A small what-if: Ju 52 with two engines and a retractable U/C instead of the 3-engined layout?

[nuuumannn]

This is arguable. The Ju-52 used an old version of the BMW 132 engine (used carbs for one thing?) and an older form of cylinder fins?
The newer version/s of the BMW 132 used fuel injection and came with a choice of 3 different supercharger gear ratios. If you were not interested in high altitude (10,000ft) you could get into the over 900hp range.
The difference in effort to manufacture should be small, depending on the fuel injection.

The Bramo 323 might be able to use similar machinery although castings/forgings would need to be changed over. That can get you to 1000hp per engine.

Swapping a pair of 960-1000hp 9 cylinder radials for a trio of 725hp 9 cylinder radials might be doable.

When is this likely to be done, is the issue and when do you stop production of one engine and begin the next? And what impact does this have on existing deliveries? This is the point I'm making. All of this seems like a lot of energy for little gain, especially since the LW never specified a need for a more advanced Ju 52 in the first place. The aircraft's performance might increase, so how does that affect operations? Can it still operate into smaller rough strips with retractable gear and a higher landing speed? How does this affect its load carrying capability?

We are talking about a slow transport here, an increase in speed probably won't offer a sufficient change in its capabilities.

This entire argument is being driven by this notion that EVERYTHING has to be all-metal with retractable gear and modern construction to be of value. None of these changes are going to make a better Ju 52.

 

[Shortround6]

LW happily jumped on any Italian transport they were able to lay their hands, since the Ju 52 was mass-limited and size limited. They tried with two types of powered gliders, Ju 252 and 352, converted Ju 90, the Ar 232. Imperative was there.

Let's not forget drafting a number of older He 111 bombers from the training schools to act as transports in Russia.

Like the motorized/mechanized Wehrmacht in newsreels, the Luftwaffe talked a good game with airborne troops and transport. It didn't deliver it.

 

[tomo pauk]

Let's not forget drafting a number of older He 111 bombers from the training schools to act as transports in Russia.

Ju-86s, of all aircraft, were also pressed into service as transports, 42 ended up destroyed during the battle of Stalingrad and the disastrous airlift.

 

[Shortround6]

When is this likely to be done, is the issue and when do you stop production of one engine and begin the next? And what impact does this have on existing deliveries?

What is the impact on deliveries to keep switching from the new engines to old ones?
They were using the newer versions in the Arado 196, Do 17P, some Fw 200s, He 115s, Hs 123s, Ju-86 E & G, and about 8 or 9 Ju 90s.

 

[nuuumannn]

What is the impact on deliveries to keep switching from the new engines to old ones?
They were using the newer versions in the Arado 196, Do 17P, some Fw 200s, He 115s, Hs 123s, Ju-86 E & G, and about 8 or 9 Ju 90s.

You do realise that what you've posted reinforces my argument, for the simple fact that if these engines are given to Ju 52s, then other types don't get them, or have the Germans managed to perfect the art of limitless resource production? Again, a pointless waste of resources. If these aircraft are powered by those engines and there's no real need to change the Ju 52, why do it? You're just depleting engine supply to aircraft that need them.

 

[Shortround6]

Ok, what part of do not build BMW 132A engines, build BMW 132 Da, Dc, F, J, K, M, N, T,U,W, Y, Z types instead.
Some of the later models were used on late Ju 52s, like the Ju 52/3mg5e and the Ju 52/3mg12e and some others.

Build the newer versions of the BMW 132 on the existing production set ups.
Design and build a more up to date aircraft that only requires 2 engines, not three, free up engine production.

Wright continued to build old versions of the R-1820 engines for replacements for existing aircraft, which may have been a pain in the butt for production of new engines.

Ford had stopped making Tri-motors in 1932. Germany could have built a new transport using newer knowledge in the mid/late 30s that would give more ton/miles for a given amount of fuel.

 

[nuuumannn]

Ok, what part of do not build BMW 132A engines, build BMW 132 Da, Dc, F, J, K, M, N, T,U,W, Y, Z types instead.
Some of the later models were used on late Ju 52s, like the Ju 52/3mg5e and the Ju 52/3mg12e and some others.

Build the newer versions of the BMW 132 on the existing production set ups.
Design and build a more up to date aircraft that only requires 2 engines, not three, free up engine production.

Again, when this happens is the issue. When do you implement these changes and which among the seven aircraft types miss out on engines because they are being diverted to Ju 52s, a version no one asked for (yup, go look through Luftwaffe records to find any reasons before the war, because that's the best time to do this, why the LW are dissatisfied with the Ju 52 as it is) and although slightly faster, offer small benefits that wouldn't amount to that much better load lifting ability simply because of the space available in the cabin, which is again compromised by the fact that, because of a higher take-off and landing speed require bigger runway surfaces, thus affecting their utility. Not to mention a less rugged and more complex undercarriage set up because we have to have retractable gear because fixed gear is so passe, which limits the surfaces the aircraft can operate from. Did I mention that a slightly higher speed is not going to prevent the extremely high losses affected by the type over Norway and Crete? Sounds like a waste of effort to me. If BMW wants to do more engine work it should concentrate on stopping the Fw 190's powerplant from overheating and starting engine fires, not waste time developing an engine for an aeroplane no one asked for.

 

[SplitRz]

with "better" engines, and you aren't going to save much in materials and labor by making 725hp BMW 132s vs 880hp BMW 132s, there were several options they could have used.

However putting retracting landing gear on a Ju 52 and keeping the corrugated sheet metal was not one of them.

You might as well keep the tri-motor around for a while until you get the propeller situation sorted out. A twin with 2 pitch props isn't going to fly much further than a twin with fixed pitch. You need either constant speed and a propeller brake or the fulling feathering propeller. And even then you need a certain power to weight ratio to maintain altitude, depending on the route for commercial traffic. Maintaining 5000ft doesn't work crossing the Alps.

This was about 30mph faster than a Ju 52
View attachment 692927
Flew at the end of 1936. So there is certainly room for improvement.

To replace the Ju 52 you need ruggedness, capacity/load (12 passenger plane won't do it) and less fuel burned per ton/mile.

That a pictchyer of a common or garden cockney Sparrah, innit?

I ve seen a good vid on the surprisingly useful and under-rated Bombay recently -

Anyone seen anything similar for the Harrow?

 

[SplitRz]

Instead of messing about with the JU52, why not turn the 'wolf in sheep's clothing' HE111 / Doppel-Blitz back into a genuine transport and develop that? More powerful engines, more modern design, better performance...?

 

[tomo pauk]

Instead of messing about with the JU52, why not turn the 'wolf in sheep's clothing' HE111 / Doppel-Blitz back into a genuine transport and develop that? More powerful engines, more modern design, better performance...?

Because the thread is about Ju 52?

 

[SplitRz]

Because the thread is about Ju 52?

(Sorry, have I been reading numerous threads here that encompass a wide variety of input and ideas around a theme, or have I been living in some parallel universe or accidentally logged onto ww2aircaft.com not net? I thought *this* was the HOME of relevant thread-creep?!)

It isn't really about the JU52 though, is it, its about an imaginary twin-engined aircraft with retractable undercarriage?

I thought it was a valid question anyway. It seems to me if that the case, some what ifs are best answered by 'why bother' - with reasons listed - and maybe begging a 'why not' instead (?)

So, to keep this indelibly on thread topic viz a viz the JU52 - if there's a reason to attempt to improve an aircraft with corrugated skin, fixed undercarriage and a design dating back to 1930 because Germany was short of transports and needed improved performance, is trying to get blood out of a very old stone (which did its existing job well enough to stay in production until 1952) worth the effort, when there were far more modern designs in mass production that would have made a possibly more logical option both from a logistical and engineering perspective? I dunno, like one that *already*had two engines and a retractable U/C - and had already been used (even if only nominally) as a transport?

Like, errr.....

I retreat into the shadows...

 

[tomo pauk]

Its isn't really about the JU52 though, is it, its about an imaginary twin-engined aircraft with retractable undercarriage?

It is about a Ju 52 with just two engines and with retractable U/C, and the related effects. Guess we can call it imaginary, since it never existed.

So, to keep this indelibly on thread topic viz a viz the JU52 - if there's a reason to attempt to improve an aircraft with corrugated skin, fixed undercarriage and a design dating back to 1930 because Germany was short of transports and needed improved performance, is trying to get blood out of a very old stone (which did its existing job well enough to stay in production until 1952) worth the effort, when there were far more modern designs in mass production that would have made a possibly more logical option both from a logistical and engineering perspective? I dunno, like one that *already*had two engines and a retractable U/C - and had already been used (even if only nominally) as a transport?

As repeated several times, it is not that much about improving the Ju 52 per se, but about improving German war material supplies. A few thousand engines freed by going into 2-engined Ju 52 instead of the 3-engined historical type means a lot in the second half of 1930s and at start of 1940s.

Like, errr.....

I retreat into the shadows...

There is really no need for that.

 

[Shortround6]

It is about a Ju 52 with just two engines and with retractable U/C, and the related effects. Guess we can call it imaginary, since it never existed.

Considering the amount of drag from thousands of sq ft of corrugated sheet metal on the wings and fuselage the drag of the landing gear is not going to be a significant portion of the drag. Unless you can reduce the drag of the basic airframe/construction it is probably not going to work.

A More modern twin might have been possible. The Luftwaffe requested designs in the summer or fall of 1939 that lead to the Arado 232. The Fieseler 156 had flown in May 1936 and had been displayed At the Aug 1937 Zurich air meet and at the Sept 1938 Cleveland air races. Hi lift devices were known to work. Smooth metal skin was known to be strong and light weight. Something between the Ju 52 and a DC-3 could have been built without going overboard like some of the German projects.

 

[tomo pauk]

Considering the amount of drag from thousands of sq ft of corrugated sheet metal on the wings and fuselage the drag of the landing gear is not going to be a significant portion of the drag. Unless you can reduce the drag of the basic airframe/construction it is probably not going to work.

I'm tempted with the wing from the Ju-86 - it is smooth instead off being corrugated, it has the retractable U/C from the get go, uses the BMW 132 engines (and much better props than the Ju 52 as-is) in the second half of 1930s. Ju 86 was rated for about the same take off weight, and it has the 'doppelfluegel' for better low-speed abilities. Shortcoming of that idea is that it still uses a lot of light metal alloys - fine for the shiny warplanes, but not much a requirement for a workhorse.

A More modern twin might have been possible. The Luftwaffe requested designs in the summer or fall of 1939 that lead to the Arado 232. The Fieseler 156 had flown in May 1936 and had been displayed At the Aug 1937 Zurich air meet and at the Sept 1938 Cleveland air races. Hi lift devices were known to work. Smooth metal skin was known to be strong and light weight. Something between the Ju 52 and a DC-3 could have been built without going overboard like some of the German projects.

Agreed all the way. Even the non-sexy Bombay offered a superior bang-for-buck than the Ju 52/3m did, despite the simple construction methods for the former, so we'd want a transport at least as capable.
The Ar 232B shows what four humble radials can do.

 

[Tanker Tom]

It would most likely look similar to a JU-252 or 352.

 

[tomo pauk]

It would most likely look similar to a JU-252 or 352.

How so?

 

[Tanker Tom]

How so?

Engines first then landing gear.
Just changing engines is not always a complete answer. The most important part of any aircraft is the wing. What affect will this change have on it? Removing the nose engine means larger outboard engines to make up the power loss at takeoff. Is the wing main spare capable of handling this extra power on the wing and the loss of thrust in the fuselage. What is the affect of a max load? What is the stress dynamic going on there? Will the rear spare be affected? Next is weight and balance or center of gravity (CG). How is the loss of that middle engine going to be affecting the CG? Will the larger engines be heavy enough to make up of the middle considering how far forward it is. (No, I am not going to get into weight, arm and moment) How will this affect the wing in both placement on the fuselage for CG, wing cord, and angle of attack, if any?
The second part is the landing gear. Some else already mentioned the corrugated skin nightmare, and they are correct, it has to go. Until it does there is no point in retractable landing gear, not enough savings in drag. Again, we come back to the wing. A lot of the structural strength in the wing came from the corrugated skin. Now the internal bracing needs to change to make up for the loss of the corrugated metal. Now for the flaps and ailerons, they have to go also. Junkers thought they would supply extra lift; they made more drag than anything. How will that affect the rear spare/bracing? With that done now back to the retractable landing gear. Since this is a cargo aircraft the gear cannot swing into the cargo bay, they would take up too much space needed for cargo. You are correct, back to the wing. Like engines, landing gear cannot just be glued on. What affect will the retracted position have on the wing spare? What direction will it fold? How will it fold? What will happen to the CG in the up, down and transit positions? How will the wing structure need to be redesigned to be strong enough to take the stress of retracting and extending? The gear itself will need to be heavier so the joints will have the strength needed for landings. Additionally retractable gear does not lend itself to side bracing. This will channel more stress on one point of the instead of spreading it out with bracing. How will that change the wing? How much weight was just added? Back to CG, back to the wing. Fuel consumption has to be figured in also. Will two larger engines use more or less fuel than the three already there? How will fuel consumption affect climb rates/range.

The JU-252/352 answers all these questions, except the third engine. Because the JU-52 was already considered obsolete the 252 was requested in December of 1938 and first flown in October of 1942. They were to have three (3) Junker Jumo 211F inverted vee of 1,350HP each, giving 35 passengers a good ride in pressurized comfort. it was almost 100mph faster and had over 1,500 more miles in range over the JU-52. It was an excellent aircraft for its purpose. Then the RLM started changing things . . .

As I mentioned this is what it may look like. I could see a scaled down version, but not much smaller, still larger than the C-47, using only two engines. The wing already had retractable gear, flush flaps and ailerons with smooth skin. The only detail to make sure of would be the stress on the wing spare using only two engines. However, if scaling down for two engines that would be part of the program.

That is why I believe it would look like the JU-252/352. Allow me the caveat of saying, although smaller. I look forward to all the points I missed in my opinion of what a JU-52 would look like with two engines and retractable landing gear.

 

[tomo pauk]

That is why I believe it would look like the JU-252/352. Allow me the caveat of saying, although smaller. I look forward to all the points I missed in my opinion of what a JU-52 would look like with two engines and retractable landing gear.

I appreciate your input.
Reason why I questioned your assessment is that Ju 252/352 was a 3-engined A/C, while the Ju 52 I've proposed was a 2-engined one; ones with generous capacity and means of loading/unloading, another without all of that good stuff.

About the points you've missed - I was not trying to make Ju 52 better, but to make it more affordable and producible for Germany of 1935-45, without loosing more than a few % or the lift capability.

 

[Tanker Tom]

I appreciate your input.
Reason why I questioned your assessment is that Ju 252/352 was a 3-engined A/C, while the Ju 52 I've proposed was a 2-engined one; ones with generous capacity and means of loading/unloading, another without all of that good stuff.

About the points you've missed - I was not trying to make Ju 52 better, but to make it more affordable and producible for Germany of 1935-45, without loosing more than a few % or the lift capability.

In their own way making it cheaper and easier to produce is making it better, so you are still correct. At the same time the additional production steps of a retractable landing gear would not make it easier to produce. There would need to be the additions of a control system hydraulic pump(s), plumbing, actuators, possibly doors, that were not there before. Plus the added weight of a retractable system could lower the aircrafts pay load lowering the % of lift capability.
In my own defense I was taking the question literally and the going through the steps needed to make it happen. I had fun with it!!! Cheers.

 

[tomo pauk]

At the same time the additional production steps of a retractable landing gear would not make it easier to produce. There would need to be the additions of a control system hydraulic pump(s), plumbing, actuators, possibly doors, that were not there before. Plus the added weight of a retractable system could lower the aircrafts pay load lowering the % of lift capability.

To be frank, I'm okay with the Ju 52 retaining the fixed U/C after all.