Dornier 217 hypothetical

[davebender]

DB603 engine was heavy but it had a surprisingly small height and width. That makes for a relatively slim engine compartment.

Air cooled radial engines are fat and space requirements for cooling air make the engine compartment even larger. All U.S. fighter aircraft powered by R-2800 engine had a huge fuselage and all were relatively heavy.

Engine Frontal Area (sq. ft.)
5.4. DB601E
5.5. DB605A.
5.8. Merlin X
6.1. Merlin 61.
6.1 to 6.2. Allison V1710 series.
6.3. Ju213A.
6.9. DB605D
7.0. DB603A
7.5. Merlin 66
12.6. P&W R1830
13.4. R2000
14.7. BMW801D.
15.0. R2800
16.0. R2600.

 

[tomo pauk]

Thanks for the numbers. I can readily agree that radials were always draggier, even when we count in the cooling system, not listed in your list. We can also note that BMW-801 was one of least draggy radials, and radiator installation in historical Do-217 was not something to brag about.

 

[davebender]

Do-217M was mass production bomber (431 produced during 1943) powered by DB603 engines.

I know nothing about this aircraft's cooling system. What don't you like?

Dornier Do 217 M, Italeri 1/72 - Ready for Inspection - Aircraft - Britmodeller.com

 

[Milosh]

Why is there such a difference between the DB605A (5.5) and the DB605D (6.9)?

 

[tomo pauk]

Do-217M was mass production bomber (431 produced during 1943) powered by DB603 engines.

I know nothing about this aircraft's cooling system. What don't you like?

Thanks for the pics.
What I don't like is that it ups the power plant frontal area some 50%, give or take.

 

[davebender]

How much is typical?

DB603 powered Me-410A should provide a direct comparison. Perhaps we could also look at Lancaster Bomber and divide by two as it has 4 engines.

 

[tomo pauk]

The 'typical' increase of power plant area would depend upon the size layout of the coolers.

For the Do-217, we need to account for also the oil cooler (atop of the engine), the BMW-801 having oil cooler 'wrapped around', located inside the cowling.
The Lancaster (and Halifax and Beaufighter) might or might not give us a clue, radial vs. in-line re. Do-217. The BMW-801 was renown as a streamlined powerplant (vs. Hercules, R-2800 etc), with tight cowling. On the other hand, the Merlin was a smaller engine than DB-603, needing also smaller Prestone and oil cooler.

 

[davebender]

Chromium. October 1944.
19.01kg. DB605.
21.95kg. DB603.

Nickel Requirements.
9.82kg. DB603. Oct 1943.
2.16kg. DB603. May 1944.

It appears to me Daimler-Benz did an outstanding job designing DB603 engine for low cost mass production. A bit more expensive then the relatively cheap DB605 but not much more and almost certainly less expensive then BMW801 radial engine.

 

[Gixxerman]

I always liked the look of the late Do 217's, pretty mean looking bombers.
I seem to recall reading in several places that they were always underpowered.
They did seem to be the heaviest of the LW's 'medium' bombers though (a bomb load of 4,400kg seems to be quoted a lot = almost 9,000lb).

It always amazes me seeing the production numbers, as with so many German bombers there seem to have been hundreds of each sub-type made (amounting to thousands of bombers) and yet what did they do with all those late war Ju88's, Ju188's, Do 217's, He 177's etc etc?

I have read that the bomber arm of the LW was the most prestigeous part of the LW and yet once the initial victories were done spent (until end 1942/Stalingrad?) it seems to have done very little besides Steinbock.
Perhaps there's a whole side to it (presumably in the east) that has gone unreported?
They must have done something with them (surely they weren't all wasted as transports hacked out of Stalingrad skies)?

 

[wiking85]

I always liked the look of the late Do 217's, pretty mean looking bombers.
I seem to recall reading in several places that they were always underpowered.
They did seem to be the heaviest of the LW's 'medium' bombers though (a bomb load of 4,400kg seems to be quoted a lot = almost 9,000lb).

It always amazes me seeing the production numbers, as with so many German bombers there seem to have been hundreds of each sub-type made (amounting to thousands of bombers) and yet what did they do with all those late war Ju88's, Ju188's, Do 217's, He 177's etc etc?

I have read that the bomber arm of the LW was the most prestigeous part of the LW and yet once the initial victories were done spent (until end 1942/Stalingrad?) it seems to have done very little besides Steinbock.
Perhaps there's a whole side to it (presumably in the east) that has gone unreported?
They must have done something with them (surely they weren't all wasted as transports hacked out of Stalingrad skies)?

In 1943 there was a switch largely to fighters, including the Do-217 night fighter, which was a waste of the aircraft IMHO, as it was far too heavy for that role and could have been useful on the Eastern Front.
By 1943 LW bombers were operating in the Mediterranean, on the Eastern Front, and against Britain in air raids, including the Do-217 in those. By 1944 the bomber arm for the LW had been decimated and was operating sporatically in Italy and France, while mostly being confined to the Eastern Front due to Western Allied air supremacy. In 1944 it was almost exclusively fighters that were being churned out and bombers were around 10% of production, meaning even those bombers that were left were often sidelined due to lack of spare parts or fuel, not to mention lack of replacement aircraft.

I think the Do-217 had a narrow window of usefulness in 1941-43 given the historical political decisions being made, poor military planning, and very poor development decisions that prevented aircraft like the Do-217 having powerful enough engines. If it had the originally planned Jumo 222 available in 1942 as initially planed (2000hp version), rather than the Jumo 222 being constantly modified to produce more power as demanded by the LW, it would have had plenty of power for the roles expected of it. Even having the DB603 ready in 1941-42 would have been a massive boon to this type, as it would have offered more power than what was available historically at the time. But even then the DB603 at 1750hp that was tested by Eric Brown (Dornier Do 217 - Wikipedia, the free encyclopedia) was apparently too little for the type. Of course the dive requirement upped the weight and slowed development, which would be different with this scenario's version of it, which wouldn't have been strengthened for a role it was never able to effectively perform. So perhaps a DB603 would have been just right for the Do217 without the dive requirement.

 

[davebender]

Arado Ar 232 - Wikipedia, the free encyclopedia
Personally I think Dornier missed the boat by not making a 4 engine variant powered by Bramo 323 engines. Change would be similiar to Ar-232.

Ar-232 Early Version. 2 x BMW801 engines.

Ar-232 Late Version. 4 x Bramo 323 engines.

Change to four engines worked exceptionally well for Ar-232. So well in fact that there were plans for a 6 engine version. Arado's good work was for nothing because RLM refused to allow production of Ar-232 transport.

Converting Do-217 to 4 x Bramo 323 engines has additional advantage of not requiring a new engine to be developed. Just increase production of existing Bramo 323 engine.

 

[johnbr]

I so a doc that showed at one time it was to get the BMW 802 in it.

 

[Denniss]

The Bramos would not be sufficient for the Do 217 - not enough power.
They could have used the Jumo 211 though.
But going from 2 to 4 engines will required a wing redesig, at least it has to be longer and stronger.
And as long as the dive bombing requirement was upheld, no chance for a 4-engine version.

 

[tomo pauk]

The four Bramos in Fw-200 have had the same take-off power as the engines for the B-17 and B-24...

 

[Vincenzo]

On the underpowererd
the BMW 801 engined Do 217 is a 1941 bomber, what twin engined bomber with similary load capability had best power load in that time? or when were available so bombers with best power load?

 

[Denniss]

The four Bramos in Fw-200 have had the same take-off power as the engines for the B-17 and B-24...

But these engines could hold power high-up, only the two-stage Bramos could keep a good alt performance up to the usual levels of ~5 km. The 1200PS were only possible for a very short time with C-3 or MW-50, real power without boosting was 1000PS

 

[tomo pauk]

But these engines could hold power high-up, only the two-stage Bramos could keep a good alt performance up to the usual levels of ~5 km.

Is that a typo, two stage Bramos?
The US heavies were twice as big airplanes as the Do-217, with much more crew and gun armament. Granted, the fictitous 4-engined Dornier would not be as small as the DO-217, but again not as big the US heavies, if the defensive armament and crew is kept at reasonable level in the design phase. Or, they might go to a full-size 4-mot, a rough equivalent of the French MB.162?

The 1200PS were only possible for a very short time with C-3 or MW-50, real power without boosting was 1000PS

Okay - so the 1st versions of the 4-engined Dornier would feature the 1000 PS engines, later increasing to 1200 PS.
BTW - is there an easily obtainable data resource about the Bramos?

 

[wiking85]

Arado Ar 232 - Wikipedia, the free encyclopedia
Personally I think Dornier missed the boat by not making a 4 engine variant powered by Bramo 323 engines. Change would be similiar to Ar-232.
Change to four engines worked exceptionally well for Ar-232. So well in fact that there were plans for a 6 engine version. Arado's good work was for nothing because RLM refused to allow production of Ar-232 transport.

Converting Do-217 to 4 x Bramo 323 engines has additional advantage of not requiring a new engine to be developed. Just increase production of existing Bramo 323 engine.

So basically a developed Do-19 worked on from 1936 instead of starting the Do-217 in 1937. I think we could refer this back to my Do-219 thread in that case.

 

[davebender]

They could have used the Jumo 211 though.
But going from 2 to 4 engines will required a wing redesig, at least it has to be longer and stronger.

If Germany wanted a bomber powered by four Jumo 211 engines they would produce the He-177B proposed in 1938.

525kg. BMW 132 dry weight.
550kg. Bramo 323 dry weight.
720kg. Jumo 211F.
920kg. DB603A dry weight.
1,012kg. BMW 810 dry weight.
.....Two Bramo 323 engines weigh little more then one BMW 801 engine. That's probably why the Ar-232 engine change worked so well. The wing doesn't need to be strengthened, as would be the case if heavier Jumo 211 engines were installed.

 

[wiking85]

Back to the DB603 as a potential engine by 1940:
I just got a new book that adds a bit more info and seems to think that 1940 was the year the engine would be operational. Apparently it was first offered in September 1936 as a development of the DB601, which had yet to enter serial production, but was progressing to that point within a year. But Udet cancelled the DB603 in March 1937; had the engine been kept in development, there seems little reason that it couldn't enter serial production by September 1940 and that it would produce some 1600hp at that period, bumping up to 1750hp the following year as the improvements from the DB601N and DB601E/F are phased into the larger engine.

As it was from the first contract to develop the DB600 series of engines in 1933 to serial production of the DB601A in November 1937 was close to 4 years. The first bench test for the DB603 would have been in 1938, which meant usually that within 2 years of a successful bench test the engine was ready for mass production. Historically with little financing and support the DB603 went from a bench test in 1939 to mass production in 1941, though because of the limited support for it, Daimler didn't dedicate the required engineering resources to it despite it jumping in horsepower output, thus experiencing heating issues when it exceeded the horsepower it was initially designed to produce.

Here the engine would stick to spec by the time it would enter serial production in late 1940, so wouldn't experience those overheating issues; they would crop up as it was upgraded in 1941 of course, but assuming it was valued more highly by the RLM, it wouldn't take as long to work them out. That would mean the Dornier 217 could have a functional engine of the 1600hp class and enter serial production in 1940.