Fighter-Bombers in the late 1930s and the Fw 187

[buffnut453]

They were using variable pitch propellers (at the least) on 109Cs. Variable pitch doesn't always mean constant speed. Variable pitch can mean two pitch, course and fine, with nothing in between. It can mean the pilot can, by means of a control, adjust the pitch anywhere between the two limits. Constant speed propellers have a governor that automatically adjust the pitch to keep the propeller turning at a preset value. Translation of books from one language to another often confuse the terms much like two speed and two stage superchargers. Perhaps the E-4 got a different type of propeller control for the same mechanism? Or different control lever arrangement? When did the Germans go to a single lever control? one lever to control the rpm, boost, and prop pitch?

Hamilton Standard introduced a constant speed propeller to the commercial market in 1935. They had introduced their variable pitch (2 pitch ?) prop in either 1930 or 1932. They were certainly not the first to build such propellers but were the first to achieve commercial success. The idea (and experimental) variable pitch propellers go back to before WW I and pictures show an S.E. 5A with an experimental variable pitch prop (continuously variable?) in 1917. The British had fooled around with several other designs of variable pitch props in the early 20s but all had faults or problems that could not be overcome at the time. This soured the air ministry on variable pitch props and it took a lot time and success by other countries (and a few forward thinking British companies) to change the air ministry's collective mind. It doesn't do a lot of good to licence a design if the air ministry won't buy them. The Air Ministry was changing it's mind by 1939 (if not a bit before) but by then they were facing a rapid increase in production of all types of aircraft and the demand exceeded supply (due to low orders in the mid 30s) for a while until the propeller factories could be expanded.
The US had been using 2 pitch propellers on the Boeing 247 airliner and others in 1933.
Hamilton Standard introduced the Hydromatic propeller in 1937 and this allowed full feathering of the propeller instead of setting the prop on the bad engine to course pitch and was a major change in twin engine safety.

Understood but your original post specifically mentioned constant speed. I'll try to do a better job in future of reading your mind before I respond so I can understand what you meant rather than what you wrote (and, yes, I say this entirely tongue in cheek).

 

[Shortround6]

Understood but your original post specifically mentioned constant speed. I'll try to do a better job in future of reading your mind before I respond so I can understand what you meant rather than what you wrote (and, yes, I say this entirely tongue in cheek).

Well, the Rotol was constant speed and the DH 2 position props were converted to variable between the limits if not full constant speed (to avoid mind reading I mean I am not sure, the conversion may have been to full constant speed operation). The thing is that fitting such propellers in the summer of 1940 was 3-4 years late. Fitting 2 pitch propellers in 1939 was 5-6 years late. The British should have been in the leading ranks of the change over if they couldn't be the first, not being dragged kicking and screaming into modern propellers

The fitting of better propellers (or planing to fit better propellers) would have allowed for higher take-off weights from existing fighter air fields using existing engines and existing fuel. The greater weight could have been used for either bombs, or more fuel, or heavier gun armament.

The British had experimented with a variety of variable pitch designs back in the 20s and found a number of drawbacks/problems. This colored their thinking in the 1930s despite an almost universal adoption of the variable pitch and constant speed propellers by just about every other major country.
I am just speculating but was the Lockheed Hudson referred to as "old Boomerang" in part because it used both more powerful engines for it's weight AND feathering propellers that allowed to return on one engine?
How many RAF bomber aircrews flying twins in the first few years of the war were lost because they did not have the ability to feather the prop on the dead engine? An ability that airliners in use by 21 airlines had in 1937 and early 1938.

It takes time to ramp up production and the Air Ministry coming in a bit late meant that production capability was lacking and priorities in propeller allocation had to be made. The Bombers got priority for the 2 pitch props because Fairey Battles and Whitleys trying to take-off with fixed pitch props is just too painful to contemplate
AS production increased the better props could be spread around more, Thanks be to Rolls-Royce and Bristol (Fedden) for agreeing to co-operate in the Rotol venture in 1937, putting the country's interest ahead of their commercial interests.

Deciding to use constant speed props in the fall of 1939 is a bit late if you have no manufacturing base for them.

 

[Juha]

IIRC the DH props were converted to constant speed propellers. British had decided in late 30s that the bombers needed more the CS props than the fighters. Probably thinking t/o. In 40 they had found out how much 2-pitch propeller handicaped fighter, so in June 40 they began a crash program to convert all fighters in service to have CS propellers, the new ones in that stage were delivered from the factories with CS prop.

juha

 

[stona]

IIRC the DH props were converted to constant speed propellers.
juha

Yes they were. The principle sticking point for CSUs on British fighters was the weight. With hindsight this was a bad misjudgement and the situation was just about rectified in the nick of time. The two pitch DH unit was already fairly heavy. The Rotol unit was specifically designed with wooden blades to reduce the weight.
Cheers
Steve

 

[tomo pauk]

I don't disagree but it was Shortround who specifically called out constant speed props. That said, having variable pitch sooner wasn't going to change fundamental issues in the design of fighters in Europe. Early war European fighters of all nations lacked the range and were typically of smaller size compared to their US equivalents. Both factors limit the adaptability of aircraft like the Spitfire and Bf109 into the fighter-bomber role. In the late-1930s, there was simply no envisaged role for fighter-bombers but the role evolved as the light bomber concept proved flawed and the need for CAS-type missions became increasingly significant. The Hurricane rather fell into that role once it became obsolete as a fighter.

Bit of a disagreement here - when introduced, Hurricane was the biggest 1-engine fighter. Spitfire was second biggest. Bf-109 was indeed small (so were French fighters, MC.200, current future Soviet fighters), being conceived around a smaller engine and smaller firepower than British fighters. US fighters of the era (P-35, P-36) were not bigger than Spitfire.
IMO the adaptability of early war fighters into fighter bombers have had much more to do with lacking number of fighters available and current doctrine, rather than with aircraft capabilities, especially the decent-sized British duo.


As for the Fw-187 as a fighter bomber - I'd have them with Hispano 12Y engines once Czech factory is in German hands (from spring 1939, so it can be in service for the Western campaign). Not that powerful as the DB 601, but weight penalty is far lower, comparable with Jumo 210, and with notably more power than it.
Once France falls, a bit better 12Ys can be installed. Then also the G&R 14N might be contemplated for the Fw 187.

 

[buffnut453]

Fair enough, Tomo. To be honest, I was getting my timelines a little crossed...I was thinking of the P-43 which, of course, was a late-comer only having its first flight in 1940. As I've already pointed out, lack of doctrine for fighter bombers was a key limitation in their evolution so we're in complete agreement there.

 

[Shortround6]

The British pair were carrying the heaviest common (Bloch 151/152 excepted) gun armament in 1937-38-39, about 410-415 lbs worth of guns and ammo for the Spitfire, a bit more for the Hurricane.

A P-36 with one .50 and one .30 was carrying 174lbs and adding a .30 cal to each wing ran the weight up another 112lbs or so.

The Americans had used constant speed propellers (?) on fighters as early as 1935/36, photos show 3 blade props with constant speed type hubs on P-30s.

Although some photos show two bladed props without the forward extension. Descriptions have to looked at carefully because in the early 30s there were 'adjustable' pitch propellers which allowed mechanics to rotate the blades in the blade holders on the ground (engine NOT running and 'adjust' the pitch that way as opposed to fix pitch props even if metal.

The need for longer take-off areas may have influenced the decision to do away with under wing loads in some cases.

 

[wiking85]

As for the Fw-187 as a fighter bomber - I'd have them with Hispano 12Y engines once Czech factory is in German hands (from spring 1939, so it can be in service for the Western campaign). Not that powerful as the DB 601, but weight penalty is far lower, comparable with Jumo 210, and with notably more power than it.
Once France falls, a bit better 12Ys can be installed. Then also the G&R 14N might be contemplated for the Fw 187.

How much difference would the Hispano really make given that it only saved a couple hundred Kgs per engine and had a higher specific fuel consumption? The better French Hispanos require 100 octane fuel too.

As to the GR 14N that does look like an interesting option, any idea how it stacks up against the DB601?

 

[tomo pauk]

Germans, Italians and Bulgarians used the late Hispano engines in captured D.520 fighters, the Vichy France was also the user.
As for the power - the Czech-made Hispano 12ydrs engine will make 850-860 CV at 4 km, vs. 670 CV for the Jumo 210G at 3,8 km, while weighting only 25 kg more (dry weight) - 470 kg. A power increase of almost 30%, for weight increase of 5% - those two factors make the difference: major increase of power with almost no need to beef up the structure, unlike what it would've taken for the DB 601. That one weights almost 40% more vs. Jumo 210, granted the power is also considerably greater. But main problem with Daimlerized Fw 187 is the lack of engines, not some great problems to install them on the 187. Hence my suggestion for installing the engines of French origin, at least until the DB production is ramped up.
12ydrs needed 87 oct, unlike the late developments.

Hispano engines will have greater specific fuel consumption, but they make 15-20% less total power, so total consumption vs. future DB engines will remain in the ballpark.
The G&R 14N will make 1050-1250 CV at rated height, the low-level version even 1400 CV?* Power-wise it is comparable with DB 601A, it should be lighter when installed (dry weight starting from 620 kg), but it will create more drag than a V-12 engine, and usage of exhaust thrust will not be as good as with a V-12.

*source: Wikipedia, take it FWIW

 

[Shortround6]

The Hispano might be a good choice, the FW 187 might not need much, if any beefing up as it was designed to use DB engines in the first place and only used the Jumos because of DB shortages.

The Gnome-Rhones are interesting but they will NEVER put out the power you see listed in Wiki. Please remember the 14N is a two bearing engine. the 14R got the center bearing and gained hundreds of pounds of weight.

See Russian M-88 engine for practical power with better than 87 octane fuel and a two speed supercharger.

 

[tomo pauk]

...
The Gnome-Rhones are interesting but they will NEVER put out the power you see listed in Wiki. Please remember the 14N is a two bearing engine. the 14R got the center bearing and gained hundreds of pounds of weight.
See Russian M-88 engine for practical power with better than 87 octane fuel and a two speed supercharger.

Checked out French Wikipedia - the last G&R 14N sub-type described there, the 14N 48/49, was claimed to be capable of 1300 CV at 2150m for short periods of time. The crankshaft bearings were improved vs. preceding models.
At 4 km (give or take), seems that no 14N model was managing above 1100 CV, per same source.

The 'version' that was supposed to make 1400 CV was the 14N 50 - later renamed 14R, ie. a wholesale redesign of the G&R radial.

Looks like I'd have to dive at the SAFRAN archives in order to get some better information if possible

 

[kool kitty89]

Exactly, and earlier Bf 109s did have a variable speed airscrew. The control, like a rocker switch, was positioned on the throttle lever and the pitch indicator was the dial at the lower right of the instrument panel, sensibly next to the engine tachometer.

Whilst a manually controlled variable pitch unit is much superior to a fixed or two pitch system it did need training to be used correctly. There are accounts from the latter stages of the BoB which show that some of the Luftwaffe's inexperienced replacement pilots struggled to operate the system even when flying in formation, never mind under the stress of combat. In this sense a constant speed unit gives an advantage.

And even so, a basic 2-pitch system is still better than fixed pitch.

Well, the Rotol was constant speed and the DH 2 position props were converted to variable between the limits if not full constant speed (to avoid mind reading I mean I am not sure, the conversion may have been to full constant speed operation). The thing is that fitting such propellers in the summer of 1940 was 3-4 years late. Fitting 2 pitch propellers in 1939 was 5-6 years late. The British should have been in the leading ranks of the change over if they couldn't be the first, not being dragged kicking and screaming into modern propellers

Yes, the likes of Kestrel and Mercury fighters should have been adopting DH 2-pitch props in the early 1930s alongside their airliners, racers, and mail planes. (possibly 2-bladed units similar to those later used with the Gipsy Twelve ... or the Jumo 210 powered 109s)

The British had experimented with a variety of variable pitch designs back in the 20s and found a number of drawbacks/problems. This colored their thinking in the 1930s despite an almost universal adoption of the variable pitch and constant speed propellers by just about every other major country.

That's very slightly reminiscent of the RAF .50 cal gun trials where .303 was seen as more efficient and 20 mm as the more realistic follow-on and no interest was given in replacing the .50 vickers with a browning derivative firing the same cartidge. (granted, had they hedged their bets for the hispano with the Oerlikon FFF -or possibly FFL- rather than the FFS with bulk, weight and recoil closer to the Hispano, that may have been a non-issue -I find it very unlikely that 4x FFF cannons wouldn't have been satisfactory in the Hurricane Mk.I)

The Hispano might be a good choice, the FW 187 might not need much, if any beefing up as it was designed to use DB engines in the first place and only used the Jumos because of DB shortages.

The Gnome-Rhones are interesting but they will NEVER put out the power you see listed in Wiki. Please remember the 14N is a two bearing engine. the 14R got the center bearing and gained hundreds of pounds of weight.

See Russian M-88 engine for practical power with better than 87 octane fuel and a two speed supercharger.

The Hispano engine is definitely an interesting option and perhaps more attractive than the Jumo 211, at least as a fighter. (a little less so as a fighter-bomber)

The 14N wouldn't be that much more attractive than the Bramo 323 and unlike the Bramo (but like the Hispano) wouldn't have been a pre-war option at all. Granted, a 12Y powered 187 could have entered production prior to the Battle of Britain, perhaps even early enough to serve there (certainly in time to be useful in Norway).

The only reason I seriously mentioned the Bramo engine was as an alternative to the Jumo 210, nothing else. The resistance to ground fire would be an added bonus, but not a deciding factor.

the XP-42 suffered from both vibration and cooling issues. Something else is that the Army wanted around 500 fighters (it ordered 524 P-40s initially) and Seversky had built under 100 planes in the companies existence and Bell had built under 20. That left Lockheed and Curtiss as established mass manufacturers. Since the P-36, XP-37, H75R, XP-42 and XP_40 all used essentially the same wing, tail and landing gear and Curtiss had built 210 P-36s and had orders for 200 Hawk 75s for France on the books in the spring of 1939 while Lockheed, despite building several hundred twin engine Airliners and Hudsons had no production set up for the P-38. Selection of the P-40 seems to have been a no-brainer, delivers to squadrons could start months if not a year earlier than most of the other contenders.

The early cowling tests on the XP-42 were pretty worthless, it's only the later refinements to using a short, tight cowling with fan and large spinner (not unlike that of the Fw 190, XP-47J or Tempest II) that it was actually worthwhile.

And while the P-40 was certainly compelling and worth production, my point was that continuing development of radial-engined counterparts would still have made sense. By the time of the P-40B/C, the Wildcat had already entered service, and by the time the improved cowling of the XP-42 was tested the initial shortages of 2-stage engines would have been well resolved. (not only that, but R-2000s would have been around) As far as I'm aware, the late XP-42 cowling was never mated with a 2-stage R-1830 for testing. (granted, for ground attack, the better low alt performance of the R-2000 would be more interesting, but by that time other aircraft were probably much more useful as fighters or fighter-bombers)


As to the .50 cowl guns, yes for ground attack replacing those with a pair of .30 guns probably would have been more effective, though in terms of operational use, .50s seemed to be preferred in spite of the disadvantages. (or at least the Finnish Air Force seemed to very much like their cowl mounted .50 brownings -replacing the .30s on both their Hawks and Buffalos with them, and preferring all cowl mounted .50 brownings for their Myrsky)

Another BTW, the figures in wiki for the XF5F are way off if that is what you are going by, those are projected figures which were never reached and the plane never flew with armament installed.

Indeed, I rather doubt the Bramo powered 187 would have managed much beyond 340 MPH and a significant decrease in range, but improved max takeoff weight, somewhat improved climb and slightly superior speed to the Hurricane and Bf 110. (without water injection, the 2-speed Bramos managed 100-175 PS less than the DB-601A depending on altitude) As a fighter, I'm not sure the losses in range and -likely- roll rate plus reduced cockpit visibility would be worthwhile, especially with weight savings in a single-seat configuration. Plus the single-seat prototypes were never tested with the slightly better performing 210G engine. (the 2-seater models also resorted to simpler fixed radiators rather than the more streamlined retractable units)


And I do realize the shopping for missions issue is akin fot what Focke Wulf did, and it may have been just as futile if RLM politics didn't change any. (alternate attempts to interest Udet notwithstanding)


That said, there is one area regarding both the heavy fighter and fighter-bomber concept that hasn't come up yet, and that's the issue of the 'fighter bomber' and 'heavy fighter' concepts from the mid 1930s or even early 1940s centering much more on taking twin engine light bombers and giving them anti-bomber armaments, or similarly creating aircraft intended to be both light bombers AND bomber destroyers AND ground attack aircraft.

This proved unworkable with the Kampfzerstorer concept and Messerschmitt managed to sway the RLM to shift towards the Zerstorer concept (though oddly without even considering provisions to mount external bombs, apparently). The Fw 187 wasn't designed with that new requirement in mind, but nevertheless was an even further departure from the bulky 'bomber as heavy fighter' concept and did away with the need for defensive armament. (albeit in true practical terms, with the inability to re-load the cannon drums and with bomber interception in mind, making modifications to allow a full 4 MG-FF cannons -perhaps omitting LMGs entirely- would have been more compelling)

And even then, the Ju 88C ended up pressed into more or less the same role the mid 1930s Kampfzerstorer concept failed in, admittedly more akin to the likes of the early A-20 at that point, but underpowered. (though I still think the Ju 88 might have fared better in a more Mosquito-like configuration -if still not quite that capable, especially with BMW 801s)

 

[wiking85]

And even then, the Ju 88C ended up pressed into more or less the same role the mid 1930s Kampfzerstorer concept failed in, admittedly more akin to the likes of the early A-20 at that point, but underpowered. (though I still think the Ju 88 might have fared better in a more Mosquito-like configuration -if still not quite that capable, especially with BMW 801s)

Ju88 S-1 was the original speed bomber spec before the dive bombing requirement and gondola fitted with BMW 801s

 

[Shortround6]

That's very slightly reminiscent of the RAF .50 cal gun trials where .303 was seen as more efficient and 20 mm as the more realistic follow-on and no interest was given in replacing the .50 vickers with a browning derivative firing the same cartidge. (granted, had they hedged their bets for the hispano with the Oerlikon FFF -or possibly FFL- rather than the FFS with bulk, weight and recoil closer to the Hispano, that may have been a non-issue -I find it very unlikely that 4x FFF cannons wouldn't have been satisfactory in the Hurricane Mk.I)

To be somewhat fair when the British conducted their trials the American .50 gun was using the 2500fps MV ammo. Since the striking energy is in proportion to the square of the velocity this means the ammo was about 75% as powerful as the ammo actually used in WW II and at short ranges (200-400yds) offered little or no advantage over the .303 for deflection shooting. Weight and bulk of the gun/ammo was the same though. one .50 cal round and link weigh about as much as 5 .303s or US .30cal.

The 14N wouldn't be that much more attractive than the Bramo 323 and unlike the Bramo (but like the Hispano) wouldn't have been a pre-war option at all. Granted, a 12Y powered 187 could have entered production prior to the Battle of Britain, perhaps even early enough to serve there (certainly in time to be useful in Norway).

The only reason I seriously mentioned the Bramo engine was as an alternative to the Jumo 210, nothing else. The resistance to ground fire would be an added bonus, but not a deciding factor.

The Yugoslavians used some Do 17s powered by Gnome-Rhone engines so a lot the engineering work was already done.

Granted most sources say they used the older G-R 14K engines rather than the newer 14Ns but while the Ms were an improvement on the K they were not the major change the R was.

The G-R engines were 38.6 liter engines compared to the 26.8 liter Bramo and while their peak power was limited by the strength of the engine (and cooling on the older ones) they may have been able to offer higher climb and cruise power ratings on 87 octane fuel. Altitude performance may have been better too as they operated on pretty low boost. Some sources say the -21 and -25 versions could make 1080hp at 5100 meters. They were throttle back for low altitude and take-off as they were single speed engines. They also had about 86% of the frontal area of the Bramo. Granted a good cowling can help make up some of the difference.

And while the P-40 was certainly compelling and worth production, my point was that continuing development of radial-engined counterparts would still have made sense. By the time of the P-40B/C, the Wildcat had already entered service, and by the time the improved cowling of the XP-42 was tested the initial shortages of 2-stage engines would have been well resolved. (not only that, but R-2000s would have been around) As far as I'm aware, the late XP-42 cowling was never mated with a 2-stage R-1830 for testing. (granted, for ground attack, the better low alt performance of the R-2000 would be more interesting, but by that time other aircraft were probably much more useful as fighters or fighter-bombers)

The timing is a bit off, Curtiss delivered 199-200 P-40 no letter aircraft by the middle of Oct 1940. The Army had allowed orders for the French and British to take priority on the production line in return for getting improved models later. By this time the French are out of it and the British are getting the benefit. Deliveries of P-40Bs to the Army start in Jan 1941. Curtiss built over 160 P-40s in each of Nov and Dec for the British. Grumman had delivered only 22 F4F-3s to the US Navy by Dec of 1940 and the first plane is issued to a service squadron. Grumman will build 324 Wildcats in all of 1941 while Curtiss will build 2248 P-40s. The R-2000 doesn't show up as a production engine until Jan of 1942. P&W were doing their own work on a P-40 equipped with a 2 stage engine but it doesn't much test flying until the summer of 1942. The AIrframe was loaned to them by the Air Force and had nothing to do with Curtiss.

And even then, the Ju 88C ended up pressed into more or less the same role the mid 1930s Kampfzerstorer concept failed in, admittedly more akin to the likes of the early A-20 at that point, but underpowered. (though I still think the Ju 88 might have fared better in a more Mosquito-like configuration -if still not quite that capable, especially with BMW 801s)

Again you have timing problem. The Ju-88 first flew at the end of 1936, it is not quite as modern as some people believe. BMW only proposes and starts work on the BMW 801 in 1938 and gets one to run in April of 1939, a commendably short time but way too late to re-configure any existing aircraft like the Ju-88 without a massive disruption in production plans.

 

[Koopernic]

From the other thread, I'm not sure the AR 240 had any issues that couldn't have been solved satisfactorily.

The main issues seem to have been marginal stability and that should not be "unfixable" for any design. The performance potential was certainly there and I think it could have been a good one ... but I'm also not sure it would have been, of course. But stability issues are correctable. perhaps it also had system or airframe problems that, taken together with the rest, made it seem not worth the effort.

In fact, I have bever seen a choerent explanation of why they didn't proceed with it. The closest I can come with an educated estimate is that the design team was asked to fix the stability issues and was given time to do it but they didn't succeed at it. If that happened, it might be the end of it in a wartime situation despite the obvious potential.

In wartime asd in peacetime, politics also plays a part and the third Reich was fond of letting people and companies "fight it out." Perhaps Arado was beaten in a conderence room.

The designer of the Ar 240 was Rudiger Kosin. He latter went on to design the Ar 234 Jet and as he had a reputation as a handling guru was called to tidy up the Handling of the Heinkel He 162. What is interesting about him is that he wrote a history called "The German Fighter" which starts from WW1 and goes through to the Tornado. In it he explains some of the handling problems of the Ar 240. According to him the development halt that occurred around the Battle with France and Poland meant the program never got back on track. They were starved of funds and manpower to make the adjustments that flight testing revealed though the effort carried over into the Ar 440. They were for instance expecting engines and gearboxes according to their design but had to settle for extension shafts ahead of the engines with annular radiators that completely changed the propeller position and gyroscopic forces outside of what they had planned for. This caused a handling problem that could have been corrected with a tail extensions and more fin area but there weren't enough money or resources allocated for that so they increased fin area with a third fin and extended it beyond the tail but it was never entirely satisfactory. I think they were after counter rotating props as well. The wing sections were also quite racked in an attempt to reduced drag, perhaps an early form of laminar flow. Many of the improvisations were carried over to the Ar 440.

Kosin had carried out an summer internship and Karl Ziess where he had an opportunity to experience various types of submarine periscope and was immediately impressed with how this could be used to aim guns remotely, with the periscope being next to the turret so that no parallax compensation was needed as in the B-29.

The system worked very well, the rear gunner reported being able to see through a periscope at night much better than through bullet proof glass, suggesting some light gathering amplification. The Ar 440 system had two heads in the dorsal and ventral position right next to the dorsal and ventral turrets. The sight switched automatically between upper and lower views. The illustration in "The German fighter" shows no less than 6 or 7 mirrors allowing the periscope route to clear equipment. Coated optics and superb glass.

 

[GregP]

Thanks Koopernic. Never read that before.

 

[kool kitty89]

To be somewhat fair when the British conducted their trials the American .50 gun was using the 2500fps MV ammo. Since the striking energy is in proportion to the square of the velocity this means the ammo was about 75% as powerful as the ammo actually used in WW II and at short ranges (200-400yds) offered little or no advantage over the .303 for deflection shooting. Weight and bulk of the gun/ammo was the same though. one .50 cal round and link weigh about as much as 5 .303s or US .30cal.

With those early tests, the Vickers .50 gun was superior anyway. I'd have expected adoption of that gun and later transition to similarly chambered updated derivatives of the browning would have been more plausible. (similar to the transition to the .303 browning)

Given the focus on wing mounting, though, ignoring the lighter Oerlikon models seems unfortunate and a bit shortsighted. (the low velocity FFF would seem the safe/conservative bet, the FFL a very good compromise and matching the .303 ballistics fairly well, while the FFS -and Hispano- were both heavier and had much higher recoil, plus a low rate of firer for the former)

The G-R engines were 38.6 liter engines compared to the 26.8 liter Bramo and while their peak power was limited by the strength of the engine (and cooling on the older ones) they may have been able to offer higher climb and cruise power ratings on 87 octane fuel. Altitude performance may have been better too as they operated on pretty low boost. Some sources say the -21 and -25 versions could make 1080hp at 5100 meters. They were throttle back for low altitude and take-off as they were single speed engines. They also had about 86% of the frontal area of the Bramo. Granted a good cowling can help make up some of the difference.

With the exception of fuel injection (I don't think any of the GR engines used pressure carbs), the 14N would seem to be a superior design all around, counter-rotating models included.

This also goes for the Hispano 12Y, counter-rotation even being an advantage over the german inlines and lack of fuel injection being the more notable disadvantage. (albeit problems with negative G could be more problematic on a twin due to hard rolling inducing this rather than just nosing down -though barreling the roll would maintain positive G)
Perhaps retrofitting a flow restrictor to prevent flooding (as on the merlin) would be practical as a retrofit.

Again you have timing problem. The Ju-88 first flew at the end of 1936, it is not quite as modern as some people believe. BMW only proposes and starts work on the BMW 801 in 1938 and gets one to run in April of 1939, a commendably short time but way too late to re-configure any existing aircraft like the Ju-88 without a massive disruption in production plans.

I meant that the Jumo powered Ju 88C 'fighter-bomber' was an example of the rather problematic pre-war Kampfzerstorer concept still dragging on and the idea of 'bombers that can be **fighters' being seemingly more emphasized than 'fighters that can be bombers.'

That said, with the Bf 110 breaking from the Kampfzerstorer requirements in terms of internal bomb bay, it's still rather odd that it wasn't planned with external bomb carrying capabilities in mind from the start. (and unless I'm mistaken, wasn't carrying bombs prior to the BoB or the C-4/B model)











Very interesting, Koopernic, that's a far better explanation than I've ever seen on the subject, but it makes sense. Arado couldn't push as much private funding into the project as some others (Heinkel, Fw and Me included) and lacked the high political standing of Messerschmitt especially.

I think they were after counter rotating props as well.

It really is unfortunate that Jumo, DB, and BMW seemed to avoid production of opposite rotating engine models. That would have improved handling (possibly speed/climb slightly too due to the lack of rudder trim drag) significantly on 2/4-engine aircraft.

For that matter, in cruise, the lack of torque might have improved fuel consumption somewhat had counter-rotating 12Y's been used on the 187. (granted, those were far too weak to be useful for much else)

Also a problem with the Merlin, and one more potential advantage for a hypothetical Hispano powered Whirlwind.

The system worked very well, the rear gunner reported being able to see through a periscope at night much better than through bulled proof glass, suggesting some light gathering amplification.

It may have been the pin-hole aperture effect coming into play, and an interesting note to be sure.

 

[Koopernic]

BTW, according to one source the Bramo was a whopping 12mm smaller in diameter than an R-1820. 1388mm vs 1400mm. abut 0.3 sq ft smaller in frontal area. The R-1820 offered anywhere from 200hp more HP at take-off and low level to 60hp more 1000ft higher at altitude. And that is compared to the 2 speed Bramo engine without water injection. Single speed Bramos offer either good performance at low altitude or sort of medium performance. The single speed engine that offered 900hp for take-off was rated at 1000hp at 10200ft. However the climb rating was 720hp at sea level and 820hp at 14,000ft. Seems like the power is close to a Whirlwinds in a bigger/heavier/ much draggier airframe? Changing the gear ratio for low altitude gave 1000hp for take-off but the climb power ratings changed to 820hp at sea level and 840hp at 6600ft.
Was the 2 speed Bramo available in 1938/39?
Another BTW, the figures in wiki for the XF5F are way off if that is what you are going by, those are projected figures which were never reached and the plane never flew with armament installed.

The earliest I can find the two speed, fuel injected, Bramo 323R2 is the Fw 200C-3 in early 1941. The power was 1200hp at optimal altitude, sea level power was 1000hp but could be increased to 1200hp with water injection, which appears to have been used when the Fw 200 carried extra fuel and was in 'overload' condition.

In 1943 the Bramo 323R2 engine appears again in the Junkers Ju 352 trimotor still with the same 1200hp rating. However instead of using water injection to temporarily increase takeoff power they are using temporary C3 fuel tanks before switching back to B4 fuel.

The 323 was used for a few outmoded aircraft such as the Fw 200C3, Arado 232B all of them second line aircraft. The R-1820 on the other hand was used in the B-17 (17000 produced) and DC-3 and some C-47.

What made the otherwise non powerful and large drag R-1820 useful was the turbo charger, quite a few German firms had been working on turbo superchargers in the 1930's and although a few DB603 and BMW801 flew experimentally few entered service (maybe a dozen Ju 88S3 Ju 388L)

It seems that BMW/Bramo stopped developing the engine after 1941.

I think of all the aircraft listed below only the Do 17 was produced in numbers greater than 300 and they weren't all Bramo versions.
Arado Ar 196
Arado Ar 232
Blohm Voss BV 222
Dornier Do 17
Dornier Do 24
Focke Achgelis Fa 223
Focke-Wulf Fw 200
Henschel Hs 126
Junkers Ju 352

 

[Shortround6]

With those early tests, the Vickers .50 gun was superior anyway. I'd have expected adoption of that gun and later transition to similarly chambered updated derivatives of the browning would have been more plausible. (similar to the transition to the .303 browning)

The Vickers .5 may have had problems of it's own. The British NEVER mounted the .303 version where the pilot couldn't at least beat on it with a fist to clear a jam

I don't think the Japanese did either except for a few early Ki 61s.

I meant that the Jumo powered Ju 88C 'fighter-bomber' was an example of the rather problematic pre-war Kampfzerstorer concept still dragging on and the idea of 'bombers that can be **fighters' being seemingly more emphasized than 'fighters that can be bombers.'

That said, with the Bf 110 breaking from the Kampfzerstorer requirements in terms of internal bomb bay, it's still rather odd that it wasn't planned with external bomb carrying capabilities in mind from the start. (and unless I'm mistaken, wasn't carrying bombs prior to the BoB or the C-4/B model)

The First 110s to get Db 601s were the C series and until then it just didn't have enough power. Since each 110 Group that attacker Poland still had one squadron or part squadron of Jumo powered machines to make up numbers it is a little hard to see how the fighter bomber version would have showed up much sooner. Especially with some of the production diverted to the long range D models. They had only built 156 of the 110s in the last 4 months of 1939.
The C-4/B version got DB601Ns to help with the increased weight (and the C-3 version was the first to get armor and that part of the reason for the C-3 to weigh 490lbs more than a C-1). Two Staffeln started operations against shipping in the English Channel in July of 1940. Bomb load was a pair of 250kg bombs.

Now you could have rigged up a fighter bomber version of the C-1 sooner with 150hp less per engine for take-off (compared to the DB601N) and no armor (or self sealing tanks?) but perhaps it would have needed to delete guns to make up some of the weight difference?

It is hard to say what what was in the minds of the designer/development team but with only so many engineers/draftsmen and with certain versions sucking up the manpower resource some versions that were contemplated in 1938 or so may have had to take a back seat to other versions or wait for things like improved engines. The C-5 recon version showed up about the same time as the Jabo but kept the lower powered engines for the first examples. The C-5 was used to replace some Do 17 recon planes.
DB was great at promising a lot and delivering a little and late in 1937-38 and 39.

 

[tomo pauk]

The earliest I can find the two speed, fuel injected, Bramo 323R2 is the Fw 200C-3 in early 1941. The power was 1200hp at optimal altitude, sea level power was 1000hp but could be increased to 1200hp with water injection, which appears to have been used when the Fw 200 carried extra fuel and was in 'overload' condition.
...

Do we have firm data about when the water injection was used on the Bramo 323R2? I've waded through several manuals for the Fw 200C-3 and can't find the mention of MW 50.
1200 PS (or 1100?* link) was for take off condition. IMO the C3 fuel for take off preceded the use of MW 50, at least in the Fw 200s, since the Fw 200C3 variant featured several 'Startbehälters', ie. 'take off tanks' that fed C3 fuel in the engines.**
We might also note that 1 min rating (1.50 ata, 2500 rpm) was allowed for take off only on the Fw, next best rating was 30 min ('Steig Kampfleistung'; 1.25 ata and 2250 rpm) - 800 PS at rated altitude in low gear? Max cont was at 660 PS (1.10 ata, 2100 rpm) in low gear; S/C gear change was at 2.6 km.

* from the link:
Motorenmuster: Bramo 323 R-2.
1 min-Leistung:
nmax 4 X 1000 PS -= 4000 PS.
nmax = 2500 U/min.
p = 1,50 ata.
Startleistung mit Krafstoff Oktan 100
4 X 1100 PS = 4400 PS.

**"Für den Start wird aus den Startbehältern Kraftstoff mit 100 Oktan und für den Reiseflug A 2 Treibstoff mit 87 Oktan verwendet." - roughly: For the take off the 100 oct fuel is used, from 'Startbehältern', and for normal flight the 87 oct fuel is used.