Junkers-Larsen JL-12; The Tommy Gun-Ship

May 20, 2024

The First World War saw aircraft take their place amongst the myriad of weapon systems that form a critical part in modern militaries. The four years of the conflict saw them used in a range of roles, which they continue to fulfil even today, but as the war continued and, desperate to break the deadlock on the Western Front, the idea of using aircraft in direct support of ground forces became pretty much a standard tactic.

While conducting these missions was often done by standard fighter scouts, such as the Sopwith Camel, these delicate aircraft were very susceptible to ground fire and so the notion grew of building dedicated attack aircraft for the role. A great example of this is the Sopwith Salamander, which provided its pilot and engine with armoured protection.

But the end of the war also largely spelt the end of these specialist attack aircraft as budgets were cut and air fleets radically reduced. However, that didn’t mean that there still wasn’t an appreciation for the potential of ground attack aircraft and one ambitious American company, hunting for orders in the lean post-war years, thought they had a better idea on how to do it.

Instead of using the standard front firing guns to conduct strafing runs, as was the norm, how about fitting a number of the new Thompson submachine guns firing directly downwards to literally carpet the ground beneath the aircraft with bullets as it flew overhead.

And when I say a few…I mean thirty!

This is the Junkers Larsen JL-12.

The development of this aircraft starts in Germany, if you hadn’t guessed from the name already. With the end of the First World War, German aircraft manufacturers faced a bit of a problem. Not only was the world now awash with surplus aircraft, the terms of the Treaty of Versailles forbade the German military from having aircraft and severely restricted the production of them in Germany altogether, especially in the immediate post-war period.

And for an aircraft magnate like Hugo Junkers, that was an issue. Junker’s and his company were the cutting edge of aircraft design at the end of the War, primarily because, in an era when just about everyone else was building their aircraft out of wood and fabric, Junkers were building theirs out of metal.

In 1919 Junkers created an aircraft that really was, in my opinion, a largely unrecognised revolution, the Junkers F 13. Today the concept of a six-seat, enclosed all metal courier/executive transport is perfectly normal, you see them literally at just about any airport on the planet. The F 13 was the first of them. I mean when you compare it to what else was flying at the time, and to be honest even for some years after, the F 13 was the future.

This was very much appreciated by many operators, and the F 13 sold widely. And amongst those who recognised the excellence of the F 13 was one John Larsen, an American who saw an opportunity.

After the F 13 set a new world altitude record in June 1919, Larsen contacted Junkers requesting a test flight of the new machine. With Junkers unable to enter the American market because of the whole, you know, world war thing, Larsen offered to be Junker’s North American agent, with the idea being that Junkers would ship F 13’s to the United States in kit form which could then be constructed at Larsen’s factory. To bypass the whole “Made in Germany” issue Larsen obtained a production licence, though this was a ruse as the aircraft were basically just assembled in the US; this would come back to bite Larsen, but we will get to that.

In December 1919 Junkers shipped a F 13 to Larsen and in early 1920 a new company was formed, Junkers-Larsen, to market the aircraft. The designation was also changed to JL-6, indicting the aircraft had six seats, and some sources have remarked that though the “JL” stood for the company name, it was also convenient that it was also John Larsen’s initials, which may have been useful for dealing with customers who may have had anti-German feelings.

And customers were certainly in the market for the JL-6 Larsen rapidly sold test examples to the US military and then achieved a number of sales to the US Postal service and to companies involved in oil prospecting in Canada.

Things were looking fairly rosy for Larsen and Junkers for the American market, and twenty-eight JL-6s were rapidly imported. As said the US Postal Service was very taken with the design, and JL-6s were used to run airmail routes between Chicago and New York, where their enclosed passenger cabin and excellent performance made them a natural fit for carrying rapid postal deliveries.

And then things went wrong.

JL-6’s started crashing, in fact they often spontaneously burst into flames and THEN crashed. Between May 1920 and February 1921 four aircraft were lost, along with seven crew members, events that caught the attention of the press and raised a lot of questions about the JL-6.

It seems the steep loss rate was attributable to two main factors.

Firstly, the American pilots were not used to flying a monoplane, especially one capable of such high altitude, long distance performance.

Secondly, it appears that Junkers Larsen performed an unauthorized modification to the aircraft when they were building them from the knock down kits, fitting the wrong type of rubber fuel hose.

These were fine while using petroleum as fuel…but the aircraft in question used benzene. This both rapidly corroded the hoses and tended to freeze at higher and colder altitudes…which is where the JL-6s were operating.

Ruptured fuel lines suddenly spilling fuel over hot engines as the JL-6s descended for landing is generally thought to have been the cause for the spectacular spate of fiery crashes, and the effect on Larsen’s sales was catastrophic.

Plus, further bad news followed. The Allied Commission responsible for policing the “no-German aircraft” policy caught wind of the export’s of F 13’s to the United States and seized eleven aircraft sitting in crates at Hamburg docks.

John Larsen had a significant problem. He had been cut off from his supplier but still had eight aircraft at his factory looking for buyers plus a number of others that were on lease but which would be returned by their clients spooked by the rash of losses amongst the JL-6 fleet.

Larsen needed to find a new customer in short order who would snap up his outstanding airframes. To do this he needed to make a splash and sell to one of the few operators with the cash to buy, the US Army, which meant turning the JL-6 passenger/light cargo aircraft into a military one.

And so, he came up with the JL-12.

In 1921 Larsen’s converted one of the JL-6’s to this new configuration, which added a surprising amount to the aircraft. Firstly, the German BMW engine was removed and switched out for a far more powerful – and American-made – Liberty engine that was significantly more powerful at 400hp than the German ones originally supplied.

Also added was a plate of belly armour, composed of aircraft-grade aluminium which when combined with the JL-6’s aluminium skin raised the total thickness to around 5mm. Probably not going to stop a lot but, as said, still generally more than contemporary aircraft of the day.

But the armament is where Larsen went full on, with twenty-eight Thompson submachine guns mounted to shoot downward from the aircraft’s belly.

These were arranged with twelve guns in the front section of the hold and sixteen more in the rear. The forward guns were tilted to fire slightly forward, while six of the rear guns were aimed directly down and the final ten aimed slightly to the rear.

Control was via three levers; the first fired only the forward guns, the second the mid and rear guns while the third would fire all of the guns together, creating an absolute blizzard of lead upon whatever the aircraft was flying over, no doubt expected to be enemy troop concentrations or trenches.

Ammunition was the standard Colt .45 with each “tommy gun” using the 100-round drum magazine for which this gun was famous. Three magazines per gun were carried and Larsen stated that reloading the whole assembly in the air took just four minutes.

To top it off two gunswere thoughtfully given to the pilot and his assistant which, as the cockpit of the JL-6 and -12 were open while the cabin was closed, could be used to repel pesky enemy fighters…or at least that was the thinking.

This all might seem a bit optimistic, but the JL-12 was actually no slouch, with a top speed reportedly being 143mph (230km/h) and the aircraft able to climb extremely quickly. In fact, reports of the day state that it could climb as quickly as many contemporary scout fighters of the time.

Unfortunately, despite Larsen’s optimism and salesmanship, the US Army wasn’t in the market for a new attack aircraft. Sales efforts continued into 1922 but nothing came of this and so the JL-12 disappeared into obscurity.

I am not really sure what happened to it, certainly Larsen returned unsold aircraft to Junkers in Germany where they would go on to be successfully sold when the Allies loosened their grip on aircraft sales restrictions in a few years, but the JL-12 just seems to have vanished. The same could be said for Junkers Larsen, who also are difficult to find accurate information on, though I suspect that if John Larsen forked out for the purchase of thirty Thompson guns then he might have had to vanish from creditors himself, because the costs of those would have added up to a small fortune.

But all in all John Larsen, and his final aircraft, are an interesting little quirk in aviation history.

Sources/Related:

https://hugo.junkers.de/blog/flugzeuge/junkers-larsen-jl-12/

http://hugojunkers.bplaced.net/junkers-f13.html

https://ntrs.nasa.gov/api/citations/19930085313/downloads/19930085313.pdf

https://web.archive.org/web/20120306172359/http://www.flightglobal.com/FlightPDFArchive/1922/1922%20-%200073.PDF

https://en.wikipedia.org/wiki/Junkers_F_13

https://www.history.navy.mil/our-collections/photography/numerical-list-of-images/nhhc-series/nh-series/NH-91000/NH-91059.html

http://hugojunkers.bplaced.net/junkers-f13-production-list.html

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