Sten SMG aircraft: productionized aircraft part 2, the what if

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In the USA, mind. There were European airliners that could match the DC-3 in economy and usability, they just weren't operating in the same conditions. It's also worth noting that the success of the DC-3, while certainly growing before the outbreak of WW2, was nowhere near as appreciated until after the war and surplus military C-47s began equipping airlines around the world that it truly gained recognition for its qualities. Before WW2 there weren't many DC-3s operating outside the USA, certainly not compared to after the war. KLM was one of the few pre-war foreign DC-3 operators, receiving its first in 1936, but it had also been a DC-2 customer. The Soviet Union was one of the first countries to recognise its qualities, and that resulted in several Douglas-built examples making their way to the SU, and licence production.
 
The thing is that the US airlines could not make money with the DC-2. They needed the government subsidy (air mail contracts) to actually make money.
The extra row of seats (50% more tickets) for very little more money for the airplane and fuel was what pushed it over the top.
Just about all of the European airlines were getting subsidies of some sort.
Just look at some of the airmail routes to South America.

There is no way this was a pure money making operation

With the DC-3 an operator could make money flying between two cities even if another operator flying between the same two cities had the airmail contract.
 
Grant, don't forget the Showa/Nakajima L2D!
 

Yes, I understand that, and I was pointing out that my above plane wouldn't per se be a plane optimized to be as cheap as possible to build, except for the point of avoiding using scarce aluminum.

Knocking an engine from Ju 52 nears it it to the concept; knocking two engines out of Ju 52 nears it further, since powerplant part of aircraft tended to be most expensive part.
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Well, yes, but the point of using several engines is you want to get off the ground with a useful payload, they're not there as ornaments (one hopes!). Ultimately for a transport aircraft it's a question of cost per ton-mile (both purchase cost and O&M cost). And I think you'll find an economy of scale there in that bigger aircraft provide lower cost per ton-mile. Though as you get bigger there's the question of useful demand for transporting large amounts of cargo/pax in one go, and possibly needing longer runways, and the really big high end engines were expensive on a per hp basis and probably reserved for combat aircraft anyway, etc. Probably in the time frame we're talking about something DC-3-like was the sweet spot.

There was the Bramo 323P, that was good for 1000 HP on 87 oct fuel; BMW 132s usually topped out at 900 HP, and were just with 1-speed S/C.
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I'm not that familiar with the Fafnir, but at least wikipedia mentions designers tended to prefer the 132 due to better BSFC.

Germans were using G&R 14N on some of their transports, 1180 HP max.
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True, that would be a good choice. However I think if this plane is going to replace the Ju 52 it needs to be in service before the war and ready to ramp up production. So at that point you cannot count on the G-R engines. Unless you setup license production of them, which I guess could have been a possibility.

Or then adopt a power-egg style approach. Use Jumo 211, G-R or others depending on availability.


Huh? If that's all there was to it, why did they even bother with the 3 engine variant?
 
z42 said:
Yes, I understand that, and I was pointing out that my above plane wouldn't per se be a plane optimized to be as cheap as possible to build, except for the point of avoiding using scarce aluminum.
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I agree.
Using light alloys on anything but 1st line combat aircraft was, in retrospect, a mistake by Germany 1933-45.


Luftwaffe indeed needed a bigger transport aircraft.
Already the Italian transports - often easily overlooked/dismissed - were much better than Ju 52/3m, despite using similar number of engines of similar power, just by the virtue of being bigger. Ju 52/3m was simply too small, thus making the investment of 3 powerplants per A/C a dubious one, IMO faulty one.

Ironically enough, it was the 1-engined Ju 52 that was cheaper once per ton-mile, since it used 60% of fuel the 3-engined types used for same cargo over distance; the lower purchase cost and maintenance cost is obvious.

z42 said:
Probably in the time frame we're talking about something DC-3-like was the sweet spot.
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It probably was.

z42 said:
I'm not that familiar with the Fafnir, but at least wikipedia mentions designers tended to prefer the 132 due to better BSFC.
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Alas, the whole passage cites no source, let alone an German-language source.


Yes, French engines will became useful after the (re)design is long finalized.

z42 said:
Huh? If that's all there was to it, why did they even bother with the 3 engine variant?
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Safety as the main concern? The engine-out situation on a 3-engined A/C should be the pretty safe thing, and aircraft should maintain altitude. 1-engined A/C does not have that luxury, and loss of many passengers' lives during peace time even due to one or two engine-out accidents might've spelled the doom on sales of such airliners.
The 3-engined type was also faster, and cruised at greater altitude (engines were with compressors, while the legacy BMW VII had no such thing; there was also much more HP to use), making the overflight above mountains feasible.
 
AS far as 3 engine planes go, there were 2 reasons, which overlap a bit. Also props come into play.

Twins are an obvious way to get more power.
However a twin with an engine out has problems, especially with primitive propellers (fixed pitch, two pitch) and only somewhat better with constant speed. You not only have asymmetric thrust you have either a prop windmilling trying to turn a dead engine or several sq ft of airbrake sticking into the air if the engine is not turning (really broken engine). Many or most early twins could not maintain altitude with one engine dead.
Thus the popularity of 3 engine planes. with 2/3rds the power, even with crappy propellers, the plane could stay in the air and not just extend the crash distance. Note that this only applies to a plane in cruising flight. Loosing an engine while taking off is still in a world of it's own. Ceiling with an engine was also important. More later.

Engines and airframes tended to zig-zag back and forth a bit. Sometimes the engine makers were ahead and sometimes they were behind. Sometimes the airframe makers wanted more power but did not want a single 1000hp engine (1920s) as the vibration and propeller requirements (size) were more than what the airframe makers wanted to deal with.

Sometimes it was the cost/availalabitly of the engines.
The Stinson company built 31 of these starting in 1934


with 3 260hp Lycoming engines. This was cheaper than using 2 400-450 hp P & W engines or Wrights. Note the ground adjustable propellers.
Some went to Australia where the 3 engine "safety" was a selling point. The two survivors were repowered with 450hp P&W's during WW II when they could not parts for the Lycomings. The change to fulling feathering propellers was dramatic. The Lockheed 10 with a pair of 450hp engines was good for 4,000ft on one engine, Using fully feathering props it could stay in the air at 10,000ft at the same weight. Airlines (and warplanes) had to take into account the terrain and weather conditions they were flying in.

With lower drag aircraft

same 8 passengers, 2 crew as the Stinson, cruising power could be much lower than take-off power and the better props allowed for matching engine rpm to speed much better.
There was a larger "reserve" of power to be used if one engine went out.
There was a version of the Lockheed 10 pictured above that used 550-600hp engines for airlines that flew in mountainous areas before full feathering props were common. Got worse gas mileage but they made the trade for safety.

Some tri-motors were a little shaky, some in the 1920s and one in the late 40s/early 50s



Somebody thought that this was a good idea, take the two 6 cylinder engines off a DH Dove and replace them with three 4 cylinder engines and shorten the fuselage a bit.
Plane shown has fixed pitch props to get around the problems they had with the variable pitch props. However the change just made the under powered condition worse.
7 out of the 20 aircraft built were repowered with Lycoming flat 4s of greater power and with full feathering constant speed props.

In the US in the 20s there was craze for using different sized engines, one large on the fuselage and one smaller one under each wing. That that did for handling with an engine out can only be guessed at. All 3 engines turned the same way.
 

As the saying goes, if you have an engine failure in a twin, the remaining engine serves to take you to the crash site faster. Many people have lost their lives when an engine conks out during the initial climb and the plane stalls and then goes into a spin due to the asymmetric thrust.

As an aside, modern airliners are a different beast. They have sufficient extra thrust to be able to climb out on a single engine, and control surfaces carefully designed to provide sufficient control authority in the entire flight envelope even with one of the engines out. Not to mention that modern turbofans or turboprops are so incredibly reliable that such cases are just very rare.
 
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WW II twin engine fighters are an exemption, WW II bombers fall into both categories.
P-38s in Asia sometimes made it back 600 miles with one engine. Obviously a P-38 had a surplus of power.
British Whitley's were going down with one engine, what the load was depended on how far before impact. Some Beaufignters could not stay in the air on one engine, depended on propellers, not all got feathering propellers, Many modern light twins do not have feathering props.

An A-26 with bombs gone and less than full fuel?? Probably in very good shape.
The Problem with transports is that it is sort of frowned on to lighten the load by throwing some of the passengers out.
Might want to check the tickets on some of the no frills airlines
 
Low effort, just serving to illustrate the point:
Say, with positive feedback wrt. the He 100 with Avia HS 12Y engine, Heinkel was given a green light to use Jumo 211 engine in further fighters produced. Heinkel have had the He 100 powered by Jumo 211B engine ready for flight in late January 1940. After a bit of polishing of the design, it was accepted in production in March 1940. Visible change being the belly radiator set aft the cockpit and two cannons, not that visible was 450 L fuel tankage instead of previous 350L.
Faster and longer-ranged than Bf 109E, it also better rolled at high speed; 109E climbed a bit better.
Still, it was not enough of an addition for the LW to prevail in the BoB - LW needed much more than a small silver bullet to change the outcome.

(basic picture is not mine; I've left the nose untouched, ditto for retractable auxiliary radiator; new, fixed radiator in red)




Heikel was already working on the Jumo 211F powered He 100 by Autumn of 1940.

Unintended consequence of the appearance of a new, high-performing fighter was that British started installing the Merlin XX on Spitfires, while wondering what to do with Hurricanes, the Mk.I experiencing 40-50 mph disadvantage in speed vs Heinkel. Even the 20 mph speed increase promised by installation of the - scarce - Merlin XX was not helping out that much.
Nobody wanted to guess the performance jump for the He 100 with the more powerful engines that Germans are ought to bring on the scene next year, thus negating any gain the Hurricane might've gotten.
 
For the British, perhaps an interesting thing might've been Percival's take on a simple and, hopefully, producible fighter, that still has a very good performance. Something shaped like one of their E2H racers, thin-winged as they were (unlike what eg. Miles Kestrel offered), but of bigger size (~40% extra in all 3 dimensions), giving the wing area of ~160 sq ft, and, obviously stressed for the military service. Start with the power-egg Kestrel in the nose etc.
Percival was designing his aircraft with wood and fabric, hopefully making it easier for an outside factory to make these, since Percival's production capacities were modest.
 
Kind of reminds me of a Ki-61.
 
SaparotRob said:
Kind of reminds me of a Ki-61.
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Size- and drag-wise, it would've been in the ballpark of the Yak-3, VG.33 (and looked a lot like these) and SAI fighters, or a tad less draggy and a somewhat smaller than the Bf-109F, Yak-1/-7/9, MC.202 & 205V, or D.520.
Obviously, much smaller than Spitfire, P-36/-40 & 51, Reggianne fighters, G.55, the Ki-61 indeed, as well as other Japanese fighters (Ki-44 being the closest in size), let alone Hurricane or F4F, to include the mass-produced no-nonsense normal fighters that were not on the heavy side.
 
SaparotRob said:
Kind of reminds me of a Ki-61.
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Many people claim the KI-60/61 resembles the MC.202, however, the Japanese Navy did purchase three He100Ds in 1940, which were assigned the IJN designation AXHei.

I've always felt it was more than coincidence that the KI-61 had similar features and one variant was even tested with an evaporative cooling system.
 
Geoffrey Sinclair said:
The AT-6 airframe in the 1943/44 period was around 52.4% of total cost, the combined P-39, 40, 43, 47, 51 and 63 airframe costs for the same time were 53.6%.
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Thank you.

This kind of points out the problem with the Sten gun school of aircraft design.
If you want to use the same power plant and armament of the standard/first line fighters you have already spent 46.6% of the total cost.
If you can reduce the cost of the airframe by 20% your Sten fighter will cost about 89.49% as much as the standard fighter. Is that "savings" worth it? as in pay for the new tooling, duplication of supply, etc.
Now if you can use a cheaper engine things get a bit more attractive at first glance but then you are very likely to loose performance. French were pretty good at keeping the speed up. Climb, cockpit view, field performance not so much.
You can get some of the performance back and save money by using less armament.

But now you need more fighters to get the same target effect. How many bullets fired to get the required hits to shoot down a certain percentage of aircraft.
 
Particularly so if you want both the standard and Sten variants in use. Due to the learning curve effects mentioned previously in this thread, this would drive up the cost of both models, likely canceling the benefit of the Sten model in the first place, compared to just producing standard fighters.

Now, due to security of supply, competition etc reasons it might be a good idea to have at least a couple of fighters in use, but that's a separate argument.
 
The US could afford multiple types easier than other countries. Also remember that the USAAC used two different generations of fighters during WW II.
The P-38,P-39,P-40 was one generation (and the P-39/P-40 may have been the "Sten" fighters compared to the P-38) and they were replaced by the P-47 and P-51.
Production of the P-39 and P-40 only lasted into 1944 to supply allies with lend lease. P-63 was out in left field someplace.
 
At the start of WWII US GDP was something like 2x larger than the next largest (Germany, UK and USSR all being relatively close). By the end of the war this had grown to a massive 5x gap. The US could simply afford a lot of things others couldn't.
 
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