Do-215 B5 as a heavy fighter/strafer

Discussion in 'Aviation' started by wiking85, Apr 22, 2015.

  1. wiking85

    wiking85 Well-Known Member

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    #1 wiking85, Apr 22, 2015
    Last edited: Apr 22, 2015
    Looking at the armament of the Do-215 B5 it had a pretty heavy forward firing gun package:
    Dornier Do 215 - Wikipedia, the free encyclopedia
    Without the IR gear could it have fitted more guns? Regardless would seem to have been as heavy an armament as the Bf110 and heavier than the Ju88C. Could it have been successful in that role, perhaps fitting gun pods like the Ju88 A-13?
    It had a 1500 mile range and 314 mph top speed. Plus it could take the cheap easily available Bramo radial engines to resist ground fire.

    Edit: the Z-10 seemed to be more ground strike capable. It appears it might have conducted some straffing missions:
    Dornier Do 17 - Wikipedia, the free encyclopedia
     
  2. Shortround6

    Shortround6 Well-Known Member

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    enough already with the "cheap easily available Bramo radial engines".

    Stick the Bramo engines back in the Do 215 and you have a Do 17Z.

    Maximum speed: 350 km/h (217 mph; 189 kn) at 8,040 kg (17,725 lb) at sea level
    ........................410 km/h (255 mph) at 8,040 kg (17,725 lb) at 5,000 m (16,404 ft)

    and that is with the 2 speed engines. At a gross weight of 18.913lbs speed dropped to 186mph at sea level and and 224mph at 13200ft which seems a bit extreme. BTW the 1500 mile range is with a 192imp gallon tank inside the bomb bay.
    DO-17Z could make 720 miles with 197 gallon bomb tank and a 1100lb bomb load.

    External loads like gun pods are going to kill speed and range.

    Come on People, look at a Bristol Blenheim with it's Mercury engines ( which were good for over 900hp for take-off on 100 octane fuel) and 840hp at 14,000ft and try to figure out how a German plane with larger diameter engines and less than 10% more power is going to be a war winning combination.
     
  3. wiking85

    wiking85 Well-Known Member

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    First of all I was not talking about it was a war winner, rather as an alternative to the Bf110/Ju88C.
    Also the weight and speed you quote for the 17Z is with bombs, which this aircraft I'm proposing wouldn't carry, nor would it fly much about 10k feet due to its mission profile.

    Why are you complaining about the Bramo? It was a mature engine, having been in production for years and was readily available, which is why it was used for the Ju52 and other secondary aircraft.
     
  4. Shortround6

    Shortround6 Well-Known Member

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    There is nothing wrong with Bramo engine as an engine. However it was a 9 cylinder radial which is about the worst configuration for power vs drag that there is (barring such things as 7 cylinder radials but they don't make enough power to begin with) and the idea that you can substitute a 26.8 liter radial air cooled engine for a 33 liter liquid cooled V-12 and get anywhere near comparable performance flies in the face of physics.

    The Bramo was fine transport engine, it was a fine flying boat engine. It was an acceptable bomber engine in the very late 30s when nobody else had anything much better. However it hit a wall in development and wasn't going to get much better unless you totally redesigned it and used C3 fuel.

    Please note that the Americans only used the R-1820G on the B-17 for major combat aircraft after 1941 and got away with it because they used a turbo-charger and operated the plane in rather thin air. Other uses were late model Wildcats and a floatplane, both of which had a fair amount of drag to begin with and they waited for an almost total redesign of the engine (new crankcase, new crankshaft, new heads, new cylinder barrels with a new way of making cooling fins, extra cylinder hold down bolts/studs, etc, etc) and 100/130 fuel (not even BoB 100/115-120).

    The Do-215 was 30-60mph faster than Do-17 depending on source and loading. Only some of the improvement was from the extra power, a major part was from the drag reduction, A Do-215 had a max cruising speed about equal to the max speed of a Do 17 running 1200lbs below max take-off weight (not over load).

    Coming up with 2nd rate aircraft to use old, existing engines doesn't really add to the Luftwaffe's capability. Anybody want to yank the Merlins from a Mosquito and replace them with Pegasus engines because of less vulnerability to ground fire?
     
  5. davebender

    davebender Well-Known Member

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    Ju-87 was more capable and less expensive to produce. So why not just increase Ju-87 production and build some as gunships with a cannon pod under each wing? Alternately you could build the proposed Fw-189 variant powered by inexpensive BMW 132 engines.
     
  6. wiking85

    wiking85 Well-Known Member

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    Range, speed, payload.
     
  7. Shortround6

    Shortround6 Well-Known Member

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    You put the radials on the 215 and there isn't that much to choose in speed between the Do 17 and the Ju 87. Granted you have range. Payload is 2200lbs vs 1100lbs but then you have a twin engine plane weighing about 13,000lbs empty but equipped and a single engine plane weighing 6,000lb empty but equipped. Crew of 3-4 vs crew of 2.
     
  8. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Both the Do-17 and Ju 87 will need fighter escort to survive and accomplish the missions vs. any competent enemy. The max bomb load for the Ju 87B was 2200 lbs; Ju-87D was at almost 4000 lbs.
    Range of the Ju 87B was increased when drop tanks were introduced, the sub-version was called the Ju 87R.

    The Do 215 was a far better aircraft than the Do 17, questionable is whether 2 Daimlers were a better investment there, than to install them on the Bf 110, or even maybe create a Ju 88 version with those. Make the strafers out of them if that is what is needed.
    Or, in case there is a surplus of Daimlers (yes, yes, I know...), better to install them on some Reggiane and/or Macchi airframes.
     
  9. wiking85

    wiking85 Well-Known Member

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    What about the Gnome Rhone 14N?
     
  10. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Pros vs. BMW: more power as-is (ie. without further development*), smaller frontal surface/less drag. Cons: 100 kg heavier. Vs. the DB 601A - less weight, but more drag and no easy way to extract much of the exhaust thrust.
    So with the 14N, it should be half-way between Do 215 and historical Do 17.

    However - the further production of Do 17/215 means that production of Do 217 is curtailed?

    *the new-gen of the BMW 132, the P, Q, R and S have had 1200 PS for take off; but the usage was rare if any?
     
  11. GregP

    GregP Well-Known Member

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    As far as the Bramo goes, you could always add one or two more rows and have a small "corncob" radial. I mean, it COULD be tried. But because it could be doesn't mean it should be. Barring experiments with adding rows actually working out for the better, I think Shortround is right about the Bramo for a frontline warplane. As he stated, it was fine for a civil engine.
     
  12. kool kitty89

    kool kitty89 Well-Known Member

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    #12 kool kitty89, Apr 23, 2015
    Last edited: Apr 23, 2015
    The advantages over the Ju 88 airframe in general should have been mostly limited to internal bomb configuration (namely the ability to carry larger bombs, if a more limited maximum load). Other than that, the Ju 88 should be a cleaner, lighter airframe when configured with similar engines, armor, and offensive/defensive armament. That includes potential to use the original smaller wing, or even clip the wings, use lower drag radiators (though the less vulnerable annular ones are probably attractive for ground attack), and possibly gaining some performance from using DB over Jumo engines. (the modest reduction in weight/bulk and smoother power curves -looking at low-alt engines here- probably would give at least a small advantage)

    We went over much of this in the recent discussions on making the Ju 88 a better fast bomber/multirole aircraft.



    Also the F2A, Martlet Mk I, several models of the Hawk 75, Dauntless, and XF5F. (I believe some of those export hawks and possibly the Marlet performed better than contemporary single-stage R-1830 powered models, at least the single-speed ones with lower FTH, while only slightly slower than the 2-speed R-1830 wildcat, though the 2-stage R-1830 was clearly superior and should have made much more sense on the F5F as well -might have been interesting on the F2A and Dauntless as well)

    Granted, some of those (especially the wildcat) were bulky designs where the added frontal area didn't have nearly as dramatic effect. (there was a bigger impact on the Hawk, fairly dramatic at altitudes were power were equal with better altitude performance of the R-1820s in question skewing things somewhat)

    With a 1200 HP R-1820, the Daultless performed better overall than the Ju-87, but that's probably more due to superior aerodynamics than anything else. (ie a Jumo 211 powered Dauntless should be faster)


    In this discussion, the Bramo engine seems pretty unattractive in general (and the airframe less attractive than the Ju 88 anyway). The BMW 801 might have made it more compelling, but the Ju 88 and Do 217 were more deserving airframes for that in general. (unless I'm grossly mistaken and the Do 215 was easier to reconfigure into a fairly fast fighter-bomber than the Ju 88 -the latter really seems like a cleaner airframe, all else equal)

    That said, compared to the much lower powered Jumo 210, the 1000 (or 1200 in the R-2) PS Bramo 323 is still at least somewhat interesting and the added durability is a bonus. In that sense I think it would have been interesting to see at least tested on the Bf 109, Bf 110, and Fw 187, though the 109's limited fuel capacity would probably make any performance gains rather moot. That would be as an alternative to the Jumo 210 mind you, not DB 601, so only relevant pre-war or very early war. (Jumo 211 would be more attractive in all cases as a lesser alternative to the 601) A Bf 109T with expanded fuel in the wings MIGHT make it more realistic but still inferior and likely inferior to the Hawker Hurricane as well. (plus german engines were water cooled, not glycol cooled, so lacked some of the concerns the USN leveled against liquid cooling ... if the aircraft carrier programm hadn't been cancelled but they still got somewhat lower priority, a Jumo 211 powered would have made much more sense and also meant a continual upgrade path rather than being a dead end like the Jumo 210)

    Herclues maybe, if the Mosquito's wooden structure wasn't a bit more vulnerable to ground fire already, or perhaps less specific to wood and more just to it being somewhat lightly built. (ie loss in speed/range would be a bigger problem) Probably still a better performer than the Beaufighter at least.


    That's a lot of engineering effort and a much bigger hypotehtical for relatively little gain. Besides that, retroactively applying experience with the BMW 801's cowling/fan design would seem far more realistic if somewhat limited by existing engines (ie existing stock of 323s, not speciallized designed for a separately geared fan, so likely having to be an accessory or run at the prop shaft speed)

    9-cylinder radials are inefficient drag-wise as mentioned above, but there should still be some possible optimizations. The large diameter yet relatively small displacement and cooling capacity needs could allow for much smaller openings in the cowling (ie tighter fitting and larger spinner) while still maintaining effective cooling. (using long, streamlined cowlings with prop extension shafts are more complex, usually heavier, and -at least in hindsight- far less effective than short, tight cowlings with large spinners)


    Applying that cowling design to the new generation of BMW 132s would make even more sense, but those seem to have been little used. (perhaps very low production runs due to stocks of existing 132s and 323s being in low demand?)



    If you wanted a new, smaller diameter engine in the 1200+ HP range, something as close as possible to the existing 801 would make more sense. (still a lot more engineering work, but a 14 cylinder radial with around 80% the stroke should have made something close to the R-2000 -a mercury to the 801's pegasus)
     
  13. Shortround6

    Shortround6 Well-Known Member

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    Please not that what I wrote was "the Americans only used the R-1820G on the B-17 for major combat aircraft after 1941" and yes I did miss the Dauntless. Good as the Big Cyclone may have been in the mid and late 30s it had a problem with streamlining (power vs frontal area) as other engines began to show up.

    We are confusing time lines again. When the Germans went for the Jumo 210 the 1200hp Bramo wasn't even a gleam in the eye of it's designers/developers. We are also comparing vastly different engines. A Bramo 323 weighed about 1200lbs (single speed) and a BMW 801 went around 2300lbs for a bare engine. The Do 17 started out at about 10,000lbs empty (or under) with the old BMW V-12s with a take-off weight of of about 15,500lbs. It went to about 17,600lbs loaded withe the Bramos in the M model and about 11,500lbs empty and 19,000lbs loaded in the 4 seat Z models. BMW 801s would have given great performance if they didn't break the airplane, adding over 2000lbs of bare engine weight to what in realty was a light airplane (early Do 17s weighed less empty than the American YP-38 fighters) The M model used Bramo 323 A engines starting in 1937. Wiki claims the Bramo 323 first ran in 1936 although it was a development of earlier Bramo engines ( the Bramo 322 being less than successful). As an indicator of the drag the very early Do 17s with the BMW V-12s which had 750hp at sea level were actually faster (about 6mph) than the Bramo powered M with 900hp at sea level. The BMW V-12s had no supercharger and performance fell off considerably with altitude. The Jumo 210 was a replacement for this engine. The Jumo 210 was being test flown 2 years before the Bramo 323.

    The 1200hp Bramo used water injection and while a 20% increase in take-off power was most welcome for heavily loaded planes it retained the same 30 minute climb and same cruise power ratings as the 1000hp version.

    We have a real good idea how this would turn out. The P-40 with the Allison engine had 22% less drag than the P-36 with P W R-1830 which was smaller in diameter than the Bramo (or Cyclone), there is some doubt about if that is all drag reduction or how much exhaust thrust may play into things. Granted on the twins (especially the Bf 110) the engines may be a smaller part of the whole drag picture than on a single engine fighter.


    Kind of misses the point I am trying to make. Two row radials are no where near as bad as single row radials in regards to frontal area/drag vs power. AN early Hercules with two speed Blower had over 40% more power at around 14-15,000 ft than a two speed Pegasus and was actually a bit smaller in diameter/frontal area. Needed more airflow through the cowling for cooling though. Hope you get the idea, This was the motivation behind the Taurus engine, about the same power or bit more than the Pegasus with about 75% of the frontal area.



    Very few of the "trick" cooling schemes actually worked in practice. The XP-42 went through at least 12 different configurations of cowling and spinner and wound up fairly close to the original P-36 cowling. It is a lot of engineering and test time for little result when applied to the single row engines as they are never going to be competitive with the two row engines or the V-12s from a drag standpoint.
     
  14. wiking85

    wiking85 Well-Known Member

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    How about the GR 14N vs BMW 132?
     
  15. Shortround6

    Shortround6 Well-Known Member

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    It is pretty much the same deal. The BMW 132 and the Bramo 323 were very similar engines in layout and general characteristics. The BMW 132 was licence built P W Hornet. BMW took it a bit further than P W did at home because P W was going to the 14 cylinder twin row engines. They had had the R-1690 Hornet and the R-1860 Hornet B and gave up on the Hornet B due to piston cooling problems in the large cylinders and went for the R-1535 15 cylinder (mainly at Navy insistence) and the R-1830.

    There is only so much you can do with 1530-1820 cu in (25-30 liter) 9 cylinder single row radials, especially if you are limited to 87 octane fuel. They are going to be similar in weight, similar in diameter and similar in power output, obviously the bigger ones are going post higher numbers in all categories than the smaller ones assuming a comparable time frame, Late 1920s engines often being direct drive (no reduction gear) with less finning being lighter than later models.

    You can argue numbers of specific models back and forth a bit but there is a reason most countries/companies went to 14 cylinder engines once they got to a certain power level (which changed as time went on) as you can only get so much power from a a given size cylinder at a given RPM and with a given fuel and it was often much more related to the cooling ability of the cylinder than valve size or configuration.
     
  16. wiking85

    wiking85 Well-Known Member

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    Were you responding to me? The 14N was a 14 cylinder engine with 1200hp (roughly depending on model). Better than the 9 cylinder BMW 132, but heavier by about 100kg.
    Gnome-Rhône 14N - Wikipedia, the free encyclopedia
     
  17. Shortround6

    Shortround6 Well-Known Member

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    #17 Shortround6, Apr 23, 2015
    Last edited: Apr 23, 2015
    I was responding to you, what I was getting at was that if you compare the 14N to one 9 cylinder radial you have pretty much compared it to all of them.

    The Bristol Mercury was about the smallest at just about 1000lbs, 51.5 in diameter, 14.5 sq ft frontal area and 840 hp at 14,000ft altitude from 24.9 liters , the R-1820 was the biggest 1320lbs, 55.1 in dia, 16.6 sq ft frontal area and 1000hp at 14,000ft altitude from 29.9 liters ( for a 1941 engine) . The two German engines, the Hornet and the Pegasus and Perseus all fell in between.

    Since some of these engines were in production for 10 years or more (R-1820 was over 20 years) and fuel changed a lot there can be wide variations in power from first to last but at any given point in time, given the same fuel, the power is going to correspond pretty well to the displacement (Mercury turned a few more rpm).

    The wiki article is a little optimistic on power outputs from the 14N. But again it depends on model and year. Few, if any, 1200hp versions saw any service use in 1940. Planed/proposed/advertised/prototypes are another story.
    But the G-R 14 was a 38.9 liter engine (same bore and stroke as a Hercules) and may have been able to operate for long periods of time closer to it's max power level than some of the 9 cylinder engines.

    edit, the G-R 14 never got a 2 speed supercharger during WW II in service except for the Russian version, the M-88. Out of the Big '9's only the Pegasus, the R-1820 and the Bramo 323 got 2 speed superchargers.
     
  18. davebender

    davebender Well-Known Member

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    If you want to strafe then we are talking about CAS. Such aircraft fly low, slow and long range is not normally a mission requirement. Nor do you need a huge weapons load. Any aircraft that can carry a 1,000kg bomb (i.e. Ju-87) can carry cannon pods with a generous supply of ammunition.
     
  19. kool kitty89

    kool kitty89 Well-Known Member

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    I was thinking more of the 1000 PS (take-off or at altitude depending on the supercharger gearing) earlier single-speed models as well as the 1000/940 ps 2-speed models. (I think the maximum power for low gear may have been slightly higher than 1000 PS at critical altitude, but I haven't seen actual power charts regarding that).

    The early single-speed altitude tuned 323A was good for 900 PS on take-off and 1000 PS at 3,100 m. That's nearly 50% more power at altitude than the Jumo 210 (closer to 40% compared to the 210G) and significantly more than contemporary BWM 132. Additionally, the 323 was actually available as counter rotating A/B engine pairs, unlike most other german engines. (another bonus for use on twins)

    That said, none of that really matters for the topic at hand as the likes of the Do 215 or Ju 88 would be poor performers with any model of the Bramo engine, plus this is for a 1940 or later application where the Bramo's advantages diminish considerably further. (especially since the captured GN 14N engines were smaller, not much/any heavier, more powerful -without water injection- and also featured L/R hand rotation, though the lack of fuel injection would be a disadvantage for some maneuvers ... but say something like ... re-engining the Hs-129 or Fw 187 with 14Ns would make more sense than Bramos as far as a strafing aircraft -and likely suit the HS-129 more than the 187 given the much greater benefits the low drag airframe of the latter would gain from liquid cooled engines, unless expanding the 129's fuel capacity was impractical, but this is bleeding more into the fighter-bomber topic again)


    That and you're comparing the R-1830/1820 to V-1710 while the Jumo 210 would be closer to the V-1570 ... unless I'm mis-reading.

    The Fw 187A-0 (or protoypes aside from the couple DB powered versions with less straightforward performance figures) and (especially) the larger Bf 110B series should have benefited significantly from the added power even the single-speed Bramo offered. (as would have the Ju 87 compared to the underpowered 210 powered models)

    Converting the 109D to 323 would be the closest comparison to the P-36 situation or, rather, 109E would be a better yardstick to compare with the P-40. A Bramo powered 109 likely would have been more in the 310-320 MPH range (probably not more than 310 for the 323A) and shorter ranged than either the E or D model if fuel capacity wasn't increased. The range issue is probably the real killer there, and increases in fuel would further degrade performance. (plus if you wanted an alternate-engined 109E/T, the 211 would be far, far better ... the lighter 109D has more advantages with the 210 than the 110 or Ju 87, and the Fw 187 would be the odd-one out given the size/drag/power/range combination -counter rotation is a plus for both the 187 and 110 though)

    Probably not worth the time and effort yes ... I only mention it as an afterthought to BMW's success with the 801's cowling. (that said, there could be some more conservative improvements on the cowls/spinners typically used with BMW/Bramo radials pre-war ... and continually during war)


    Perhaps the ability to accelerate and run from opposing air support? Or at least evade well enough to make escorts more effective. (though those are arguments that point more towards a fast, good accelerating fighter-bomber)

    Aside from that, for CAS, endurance may be more important than range, and potential ability to drop bombs and then continue to make several strafing passes before returning to base. Twins with ample power also have the ability to limp home on a single engine.
     
  20. davebender

    davebender Well-Known Member

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    Local air superiority is a prerequisite for survival of CAS aircraft. That holds true even for fast aircraft such as Fw-190F and P-47 as enemy fighter aircraft in the area will almost always have an altitude advantage.
     
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