Ju-288 vs Do-317

[davebender]

When powered by similiar engines these aircraft had similiar performance. If anything the Do-317 looks a bit superior.
406mph. Ju-288C. 3,000kg bomb bay. DB610 engines.
416mph. Do-317B. Essentially a Do-217 with larger DB610 engines. 2,500kg or 4,000kg bomb bay.
.....The version with larger bomb bay carried less fuel.

January 1941. Ju-288 prototype first flight.
By this date the Do-217 was entering operational service. Test pilots reported the Do-217 performed well even when powered by 1,100hp DB601A and 1,200hp Jumo211B engines.

It appears to me the Luftwaffe just didn't like Dornier. Why else would they spend money to develop the Ju-288 and Fw-191 airframes when the Do-217 airframe had already proven itself and was already in production?

 

[GregP]

Luftwaffe procurements appear to me to have been even more political than the Allied procurements were. They didn't like Ernst Heinkel and didn't like Willy Messerschmitt at first. The Me 109 was bought only because it out-performed the competition, despite Milch's dislike of Willy.

Perhaps Claudius Dornier was also disliked by Milch? Or maybe Hugo Junkers was judt a much better salesman.

I have often wonderred why the Dornier 17-series of aircraft were not used more. They seem like good-performing, tough aircraft, with better than average serviceability.

But the Nazis made a lot of seemingly strange decisions, so I never considered it any worse than other mistakes they made.

 

[michaelmaltby]

".... Hugo Junkers was just a much better salesman". If I recall, the Junkers Werks had been expropriated by the Nazis from Hugo in 1933 - and placed in the hands of a manufacturing experten (ultimately) to focus on the Ju-88 - which was to be the Swiss Army Knife airplane of the LW.

Here's what Wikepedia says:


".. Hugo Junkers is mainly known in connection with aircraft bearing his name. This includes such he reluctantly developed for the German Empire during World War I, later in minor association with Anthony Fokker, as well as civil aircraft designs during the Interwar Period produced by Junkers Flugzeugwerke (Junkers Aircraft Works). Junkers, a pacifist and not on good terms with the Nazis, deceased in 1935 and was not involved in the development of Junkers military aircraft for the Third Reich's Luftwaffe before and during World War II."


MM

 

[davebender]

The Hugo Junkers Homepage
Dec 1931.
Hugo Junkers fires most of his management team.

March 1932.
Junkers consortium unable to pay it's bills.

April 1932.
Junkers Flugzeugwerke shareholders fire Hugo Junkers as manager.

April 1932.
Junkers consortium reorganized in an effort to avoid bankruptcy. Shareholders ask Hugo Junkers to transfer his patents to the new company but he refuses.

December 1932.
Hugo Junkers returns to a management position at Junkers Co.

This happened before Hitler was appointed Chancellor during 1933. The new German Government inherited an ongoing power struggle between Hugo Junkers and company shareholders.

The German Government finally sided with company shareholders vs Hugo Junkers. Any other action would likely have destroyed the largest German aircraft manufacturer and probably the largest European airline (i.e. Lufthansa) as well.

 

[Siegfried]

When powered by similiar engines these aircraft had similiar performance. If anything the Do-317 looks a bit superior.
SNIP

It appears to me the Luftwaffe just didn't like Dornier. Why else would they spend money to develop the Ju-288 and Fw-191 airframes when the Do-217 airframe had already proven itself and was already in production?

It's unusual to develop 4 airframes Ju 288, FW 191, Do 317 (and Ar 340)

There may be other factors that were attractive about the Ju 288: eg perhaps better dive bombing capabilities etc. The "Bomber B" program seems to have failed because the engines could not be developed in time: neither Jumo 222, DB604 or BMW 802 was taken into production, though they all ran and the Jumo 222 was in low series pre-production and 'fixed' by the end of the war and ready for production. The reasons behind this include politics (ie quality versus quantity beliefs, desire of Milch to breakdown the junkers monopoly) , extremely tight development schedules for the engine, airframe weight growth (Ju 288 had a 4th crew member added and a wider fuselage) that then demanding full engine performance from the get up and go. Plus the Ju 288 had a fancy ejectable pressurized crew escape capsule.

It's interesting to speculate as to whether at least one of the DB604, Jumo 222 or BMW 802 could have been kept as a priority program perhaps by sacrificing work on the DB603 or Jumo 213 (which duplicated each other) or by introducing one of these engines in derated form. The Jumo 222 was lighter than the BMW 801 so it might have been used in derated form doing the job of powering FW 190As and Ju 88's on B4 fuel instead of C3.

The FW 191C, which used four equally distributed engines to get around the engine issues might have given the Luftwaffe a very fast bomber able to operate without significant escorts.

 

[davebender]

A fine idea. But why not design the Do-217 that way so it enters mass production during late 1940 powered by four readily available Jumo211 engines? During 1941 it would be a world beater, as fast as many fighter aircraft while carrying a 2,500kg bomb load.

 

[Milosh]

A fine idea. But why not design the Do-217 that way so it enters mass production during late 1940 powered by four readily available Jumo211 engines? During 1941 it would be a world beater, as fast as many fighter aircraft while carrying a 2,500kg bomb load.

The Do217 didn't enter mass production til 1941, (1 qtr - 27, 2 qtr - 52, 3 qtr - 105, 4 qtr - 73), if one wants to call that mass production, so how do you expect the Do317 to be in mass production in late 1940?

 

[davebender]

Historical Do-217 production was greatly hindered by a lack of suitable engines. I suppose that's Dornier's fault. They should have discussed engine production plans with RLM rather then building for the engines they wanted and hoping they would be available.

Dornier preferred the DB603 engine but that program was cancelled during 1937. Reinstated during 1940 but funding for development and production of the DB603 engine was never adequate.

Second choice was the BMW801 radial. Early models were unreliable. Expensive to produce. Production unable to meet demand until at least 1943.

RLM didn't get serious about DB601 engine production until 1940. Consequently production was inadequate until 1943. Fighter aircraft had first priority for this engine type so the Do-217 bomber program doesn't stand a chance to get them.

RLM established modern mass production facilities for the Jumo211 V12 engine at Magdeburg during 1937 and at Kothen during 1938. Consequently it was the only aircraft engine Germany had plenty of during the first half of WWII. If Dornier had designed the Do-217 bomber to be powered by Jumo211 engines the historical production bottleneck would be eliminated, allowing the Do-217 bomber to be produced in significant numbers.

 

[Milosh]

Jumo powered prototype a/c were flying in early 1939.

 

[davebender]

Dornier knew the Do-217 was too large to be powered by only two Jumo211 engines. They were working teething problems out of the airframe while hoping more powerful engines would be available for production aircraft. It's a gamble they lost. To make the Do-217 viable for mass production during 1941 it needs to be designed for four Jumo211 engines right from the beginning.

 

[Shortround6]

Then you have to ditch the dive bombing requirement, add about 20 feet of wingspan.

 

[davebender]

In this instance timing for making that sales pitch to RLM is perfect as the Do-217 bomber and new Lotfernrohr 7 bombsight become operational about the same time. With the new bombsight the Do-217 can level bomb accurately from an altitude of 3,000 meters. Less stress on the airframe and safer from enemy flak too. What's not to like?

 

[Siegfried]

Ditch the Dive Bombing requirement

The Lotfe 7 and the Stuvi 5B ( a computing dive bombing sight also good for shallow accurate slide bombing without dive brakes) were not really available till 1942, perhaps 41 so it is a somewhat brave decision to abandon the dive bombing requirement before then. Nevertheless I feel any any of the "Bomber B" proposals Ju 288, 317, FW 191 and Ar 340 could have been, without too much trouble, converted to 4 seperate engines and at least one should have been prepared in this way as a backup fast bomber. The pendulous inertia and stress of the over hanging outer engines creates aeroeleastic and structural issues that adds some weight that mitigates against dive bombing. However the RLM/Luftwaffe didn't seem to be thinking the way of 4 engined aircraft either for the bigger Bomber A (He 177) let alone Bomber B and by the time they were it was probably too late to find resources. Remember they had a disaster with Me 210 as well as the early He 177A1 and so didn't have the stomach for more hassles. The Manchester and Halifax of course both started as twin engine designs (woefully underpowered) so the British made the sensible decision to convert to 4, it seems Chadwick started on his own initiative. As it was the He 177 when converted to the He 277 had the potential to be a world beater as progressively more capable engines (more power higher rated altitude) became available and made it match or exceed even the B-20 but even this opportunity was missed, it doesn't seem that Goering was standing in the way of this either; it seems it was just politics and resource issues. The problem can be seen early on: the failure to see the FW 187 as a long range escort fighter rather than the "zerstorer" (a more cumbersome concept of a first strike fighter bomber and bomber interceptor), the desire to use the He 177 as a dive bomber. By the time these flaws were recognized the Reich was scrambling for every man hour it could get. What is bizzare is that the RLM built backups (eg Ar 240/440 for the Me 210/410) and no less than 4 proposals for Bomber B but implemented non of the backups and in some ways made them subject to the same risk eg new engines. I don't want to blame Ernst Udet, Goering appointed him, but it did occur under his 'watch'. I'm sure he was struggling under many pressures and requirements and there was more too it.

 

[davebender]

I agree. But that historical attitude was very risky.

The powerful DB603 V12 was canceled during 1937 to 1940. The BMW801 radial and various V24 projects were little more then designs on paper when Bomber B specifications were issued during July 1939.

Germany was staring a major European war in the face during July 1939. Under such circumstances building the Do-217 level bomber with four readily available Jumo211 engines looks pretty logical to me. It would replace the Jumo211 powered He-111 (a converted transport aircraft), providing the Luftwaffe with their first purpose built level bomber.

 

[Shortround6]

It would replace the Jumo211 powered He-111 (a converted transport aircraft), providing the Luftwaffe with their first purpose built level bomber.

The He 111 was not a converted transport, It was dual role from the beginning ( of the first 4 prototypes two were bombers and two were transports). If viewed as a transport if had some rather dubious features that showed that few compromises had been made for the bomber role. The same applies to the Ju 86. The older Dornier 11 and 23 were nothing but bombers, the thin disguise as a "mail plane" should have fooled no one. A bomber to replace the He 111 would have been the Luftwaffe's FOURTH purpose built bomber.
The He 111 was actually a pretty good bomber and with a little more timely development applied to it instead of haring off on some of the more lunatic bombing schemes might have paid the Germans good dividends.

 

[davebender]

This picture suggests otherwise.

 

[Shortround6]

This picture suggests otherwise.

Ok, what part of "dual role" didn't you understand?

It was designed to be both a bomber and a transport with minimal changes needed. It's ability to be a "profitable" transport was secondary to it's military role. At the time it first flew using a pair of 660hp engines to haul just 10 passengers was behind the worlds better transports. Look at the window layout, notice the gap between the first two windows on each side and the last three? It is where the rear spar goes through the cabin. Front four passengers are in the "smoking compartment" (bomb bay) while the rear six passengers are in the "main cabin".

 

[Milosh]

The powerful DB603 V12 was canceled during 1937 to 1940. The BMW801 radial and various V24 projects were little more then designs on paper when Bomber B specifications were issued during July 1939.

The first BMW 801A's ran in April 1939.

 

[davebender]

1,539hp
Service life of about 25 hours. Serious problems with engine overheating.
Dry weight about 1,000kg.
Dr. Tank was so disappointed with performance that he threatened to power the Fw-190 with something else.

The 1937 DB603 engine prototype performed at least as well yet RLM canceled funding for the program. During July 1939 the BMW801 radial looks like a longshot to me.

 

[Siegfried]

I agree. But that historical attitude was very risky.

The powerful DB603 V12 was canceled during 1937 to 1940. The BMW801 radial and various V24 projects were little more then designs on paper when Bomber B specifications were issued during July 1939.

.

Interesing, the suspension of DB603 engineering would have had a significant effect in several German aircraft programs which needed this engine. The suspension possibly makes sense when one considers that it might have helped to ensure focus so that the DB601A (1100ps) and DB601A1a (1170hp) was available in great quantities by the Battle of France. The French MS406 and other modern French fighters only had 880hp maybe 960hp Hispano Suiza HS-12Y engines.

However the DB603, if available earlier, might even have allowed Bomber-B to continue.

The DB603A and DB603AA had good but modest power outputs for their size (the AA had different supercharger gearing) but the DB603E produced good power and the MW50 version the DB603EB produced 2260hp. If the program ran 1 year ahead of schedule one can immagine the FW 190D9 DB603 version possibly seeing service in 1943. The Do 217M-1 managed a respectable 347 mph on the DB603A and a version with the DB603EB would have been quite fast. The interesting models are the two stage DB603L which was expected to drive the Do 335 to 495 mph. The C3 optimised DB603N was expected to produce around 2800hp.

The DB603 is not as powerfull as Jumo 222, DB604 or BMW802 but it is potentially a better engine than the BMW 801 and it is realistically its growth in performance is achievable in the same time frame as the DB605, perhaps even better. One can even immagine the DB605 and late model Me 109G being being bypassed and direct move to the Me 209-II, FW 190D or Me 309.

The Me 309 managed a stupendous 466mph on the DB603 but then for some reason much time was spent converting it to run on the msaller weaker DB605. The Me 309 had a laminar profile wing (all the Germans own work). Supposedly the Me 309 was less manoverable than the Me 109 but this may refer to low turn rates due to low power, it probalby could have been fixed with a wing area increase.

Realistically the conversion of Bomber-B and Bomber-A to 4 seperate engines is the only sure bet, the Jumo 211 being the one that is available.