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

tomo pauk

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So not quite a 'German DC-3', but it might be what Junkers can quickly introduce in production after the 1-engined Ju 52. There was ~4200 of Ju 52s produced in Germany, so there is ~4200 of engines & props saved. Yes, the engine-out situation is trickier, if indefinitely better than with 1-engined transports. A move to the 'better' 132s (-F and -N, like what Ju 86 had) will be needed once these are available.
 

Thumpalumpacus

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If the engines stay the same, would the tradeoff between losing 1/3 of your power, and lugging the weight of retraction gear (which might weigh close to the engine we've removed), be compensated by the reduced drag and increased aerodynamic efficiency? Would the complication of retractable gear have a real impact on servicing what was apparently a simple and reliable airframe?

I don't know enough to argue one way or the other, but these are the questions that popped in my head immediately.
 

Shortround6

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So not quite a 'German DC-3', but it might be what Junkers can quickly introduce in production after the 1-engined Ju 52. There was ~4200 of Ju 52s produced in Germany, so there is ~4200 of engines & props saved. Yes, the engine-out situation is trickier, if indefinitely better than with 1-engined transports. A move to the 'better' 132s (-F and -N, like what Ju 86 had) will be needed once these are available.
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
row-046f8f58-18b4-4f9c-963a-cebb3463b8c-resize-750.jpg

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.
 

Shortround6

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If the engines stay the same, would the tradeoff between losing 1/3 of your power, and lugging the weight of retraction gear (which might weigh close to the engine we've removed), be compensated by the reduced drag and increased aerodynamic efficiency? Would the complication of retractable gear have a real impact on servicing what was apparently a simple and reliable airframe?

I don't know enough to argue one way or the other, but these are the questions that popped in my head immediately.
You have got a good very good idea of the trade offs.
 

tomo pauk

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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.

Yes, the 3-engined version preceeding the 2-engined ones might be a good idea, redundancy-wise, especially since the better BMW 132s will not be available until 1935-36? Ditto for much better props.

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

Interestingly enough, the 1-engined Ju 52 carried about 10-15% less of cargo than the 3-engined versions.
Installing the 2 better 132s instead of 3 'worse' ones will remove 400-500 kg per aircraft, and it should also gain a less draggy nose. retractable U/C is not a panacea, just another way of removeing some drag from the Ju 52.
All of this should improve the mileage, too.
Ju 52/3m was supposed to carry 15-17 passengers.

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.

With two engines instead of three, save in materials and labor is self-evident.
 

Shortround6

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Interestingly enough, the 1-engined Ju 52 carried about 10-15% less of cargo than the 3-engined versions.
More power limited than lift limited.
Installing the 2 better 132s instead of 3 'worse' ones will remove 400-500 kg per aircraft, and it should also gain a less draggy nose. retractable U/C is not a panacea, just another way of removeing some drag from the Ju 52.
All of this should improve the mileage, too.

Ju 52/3m was supposed to carry 15-17 passengers.
I misunderstood you. I was thinking of a new airplane and a twin along the lines of the Ju 86 and He 111 commercial aircraft with 10-12 passenger fuselage wasn't going to do it.

But taking a Ju 52 and putting larger engines on the wings, smoothing up the nose and having the landing gear retract wasn't really going to do it either. It will help but as has been point out by others it may not be worth the expense and extra maintenance.

The Ju 52 was a high drag aircraft so fitting retracting landing gear may not get you much.

The Italian S.73 was considerably faster using similar engines.
5939177715_7791e56512_z.jpg

Max speed over 200mph?
One source says it was about as fast on two engines as the Ju 52 was on all three?
I don't know if the low speed (landing) was better than the Ju 52.
The Savoia-Marchetti SM.75 showed what could be done with a tri-motor using low powered engines in 1937-38.
SM.75-Marsupiale-Civilian.jpg


You won't get your reduction in engines used directly but since the SM. 75 could carry more payload (or at least more men) further and faster using about the same fuel you might need fewer planes to do the same job.
 

tomo pauk

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More power limited than lift limited.
Agreed.

But taking a Ju 52 and putting larger engines on the wings, smoothing up the nose and having the landing gear retract wasn't really going to do it either. It will help but as has been point out by others it may not be worth the expense and extra maintenance.

This is a small what if.
Main point that I was making is that this scenario is less taxing on German/BMW engine production than it was the case historically, while not impacting the total lift capability of the Ju 52 fleet. It is also less taxing on German economy that was at the limit during from 1935 on due to the huge re-militarization and war.
Having to do maintenance on two engines instead on three will decrease the maintenance wrt. propulsion group. Engines themselves are not larger than what was used on the Ju 52/3m.

The Italian S.73 was considerably faster using similar engines.
Max speed over 200mph?
One source says it was about as fast on two engines as the Ju 52 was on all three?
I don't know if the low speed (landing) was better than the Ju 52.
The Savoia-Marchetti SM.75 showed what could be done with a tri-motor using low powered engines in 1937-38.

You won't get your reduction in engines used directly but since the SM. 75 could carry more payload (or at least more men) further and faster using about the same fuel you might need fewer planes to do the same job.

No doubt that Italian trimotors were better, pointing out to Germany needing to have a new-gen transport in production by late 1930s. Until that happens, the Ju 52 will soldier on.
 

Big Jake

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The Germans should have thrown the Ju-52 to the dump and build the Italian Savoia-Marchetti S.M. 82 as a twin engined transport, powered by Gnome-Rhone 14N radials of 1,140 HP each or the BMW-Bramo 323 engine of 1,000 hp. The vertical stabilizer and rudder would have had to be enlarged to address engine out maneuvering capability. The resultant airplane could have carried 15,000 lbs of weight for at least 1,500 miles at 186 mph. For comparison, the C-47, with 2 R-1930s of 1,200 hp each, could carry about 10,000 lbs at least 1500 miles at 185 mph. The Ju-52 with its antiquated (even for the time) structure could not have made any better no matter what.
 

Snautzer01

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The Germans should have thrown the Ju-52 to the dump and build the Italian Savoia-Marchetti S.M. 82 as a twin engined transport, powered by Gnome-Rhone 14N radials of 1,140 HP each or the BMW-Bramo 323 engine of 1,000 hp. The vertical stabilizer and rudder would have had to be enlarged to address engine out maneuvering capability. The resultant airplane could have carried 15,000 lbs of weight for at least 1,500 miles at 186 mph. For comparison, the C-47, with 2 R-1930s of 1,200 hp each, could carry about 10,000 lbs at least 1500 miles at 185 mph. The Ju-52 with its antiquated (even for the time) structure could not have made any better no matter what.
You never saw a ju52 land or take off i think. Very STOL like. Take that and the manner the germans fought and perhaps you can see some befits to Auntie.
 
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tomo pauk

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The Germans should have thrown the Ju-52 to the dump and build the Italian Savoia-Marchetti S.M. 82 as a twin engined transport, powered by Gnome-Rhone 14N radials of 1,140 HP each or the BMW-Bramo 323 engine of 1,000 hp. The vertical stabilizer and rudder would have had to be enlarged to address engine out maneuvering capability. The resultant airplane could have carried 15,000 lbs of weight for at least 1,500 miles at 186 mph.

SM.82 as a twing-engined aircrafr with two 1000 HP engines will not work - unlike the Ju 52, it used three from the get go, while empty weight was in ballpark with Ju 52/3m take off weights.
As-is, with three engines, it was fine. Germans tried to reinvent the wheel with the Jumo 252 and 352.

The Ju-52 with its antiquated (even for the time) structure could not have made any better no matter what.

You can note that I'm not trying to make Ju 52 better (yes, it's structure was antiquated past early 1930s), but to make it more affordable for the German economy and military budgets from 1935-ish on, both to purchase and operate, all without hurting the total lift capacity.
 

Shortround6

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If I am understanding this right,

Can fitting retracting landing gear on a Ju 52 make up for about a 10% loss in power (two 1000hp engines=2000hp vs three 725hp engines=2175hp) combined with a better nose cone and perhaps straightening out the nacelles so both engines point in the same direction?
And whatever you have to do to the vertical fin and rudder to maintain control in an engine out situation.

Not sure what a 10% loss in take-off power does to the take-off run?
The Ju 52 cruised between 130-150mph? Not saying that drag isn't important but it's real effects go up much faster than actual speed.
A little factoid, the Ju 52's wing was about 20% larger than the wing on a DC-3.
You may save on engines, it doesn't do much for the saving on fuel.
 

tomo pauk

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Can fitting retracting landing gear on a Ju 52 make up for about a 10% loss in power (two 1000hp engines=2000hp vs three 725hp engines=2175hp) combined with a better nose cone and perhaps straightening out the nacelles so both engines point in the same direction?
And whatever you have to do to the vertical fin and rudder to maintain control in an engine out situation.

It probably can. We shave drag due to the absence of one 9-cylinder engine in the nose, as well as from having the retratable U/C. We also move from the low cruise altitudes of the Ju 52/3m - 900m/3000 ft - that were dictated by the engine charactristics of the BMW 132A (and it's siblings, like the D, E, L and G; the F, N and later were much better). Higher cruise altitude enabled by better engine should again improve mileage. Some weight can be saved by having two 525 kg engines instead of 3 x 430 kg ones, as well as lack of one oil system, cowling and engine mount. Two better props vs. three 'toothpick' props with just 10 degrees of pitch change, as it was the case with the prop installed on the Ju 52/3m.

Not sure what a 10% loss in take-off power does to the take-off run?
The Ju 52 cruised between 130-150mph? Not saying that drag isn't important but it's real effects go up much faster than actual speed.
A little factoid, the Ju 52's wing was about 20% larger than the wing on a DC-3.
You may save on engines, it doesn't do much for the saving on fuel.

It cruised that slow because it was one draggy aircraft, and because it's best cruise speed was between 500 and 1000 meters. Thick air messes with small and streamlined A/C, let alone with big and draggy ones, like the /3m was.
Weight is decreased because the 3rd engine is not installed, also less fuel needs to be carried, so we have a power-to-weight deficit of perhaps 5-6% vs. the Ju 52/3m for the same range. Or, fuel can be left as-is, for greater range than the original, while accepting the longer t-o run.
A save of just 3000 engines out of 3000* Ju 52/3m being actually produced as Ju 52/2m (all rights reserved ;) ) is a hefty amount for the era of ~1936 to the mid ww2. Saves on maintenance are also big.

*production of military models of Ju52/3m was about 4040 examples in Germany from 1934 on
 

tomo pauk

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The difference in internal useful volume between the DC-3 and Ju 52 was staggering:
inside of DC-3
inside of Ju 52/3m (same as with it's predecessor)

Germans really indeed needed to introduce a much better transport aircraft than the Ju 52 by the late 1930s, as noted by fellow members in the posts above.
 

Shortround6

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While it isn't big as the DC-3 inside the Bristol Bombay had potential.

bristol-bombay-interior.jpg

04632c07c6feb54418a7b1cdb00af9c6.png


Quite a write up on it here with many pictures.


Including " In 1937 the prototype was even used to fly British Army staff to Berlin to witness German Army manoeuvres."

And it was shown at several air shows.

The Germans had to know just how far behind the Ju 52 was. The Bombay was about 30mph faster and at these speeds that is 18-20%, a substantial difference.
 

Snautzer01

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The Germans should have thrown the Ju-52 to the dump and build the Italian Savoia-Marchetti S.M. 82 as a twin engined transport, powered by Gnome-Rhone 14N radials of 1,140 HP each or the BMW-Bramo 323 engine of 1,000 hp. The vertical stabilizer and rudder would have had to be enlarged to address engine out maneuvering capability. The resultant airplane could have carried 15,000 lbs of weight for at least 1,500 miles at 186 mph. For comparison, the C-47, with 2 R-1930s of 1,200 hp each, could carry about 10,000 lbs at least 1500 miles at 185 mph. The Ju-52 with its antiquated (even for the time) structure could not have made any better no matter what.
1668110434566.png
 

tomo pauk

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The Germans had to know just how far behind the Ju 52 was. The Bombay was about 30mph faster and at these speeds that is 18-20%, a substantial difference.

Anyone air-minded in Germany knew that Ju 52 was behind the curve once the companies started buying DC-2s. With the 'widebody' DC-3, the writing was at the wall.
Junkers upped the bar with Ju 90, Fw with Fw 200, but those were not proceeded with as series- or mass-produced military transports because of different reasons.
 

Shortround6

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Anyone air-minded in Germany knew that Ju 52 was behind the curve once the companies started buying DC-2s. With the 'widebody' DC-3, the writing was at the wall.
Junkers upped the bar with Ju 90, Fw with Fw 200, but those were not proceeded with as series- or mass-produced military transports because of different reasons.
True but the Bombay and the Harrow show that you could have a bit more speed and a bit more capacity while using the same installed power as the JU 52 without the need to go to 4 engines. The two British planes also had low stalling speed and very good short field performance.
 

tomo pauk

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True but the Bombay and the Harrow show that you could have a bit more speed and a bit more capacity while using the same installed power as the JU 52 without the need to go to 4 engines.

Both of these were with longer fuselages, especially the Harrow - 6 meters longer (!).
One wonders how the fuselage of the Ju 52 might've gotten the 'plugs' to increase length of the cargo bay - talk about 75cm between the cockpit and the bay, and 75cm aft the cargo bay? Might afford enough of place for extra 4 soldiers.

But at any rate, I'd go with steel/wood/canvas materials for the proper, new transport aircraft, no need to go with light alloys on a transport here.
 

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