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

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A lot of air forces indeed were specifying better props, and were not trying to saddle the future designs with 60 mph stalling speed like RAF did it in better part of the 1930s.


Look at these HS engines from the German point of view - hundreds of them are free, and can still be good in a streamlined fighter. Ironically enough, Czechoslovakians were installing better HS engines on their biplanes than what the French were installing o their MS 406s.
Avia factory can be re-tooled for production of DB engines for example, without waiting for a few years like it was the case.


I was trying to point out that, if Soviets churned out the sets for 10000+ worth of fighters in the 1930s (plus thousands for other A/C), other aircraft-producing countries should be able to do it in hundreds/low thousands in the same time, obviously depending on the size and capability of industry of a particular conutry.
 
I never thought Hispano-Suiza could be so entertaining.
 
tomo pauk said:
A lot of air forces indeed were specifying better props, and were not trying to saddle the future designs with 60 mph stalling speed like RAF did it in better part of the 1930s.
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True but by total accident (no planning involved) the low stalling speed meant the the two British planes (with new propellers) made usable carrier aircraft. I am not saying good, just saying they could be used.

I would also think carefully about some of the French high performance fighters in actual service use. Even the Hawk 75s had a higher than expected attrition rate just from landings.
French airfield construction/upgrading may not have kept pace with actual field requirements. Some small nations kept all of their fighters on just a few airfields (or only one?)
The only way you are going to get hundreds of "free" H-S engines is to steal them from the hundreds of Avia 534 fighters. And since the Germans were using the Avia 534s as fighter trainers, target tugs, glider tugs and export fighters to Bulgaria I am not sure where the balance sheet winds up after you build several hundred new airplanes (at a minimum) to take over those duties.
I am not sure if the Czech HS engines were better than MS 406 engines. The Spec sheets say the Czech engines were good for another 750meters of FTH, but they don't say why.
I am not going to worry about a 5hp difference in take-off power.
tomo pauk said:
other aircraft-producing countries should be able to do it in hundreds/low thousands in the same time, obviously depending on the size and capability of industry of a particular conutry
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And that is pretty much is the key. Many of the minor countries did not have the industrial infrastructure to handle even small scale aircraft production once you get out of the fixed landing gear, wood and fabric construction.
In 1938 The Czech's had 7 different companies build aircraft, and 6 making engines (even if one of them was making 4 cylinder 45-55hp engines).
The British were buying armor plate for the RN from Czech steel works.
The Balkans or Baltic states were nowhere near as advanced in infrastructure. They many have had a clever designer or two but building advanced aircraft in numbers is not really something they could do.

Romanian I.A.R. 15 fighter 5 built in 1933-35?

very good but not really any better than the PZ 11 that they built under license.
This airplane used a Gnome-Rhone 9Krse 600hp radial.
The wing was of extremely mixed construction. two duralumin box spars with with tubular drag struts and wire bracing with duralumin ribs and sheet while the outer wings used Romanian pine and plywood ribs and fabric covering. Chrome moly steel tube fuselage with forward part covered with duralumin panels and the rear covered with fabric.
Now figure out what the various small countries had for automotive manufacturing (or motorcycle) or train locomotive (or rail cars) or other industry that could make parts/components for aircraft.
Italy was bit player as far as industry went.
Going 1 or 2 levels below Italy was not going to work.
 
Shortround6 said:
True but by total accident (no planning involved) the low stalling speed meant the the two British planes (with new propellers) made usable carrier aircraft. I am not saying good, just saying they could be used.
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Carrier suitability was beyond the scope of 90% of the fighter designs between 1925 and 1940.


Trainers can be powered by 3rd tier engines, both of German and now Czech production. The HS 12Y engines can be improved by installing a better S/C, mimicking the improvement that was done in France by S-P duo.
I am sure that the Czech HS 12Ys, that also ended up in the IK-3 fighters, were the better than what the MS 406 gotten, despite the French having in production the better 12Ys. Spec sheets are many times skimpy on details, however 2460 ft worth of difference is similar of what Merlin III had over the DB 601A, or what V-1710-81 had over the -39, or what Merlin XII had over the Merlin III.


Czechs made aircraft in hundreds between 1935 and 1939, plus a lot of other military and civilian hardware, so they are probably in best shape between the small-ish countries to pull this one. Poland is probably after them, they were also making aircraft in hundreds, and exporting them. However neither of the countries made much of a monoplane fighter with low-set cantilever wing (small series of the Avia modern fighters aside), so there was a lot to improve even before we start thinking about the retractable U/C for them.
Italy and France should've be getting a greater level of criticism, both countries being on forefront of development of A/C (both actually and in propaganda terms), and with more developed industry.


Kinda shows how much going with biplanes after the 1st half of 1930s was obsolete thinking
It was much easier to up-engine the existing design, than to 'under-wing' an existing biplane design.
 
tomo pauk said:
Carrier suitability was beyond the scope of 90% of the fighter designs between 1925 and 1940.
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Merely pointing out unintended benefits or possible consequences.
tomo pauk said:
Trainers can be powered by 3rd tier engines, both of German and now Czech production. The HS 12Y engines can be improved by installing a better S/C, mimicking the improvement that was done in France by S-P duo.
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Problem is the timing of the programs. The Avia 534s were intended to be 1st line combat aircraft and many of them were built before the German take-over. If you want to use the H-S engines in new, better airframes (He-100s?) you have hundreds of Avia 534s sitting around airfields with no engines and you need the trainer and tug aircraft.
Using Argus, Hirth or Walter air cooled V-12s of 400-500hp is probably not going to work well and you have the cascading effect. What aircraft don't get engines while you build several hundred air cooled V-12s.
Please note that Argus, Hirth and Walter used common cylinders between many of their 4, 6, 8 and 12 cylinder engines so one V-12 may replace three 4 cylinder basic trainer engines.
Well, many of the higher HP H-S engines traded altitude performance for the higher power. They swapped the 10.0 supercharger gears for 7.0 supercharger gears and gained around 120hp for take off and 50-70hp at low altidude in exchange for 1000-1500meters of FTH. A few engines used 8.3 supercharger gears. Sort of like the Merlin VIII.
Unless you are building flying boats or transports you probably want the 10.0 gear engines.
The later Allied engines used higher supercharger gears to gain altitude performance with better fuel.
There were a number of problems with the H-S engines which were only mildly papered over (if you take your glasses off) during the late 30s. Due to the basic construction the bemp was limited and the allowable rpm was limited. H-S did raise the compression on some models to suit newer fuel but they may have over done it. They went to 7.0 to 1 but that limits the amount of boost you can use, but since the H-S supercharger was really pretty crappy it may have been a good short term solution. The older engines used 5.8 compression (mostly)

Now in the very late H-S engines (like a -50) they changed the connecting rods and few other things and got the engines to run at 2500rpm. Using 40.4in of boost for take-off this gave them 1100hp and 158bmep. Also gave Piston speed of 1787fpm. However this also meant that the 1000hp rating was 3260-3300 meters (10,800ft) which was significantly lower than the DB 601, Merlin III or even the Allison C-15.

The -45 engine with the SP supercharger was rated at 920hp at 4200 meters (13780ft)
The -49 engine with SP supercharger and 11.46 gears was good for 910hp at 5250 meters ? (17,220ft) while only loosing 25hp for take-off.
Please note that these two engines used concentric yoke connecting rods and dampers despite remaining at 2400rpm.
Please note that the -31 engines used in the MS 406 was supposed to use the concentric yoke connecting rods and dampers while the 12-Ydrs engines used articulating connecting rods and no damper at the same rpm. Something other than performance on the spec sheet was going on (like engine life?/durability?)

tomo pauk said:
However neither of the countries made much of a monoplane fighter with low-set cantilever wing (small series of the Avia modern fighters aside), so there was a lot to improve even before we start thinking about the retractable U/C for them.
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A problem for the lower tier nations is that they need to leap frog.
Building fixed landing gear monoplanes with 2-4 mg guns was better than using biplanes but the difference was slight if you are being attacked by retracting gear monoplanes with 6-8 guns (or equivalent). You shoot down a few more attackers and surrender 4 days later?
It is an impossible situation. The rate of progress in aviation from the late 20s to the late 30s required much more industrial infrastructure.
 
Shortround6 said:
Merely pointing out unintended benefits or possible consequences.
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I know. But, FWIW, not a factor for 90% of fighter designs of the era.


There is still more than 12 months before the German take over of Czechia and onslaught on the West - a lot of time to not just make a few hundred extra engines (so in total these engines are at half price as far as Germans are concerned) but also to re-engine a portion of the trainers 534s with perhaps Walter Saggita of 600 HP?


I wouldn't mess too much with engine internals, but try to retrofit a better S/C (from the DB 601A, preferably) on the basic Ydrs engine so it comes close to the altitude performance of the HS 12Y-45 the French are getting, sacrifying a bit of take off power need-be.
 
tomo pauk said:
I know. But, FWIW, not a factor for 90% of fighter designs of the era.
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True but the Hurricane would operate from crappier airfields. The Spitfire would at least take off and land from short ones, surface conditions were more critical. We get a lot of discussion on the Miles M.20 which landed (and took off) at at least 80mph or over 33% faster than the early Hurricane and Spitfire. Accidents on primitive air strips?
They were completing the last of the 534s in the Spring of 1939. Some sources claim 78 (? numbers vary)) of the already built aircraft went to Bulgaria later.

I have no Idea how many of the Walter Saggita engines were built. The number seems to have been small. 4 Different twin engine aircraft (1 each) and 1-3 single engine aircraft?
Granted there were both an inline 6 and an inline 4 (unsupercharged) so it might not have been very difficult to expand production. Given the size of the cylinders think of these as DH Gypsy 4 and 6 engines with the Gypsy King only a bit lighter.


Well, this may go well or go badly.

A power curve for the 12 Ydrs was posted today in the Avia 534 photo thread. ebay: Avia B534
Also a rather detailed list of the J-S engines.

There also may an explanation as to the different altitude ratings. The Power curve for the Ydrs engines shows 860hp at 3250meters (trying to read a small graph) and the wording is French. However with what looks to be 400kph of speed and 2nd line on the chart shows 890hp at 4200meters (?) or 860hp at 4450.
The difference may be in how they were measured. With or without RAM???

You need the angle drive to get the supercharger out of the way of the gun if you go for a large diameter supercharger. Impeller on the HS was 240mm (?)
Now for some reason the larger HS engine was making a lot less power at the same rpm as the DB 601A despite having a similar compression ratio.
Trying to blow through all the carbs? The lousy 2 valve heads? The HS supercharger was heating the air an awful lot (and is some evidence of that)
But the problem with getting more power is how much actual boost can the engine stand?
Or driving a big supercharger until you get enough altitude to allow you to open the throttle.
 
The Gypsy engines were probably too heavy due to the technological legacy being 10-20 years old by late 1930s?
At any rate, my go-to engine for Luftwaffe trainers and similar would've been actually their take on the Mercury theme. Light, compact and powerful enough, low tech so it is not a big drain on the most modern production facilities (keep it with 2 valves per cyl) and beyond pre-war German borders.



I've read the 860 HP @ 4000 m value in the table at Wikipedia. It does come from a book about the HS engines, however I don't have the book. The power chart certainly suggests that the above value might be wrong.
B Bretoal2 - help


Inefficient S/C certainly played the role, as it was evident once S-P supercharger was installed. 2 valve head - again a shortcoming that will rob some power, even a loss of 4% is more than 30 HP. Soviets extracted about the same power from the M 105 engine as the Germans had on the DB 601A via the 3 valve heads and probably/certainly a better S/C, as well as due to the stronger & heavier construction (that gotten heavier still as war progressed).
Fuel injection was worth how much - 10%? since it made possible the increased valve overlap and thus better scavenging.

All added, 20-25% surplus of power for the DB 601A at altitude, and even more (30-35%) down low since the variable speed drive was installed on the 601. Again, the much improved S-P supercharger cut the difference in altitude power to about 10% on the -45 engine, and perhaps to 20-25% down low due to the variable inlet vanes; granted, Germans will not have an easy access to the S-P supercharger before mid-1940, so they will need to look at their parts box in order to improve on the Ydrs S/C 'side' in a timely fashion.

Shortround6 said:
But the problem with getting more power is how much actual boost can the engine stand?
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I don't expect more than it was the case already.
 
tomo pauk said:
I've read the 860 HP @ 4000 m value in the table at Wikipedia. It does come from a book about the HS engines, however I don't have the book. The power chart certainly suggests that the above value might be wrong.
Click to expand...
I have the book and the tables are rather widely separated and not any more detailed than Wiki. Paragraphs of text may not be on the same page as the tables.
The book is arranged by time periods (decades) so you have to go through everything that happened in that time span, car engines, railroad engines, guns, aircraft and aircraft engines.

The Soviets did get a lot more power out of the HS engine, they also reduced the bore by 2mm (strong cylinder walls) added a 3rd valve, beefed up the crank, added a two speed supercharger and added about 100kg of weight. and accepted a shorter time between overhauls with the last version of 105 as you well know.

To me it seems like a lot of work to get an under 900hp engine (84% ?) of the power of the DB 601 and the cooling situation was bit unknown? Water or Glycol?

That is a sizable radiator.
 

I don't have any intention to mess with engine internals of the 12Y, just add a better S/C and that's it.

Soviets not investing much more on Mikulin V12s, M-82s and M-71s, and less and less on the M-88 and M-105 was their self-inflicted wound.

Shortround6 said:
and the cooling situation was bit unknown? Water or Glycol?
Click to expand...

Not sure.
'My' He 100 + HS12Y would've had the nose from the Avia B.35, the monoplane fighter.
 

NACA tests in 1941 demonstrated that Planiol-Szydlowski (Turbomeca) S/C was equal, and probably better, than DB 601 one.
Probably better because the P-S S/C they tested was slightly damaged !


Yes. The "Puissance moyenne en vol 400 km/h" curve is mean power in flight at 400 kph, i.e. with ram effect. It's very theoretical, depending on carburetor intake design !



HS 12Y-50/51 had increased diameter inlet valves, better cam profiles, modified oil pump and ran at 2500 rpm. But its S/C was Hispano design with a 225 mm diameter at 10/1 ratio - this explains the lower altitude performance. However, 12 Y 52 were to receive a P-S S/C.

See

ebay: Avia B534

Nr F13 Nr K11 https://www.ebay.de/itm/295804056783?hash=item44df4bb4cf:g:hfgAAOSwr5Bkp6cf
ww2aircraft.net
 
To expend a bit on the small-ish fighters powered by 2nd tier engines.
In the vein of He 100, the French were trying with the D.550 (small fighter/racer; wing was about the size of record-breaking He 100 versions) and the D.551 (similar to the D.550, but with bigger wing and up to 410 L of fuel (vs. 300 L on the 550; the D.520 carried more fuel than the D.551). D.551 came about probably also due to criticism of the high landing speed of the 550.
Apart from the problem with timing, that was even later than of the D.520, both aircraft were with very long nose, and consequently with bad visibility during the taking off and landing. Both aircraft were still faster and cheaper to make than the D.520, making them candidates for this thread. Speed figures with 1000 HP HS 12Ys were supposed to be up to 700 km/h for the 550 (seems like 702 km/h was attained in 22nd Nov 1939), and no worse than 650 km/h for the 551 (it never flew).
With Dewoitine being faster with these designs (so they can play a part in 1940 at least), the D.550 would've been less of the handful with the lighter and smaller engine. From the French stocks, that is the HS 12X (about 700 Hp at 4km by the late 1930s, depending on the version - compares well with the SAI 207 and it's 575 km/h on 750 HP and a bit bigger wing), capable for motor cannon. 300L of fuel will come a long way for the French needs in 1939-40.

The bigger 551 (but still smaller than the D.520) should've been fine already with the 'normal' HS 12Ys of the day.
 
Back to the old customer of ours

The monoplane offspring from the Fury might've been interesting. Talk fuselage of the fighters (together with engines etc.), mated to the outer 2/3rds of what will became Hurricane.
(also gets rid of the thickest wing section, too)
Six .303s, fixed U/C, closed cockpit. Might've gotten us to the performance figures in league of the Ki-27 (~290 mph) rather than what Gladiator offered (~240 mph).
 

The D 550 had been conceived only as a record plane - and, yes, 702 km/h was officialy attained.

Its military derivative D 551 had naturally bigger wing area and fuel capacity owing to the weapons weight.

I dont think the nose was so long....
 
A lot has to go right for the French proposal to worth much.
Like having a decent supply of H-S 12 X series engines already overhauled and sitting around in crates ready to be sent to the airframe maker.
Otherwise you are spending a lot of money building new airframes (and flight instruments, radios, guns) on airplanes with engines of, shall we say, dubious ancestry or history?
See how well that worked out for the British Buffaloes
Most of the H-S 12 X engines date from the first 1/2 of the 30s. Even just under 30% of the D. 500/510 series had 12 Y engines just to show the timing.
The French already had this in the works,

Potez 230 Along with 3/4 other "light fighters".
However the French were a little too obsessed with speed and not so much with actual usefulness. The little Potez was supposed to do 342-350mph. depending on source although it was never fitted with guns (same as a D. 520) so actual in service speed is a little questionable. The other problem was it's 118sq ft wing. This might be a misprint but it's 3 stable mates all used small wings.
Bloch 700. 134sq ft G-R 14 M engine
C. 714 135sq ft Renault V-12
Roussel R. 30 110 sq ft G-R 14 M

All had wing loading on the high end for their time and French Airfields were often not the Best (understatement).
The C.714 had two derivatives, one with the Italian I-F Delta engine and the other with an experimental Renault V-16 (broke it's crankshaft on the first flight, go figure).

Squeezing another airframe into that mess and expecting a different result?

For the British?
Used airframes and engines or new construction (and/or rebuilt engines?)
Hawker Furies had a number of models. including

Which hit 242mph. Landing gear of similar type to the Gladiator.
Several versions had a pair of guns in the cowl top and an gun in each side of the fuselage (Vickers guns, British didn't put them in the wings) although one customer put a gun under each wing.
But you are expecting a lot from a 700hp engine even if you cut the wing a bit compared to the 1030hp Hurricane.

The Ki-27 only had to deal with two guns and it used a 199.8 sq ft wing. 330 liters of fuel.
 

Historically, as I'm sure we all know, the monoplane version of the Fury, with a new engine and retractable U/C, became the Hurricane, which for all its faults was still a phenomenally successful aircraft. How much cheaper will the above suggestion really be compared to the Hurricane, and is the savings in cost really worth the cost in performance compared to the Hurricane? Further, if Hawker would have concentrated on making the above product, that would probably have delayed the Hurricane project, likely putting Britain into a much more difficult position in the early war years.

Just put the second-tier engines into transports, patrol aircraft and some bombers, and use the best engines you have for fighters. Yes, not the topic of this thread, but that would be my recommendation. If one wants cheaper, what could e.g. Hawker have done to make the Hurricane cheaper to produce and operate, without sacrificing much capability of the aircraft?
 

Hmmmm.
Use a cheap, easy to build fixed pitch wooden propeller?
Use a fabric covered wing that used existing tooling and methods, both in construction and in repair?

Oh, wait, they did both
They made them more expensive after the first year or so.

More seriously this also shows flaws in the build cheap and/or use old engines plans (not just by Tomo, a few air staffs in different countries spent a lot of money on this)
British were crippling their early planes using Merlins by using crappy, but cheap, propellers.
French used better more expensive propellers but that moved the total cost of the airplane up, regardless of the engine.

The use of metal skinned wings increased the dive speed of the Hurricane a fair amount. Using old style fabric covered wings even with a Kestrel engine was just another limitation.
Perhaps it could be gotten around by using wood (plywood) covering (both for strength and for aerodynamics ie, less ballooning) but that involves more testing and a bit different structure (you can use fewer ribs? different spars? less bracing like drag struts? )

French also tried to use the same armament as the standard fighters, except for the C. 714 and with only 500hp they weren't dumb enough to try that for real although they tried in a prototype.


A pair of 20mm cannon, at least they used a variable pitch prop

The French, as I mentioned earlier, tried to use small wings for low drag to retain speed with low power, this also means high landing and take-off speeds or at least not much of decrease even with lighter planes. The power available for climb is almost always lacking compared to the planes using 1st line engines which means both poor climb and poor sustained maneuver.

Small countries were in a bind. Technology was moving faster than they could keep up with. Small countries, like Norway, could build a dozen or so licensed biplanes in the late 20s or early 30s by the time the mid 30s came along things were moving too fast, any hope of getting effective aircraft depended on buying foreign aircraft, trying to set up license and local manufacturing meant they would be obsolete when built. Cost of local manufacturing was often higher than direct purchase.
Hawker built Furies (including at least types of radial engines) for a number of countries in the early 30s. and since Furies used at least a few parts and identical construction to the Hart series of bombers Hawker could offer decent prices.
 
Going back to the earlier premise of ease of production instead of just light weight and one of the Finnish
examples

Same engine as the Bf109G. They address the landing gear problem. They also added about 14% in wing area.

Unfortunately details are lacking or inconstant (or not identified correctly). Apparently the prototype was never given guns? so weight are either off or performance is off or ???

Another, earlier, Finnish fighter is more instructive. VL Myrsky


Now the project started in May 1939 (?) with the initial requirements, first flight took place Dec 23rd 1941 and first units got production aircraft in 1944. Which is actually not too bad.
It also allowed some later innovations to be used. Like cowling and exhaust thrust ideas that were not in existence in 1940-41. This did allow for better performance than was allowed by 1939-41 production fighters using similar engines. Yes it used wooden construction as noted earlier and it had problems with bad glue.
More subtle problems were the 300 liter fuel capacity and the rather restricted ammo capacity one source says 220rpg for the inner guns and 260rpg for the outer guns. This may have suited conditions in Finland but perhaps not in some other areas?

Aircraft design was always a series of trade-offs and good designers often tried to have 1 part do several jobs, not just two. And you have to figure out you total resources and your ability to build in quantity. Not what you can do with 1-3 prototypes. One of my favorites for showing this the Langley Twin

they built 3, two of them were covered with fabric and paint for protection. Used two 90hp engines and a lot of wood
They also used over 50 gallons of resin, lots of veneer grade wood (and veneer cutting equipment) and the wood parts were baked in autoclaves. Which means most privative countries had neither the access to the resins or access to the autoclaves. The Resins for this plane were allocated for other uses even in the US as the US geared up for mass production even before Pearl Harbor.
The ability to repair was limited on airfields remote from the manufacturer.

On the other side using steel tube fuselages with metal panel covering is both simple to make and easy to repair (or service) but it is heavier than semi-monocoque construction. The tube structure has to be strong enough to hand the entire load (or darn close). How much of a trade off you can do may depend on your engine, and when. Some engines gained a lot of power for a small increase in weight which allows for a bit more structural weight. If you are down on power to begin with and you use heavy construction you have to make sacrifices in other areas, like fuel/range and/or armament.
 

A steel framework supporting a stressed plywood skin could be a decent and affordable compromise without going to the expense of an all-aluminum stressed skin construction, or going all-in on high end wood composite construction like the Mosquito.
 
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