WI: The Luftwaffe gets 1942-1943 performing aircraft at the start of the war

[Asp]

So the way I was thinking this could happen was if the DB 605 engine was developed earlier. IOTL Luftwaffe aircraft like the Bf-109, Bf-110, etc. were powered by the DB-601, which offered 1,158.9 HP at takeoff. Other German aircraft (everything made by Junkers and Heinkel basically) used the Jumo 211, which was a more finicky engine that had basically the same performance. The DB-605, however, was a much superior engine that was basically internally identical to the 601 except in that the Messerschmitt engineers discovered they could drill the cylinders out four millimeters wider than on the 601 without causing any problems and in that it had altered valve timing to compensate for that change. This really minor difference significantly raised the performance of the engine...it could hit 1,450 HP at takeoff, and later models could hit 1,775 HP. The resulting change in performance among aircraft that used both models was tremendous. To give you an idea, the Bf-109 with a DB-601 maxed out at 552 kmh/343 mph, one with a DB-605 could break 622 kmh/400 mph. The original Ju-88 prototype hit 360 mph with DB-600 engines (986 HP) in late 1936, with a ~50% horsepower boost from an earlier DB-605 it seems reasonable to believe it would have been able to break 400 mph. In 1936. IOTL it was late in the war before aircraft were hitting those kinds of speeds. As long as someone can keep Udet from screwing up with the dive-bomber modification, it would basically give the Germans the late-war Mosquito.

The DB-601 was developed IOTL in 1935 and began production in 1937. Let's say in 1935 that someone decides it would be a good idea to see if they can drill out the cylinders just a bit further and you get the DB-605. Such an obviously superior engine would probably be enough to get the Luftwaffe to kill production of the Jumo piston engines and just go with DB models, something they should have done IOTL that would have had all kinds of benefits (see this thread).

What would the effects on the war be? The Luftwaffe would have a huge advantage coming in, literally an 80-90 kmh/50-60 mph speed advantage over the top RAF fighters and more over the French fighters. And possibly light bombers that are similar. The Battle of Britain starts to look pretty ugly for the Allies at that point, among other effects. The first year on the Eastern Front was pretty much a bloodbath in the air for the USSR, too. This might give the Reich outright air superiority on the Eastern Front.

Anyone got any other ideas?

 

[tomo pauk]

The DB-605, however, was a much superior engine that was basically internally identical to the 601 except in that the Messerschmitt engineers discovered they could drill the cylinders out four millimeters wider than on the 601 without causing any problems and in that it had altered valve timing to compensate for that change. This really minor difference significantly raised the performance of the engine...it could hit 1,450 HP at takeoff, and later models could hit 1,775 HP.

You are giving too much of credit to the over-boring.
The DB 605A, fully rated, was making 2800 rpm vs. 2400 rpm made by most (not all) of the DB 601As. It was using boost of up to 1.42 ata vs. 1.30 ata. It also have had a better supercharger, strengthened internals to withstand greater pressures, boost and temperatures, weight going up from 620 kg to 710. Oil de-aerator was present on the fully-rated DB 605A (second half of 1943 on) to prevent oil foaming at greater powers and altitudes, otherwise the rated RPM was down to 2600 and max boost down to 1.30 ata; lower RPM means lower power, ditto for lower boost. DB 605A was also with greater compression ratio - 7.5 or 7.3:1 vs. 6.9:1; greater CR improves the power a bit, while different CR for right vs. left bank improve oiling on inverted V engines.
Oil de-aerator was present on Jumo 211 engines from day one.
Then we have a thing of radiators. The DB 605A was outfitted with high-pressure cooling (sometimes called over-pressure), a carry-over from DB 601E. High-pressure cooling requires tough radiators, both from material and layout viewpoints. The Bf 109E was outfitted with radiators with weak tubing, simply the corrugated tubes squished and formed into radiator core. Enough for DB 601A cooling pressures, not for DB 601E and on.
The spark plugs also need to be more rugged for increased power.
This needs to be addressed before the 605A is installed.
The DB 605s that hit more than 1500 HP were helped out with MW 50 system, winter 1943/44. If you have that working in 1939/40 (the DB 601R seems to have used the water-methanol injection before ww2), there is nothing in theory against the MW 50 attached to DB 601A. Even better if the DB 601A can be rated for 2600 rpm operation before BoB, not after. Better radiators will still help, though.

This might be of interest for technically-minded people with interest in ww2 aviation: video

 

[tomo pauk]

The resulting change in performance among aircraft that used both models was tremendous. To give you an idea, the Bf-109 with a DB-601 maxed out at 552 kmh/343 mph, one with a DB-605 could break 622 kmh/400 mph. The original Ju-88 prototype hit 360 mph with DB-600 engines (986 HP) in late 1936, with a ~50% horsepower boost from an earlier DB-605 it seems reasonable to believe it would have been able to break 400 mph. In 1936. IOTL it was late in the war before aircraft were hitting those kinds of speeds. As long as someone can keep Udet from screwing up with the dive-bomber modification, it would basically give the Germans the late-war Mosquito.

(sorry if my comments come out as I'm trying to rain on your parade, that is not my intent)

It was not Udet that killed off the Schnellbomber idea materializing in Ju 88. It was Junkers and RLM that made the Ju 88 incapable of carrying bombs of 100 kg and greater in the bomb bays, due to bomb bays being too small & restricted - and that was a direct consequence of Ju 88 having the low-wing configuration (later, Junkers will make a proper bomb bay no the Ju 288). Small bombs were RLM's idea in mid-1930s, once they changed their minds it was too late for Ju 88.
Having bombs hanging in the breeze, along with bomb racks, will kill the speed. Even the new, bulkier undercarriage cost 5 km/h since it required bulged doors, and 3 km/h was cost for cammo paint. Then, the record-breaking Ju 88s were with slender & well stremlined cockpit, unlike the service-worthy examples with big & draggy cockpit. No self-sealing tanks, no armor, no gun barrels, no radios with their antennae - all of this is deemed necessary by Luftwaffe, and all of this decreases speed, even the guns pointed backwards.
The original prototype, powered by DB 600 Aengines, was good for 485 km/h (no military equipment, no bomb racks). With military equipment the speed went down to 430 km/h, that was also a consequence of DB 600A having supercharger that was geared to give max power at low altitudes. With Jumo 211A, speed went upwards, 520 km/h max for short time for the prototypes. Jumo 211B was installed on record-breaking machines, they were doing 520 km/h on average on 1000 km long track.

So for our extra-fast Ju 88, Germans need to keep it to carry only small bombs that can fit in the bomb bay, don't go overboard with cockpit size, keep the front end of aircraft streamlined and not blocky, install just one defensive MG. This might return the Ju 88 back to 500 km/h on 30 min engine rating. Plausible engine upgrade (say, 20% more on all altitudes) probably buys another 20-25 km/h?
The Ju 88B line (ancestor to the Ju 188 series, also featuring the streamlined cockpit) was to do 530 km/h with BMW 801 engines, while the Ju 88A-5 with 1400 HP Jumo 211J was to do 510 km/h without bombs and racks.

 

[SpicyJuan]

So for our extra-fast Ju 88, Germans need to keep it to carry only small bombs that can fit in the bomb bay, don't go overboard with cockpit size, keep the front end of aircraft streamlined and not blocky, install just one defensive MG. This might return the Ju 88 back to 500 km/h on 30 min engine rating. Plausible engine upgrade (say, 20% more on all altitudes) probably buys another 20-25 km/h?

That's still pretty slow then, huh

 

[ferdi254]

Maybe a stupid question but would the higher performance not come with the price of lower range? And then it would not help that much in the BoB.

 

[Garrison]

So the way I was thinking this could happen was if the DB 605 engine was developed earlier. IOTL Luftwaffe aircraft like the Bf-109, Bf-110, etc. were powered by the DB-601, which offered 1,158.9 HP at takeoff. Other German aircraft (everything made by Junkers and Heinkel basically) used the Jumo 211, which was a more finicky engine that had basically the same performance. The DB-605, however, was a much superior engine that was basically internally identical to the 601 except in that the Messerschmitt engineers discovered they could drill the cylinders out four millimeters wider than on the 601 without causing any problems and in that it had altered valve timing to compensate for that change. This really minor difference significantly raised the performance of the engine...it could hit 1,450 HP at takeoff, and later models could hit 1,775 HP. The resulting change in performance among aircraft that used both models was tremendous. To give you an idea, the Bf-109 with a DB-601 maxed out at 552 kmh/343 mph, one with a DB-605 could break 622 kmh/400 mph. The original Ju-88 prototype hit 360 mph with DB-600 engines (986 HP) in late 1936, with a ~50% horsepower boost from an earlier DB-605 it seems reasonable to believe it would have been able to break 400 mph. In 1936. IOTL it was late in the war before aircraft were hitting those kinds of speeds. As long as someone can keep Udet from screwing up with the dive-bomber modification, it would basically give the Germans the late-war Mosquito.

The DB-601 was developed IOTL in 1935 and began production in 1937. Let's say in 1935 that someone decides it would be a good idea to see if they can drill out the cylinders just a bit further and you get the DB-605. Such an obviously superior engine would probably be enough to get the Luftwaffe to kill production of the Jumo piston engines and just go with DB models, something they should have done IOTL that would have had all kinds of benefits (see this thread).

What would the effects on the war be? The Luftwaffe would have a huge advantage coming in, literally an 80-90 kmh/50-60 mph speed advantage over the top RAF fighters and more over the French fighters. And possibly light bombers that are similar. The Battle of Britain starts to look pretty ugly for the Allies at that point, among other effects. The first year on the Eastern Front was pretty much a bloodbath in the air for the USSR, too. This might give the Reich outright air superiority on the Eastern Front.

Anyone got any other ideas?

Your title sounds like you are invoking ASB and frankly it seems like you are close to doing so. You can't just skip over years of operational experience and iterative development to magic up mid war aircraft in 1939. These better aircraft were the based on the lessons learned with those earlier models and you can't compress those years of experience into mere months, let alone have them happen spontaneously for no readily apparent reason.

 

[tomo pauk]

That's still pretty slow then, huh

It is. A 600 km/h bomber was a pretty tall order before Mosquito.

Maybe a stupid question but would the higher performance not come with the price of lower range? And then it would not help that much in the BoB.

Not stupid at all. Mileage will suffer, with short-range Bf 109Es suffering the most (bombers and Bf 110 will still do okay, they have had a lot of fuel to start with).

 

[Catspoke]

(sorry if my comments come out as I'm trying to rain on your parade, that is not my intent)

It was not Udet that killed off the Schnellbomber idea materializing in Ju 88. It was Junkers and RLM that made the Ju 88 incapable of carrying bombs of 100 kg and greater in the bomb bays, due to bomb bays being too small & restricted - and that was a direct consequence of Ju 88 having the low-wing configuration (later, Junkers will make a proper bomb bay no the Ju 288). Small bombs were RLM's idea in mid-1930s, once they changed their minds it was too late for Ju 88.
Having bombs hanging in the breeze, along with bomb racks, will kill the speed. Even the new, bulkier undercarriage cost 5 km/h since it required bulged doors, and 3 km/h was cost for cammo paint. Then, the record-breaking Ju 88s were with slender & well stremlined cockpit, unlike the service-worthy examples with big & draggy cockpit. No self-sealing tanks, no armor, no gun barrels, no radios with their antennae - all of this is deemed necessary by Luftwaffe, and all of this decreases speed, even the guns pointed backwards.
The original prototype, powered by DB 600 Aengines, was good for 485 km/h (no military equipment, no bomb racks). With military equipment the speed went down to 430 km/h, that was also a consequence of DB 600A having supercharger that was geared to give max power at low altitudes. With Jumo 211A, speed went upwards, 520 km/h max for short time for the prototypes. Jumo 211B was installed on record-breaking machines, they were doing 520 km/h on average on 1000 km long track.

So for our extra-fast Ju 88, Germans need to keep it to carry only small bombs that can fit in the bomb bay, don't go overboard with cockpit size, keep the front end of aircraft streamlined and not blocky, install just one defensive MG. This might return the Ju 88 back to 500 km/h on 30 min engine rating. Plausible engine upgrade (say, 20% more on all altitudes) probably buys another 20-25 km/h?
The Ju 88B line (ancestor to the Ju 188 series, also featuring the streamlined cockpit) was to do 530 km/h with BMW 801 engines, while the Ju 88A-5 with 1400 HP Jumo 211J was to do 510 km/h without bombs and racks.

50 kg bombs would make it a pretty crappy naval bomber it seems. But might make a pretty good ju88c fighter version. Or a pretty good train buster.

 

[Asp]

You are giving too much of credit to the over-boring.
The DB 605A, fully rated, was making 2800 rpm vs. 2400 rpm made by most (not all) of the DB 601As. It was using boost of up to 1.42 ata vs. 1.30 ata. It also have had a better supercharger, strengthened internals to withstand greater pressures, boost and temperatures, weight going up from 620 kg to 710. Oil de-aerator was present on the fully-rated DB 605A (second half of 1943 on) to prevent oil foaming at greater powers and altitudes, otherwise the rated RPM was down to 2600 and max boost down to 1.30 ata; lower RPM means lower power, ditto for lower boost. DB 605A was also with greater compression ratio - 7.5 or 7.3:1 vs. 6.9:1; greater CR improves the power a bit, while different CR for right vs. left bank improve oiling on inverted V engines.
Oil de-aerator was present on Jumo 211 engines from day one.
Then we have a thing of radiators. The DB 605A was outfitted with high-pressure cooling (sometimes called over-pressure), a carry-over from DB 601E. High-pressure cooling requires tough radiators, both from material and layout viewpoints. The Bf 109E was outfitted with radiators with weak tubing, simply the corrugated tubes squished and formed into radiator core. Enough for DB 601A cooling pressures, not for DB 601E and on.
The spark plugs also need to be more rugged for increased power.
This needs to be addressed before the 605A is installed.
The DB 605s that hit more than 1500 HP were helped out with MW 50 system, winter 1943/44. If you have that working in 1939/40 (the DB 601R seems to have used the water-methanol injection before ww2), there is nothing in theory against the MW 50 attached to DB 601A. Even better if the DB 601A can be rated for 2600 rpm operation before BoB, not after. Better radiators will still help, though.

This might be of interest for technically-minded people with interest in ww2 aviation: video

IIRC though all of those changes except for the MW-50 injection were just to handle the increased power and RPM right, the actual power boost, at least before they installed the MW-50 on later 605 variants, came from the greater displacement from the wider bores right?

I did not know about all of the details you cited, still learning about Luftwaffe engine development, but it seems like most of the stuff like MW-50 injection and oil deaerators were around before the war and details like the tougher radiator could have been added earlier but weren't just because it wasn't necessary for the power level the 601 operated at. Maybe 1935 is too early for development, but do you think it's possible Daimler-Benz could put the results together before WWII?

(sorry if my comments come out as I'm trying to rain on your parade, that is not my intent)

It was not Udet that killed off the Schnellbomber idea materializing in Ju 88. It was Junkers and RLM that made the Ju 88 incapable of carrying bombs of 100 kg and greater in the bomb bays, due to bomb bays being too small & restricted - and that was a direct consequence of Ju 88 having the low-wing configuration (later, Junkers will make a proper bomb bay no the Ju 288). Small bombs were RLM's idea in mid-1930s, once they changed their minds it was too late for Ju 88.
Having bombs hanging in the breeze, along with bomb racks, will kill the speed. Even the new, bulkier undercarriage cost 5 km/h since it required bulged doors, and 3 km/h was cost for cammo paint. Then, the record-breaking Ju 88s were with slender & well stremlined cockpit, unlike the service-worthy examples with big & draggy cockpit. No self-sealing tanks, no armor, no gun barrels, no radios with their antennae - all of this is deemed necessary by Luftwaffe, and all of this decreases speed, even the guns pointed backwards.
The original prototype, powered by DB 600 Aengines, was good for 485 km/h (no military equipment, no bomb racks). With military equipment the speed went down to 430 km/h, that was also a consequence of DB 600A having supercharger that was geared to give max power at low altitudes. With Jumo 211A, speed went upwards, 520 km/h max for short time for the prototypes. Jumo 211B was installed on record-breaking machines, they were doing 520 km/h on average on 1000 km long track.

So for our extra-fast Ju 88, Germans need to keep it to carry only small bombs that can fit in the bomb bay, don't go overboard with cockpit size, keep the front end of aircraft streamlined and not blocky, install just one defensive MG. This might return the Ju 88 back to 500 km/h on 30 min engine rating. Plausible engine upgrade (say, 20% more on all altitudes) probably buys another 20-25 km/h?
The Ju 88B line (ancestor to the Ju 188 series, also featuring the streamlined cockpit) was to do 530 km/h with BMW 801 engines, while the Ju 88A-5 with 1400 HP Jumo 211J was to do 510 km/h without bombs and racks.

Not at all, don't worry.

I see your point about the bomb bays and how production models won't do as well as the prototype, but Udet did really mess up the development of the Ju-88 (and a bunch of other aircraft) with his dive bomber obsession from what I've been seeing in my research. He was the one who made them lengthen the fuselage, reinforce the wings, add dive brakes (they eventually wised up and took those out at least) plus a bunch of other stuff that added weight and drag. Take that stuff out and add a significantly more powerful engine and it might still be capable of much better performance, to the point of achieving the schnellbomber goal. The DB-605 added like 80-90kmh/50-60 mph to aircraft of comparable weight that used it over the 601, that plus less weight and drag might do it. If I'm wrong though, I'll listen.

Your title sounds like you are invoking ASB and frankly it seems like you are close to doing so. You can't just skip over years of operational experience and iterative development to magic up mid war aircraft in 1939. These better aircraft were the based on the lessons learned with those earlier models and you can't compress those years of experience into mere months, let alone have them happen spontaneously for no readily apparent reason.

You can if it's a relatively easily technological change to make to an engine that had about 90%+ parts similarity to one from 1935, I'm just trying to determine whether that's possible.

It is. A 600 km/h bomber was a pretty tall order before Mosquito.

Not stupid at all. Mileage will suffer, with short-range Bf 109Es suffering the most (bombers and Bf 110 will still do okay, they have had a lot of fuel to start with).

Yeah, they'd have to give some of the potential speed gains back to pack more fuel, the main reason IIRC later Bf-109s were a solid tonne heavier than earlier ones.

 

[tomo pauk]

IIRC though all of those changes except for the MW-50 injection were just to handle the increased power and RPM right, the actual power boost, at least before they installed the MW-50 on later 605 variants, came from the greater displacement from the wider bores right?

I did not know about all of the details you cited, still learning about Luftwaffe engine development, but it seems like most of the stuff like MW-50 injection and oil deaerators were around before the war and details like the tougher radiator could have been added earlier but weren't just because it wasn't necessary for the power level the 601 operated at. Maybe 1935 is too early for development, but do you think it's possible Daimler-Benz could put the results together before WWII?

Wider bores were not that important. Note that DB 601N was being allowed to do 2600, and later 2800 rpm; the 601E was rated for 2500 and 2700 rpm. They even allowed for DB 601A to run at 2600 rpm by late 1940 (obviously too late for BoB). link
Oil de-earator was a thing by late 1930s, and indeed the DB engines would've benefited from it. Someone also needs to design, test and produce bette radiators, so the high-pressure cooling can be applied to the DB 601A instead of waiting to the 601E (another ting that didn't require over-boring). High-pressure cooling allows for engine to be run at higher boost an RPM for more power without worrying that engine will overheat. The supercharger of 601/605 line of engines was changed 5-6 times between 1938 and 1942, including the increase of impeller (again not related to over-boring).
Indeed, if DB applies all of these advances to the DB 601A line by 1937 to 1939, including the 2600 rpm operation, the resulting engine would've probably been doing perhaps 1200 HP at 5 km, instead of 1020 PS at 4 to 4.5 km. Over-revving to 2800 rpm will add another 100 HP, at least it looks like by looking at the DB 601E power chart. A bigger and better S/C can also add another 500 if not 1000 m to the rated altitude.

More later, got to go

 

[tomo pauk]

I see your point about the bomb bays and how production models won't do as well as the prototype, but Udet did really mess up the development of the Ju-88 (and a bunch of other aircraft) with his dive bomber obsession from what I've been seeing in my research. He was the one who made them lengthen the fuselage, reinforce the wings, add dive brakes (they eventually wised up and took those out at least) plus a bunch of other stuff that added weight and drag. Take that stuff out and add a significantly more powerful engine and it might still be capable of much better performance, to the point of achieving the schnellbomber goal. The DB-605 added like 80-90kmh/50-60 mph to aircraft of comparable weight that used it over the 601, that plus less weight and drag might do it. If I'm wrong though, I'll listen.

Dive brakes 'cost' was 5 km/h (this and other performance loss figures are from Nowarra's book about the Ju 88 family). Longer fuselages rarely, if ever add to drag.
Swapping the DB 601A for DB 605A gave 50 km/h (~35 mph) for the MC.202 ->205. If same engine power was used, the draggy-as-a-brick Bf 109E was ~30 km/h slower than MC.202 or Bf 109F. It was also slower than the bigger and much heavier Ki-61. We'd perhaps see 680+ km/h with Bf 109E having a 1250+- HP at 5000 m? Unintended consequence is that new aircraft has even shorter range due to the greater engine power combined with, still, a draggy airframe.
We can take a look on how fast were the real-word German aircraft with DB 605A. Bf 110G-2 was good for 576 km/h (on 1250 HP at 6.5km without ram effect - note that was still on restricted setting: 2600 rpm and 1.30 ata). Me 210 was in the ballpark; it took Me 410 with it's DB 603A engines to beat 600 km/h mark.
Think that we can agree that both Bf 110 and Me 210 were less draggy than even the best streamlined Ju 88.

 

[Garrison]

You can if it's a relatively easily technological change to make to an engine that had about 90%+ parts similarity to one from 1935, I'm just trying to determine whether that's possible.

There needs to be an awareness that such a change is either necessary or useful and again there is a learning process. Sure with 20/20 hindsight those changes are obvious and easy, much less so when you are on the ground at the time and facing the pressures of actually maintaining an operational airforce.

 

[Asp]

Dive brakes 'cost' was 5 km/h (this and other performance loss figures are from Nowarra's book about the Ju 88 family). Longer fuselages rarely, if ever add to drag.
Swapping the DB 601A for DB 605A gave 50 km/h (~35 mph) for the MC.202 ->205. If same engine power was used, the draggy-as-a-brick Bf 109E was ~30 km/h slower than MC.202 or Bf 109F. It was also slower than the bigger and much heavier Ki-61. We'd perhaps see 680+ km/h with Bf 109E having a 1250+- HP at 5000 m? Unintended consequence is that new aircraft has even shorter range due to the greater engine power combined with, still, a draggy airframe.
We can take a look on how fast were the real-word German aircraft with DB 605A. Bf 110G-2 was good for 576 km/h (on 1250 HP at 6.5km without ram effect - note that was still on restricted setting: 2600 rpm and 1.30 ata). Me 210 was in the ballpark; it took Me 410 with it's DB 603A engines to beat 600 km/h mark.
Think that we can agree that both Bf 110 and Me 210 were less draggy than even the best streamlined Ju 88.

Huh, smaller penalty than I'd read in a different place. The longer fuselage didn't add much drag, but it did increase the weight.

It added 86 kmh to the speed of the Reggiane Re. 2005 though versus the Re. 2001.

True. The range could be compensated if someone had thought to add a drop tank though, which would be an easy thing to do. If Walther Wever had lived and they'd kept a rational R&D program I think a lot of these changes could have happened.

Wider bores were not that important. Note that DB 601N was being allowed to do 2600, and later 2800 rpm; the 601E was rated for 2500 and 2700 rpm. They even allowed for DB 601A to run at 2600 rpm by late 1940 (obviously too late for BoB). link
Oil de-earator was a thing by late 1930s, and indeed the DB engines would've benefited from it. Someone also needs to design, test and produce bette radiators, so the high-pressure cooling can be applied to the DB 601A instead of waiting to the 601E (another ting that didn't require over-boring). High-pressure cooling allows for engine to be run at higher boost an RPM for more power without worrying that engine will overheat. The supercharger of 601/605 line of engines was changed 5-6 times between 1938 and 1942, including the increase of impeller (again not related to over-boring).
Indeed, if DB applies all of these advances to the DB 601A line by 1937 to 1939, including the 2600 rpm operation, the resulting engine would've probably been doing perhaps 1200 HP at 5 km, instead of 1020 PS at 4 to 4.5 km. Over-revving to 2800 rpm will add another 100 HP, at least it looks like by looking at the DB 601E power chart. A bigger and better S/C can also add another 500 if not 1000 m to the rated altitude.

More later, got to go

This is really interesting, thanks for all the links you've been posting. Looks like the changes made were bigger than I had read before this.

Do you have any advice for really good resources on Luftwaffe R&D and engine development? I'm trying to read up on it, and it seems like you know this stuff.

There needs to be an awareness that such a change is either necessary or useful and again there is a learning process. Sure with 20/20 hindsight those changes are obvious and easy, much less so when you are on the ground at the time and facing the pressures of actually maintaining an operational airforce.

I know that, but the relative technical changes for this piece of technology seemed pretty small (I might have been wrong about that), and the Luftwaffe's R&D was so incoherent that there was plenty of slack that could be used for earlier POD under more competent management.

 

[Garrison]

I know that, but the relative technical changes for this piece of technology seemed pretty small (I might have been wrong about that), and the Luftwaffe's R&D was so incoherent that there was plenty of slack that could be used for earlier POD under more competent management.

You say you recognize the point but it really doesn't seem you do. It isn't anything to do with competence, its to do with the fact that things tend to proceed in a linear fashion with iteration based on experience. Once a model of aircraft enters service any deficiencies may become apparent and get fixed but the reality was that the Bf109 was more than good enough for the job it was designed for right up until it had to engage the RAF over Southern England and that had as much to do with pressing the plane into service in a role it wasn't intended for as any technical deficiencies.

 

[Reggieperrin]

For anyone interested in the technical details of the WW2 aero engines, an excellent excellent new book is “The Secret Horsepower Race” by Calum Douglas which goes into a ton of obscure but critical details and how they played out year by year for the Germans, Brits and US. Among other things it also gives a very decent overview of the fuel situation which turns out to be considerably more complicated than just octane ratings or performance numbers.

Having read that book, I think it’s pretty much impossible for the LW to get their 1942-1943 performance at the start of the war for the simple reason that first a whole lot of learning was iterative, you can’t just deduce your way to a motor with 2-3 years worth of incremental engineering development in it. Secondly, after going to war their whole engine program turned to shit due to the loss of strategic materials and the switch to synthetic fuels. So they had to spend a whole lot of time getting their early engines just to run reliably again, and then rework their planned engines to deal with the new industrial environment before trying to develop the necessary horsepower.
For example the DB601N was meant to be a spiffy spiffy high-performance engine that worked just great in the engineering labs, but when deployed turned out to an inflammable exploding boat anchor, since the design operating temperature was high enough to boil prewar fuel out of the oil, but too low to boil out synthetic fuel with a comparable octane rating. So after a handful of hours running time with the bearings lubricated by oily gasoline the engine would fail catastrophically. Absolutely nothing wrong with the design other than an unforeseen change to the operating requirements. Back to the drawing board.

So even if the Germans do manage to leap a couple years ahead by the start of the war, the more capable and high-performing the engines they start with, the worse the problems become when suddenly EVERYTHING has to become ersatz. Imagine a 1942 Merlin XX if suddenly RR are told overnight they can have a tiny fraction of the nickel, tin, cobalt, indium, etc they have been using and it has to run on fuel with different combustion characteristics. No stellite valves or seats, no fancy bearings, crappy lubricants, awful spark plugs etc. etc. Chances are the whole engine either stops working completely or is only good for 50% of output whereas a 1940 Merlin III might only lose 10%. And of course, even if they were to coincidentally give exactly the same power, there is a world of difference between a plane built for 1000hp getting only 900, and a plane built in the expectation of 1800hp but getting only 900.

So what if the RLM in about 1936 comes down with Foresight Flu and specifies that all engines have to be designed for minimum strategic materials and the characteristics of experimental synthetic fuels that may become available and may be required if some nutcase decides to get into a long war with multiple great powers?
That might solve some of the long-term problems from 1941 onwards but almost certainly meansthat in 1938-1940 German engines are handicapped enough to make their OTL achievements unrealistic.

 

[tomo pauk]

Huh, smaller penalty than I'd read in a different place. The longer fuselage didn't add much drag, but it did increase the weight.
It added 86 kmh to the speed of the Reggiane Re. 2005 though versus the Re. 2001.
True. The range could be compensated if someone had thought to add a drop tank though, which would be an easy thing to do. If Walther Wever had lived and they'd kept a rational R&D program I think a lot of these changes could have happened.

Re.2005 featured changes that can earn speed, like the undercarriage that now lay flush with wing, wing wheel covers (similar covers were later introduced on latest Bf 109s and Spitfires), retractable tailwheel, as well as redesigned cooling system. Fuselage was also longer.
All in all, while we might attribute the jump in speed to the new engine installed, the aerodynamic improvements certainly played their part.

This is really interesting, thanks for all the links you've been posting. Looks like the changes made were bigger than I had read before this.

Do you have any advice for really good resources on Luftwaffe R&D and engine development? I'm trying to read up on it, and it seems like you know this stuff.

As noted above by @Reggieperrin , Calum's book is a great resource on just how German engine development was plagued from all sides (it is a very good book for all the gearheads interested in ww2 aviation). From RLM not having the grasp on situation and not being able to co-ordinate the devopment effort between engine companies and different laboratories, to the engine companies biting much more that they can chew, and material shortages that were really severe. I've linked his webinar above.

 

[BELFAST]

What the Germanys need is higher octane fuel.
Later ww2 engines need higher octane fuel than was being produced in 1939.
The quality of metal available in 1939 was better than later in the war and there more skilled people building them.
Shortages of fuel after 1941 meant less training for pilots so pilot quality went down after 1941.
The link below shows the many problems the German airforce had.

Strategy for Defeat​

The Luftwaffe​

1933-1945​

by
WILLIAMSON MURRAY

Strategy for Defeat: The Luftwaffe 1933-1945

Strategy for Defeat: The Luftwaffe 1933-1945

www.ibiblio.org

 

[tomo pauk]

What the Germanys need is higher octane fuel.
Later ww2 engines need higher octane fuel than was being produced in 1939.
The quality of metal available in 1939 was better than later in the war and there more skilled people building them.
Shortages of fuel after 1941 meant less training for pilots so pilot quality went down after 1941.
The link below shows the many problems the German airforce had.

Germany had higher octane fuel. The C2 and C3 were used in some engines, erstwhile in DB 601N and later in BMW 801C and D. Octane and performance rating was on par with Allied hi oct fuel. That DB 601N have had increased compression ratio was the self-inflicted wound - one does not increase compression ratio in supercharged engines, or else. Hi-oct fuel requires high quality spark plugs.
Hi-oct fuel was wrecking the fuel tanks of the Bf 109Fs, that previous low-octane fuel (B4, 87 oct) did not. Germans reverted to the 87 oct with DB 601E and 605A that were making better power on low-oct fuel than DB 601N on hi-oct fuel, even with reduced RPM. Hi-oct fuel is not a replacement for increasing the RPM and improvement of supercharger.
The BMW 801C and D were suffering too, right when material shortages kicked in. Valves needed nickel or chrome in order not to be eroded by high pressures and, and BMW struggled for many months until they discovered that chromium can help when applied to the valves outside; nickel was lacking far more than chromium in ww2 Germany. It took then many months for people at Daimler Benz to be introduced in this simple 'trick'. New spark plugs also helped the 801D to finally make its 'book ratings'; DB 605A needed the oil de-aerator to help.
Neither of those main German engines ever received a 2-stage supercharger, bar prototype engines. Ditto for Jumo 211.

tl;dr - One can't just pour the in the hi-oct fuel in tank and go it's own marry way; hi-oct fuel does not solve power deficiencies above 15000-20000 ft since it is not a replacement for better supercharger. It also does not solve the lack of fuel problem (that was The Problem),

 

[BELFAST]

Germany had higher octane fuel. The C2 and C3 were used in some engines, erstwhile in DB 601N and later in BMW 801C and D. Octane and performance rating was on par with Allied hi oct fuel. That DB 601N have had increased compression ratio was the self-inflicted wound - one does not increase compression ratio in supercharged engines, or else. Hi-oct fuel requires high quality spark plugs.
Hi-oct fuel was wrecking the fuel tanks of the Bf 109Fs, that previous low-octane fuel (B4, 87 oct) did not. Germans reverted to the 87 oct with DB 601E and 605A that were making better power on low-oct fuel than DB 601N on hi-oct fuel, even with reduced RPM. Hi-oct fuel is not a replacement for increasing the RPM and improvement of supercharger.
The BMW 801C and D were suffering too, right when material shortages kicked in. Valves needed nickel or chrome in order not to be eroded by high pressures and, and BMW struggled for many months until they discovered that chromium can help when applied to the valves outside; nickel was lacking far more than chromium in ww2 Germany. It took then many months for people at Daimler Benz to be introduced in this simple 'trick'. New spark plugs also helped the 801D to finally make its 'book ratings'; DB 605A needed the oil de-aerator to help.
Neither of those main German engines ever received a 2-stage supercharger, bar prototype engines. Ditto for Jumo 211.

tl;dr - One can't just pour the in the hi-oct fuel in tank and go it's own marry way; hi-oct fuel does not solve power deficiencies above 15000-20000 ft since it is not a replacement for better supercharger. It also does not solve the lack of fuel problem (that was The Problem),

As you say fuel octane was only one problem of many the Luftwaffe had.
Lack of fuel too.
The lack of a 2 stage supercharger. Bf109 did not have room in the engine bay for 2 stage supercharger.
And as you say a shortage of materials like nickel were a problem too.
Engines were only one of many problems the German air force had in ww2.

 

[Reggieperrin]

As you say fuel octane was only one problem of many the Luftwaffe had.

In the book mentioned above it states that British technical reports on crashed/captured German planes midwar mention the conundrum of why the engines were not able to run to the limit of the fuel in the tanks. The Brits couldn’t figure out why the Germans were going to the trouble of manufacturing good fuel and then not making the best use of it, seemingly not realising the German constraint was in the engine materials not the fuels, supercharger etc.

Odd to realise that the LW would likely have done very much better of the much-maligned Air Ministry had been in charge of their fighter program. Stupid nonsense like the engine manufacturers developing and testing their engines on prewar petroleum fuel blend while the squadrons were being issued synthetic fuel blends. New engines being developed without suitable airframes to fit them into and aircraft being developed without suitable engines. Militarily significant research published in scientific journals. Just on and on with the idiocies.