensibly used as transports (including airborne assault), not bombers. That suggests that commercial bombers might have been more attractive to smaller air forces like Greece's, or ones created from scratch like Franco's. But then again, the airlines available to them were also small, and also more diverse in terms of aircraft types (so more logistical, training, tactical headaches). So it usually wasn't worth it, except in desperation. Which also fits the available evidence.

    South Africa is an interesting case though. You're right about the Ju 86s, I was thinking of the Airspeed Envoys -- though contrary to what I said, these would have to be called planned-for conversions (they were even termed 'Convertible Envoys'). Seventeen aircraft was quite a big purchase (they also had a dozen or more Ju 52s), enough for a squadron with some spare airframes: a useful addition to the SAAF (in secondary theatres at least). But even though they were bought as straight airliners, I wonder if they were bought with conversion in mind? The Envoys show that the South African government was thinking about this (the Envoys were modified at South Africa's request), and the fact that a single military variant of the Ju 86 was purchased perhaps suggests that they wanted some experience in the type before war (and conversion) came. But I'm just guessing...

  10. It's an interesting area, and I think it needs to be separated between what people thought and lobbied about, and on the other hand, what could be done technically and how practical that was.

    Taking the technical side (leaving the former to you!) in 1919, generally aircraft were fabric covered and bombs could be carried externally without much penalty, as well as by literally removing fabric on the belly and adding simple racks to existing structure internally. Likewise gun positions were not so hard to create. And of course, the first airliners of the inter-ar period *were* converted bombers, either two seaters like the DH-4 and 9, Bristol 'Tourer' from the F-2B fighter or heavies like the O/400, 1500 and Vimy derivatives.

    The Ju 52/3m and Ju 86 were all-metal stressed skin construction, and it was a more major job (though possible) to modify that structure to allow for internal racks and spring loaded or lever operated bomb doors. The alternative was to carry bombs externally, much easier to do by attaching racks to structurally strong points; but the bomb carriage would always be a bad compromise (sizes, weights, loading related to c of g and ground clearance and so on...) and then there was the question of aiming them (adding a bombsight and bomb aimer with a view of the target was needed) as well as the performance degradation of drag and weight of the bombs. None of this was impossible, but it was a compromise, with all the shortcomings of compromise rather than dedicated design.

    There are profiles online showing the SAA Ju 86Z airliners in SAAF use with external bomb racks but dorsal gun position and 'dustbin' ventral position of standard Luftwaffe type, which seems a bit suspicious to me. Rather obviously, as well as needing the actual retractable dustbin structure, the aircraft needs a reinforced structure in that area to hang and operate it from. That would lead back to the 'bought convertible' argument, but with the Germans supplying the gun positions but not the offensive weapon setup. Needs further evidence.

    Countering that were those 'mailplanes' which were really fast or light bombers in civil disguise. (Plus deliberate misinformation campaigns like the mailplane origins of the Dornier Do 17, repeated long after the war in credible publications, despite being propaganda only.)

    No one built civil transports that could be bombers in the way that the RAF had transports that could be bombers like the Bristol Bombay and Handley Page Harrow; while civil Junkers could be converted to bombers it was either depot-level workshop or ad-hoc.

    Of course there was one civil airliner turned bomber of import in W.W.II that I mentioned earlier: von Rosen's DC-2, "Hanssin Jukka" which, wonderfully, survives and was recently restored, providing a fascinating source document on the concept, and illustrates very well how such things could work and their limits.

  11. I've always wondered about those SAAF Junkers, AFAIK the only German aircraft operated by the Allies. That link says that they dropped from squadron strength down to a flight on ops because of serviceability; presumably, even though the engines were either R-R Kestrel or P&W, getting parts was a real headache.

  12. There were a number of other German types operated by the Allies, from memory, He 115, Bf 108, Fi 156 and so on, but none in squadron strength, which may be the differentiator.

    All the wartime images I've seen of the SAAF Junkers show radials, Pratt & Whitney Wasp or Hornet power, and so I believe the Kestrel ones were re-engined.

  13. Post author

    JDK:

    There are profiles online showing the SAA Ju 86Z airliners in SAAF use with external bomb racks but dorsal gun position and 'dustbin' ventral position of standard Luftwaffe type, which seems a bit suspicious to me. Rather obviously, as well as needing the actual retractable dustbin structure, the aircraft needs a reinforced structure in that area to hang and operate it from. That would lead back to the 'bought convertible' argument, but with the Germans supplying the gun positions but not the offensive weapon setup. Needs further evidence.

    Your sources are going to be better than mine, it's certainly hard to find photos of the South African Ju 86s online. In this one, though, it does look like there is something there where a retracted dustbin might be. Then again, the photo here is clearer, and does show something there, but it's hard to tell what it actually is. I also found a photo on this site labelled as showing SAAF Ju 86s in flight (it's a family history of someone who flew in them) and the dustbins can clearly be seen. Maybe it's just the angle, but the roundels look more Swedish to me; it looks like the Swedish air force did use military and civil versions of the Ju 86. From the noses these look like the latter, which again would be interesting in terms of the amount of conversion that's been done.

    Anyway, enough of my amateur planespotting! You make very good points about the practicalities involved and how these changed over time. I wonder how much commercial bomber advocates were aware of these? P. R. C. Groves, for example, was never much of an airman. Before the war he had no involvement in aviation. He served a couple of months as an observer on the Western Front at the end of 1914, then served in a number of staff roles; got his wings in 1917 in Egypt and commanded a reserve wing; but then went back to (increasingly senior) staff duties, culminating in 1918 as Director of Flying Operations at the Air Ministry and thereafter represented Britain on air matters at Paris and Geneva. It's questionable how across the technical details involved in his confident pronouncements about the danger of convertibility he actually was. As secretary-general of the Aerial League and editor of its journal Air at the end of the 1920s he would have been in a good position to keep in touch with developments, but by then his views were fixed and he wasn't the sort of person to change them.

  14. "I also found a photo on this site labelled as showing SAAF Ju 86s in flight..."
    Good find, but I'll tell you something else about the angle of *the* Ju 86 - it's a composite image with three copies of the same shot of a single aircraft superimposed and then a poor quality copy made of that (the generally muddy look). Note that every coincidental juxtaposition of every foreground/background item of each aircraft is exactly the same. That would be remarkable formation flying! And raises suspicions of the image's provenance.

    Other thoughts to come later...

  15. Post author

    Ha! You're right. If you look at the clouds in the background it becomes clear that they are identical. I wonder what the motive was? Propaganda? Aesthetics? Sales? Whatever the reason, it's kind of hard to accept it as any evidence for the SAAF Ju 86s now.

  16. Having looked at the other images, there's some interesting evidence, but not what it seems at first glance! In the 'that went to war' image, the 'dustbin' of the aircraft on the left of the image is actually the mainwheels and doors of another Ju 86 behind (the tailwheel is also visible, plus the tip of a fin & rudder, proving it). On the Ju 86 background right the oddity below the midships position is actually the Junkers flap arrangement, where the flap (and aileron) actually sit behind and below the wing, with a slot above. And that's what's visible on the apparently unarmed Ju 86 in the SAAF official website shot.

    However on the other side of the ledger, the 'that went to war' image shows a dorsal position that could be a standard German style one, and the sway braces for external, centre-section bomb-racks on the nearest aircraft. More data still needed, but we progress!

  17. JDK: on the Do 17, do you mean that it was never tested by Luft Hansa, or that it was a convenient cover story? ’Fast mail plane' does seem to be a convenient placeholder for 'insert future military use here' more generally; cf. Whittle's claim that that was what he initially thought the jet would be good for...

  18. TF Smith

    Interesting discussion - may be too late to the party, but I think that various US and Soviet-manufactured transport aircraft (C-130s and An-24s, for example) have been pressed into service as makeshift bombers in the Cold War and post-Cold War era. Those may come close to the converted transport to attack (AC-47, AC-119, AC-130, etc) type function, but does show the utililty of a large, relatively slow, tactical support aircraft.

    On the "German aircraft used in action by Allies during WW II" I believe the Dutch had several models of German-desgned/built flying boats in service with their colonial (NEI) army and naval air forces in 1942...

    The Fiat BR.20s in the IJAAF over China and Manchuria always struck me as an odd procurement story.

    Best,

  19. Good points! The post war use of transports is a fascinating field, but operated under different social aspects (Brett's angle) and technical expectations (mine!) but it's good to mention.

    Indeed, the Dutch NEI air force had Dornier Do 24T flying boats, which went onto RAAF use, after the Japanese advance. They're often sort-of-legitimately left off this kind of list though, as the Do 24 was designed for and used by the Dutch (and licence built at Aviolanda) while the German forces only adopted the design later after initially rejecting their trial examples.

    Odder still than the Br 20s (though I agree) is the attempt by the British Air Ministry to buy Regianne Re 2000s just pre-war for the RAF to bolster a equipment shortfall for what was to be the Battle of Britain, where they'd have ended up fighting Regia Aeronautica Br 20s and Fiat CR 42s! But that's well off topic.

  20. Jakob, re Do 17, neither. It seems the pre-war propaganda / cover story morphed post-war into an unlikely tale that it was built as a six-seat mailplane, rejected by Luft Hansa as the seating was too cramped, and lay, forgotten in the back of a hangar until re-discovered by a Luft Hansa pilot who found it would make a wonderful bomber. This illogical myth has been repeated as fact by most publications on the type until the 1990s, where going back to contemporary documents, payments and context, showed there was no credibility of the touching tale being possible but that it was just built as a bomber, with a freight aircraft cover story. See the 'history' section here http://web.wt.net/~kikuko/Do17depot/Do17index.htm under 'the big lie' (great headline...)

  21. Post author

    Pers. comm. from a Dutch historian I met at the AAEH this week -- apparently (some? most? all?) interwar KLM airliners were intended to be converted (ad hoc? pre-fitted?) into bombers in wartime. It didn't happen because the Netherlands was defeated too quickly. I haven't yet found any documentation for this, though.

  22. I would be interested in some evidence on that, because it seem highly unlikely.

    Certainly the 1920s Fokker F.VII family could be made into bombers (and were - how usefully, I don't know) but by 1939, most types still around were unsuitable (too old or slow) and I don't recall ever seeing any mention of such built-in or specified convertibility. In 1939 KLM's main fleet were DC-2 and DC-3 airliners, for which Fokker was an agent. Both were later used as bombers (see again the Count's DC-2, as mentioned above!) but not as a prior requirement by any customer via Fokker, or pre-war from Douglas - happy to see sources saying otherwise, of course.

    At base, convertibility of a stressed skin type without the design-spec dual role is a bigger (and usually well documented requirement) than was the case in the fabric-cover era.

  23. Post author

    Our conversation didn't get down to specifics so I can't speak to that; but I hope to follow it up.

    In my present research in Archives New Zealand, I've found a 1913 private proposal for a convertible passenger airship company (which seems to have been ignored), as well as high-level discussions in the NZ military in 1918 about another private proposal to subsidise the Walsh Brothers' flight training school's planned purchase of 'highpowered seaplanes suitable for coastal patrol'. This was ultimately turned down, but it was taken seriously. With no air force NZ would have had to impress private aircraft in any serious emergency anyway.

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