You are Josef Kammuber in 1941, how do you structure German night defenses?

[wiking85]

https://en.wikipedia.org/wiki/Josef_Kammhuber
Assuming you have control over the German night defenses like Kammhuber starting in 1941, how do you structure German night defenses to defeat RAF Bomber Command?

 

[Koopernic]

https://en.wikipedia.org/wiki/Josef_Kammhuber
Assuming you have control over the German night defenses like Kammhuber starting in 1941, how do you structure German night defenses to defeat RAF Bomber Command?

The problem of intercepting nigh bombers seems to have been mainly a technical problem of getting the correct radar. However a proper organisation is needed to carry the influence to demand the development and production of the correct radar types.

The technology the Germans had was as follows:
Freya radar: this radar had a very long range but lacked height finding abilities, it also did not have a PPI display (Plan Postion Indicators were refered to as Panorama radars in the German literature)
Later variants of the Frey radar added other technologies: Freya A/N added lobe switching and could track an aircraft to within 0.2 degrees. Dreh Freya could work with a PPI display.

Wurzuburg-D, this common radar was available from 1940, Wurzburg-D from mid 1941 and had conical scan for 0.3 degree accuracy and 25-40m range accuracy. It had a 3m diameter dish. Synchro's could pass range data directly to a FLAK predictor and a computer could convert the sphercal co-ordinates into linear along with speed and heading information for direct read out and incorporation into a plotting table.

Wurzburg-Riesse (Riesse means Giant) this was the same electronics attached to a 7m diameter power driven dish. It also became available ie in mid 1941. The larger dish doubler the range to about 74km and greatly increased accuracy. It was actually designed as a FLAK directing blind fire radar but was 'misused' to intercept aircraft.

Kammhuber's "Himcelbelt" line (Heavens Gate) Initially only had a Freya radar thus became one Freya radar, two Wurzburg-D or Wurzburg Riesse radars. Had they have been fitted (I expect they were) FuG 16ZY radio of the night fighters also would have allowed the night fighters bearing and range to be tracked by the Himmelbelt station.

By using a 'blue' and 'red' radar for the fighter and the target bomber great accuracy of the Wurzburg-Riesse allowed even non radar equipped night fighter to be guided to within less than 100m.

One downside is that this represents rather a lot of equipment for a single interception. I suspect that a Himmelbelt could probably guide two interceptions by using Freya-AN to guide one interception and the night fighters FuG-16 radio which could provide bearing and range as well.


Bomber commands solution was simply to create a massive and dense bomber stream to saturate the system. Of ciouse when aircraft became available with their own Lichtenstein radars the radar nstations did not have to doi so much detail work.

The other problem is that the RAF slowely learned to Jam or degrade the German radar defences and although the German side developed cleaver counter counter measures they didn't keep up because they had focused their radar technology in too tight an area and 500 bombers with barrage jamming equipment represents a difficult problem.

It's worth looking at what the British were doing at this time. They had a similar radar to Wurzuburg in that AMES had a 25ft diameter dish, it lacked an accurate conical scan (so useless as a FLAK radar) but it did have multiple feeds that could be rapidly and automatically switched to find target height. This allowed one radar to acquire and then track multiple targets and collect crude height information. Airborne radar usually guided the terminal phase of the interception and the speed of the Mosquito ensured interceptions did not take long.

What the Germans needed was:
1 To diversify their radar types asnd move to higher frequencies to make jamming more difficult (higher frequencies = smaller cheaper antenna and tighter beams harder to jam).
2 To deploy PPI (Panorama Technology) to make each radar able to guide a greater number of interception.
3 Agressively incorporate anti jamming measures.

The Germans had built PPI radars by 1940 but it took a while to make them practical as it did on the allied side. A set called "Jagdscloss" or Hunting Castle saw some service in late 1943 but really was a 1944 radar. Likewise with Dreh Freya.

In terms of higher frequencies this was an own kill. In 1942 both Lorentz and Telefunkien were at the verge of perfecting radars that could operate at around 21.5-30cm (typically 27cm) instead of 56cm or so. They used highly evolved conventional technology (disk triodes) rather than magnetrons but it should have been enough as these radars were also more powerfull. It also would have allowed smaller beams less prone to picking up jamming energy. The program was effectively cancelled in 1942 just before the British magnetron was discovered in a downed Sterling. A small scale program trickled on a Telefunken but headed and resourced by the German navy to provide radar for directing guns on a ship (FuMO 231 Euklid) but many of the technicians had been disbanded and sent to the front!

In 1940 its possible to see several different types of Magnetron in Germany. A multicavity wheel magnetron (with square rather than circular cavities and narrow slits) able to provide pulse power of several kw. A small signal magnetron with the optimally shaped British style cavities, the use of cathode coatings. Had they have been put together the Germans could have matched the British magnetron. They missed it narrowly, mainly because they weren't trying to get to 9cm or were hamstrung by ideas that required tuneable devices, that their existing 50cm systems were adequate.

What Kammhumber needs to do is get massive resources, special priorities to hang on to workers and focus researchers and he has to do it as early as possible. This is a massive political problem as he already has been given massive resources and is in trouble for lack of results, but he needs more and he needs to develop more efficient radar systems. You need to only think of what he was up against.

 

[tomo pauk]

Koopernic's suggestions look good to me.
I'd suggest abandoning/not creating the 'Kammhuber line' - it cancel's out the main advantage the night fighters have had vs. Flak, that being the great ability to shift them around into critical areas. Also, gretater emphasis on offensive night operations vs. RAF bases in 1941, conducted by faster aircraft (Bf 110, Ju 88), before the RAF has time other resources to perfect their defenses. The attack on Taranto, where flares were used, should give some clues, though the airfield on the English countryside is a bit harder to spot than a major naval base. The timed bombs might make operations on RAF bases a tricky business.
As for defensive hardware - more emphasis on night fighters than on heavy Flak. Also the greater emphasis than it was historically for the concealment and false targets to lure away RAF bombers, though the Germans have done a decent job on this anyway.

 

[Balljoint]

More a description of the give and take and problems rather than a brilliant analysis on my part;

https://books.google.com/books?id=D...=0CDgQ6AEwAw#v=onepage&q=trenchardist&f=false

 

[stona]

The problem facing the Luftwaffe was to get enough night fighters into the bomber stream where they could then detect the RAF's bombers and shoot them down in sufficient numbers. I believe that it actually did quite well at this bearing in mind the problems it had doing the same thing in daylight against US formations.
The box system made perfect sense at the time, it was overwhelmed by the RAF's reaction to it.

Given the technology of the day it is entirely understandable why large resources were directed towards flak rather than fighters for night defence. The German flak was part of the Luftwaffe (though the Army repeatedly attempted to organise its own, independant, flak arm) and Luftwaffe doctrine held that it should operate in close cooperation with fighter forces in a defensive role.

The data the Germans had for 1941 showed that flak was a more effective means of destroying enemy aircraft than fighters. In the last six months of the year flak in the Reich and West shot down 647 aircraft (242 at night) compared with 421 during the entire year for the night fighter force. Decisions have to be made with the data to hand and in 1941 the night fighter force didn't look a particularly good bet. We have the luxury of hindsight, something prominent in many forum discussions, the Germans did not.

Cheers

Steve

 

[parsifal]

Given the technology of the day it is entirely understandable why large resources were directed towards flak rather than fighters for night defence. The German flak was part of the Luftwaffe (though the Army repeatedly attempted to organise its own, independant, flak arm) and Luftwaffe doctrine held that it should operate in close cooperation with fighter forces in a defensive role.

The data the Germans had for 1941 showed that flak was a more effective means of destroying enemy aircraft than fighters. In the last six months of the year flak in the Reich and West shot down 647 aircraft (242 at night) compared with 421 during the entire year for the night fighter force. Decisions have to be made with the data to hand and in 1941 the night fighter force didn't look a particularly good bet. We have the luxury of hindsight, something prominent in many forum discussions, the Germans did not

Westermann in his book about the German flak arm claims that the dominance of the flak arm to the end of the war remained. it continued to outshine the numbers of shoot downs compared to the airborne defences by a considerable margin, according to him.

as the war progressed the rounds per kill (rpk) started to climb to uneconomic proportions. it was taking about 4000 rpk of HAA to bring down a bomber in 1942, this had risen to over 16000 rpk by 1944. Part of this was due to the increasing dilution of trained crews as the war progressed. in 1942, the crews wwere at peak efficiency and the detection and fire control systems unaffected by allied countermeasures. by 1944 many of the defences ringing German cities were manned by amateur home guard types, many of the detection systems were being effectively neutered by allied countermeasures and the proliferation of guns were resulting in sub-optimal emplacement for the batteries. overuse of the batteries also meant a marked drop off in the gun performance of many batteries and a massive increase in weapon related misfires and failures. but the guns held a lead in success rates that they never relinquished until wars end even though by 1944 they were reduced to firing in barrage mostly....basically pointing the guns in the general direction of the bombers and hoping to scare them away with a noise and light show.

 

[Koopernic]

The figure of 16000 rounds fired per aircraft downed comes from a period when the Luftwaffe were recovering from the introduction of Windows and had not yet introduced countermeasures. It also incorporates the use of smaller lower powered FLAK 36 and FLAK37 8.8cm guns, worn out barrels and a high proportion of 'dads army' style reserve forces with older less sophisticated equipment such as predictor computers. When current equipment and professional units were used the ratio of rounds to kills was between 2000-4000 per aircraft destroyed. This fits in well with the oft cited experience of the US Navy in the pwcific of around 2500 rounds per kill, mostly using the highly regarded 5" DP gun in sophisticated power driven turrets (admittedly against closer but smaller targets)

The anti windows effort responded quite quickly in that the first experimental wurzlaus sets were in service in only 2 weeks after the Hamburg raid. Wurzlaus was a coherent pulse Doppler moving target indicator that distinguished stationary tqrgets from moving ones.

These circuits became more sophisticated with improvements such as tastlaus, k-laus and windlaus. Windlaus allowed an offset to account for high altitude winds which cause windows to appear moving while k-laus allowed both moving target indication, coding to reduce noise jamming and a full range of frequency changing. k-laus allowed Wurzburg-Riesse to work till the very end of the war though only a handful were in use over Berlin.

The other problem was allied "carpet" noise jammers which pretty much shut down most radars since the amount of noise that could be generated by dozens or even hundreds of bombers was enormous.

Apart from signal processing options there are two other methods for evading jamming: by increasing the antenna size or reducing the wavelength a tighter beam can be form that intercepts less noise and focuses more energy on the target. Halve beam width and one intercepts 4 times less energy. The other method is the use much higher power levels to restore the signal to noise ratios. Thus there was a variant of Wurzburg-Riese called the Gigant that was able to generate a 120kW pulse instead of a 8kW pulse. This version never entered service though in the course of development of allied equipment the Germans measured the distance to the moon.

In General the Germans couldn't respond quickly enough since without microwaves the effort was to great.

Night fighters with own radar were extremely effective whenever the system was introduced and free from effective jamming.

Below: Spanish crews man a Wurzburg-D. At the focus of the reflector is the conical scan system.

Below a Wurzburg-D in the foreground and a Wurzurg-Riesse in the background.

Below a Manheim FuSE 64 radar. An advanced progression of Wurzburg it featured twice the output power, greater range, more precise tracking electronics (0.2 degrees and 6m in range) and auto-track for the range gate though used similar 50cm wavelengths. Even if the target couldn't be found visually on the oscilloscope once the range gate was locked on it was possible to track it in the heaviest jamming. This shows the importance of using sophisticated equipment. About 100 entered service starting in late 1943. I required over 100 vacuum tubes. The electronics of this unit combined with the 7m dish of Wurzburg-Riesse were one option for guiding Germans anti aircraft rockets.

 

[tomo pauk]

The problem facing the Luftwaffe was to get enough night fighters into the bomber stream where they could then detect the RAF's bombers and shoot them down in sufficient numbers. I believe that it actually did quite well at this bearing in mind the problems it had doing the same thing in daylight against US formations.

Agreed all along.

The box system made perfect sense at the time, it was overwhelmed by the RAF's reaction to it.

IIRC Napoleon was quoted to say that armies deployed in line are good for catching smugglers, but that a competent enemy army can defeat them with ease. The German army devoted time, effort and money to develop the Blitzkrieg, a good 'tool' against line of defense. Too bad LW Flak NF arm was deployed in the line fashion, the concept of local superiority worked just fine against those - 1-5% of Flak deployed and 10-20% of NFs deployed were against 100% of RAF bombers in a given night.

Given the technology of the day it is entirely understandable why large resources were directed towards flak rather than fighters for night defence. The German flak was part of the Luftwaffe (though the Army repeatedly attempted to organise its own, independant, flak arm) and Luftwaffe doctrine held that it should operate in close cooperation with fighter forces in a defensive role.

Both Flak and NF were dependant on searchlights and, however low on quantity and quality, on ground based radars early on the war. The 'helle nachtjagd' was a practice that involved radar-less interception, 1st kill made by Werner Streib at 20th July 1940; all together 8 RAF bombers were shot during July 1940 using same technique.

The data the Germans had for 1941 showed that flak was a more effective means of destroying enemy aircraft than fighters.

What would be the numbers involved? Do the German numbers also count the Alied aircraft downed 5 and more miles away from frontline/coastline?

In the last six months of the year flak in the Reich and West shot down 647 aircraft (242 at night) compared with 421 during the entire year for the night fighter force. Decisions have to be made with the data to hand and in 1941 the night fighter force didn't look a particularly good bet. We have the luxury of hindsight, something prominent in many forum discussions, the Germans did not.

With thousands of heavy Flak, and more than 10 thousands of light Flak deployed after 1941, the number of 3.5 aircraft destroyed per day, the arithmetic does not agree that Flak arm was such a devastating weapon IMO. In second half of 1941, the ratio between NF and heavy/light Flak was maybe 100 aircraft vs. 4000/12000 guns deployed.

 

[stona]

Those figures are just for flak deployed in the Reich/West. I don't know how many of the various batteries fall under that definition in 1941, the numbers will be out there somewhere. I don't know how many were in the east either, but they were credited with more than 1,000 Soviet aircraft shot down in the last 3 months of 1941 alone.

People look at the bottom line, then as now, and flak was shooting down more RAF bombers than the Nachtjagd.

Increasing the number of night fighters is NOT an easy or economical option. It not only puts pressure on the already shambolic aircraft production sector but increases demand for highly trained crews and the resources (notably fuel, radically reduced to training command in 1942) to train them. It also requires heavy investment in the infrastructure and command and control systems to operate these extra fighters IF you can build and crew them.

Cheers

Steve

 

[parsifal]

German flak effectiveness suffered increasingly in terms of efficiency as 1944 wore on. Despite the claims of uber increases in the weaponry and detection systems, the number of rounds per kill continued to rise steadily as the year wore on, and BC losses to flak (and all causes) continued to fall as the year rolled on.

The peak year of shooting accuracy for the LW was 1942, where rounds per kill were averaging about 3500 per a/c. this in no way compares to the USN experience. The targets were different, flak concentrations different, operating altitude were different, but by 1945, the rounds per kill in the USN were down to under 500 against highly vulnerable, but determined, Kamikaze targets.

people will often talk about the technical excellence of the German equipment, and omit some of the cruel home truths that just blow the whole thing out of the water. yes, the germans were introducing some very impressive technology, but no they could not recover from the overwhelming smothering they were receiving throughout 1944. In fact, that drubbing, in the air, AND on the ground (with its Flak) was a process that began as early as the end of 1943. Loss rates for the allies just don't reflect or suggest any appreciable change in efficiencies due to new german technologies at any stage in that final year or so. And yet, the numbers of barrels devoted to Reich defences approximately doubled (very roughly....ive got the figures at home somewhere). so despite increasing technology, increasing numbers, we see dramatically falling lethality and effectiveness of german flak defences. Why? To answer that, a few bitter home truths need to be accepted.

 

[mhuxt]

I read Lorant's JG 300 recently - at one point it says the commander of the Berlin flak said he'd pooped off 20,000 rounds at a couple of Mossies over Berlin some time in summer '43, without success. Rather a breathtaking stat, especially given how often the Mossies were over the Big City.

 

[parsifal]

Like anything they had good and bad days.But the trend was a steady improvement 39-42, with major steps forward in 41 and 42 as radar control began to be used extensively and crew training reached peak efficiencies, and thereafter a steadily increasing nosedive as various things took effect

 

[Balljoint]

Along with fuel the German munitions were also being awkwardly manufactured from coal energy and, I suppose, nitrogen from air. I've read that cannon propellants, probably tank, were down rated by dilution with saltpeter. There's the possibility that FLAK was also derated with, assumedly, new ballistics tables.

I thought I read this in Calvocoressi et al Total War but I can't track it down.

 

[Balljoint]

Double post

 

[wiking85]

Like anything they had good and bad days.But the trend was a steady improvement 39-42, with major steps forward in 41 and 42 as radar control began to be used extensively and crew training reached peak efficiencies, and thereafter a steadily increasing nosedive as various things took effect

Depends on the metric you're using; in terms of shells per bomber sure, same with overall Allied loss rate, but overall there were greater losses to FLAK and German defenses in 1944-45 than in 1942, but it was a function of the Allies having more aircraft to continue on regardless that mattered.

On another forum there was the issue of FLAK buffs potentially being a bigger deal than night fighters to defeating the RAF/USAAF, any thoughts?
1944: Flak Alone Blasts the Allies out of the Sky - Axis History Forum

 

[tomo pauk]

Those figures are just for flak deployed in the Reich/West. I don't know how many of the various batteries fall under that definition in 1941, the numbers will be out there somewhere. I don't know how many were in the east either, but they were credited with more than 1,000 Soviet aircraft shot down in the last 3 months of 1941 alone.

Quirk might be that bulk of the heavy Flak remained West of Poland, so the shooting down was done mostly by light Flak? I've suggested less of the emphasis on the heavy Flak, but not a reduction of light Flak.

People look at the bottom line, then as now, and flak was shooting down more RAF bombers than the Nachtjagd.

3.5 RAF aircraft downed per 24 hours is a lousy bottom line for thousands of heavy Flak, thousands of light Flak, and half a million men in Flak arm. The NF force is as good as owerwhelmed by early 1945, so no meaningful comparison can be made.

Increasing the number of night fighters is NOT an easy or economical option. It not only puts pressure on the already shambolic aircraft production sector but increases demand for highly trained crews and the resources (notably fuel, radically reduced to training command in 1942) to train them. It also requires heavy investment in the infrastructure and command and control systems to operate these extra fighters IF you can build and crew them.

In 1st 4 moths of 1941, the Flak arm expanded 990 thousands of heavy shells and 1900 thousands of light shells in order to destroy 144 RAF aircraft. Makes 85 tons of war material to shoot down an average 7 ton RAF aircraft. Flak arm also employs more than 500 thousands of men, and has 3100 heavy Flak guns and 9900 light Flak guns by mid 1940 already. They manage to down 2 aircraft per each 24 hours in April 1941. Now if anyone can see economic viability in this, I'd be grateful to see the bottom line.

 

[stona]

Up until mid 1943 the investment in and expansion of the flak arm appeared to be paying good dividends. The Luftwaffe had effectively made this investment as flak was the means of air defence. After 1943 things changed, largely due to technological advances by the British and obviously the arrival of the USAAF bomber forces.

Flak always remained the most effective way of damaging if not destroying enemy aircraft and wounding or killing their crews. Many aircraft finally destroyed by fighters had previously been damaged by flak.

It also remained the primary factor in reducing bombing accuracy, both by disrupting bomb runs and most importantly by forcing both the the RAF and USAAF to bomb from ever increasing altitudes. These factors were known to the German decision makers and acknowledged by both air forces carrying out the combined bomber offensive.
It cannot be lightly discarded in favour of a night fighter force which would itself eventually be rendered useless by similar advances in British and to a lesser extent US technology. It is no accident that by August 1944 a complete volte-face had occurred from the positions adopted by Milch and Goering in July 1943, in favour of the fighter arms, and there was talk of disbanding the fighter arms altogether in favour of flak.

Cheers

Steve

 

[tomo pauk]

The heavy Flak did not make the RAF change current doctrine or operations (or other AFs) - it was LW fighter arm that made RAF BC switch from day to night ops. As for the bombers 1st damaged by Flak, and then destroyed by fighters - I've suggested that number of fighters need to be increased at the expanse of heavy Flak.

Re. change of appeal fighters vs. Flak in 1944, there are several major caveats to that. 1st - neither Goering nor anyone in Germany was calling the shots how the air war is going to be conducted, it were Allied AFs that were in charge. 2nd, with almost 11 thousands (~ 10970) of just 8,8 cm around, plus a gazillion of light Flak an a number of heavier guns, along with shattered LW day and night fighter arm, choices are very limited. 3rd, even such lavish number of Flak was unable to forestall Allied air operations (despite the toll extracted).

As for NFs being rendered uselles by Allied advances in electronics - the Flak batteries were equally blind when ground-based radars were under jamming.

 

[stona]

The heavy Flak did not make the RAF change current doctrine or operations (or other AFs)

It forced both the RAF and USAAF to bomb from higher altitudes. Higher equals less accurate. It also caused USAAF crews, bombing by day, to take evasive action despite orders to the contrary which also further reduced their bombing accuracy. Le May complained that his bombers were 'throwing bombs every which way' as a result of such evasion. In March 1945 Spaatz said that flak was the biggest factor affecting bombing accuracy. A post war report ascribed 61.4% of the USAAF's radial bombing error directly to flak defences.

The economics of a flak shoot down are positive for Germany. It cost the German heavy flak less than half the cost of a fully equipped B-17 to shoot it down ($107,000/$292,000) about a third the cost of a B-24 ($327,000). That is not a bad return on the investment.

The damage inflicted was significant too. It is not always necessary to shoot down an aircraft to cost your enemy. Between December 1942 and April 1945 flak damaged 54,349 8th AF aircraft, that's more than 1 in 5 of total sorties. About one quarter of these (about 15,000) were seriously damaged, some beyond repair. These are big numbers.

Cheers

Steve

 

[tomo pauk]

It forced both the RAF and USAAF to bomb from higher altitudes. Higher equals less accurate. It also caused USAAF crews, bombing by day, to take evasive action despite orders to the contrary which also further reduced their bombing accuracy. Le May complained that his bombers were 'throwing bombs every which way' as a result of such evasion. In March 1945 Spaatz said that flak was the biggest factor affecting bombing accuracy. A post war report ascribed 61.4% of the USAAF's radial bombing error directly to flak defences.

When needed, RAF was ready to go down low and so the job, even during the daytime. RAF's bombers were anyway flying between 15 and 18 kft, the 15 kft being the upper limit of the 3,7cm (a light Flak piece). I'd agree that going high meant the bombers are less accurate, that combined with newer devices (like H2S) lead to another thing - city busting. As said here, the Germans chased rabbit, but wolf came from the bushes instead.
Despite the thousands of Flak deployed, the Allied bomber units grew in numbers, especially once LW was defeated above Germany in spring/summer of 1944, the losses per sortie dropping down from 7-10% down to 2-3%.

The economics of a flak shoot down are positive for Germany. It cost the German heavy flak less than half the cost of a fully equipped B-17 to shoot it down ($107,000/$292,000) about a third the cost of a B-24 ($327,000). That is not a bad return on the investment.

Do we have the comparison of expanses hat would include shells fired at high flying bombers (ie. those fried by heavy Flak), that went from 4000 per aircraft in 1942, to 16000 (16 thousand) in 1944, and the radars deployed?

The damage inflicted was significant too. It is not always necessary to shoot down an aircraft to cost your enemy. Between December 1942 and April 1945 flak damaged 54,349 8th AF aircraft, that's more than 1 in 5 of total sorties. About one quarter of these (about 15,000) were seriously damaged, some beyond repair. These are big numbers.

Cheers

Steve

A good deal of those aircraft was damaged also by light Flak, or only by light Flak.