JU 252 352

[pbfoot]

On a lot of passenger/cargo planes the useful payload is NOT for a "fully' fueled and oiled aircraft. depending on the stage length ( particular route flown) a plane could be filled with less than full tanks and allowed more passengers or cargo, exact same plane could then fly the next stage of the flight with a different fuel/cargo combination. Even DC-3s had what were referred to as auxiliary tanks. On modern jets the "useful" load can vary by tens of thousand's of pounds depending on fuel load.

I think I get it having worked in Flight Planning for years I was preaching to the ones who don't get it , that is is why I always question cruising speed because almost no flight plan ever had a C47 or 46 any where near there max cruise speed .

 

[Shortround6]

For "Normal" operation an Pre-war civilian DC-3 with P&W R-1830 S1CG engines (1050hp/7500ft/2550rpm) 1200hp at 2700rpm take off initially had an empty weight of 16,430lbs, a useful load of 8370lbs and a gross weight of 24,800lbs. "Payload" with 600 gals of fuel was 3950lbs ( 14 passengers, 3 crew, and 1570lbs of baggage, mail, cargo.) this was a "Sleeper" model with bunks for 14 passengers. Max speed was 229mph at 8500ft and this would have been at the 1050hp rating or close to it, there was no "Military rating" or anything above "max continuous". Cruise at 75% power was 204mph at 7,500ft. Fuel burn was 105 gallons an hour at 75% for a range of 1050 miles on 600 gallons. Take off run at this weight is given as 1000ft.

The plane had two 210 gallon main tanks forward and two 201 gallon auxiliary tanks aft in the wing. total fuel was 822 gallons, with full tanks and not operating in an overload condition "payload" would have to be reduced by over 1300lbs (not including additional oil.) oil capacity was 48-66 gallons. Longer flights needing more oil.

a 1942 edition of Janes gives almost identical weights and performance but does give a range of 2125miles with max fuel at the most economical speed but does not say what that speed is. With a range of over 1450miles with max fuel at 75% power I think we have a good basis for figuring out the C-47 could do. They may have used speeds around 185mph as a more economical cruise. "normal" ranges may have been around 1500miles even at around 185mph in order to carry more "payload" or to allow for adequate fuel reserves.

 

[pbfoot]

Not going by some book but what I filed when in Winnipeg in 84 and 402 Sqn reserve had I believe 5 Daks ( give me few minutes and I could even remember their skin#s) and they usually filed at 125-145 the C46 that flew out of the Peg were usually about 160-180.

 

[Shortround6]

I just found this so we don't have to guess.

http://www.ww2aircraft.net/forum/other-mechanical-systems-tech/dc-3-manual-5163.html

1942 pilots manual for the C-47.

 

[fastmongrel]

I remember my father telling me about a Dakota on the Berlin Airlift. It landed in Berlin having just about made it, the crew said it barely lifted off the ground and they had to fly at full emergency throttle at rooftop height all the way across the Soviet zone. When it was unloaded it was found that it had been loaded with a load intended for an Avro York and had taken off with 8 tons instead of its normal load of 3 tons.

 

[SpicyJuan11]

If in 1938/39, the Ju 252 was given maximum priority as a military transport, when could the Ju 252 have entered service? There doesn't seem that much that could hold it up, as the Trappoklape worked in 1939 with the Ju 90, and the Jumo 211's were there.

 

[davebender]

Three years after RLM offers a contract for aircraft development. However not earlier then 1938 as that's when Jumo 211 engine will be available in quantity.

 

[GregP]

Does anybody know how much fuel and oil the Ju 252 and 352 carried? Or the weight of the armament / crew. You cna go from impressive to no payload depending on fuel, oil, crew, armament, etc.

By way of example, a Ju 52 could carry 654 US gallons of fuel. I will assume a minimum of 200 US gallons. Bsic weight 14,600 lbs. Max weeight: 20,330 lbs. Crew weight 483 lbs. 300 lbs oil. 63 lbs emergency kit. So full fuel payload would be 1,096 pounds or 497 kg. If we go with only 200 US gallons of fuel, the payload becomes 3,825 lbs or 1,735 kg. Big difference.

I was taking gross weight minus basic weight (not empty weight) minus fuel weight minus oil weight minus crew weight minus emergency kit for the payload. I figured 2 crew at 170 lbs each.

With some cargo planes, you can't fly with full fuel because they can be fitted with enough fuel capacity to reach overload for ferry purposes, so you HAVE to know how much fuel to account for.

 

[davebender]

2 tons. Ju-52 cargo average.
2.4 tons. He-111 cargo average. About 190 participated in airlift.
5.1 tons. Fw-200 cargo average. Unfortunately (for Germany) only 7 available.

Ju-252 payload (max weight minus empty weight) was 1,800kg greater then Fw-200. So it's probably safe to say it could average 6 tons of cargo on a typical mission. About three times as much as older Ju-52.

Tonnage alone doesn't tell the entire story. Ju-252 had a far larger cargo compartment and a rear loading ramp. So it could carry artillery pieces, towing tractors, palletized cargo etc. which Ju-52 could never carry. Furthermore Ju-252 was a modern aircraft with higher cruise speed and better able to operate in bad weather such as was typical at Stalingrad. This adds up to an aircraft which could fly to Stalingrad at night (to avoid enemy air defenses), quickly unload cargo and be gone before daylight.

 

[Shortround6]

I don't know about the fuel and oil but the JU 252 started with 1350hp engines. In 1938 The Jumo 211A as used in the He 111E was giving 1010hp for take off and 960hp at 4,920ft. With about 75% of the power available I doubt either performance or payload would be described as "sparkling"

 

[GregP]

I was wondering becasue the empty weight means almost nothing. What we need is the basic weight, which is the flyable aircraft with oil, unusable fuel, emergency kits, etc. minus crew, usable fuel, and payload. A plane with an empty weight of 30,000 pounds usually has a basic weight somewhere near 31,200 - 31,800 lbs. If it has radials, it probably has a 20 - 50 US gallon oil tank behind each radial ... etc.

So I was trying to find out some useful numbers. I can find them for the C-46, C-47, C-54 ... but finding them for mass-produced German planes is hard enough, much less a plane with a "production" run of 7 to 65. I'd think a Ju 290, for instance, had maybe 90 gallons or more of oil, a minimum fuel load even for short range of some 300 gallons, a probable max fuel quantity around 1,400+ gallons, a crew of 2 - 4, etc. But since the fuel and oil is a guess, it can have a significant effect on payload.

It's nice to compare gross - empty if nothing else is available, but it certainly wasn't all avialable as useful payload in real life. Still, it may be the best we can do ... and is maybe useful as a rough comparison among several aircraft for a first-order approximation.

 

[Shortround6]

If you are comparing "like to like" the empty and loaded weights may work, like comparing a C-54 to a Ju-90. Both 4 engine and empty and loaded weights are not that far off.
Comparing even a big twin ( C-46) to a 4 engine plane may get a little more difficult.

With the Germans throwing in gun mounts (and gunners?) on some planes it gets a little harder to estimate "empty equipped" or basic weight.

 

[GregP]

Yeah, it is difficult. Maybe we could get more utility out of empty weight .... since the POH is often not avialable. If you DO have the POH, you can get good numbers.

But SOME comparison is better than none.

 

[Koopernic]

The figure obtained from the following subtraction:
MTOW - Empty Weight Equipped given an indication of the fuel, lubricants, crew and cargo that can be carried.

Noteworthy the Ju 252 cruise efficiency (and DC3) was much much better than the Ju 52. This meant that to carry a ton of cargo a fixed distance required only around half the fuel. This of course meant either greater range or greater cargo as they could be traded off against each other for missions greater than a few hundred km.

The Ju 52 and its predecessors such as the Junkers G24 were good aircraft and like the Ford trimotor were a safe way to fly and relatively economical and comfortable. Bad weather sometimes stopped flights to London for most aircraft but Ju 52 could keep going. Ranges that may cover say a trip from Berlin to Munich or say to London, Zurich etc where fuel wasn't a major part of costs could be conducted with reasonable economy. Journey's of up to just over 3 hours over 800km/500miles.

Only 3 years separates the DC2 and Boeing Model 247 and Ju 52 (first flight 1930) in first flight but the change in technology and improved performance was very significant. The Germans had been the leader in producing all metal aircraft both of the corrugated skin and stressed skin flat sheet type, ahead of the US by a margin. They had the technology and it appeared in aircraft such as the He 111, Do 17, Ju 86 either mail planes or military aircraft but not cargo passenger aircraft in numbers (Maybe Fw 200). (that I can think of in 1935 though the He 111 was used as a passenger aircraft at that time.)

The Ju 252 started as only slightly enlarged compared to the Ju 52 but faster, longer ranged and pressurised. Lufthansa recognised the size as too small to meet upcoming commercial realities and had the aircraft enlarged, as the war approached the RLM Luftwaffe sought to militarise it and it ended up with a rear loading ramp or trappoklappe a very useful device in greatly reducing turnaround and increasing lift capacity. The war brought development to a temporary pause adding further delay. By being 5 years latter than the DC3 it was very difficult to sacrifice the resources to tool up for mass production.

The Luftwaffe did have some good transport aircraft, the He 111 performed very well, the Fw 200 was useful (though used as a long range maritime reconnaissance aircraft), the Ar 232 was very innovative and offered superb short field performance an the Me 323 Gigant also gave outstanding capabilities.

The Ju 352 however seems a waste, broadly it was a wooden version of the Ju 252 with cheaper surplus radial engines. The delay meant it was a non player so all the engineering resources were wasted. The weaker Bramo engine gave greatly reduced range and cargo (though still much better than the Ju 52). It would have been better to shift resources such as aluminium from Ju 52 production to Ju 252.

Nevertheless the planned Ju 352 with the BMW 801 radial (likely to be in surplus from 1945) would have had outstanding performance.

The timing of the Ju 252 was all screwed up and only got worse.

A factor in this was the needs of the US airline industry in developing east coast to west coast flights which demanded longer ranges and efficiencies.

 

[davebender]

That's because it started as a commercial aircraft for Lufthansa. If RLM had written specifications for a Jumo 211 powered military transport to replace Ju-52 during 1936 there's no reason it couldn't have been in production by 1940, replacing Ju-52 on the assembly line.

 

[kool kitty89]

I don't know about the fuel and oil but the JU 252 started with 1350hp engines. In 1938 The Jumo 211A as used in the He 111E was giving 1010hp for take off and 960hp at 4,920ft. With about 75% of the power available I doubt either performance or payload would be described as "sparkling"

I doubt the Ju 252 would have reached mass production any earlier than 1940 even with higher priority, though more limited engines would obviously need to be used for prototypes. (the Bramo 323 might even be favored there due to engine availability, at least for protoypes and possibly early production or preproduction models)


The 252 really seems more like a C-46 counterpart than anything, and (at least in basic layout, size, engine power, and passenger capacity) the Fw 206 seems much more in line with the DC-3. Given the design relation to the Fw 200 and the less advanced features compared to the 252, that might have been practical to get into service in numbers sooner as well. (in spite of its relatively late design start) That design never progressed beyond models and mock-ups before its cancellation, from what I've read, so a lot more left to speculation than the Ju 252.

 

[GregP]

My problem is not figuring out how to calculate the payload, it is finding the equipped weight and fuel capacity. Many places will have some performance figures, but few have fuel capacity and equipped weight.

 

[SpicyJuan11]

Here's another what-if question, how much of a performance increase would the 252 have with 2 or even 3 of our fabeled Jumo 222's (A/B)?

 

[Shortround6]

Kind of depends on how much time you want to spend redesigning the whole thing. Trading three 1350hp engines that weigh around 13-1400lbs for two 22-2400hp engines that weigh around 2400lbs, shouldn't be too hard but then you done't get much, if any performance increase. You also have a bit of a problem if one quits.

Keeping 3 engines gives more performance but also increases the empty weight by well over 3000lbs. You aren't going to use Jumo 211 radiators to cool Ju 222 engines and you sure aren't going to use Jumo 211 propellers. If you use the extra power you are going to burn more fuel per mile/km. Payload is cut significantly. Now with the extra power you can certainly lift a bigger load but are the tires, landing gear, brakes up to it? Is the wing up to handling not only the extra weight but whatever extra speed you are using? and so on. Most passenger/cargo planes were built with much lower reserves of strength than Fighters or even bombers.

ANd do you really need a faster transport? If you go for the 66-7200hp installed power option is the plane now volume limited? Can lift more weight than the normal cargo items use up in volume?

 

[Koopernic]

I doubt the Ju 252 would have reached mass production any earlier than 1940 even with higher priority, though more limited engines would obviously need to be used for prototypes. (the Bramo 323 might even be favored there due to engine availability, at least for protoypes and possibly early production or preproduction models)


The 252 really seems more like a C-46 counterpart than anything, and (at least in basic layout, size, engine power, and passenger capacity) the Fw 206 seems much more in line with the DC-3. Given the design relation to the Fw 200 and the less advanced features compared to the 252, that might have been practical to get into service in numbers sooner as well. (in spite of its relatively late design start) That design never progressed beyond models and mock-ups before its cancellation, from what I've read, so a lot more left to speculation than the Ju 252.

The DC3 flew and was in service by 1936, even the DC2 was an excellent aircraft. The best hope the Germans might have had was a He 111 with the fuselage physically widened out but using the same wings and empennage. similar to how the DC2 became the DC3. The great economies of production then make the transport viable and as the He 111 bomber was superseced production could shoft to the transport version. One then ends up with a conflict between He 111 bomber production and He 111 Transport production. The bomber would tend to win in the early part of the war. One might have to put radials on that He 111 Transport to spare Jumo 211 production.

The realties of German airline routes and competition probably didn't challenge the Ju 52 too aggressively, it was satisfactory in many cases so they took their time replacing it. Interesting long range routes would have been established by the Fw 200 such as Berlin New York (as engine power grew) and also Berlin to Sth Africa then across to Rio and other Sth American capitals. It was also optimal for routes of about 1000 miles or so. More of these might have added greatly to German transport capabilities, if they weren't used as maritime reconnaissance bombers. Its light weight frame was produced in a single piece and it cound't be split for subcontracting in smaller factories.

That's because it started as a commercial aircraft for Lufthansa. If RLM had written specifications for a Jumo 211 powered military transport to replace Ju-52 during 1936 there's no reason it couldn't have been in production by 1940, replacing Ju-52 on the assembly line.

Yes but who was thinking of resupplying whole divisions and even armies enough so that they would write a spec. There were some superbly thought out airliners planned (they often appear in Luft46 style aircraft) but they would have started production in the war years. Aint going to happen. Even the Ar 232 was effectively cancelled.

Any transport would need to be in production by 1937 else it comes into conflict with military priorities I would think.