Tirpitz and Graf Zeppelin 1941

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Re: Tirpitz and Graf Zeppelin 1941

Post by dunmunro » Mon Dec 19, 2011 9:10 am

Pandora wrote:yes, that is the report.
no ASV onboard Catalina and as I said I suspect no ASV in other recon planes too.
Not having ASV on-board was remarkable enough to be mentioned in the report.

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Re: Tirpitz and Graf Zeppelin 1941

Post by Pandora » Mon Dec 19, 2011 9:26 am

dunmunro wrote:
Pandora wrote:yes, that is the report.
no ASV onboard Catalina and as I said I suspect no ASV in other recon planes too.
Not having ASV on-board was remarkable enough to be mentioned in the report.
... to the point that if it hadnt been mentioned you would still be trying to convince us all that the Catalina had ASV. :wink:

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Re: Tirpitz and Graf Zeppelin 1941

Post by dunmunro » Mon Dec 19, 2011 10:05 am

Pandora wrote:
dunmunro wrote:
Pandora wrote:yes, that is the report.
no ASV onboard Catalina and as I said I suspect no ASV in other recon planes too.
Not having ASV on-board was remarkable enough to be mentioned in the report.
... to the point that if it hadnt been mentioned you would still be trying to convince us all that the Catalina had ASV. :wink:
There are references such as the IWM which implied that the aircraft was equipped with ASV:

A Catalina equipped with this ASV detected the German battleship Bismarck after her destruction of the Hood. Swordfish strikes from Victorious and Ark Royal, which ultimately crippled the Bismarck ,detected the battleship using ASV Mk II radar.

but regardless ASV was common on CC aircraft by mid 1941:
The engineering of the equipment, to make it more rugged and reliable, was carried out at the Royal Aircraft Establishment (RAE) under the supervision of a senior member of Bowen's original group (AG Touch). The set which they developed (ASV MkII) was produced in far greater numbers than MkI; in the UK alone, 6 000 sets were made, and many thousands were produced in the USA and Canada. It was fitted to patrol and reconnaissance aircraft all over the world and used in anti-submarine patrols, anti-shipping strikes, convoy escort and many other duties. Its principal value was in the first phase of the Battle of the Atlantic when the Germans were using the captured French ports to give their U-boats easy access to the Atlantic. In April 1941 Coastal Command was operating anti-submarine patrols with about 110 aircraft fitted with ASV MkII, and the use of radar by these aircraft increased the daylight sightings of submarines significantly. More importantly, it made it possible to attack submarines at night as they travelled on the surface; in 1941-42 over 90 per cent of night attacks were made as the result of ASV contact. However very few of these attacks were lethal until the introduction in mid-1942 of a powerful searchlight (Leigh Light) that illuminated the submarine. The combination of this light with ASV MkII was so effective that the submarines tended to submerge by night and surface by day, thereby increasing their destruction by daytime patrols. This satisfactory state of affairs lasted for a few months until the Germans introduced a listening receiver – Metox – which warned the submarine of the approach of an ASV-equipped aircraft so that it could dive. As far as metre-wave ASV was concerned the introduction of this listening device marked the end of the first phase of the Battle of the Atlantic; the second phase was taken up by centimetre-wave radar.
http://www.csiropedia.csiro.au/display/ ... 28Taffy%29

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Re: Tirpitz and Graf Zeppelin 1941

Post by Pandora » Mon Dec 19, 2011 12:20 pm

but now we know it didnt have ASV, and it was exclusively a visual sighting by an aircraft hundreds of miles from its base.
which makes me believe that a squadron of Stukas wouldnt have much problem finding a shadower following GZ closely behind.
heck, Luftwaffe planes without ASV were attacking ships at see from France since 1940!

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Re: Tirpitz and Graf Zeppelin 1941

Post by alecsandros » Mon Dec 19, 2011 2:21 pm

Dear friends,

Excuse me to drop in, but do I understand correctly the problem at hand ?

1) some of you regard a TZ + GZ sortie as a big threat to the communications in the North Atlantic
2) others, notably Duncan, consider that this would be a modest threat, as the RN had the means to block such a sortie.

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Re: Tirpitz and Graf Zeppelin 1941

Post by srgt rock » Mon Dec 19, 2011 3:38 pm

It is the ADMIRALTY that considered the presence of an operational Carrier to be a graver threat than even Bismarck. See the report of the Admiralty meeting on 29 Jan 1940.

I think it is likely the British find the Northern Battle Group as they approach the Iceland-Faroes Gap but DO NOT think the British could prevent them from breaking out. The convoy system would be disrupted. The amount of disruption would depend upon the number of tankers in the Mid-Atlantic with the German task forces.

I think a very good discussion could center on how close would the Northern Battle Group come to the narrowest part of the Iceland-Faroes Gap (240 miles) before the British could reasonably be expected to locate them.

The refueling would have been in the Arctic Ocean somewhere above the Narvik-Jan Mayan line. The breakout attempt would not be made in the Denmark Strait as had all other breakouts so far. It appears from the historical weather reports from Iceland that a front was moving into the Denmark Strait at the end of November 1941 but that the weather in the Iceland-Faroes Gap would be better. British naval forces would have needed to cover both the Denmark Strait and the Iceland-Faores Gap.

The only naval force that had a chance of stopping Rapier prior to or during breakout would the British Carrier Groups. I do not believe an effective strike could have been launched from more 150 miles. One Carrier Group would most likely been stationed south of Iceland and one south of the Faroes islands.

It needs to be established how large a SEARCH FOOTPRINT the British would have had. By footprint I mean both visual and by radar. How many ASV equipped planes did the British have stationed in Iceland and Northern Ireland that could be used to search? How many surface would have been stationed in the Iceland-Faroes Gap?

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Re: Tirpitz and Graf Zeppelin 1941

Post by alecsandros » Mon Dec 19, 2011 6:16 pm

I don't know if you realy need to dig so deep into details, Sgt Rock.
The most probable outcome, IMO, would be that the German raider force breaks into the open waters of the Atlantic, and attacks 1-2 convoys, that are scattered with great losses for the Allies. AFTER THAT however, shortage of fuel and ammo aboard TZ and GS would be greatly felt. AND, considering the response Bismarck triggered, there would be several (4-5 ?) convergent task-forces, with at least 3 carriers and 6 BBs and BCs present. Coastal Command woudl add to the search efforts, and so would every ship from every convoy the raiders encounter.

The German raiders would play a huge gamble by this time, either trying to refuel/rearm by sea (an operation which takes many hours, during which the ship is most vulnerable) OR trying to race back to Brest, somehow through the net of British task-forces.

Either way, it's a big, big gamble, with a moderate payoff.

Just my opinions, of course...

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Re: Tirpitz and Graf Zeppelin 1941

Post by dunmunro » Mon Dec 19, 2011 7:55 pm

Pandora wrote:but now we know it didnt have ASV, and it was exclusively a visual sighting by an aircraft hundreds of miles from its base.
which makes me believe that a squadron of Stukas wouldnt have much problem finding a shadower following GZ closely behind.
heck, Luftwaffe planes without ASV were attacking ships at see from France since 1940!
No it wasn't exclusively a visual sighting. The UK used ULTRA decryptions and RDF info to determine the probable path of the Bismarck and then sent aircraft to search along that route:
By a remarkable chance, during the battle BP has learnt from a Luftwaffe signal that the Bismarck is heading for Brest. Their decrypt reaches the Admiralty on the early evening of 25th, but unknown to BP this is a few minutes after the decision has been made on the basis of the DF information. Though Hut 8 is unable to decypher the Bismarck signals, Hut 6 has read a signal in the Luftwaffe Enigma to a senior Luftwaffe Staff Officer who is in Athens preparing for the Crete invasion; by chance he has a son on the Bismarck and in answer to his enquiry the Luftwaffe HQ passes on the gist of one of the Bismarck signals giving the vital information. It would seem that BP believed that it was this signal that determined the fate of Bismarck, and used the story in training courses so it became well known. BP never broke the Barracuda key.
http://www.bletchleypark.org.uk/content ... y1941.rhtm
There's a huge difference between aircraft flying from and returning to, fixed bases, over aircraft flying from a moving base in atrocious weather. Victorious, for example, had 4 of her 15 aircraft ditch because they couldn't find their carrier again. A purely visual search from Victorious would have had a very low probability of finding Bismarck, even with the aid of shadowing RN ships, and in fact, she never did find Bismarck with her air searches.

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Re: Tirpitz and Graf Zeppelin 1941

Post by dunmunro » Mon Dec 19, 2011 8:02 pm

alecsandros wrote:Dear friends,

Excuse me to drop in, but do I understand correctly the problem at hand ?

1) some of you regard a TZ + GZ sortie as a big threat to the communications in the North Atlantic
2) others, notably Duncan, consider that this would be a modest threat, as the RN had the means to block such a sortie.
It is not that I consider GZ and TZ to be a modest threat, but that GZ's capabilties will be greatly degraded by attempting to use her in December, when weather and visibility will probably curtail flight operations, most of the time, which even under the best of conditions will amount to no more than 6 hours/day.

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Re: Tirpitz and Graf Zeppelin 1941

Post by Pandora » Tue Dec 20, 2011 5:52 am

dunmunro wrote: No it wasn't exclusively a visual sighting. The UK used ULTRA decryptions and RDF info to determine the probable path of the Bismarck and then sent aircraft to search along that route:
By a remarkable chance, during the battle BP has learnt from a Luftwaffe signal that the Bismarck is heading for Brest. Their decrypt reaches the Admiralty on the early evening of 25th, but unknown to BP this is a few minutes after the decision has been made on the basis of the DF information. Though Hut 8 is unable to decypher the Bismarck signals, Hut 6 has read a signal in the Luftwaffe Enigma to a senior Luftwaffe Staff Officer who is in Athens preparing for the Crete invasion; by chance he has a son on the Bismarck and in answer to his enquiry the Luftwaffe HQ passes on the gist of one of the Bismarck signals giving the vital information. It would seem that BP believed that it was this signal that determined the fate of Bismarck, and used the story in training courses so it became well known. BP never broke the Barracuda key.
http://www.bletchleypark.org.uk/content ... y1941.rhtm
It was a exclusively visual sighting. that they had an approximate idea of where Bismarck was after incercepting signals means nothing at all. the searching area was still hundreds of square miles (as large than England!).
dunmunro wrote: There's a huge difference between aircraft flying from and returning to, fixed bases, over aircraft flying from a moving base in atrocious weather. Victorious, for example, had 4 of her 15 aircraft ditch because they couldn't find their carrier again. A purely visual search from Victorious would have had a very low probability of finding Bismarck, even with the aid of shadowing RN ships, and in fact, she never did find Bismarck with her air searches.
which would prove then that either ASV was not that effective in bad weather or the air crews were very inexperienced, or a combination both. any case at least we agree that bad weather affects both British and German operations. still Luftwaffe was finding ships hundreds of miles away without ASV, having a fixed base help them return to base AFTER they already found and attacked enemy but they had to find enemy in first place.

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Re: Tirpitz and Graf Zeppelin 1941

Post by Paul L » Tue Dec 20, 2011 6:19 am

Bletchley park did not determine the Bismarck’s location or destination by decryption. What happened was the station chief just happened to notice the German transmission base had shifted to the south and from this he guessed they were not heading back to Norway but to France. It was a good guess but the info came after the RN fleet had come to the same conclusion. According to Montrfiore, "Enigma-The Battle for the Code", throughout 1941 Bletchley Park was in another black out period. In each 48 hour cycle they were only able to average 2 hours of translation in 'near real time'. All other transmission transcription suffered a average two day delay. This means they could not provide useful tactical information but maybe help to confirm operational choices.

While the Bismarck operation allowed the Atlantic Supply net to be 'rolled up', this only effected about 15% of the German supply network and was only possible because of the capture of code books from U 100 or 110?. The Fleet commander under pressure from Hitler was forced to refocused the new resupply network and strategic direction from Atlantic interdiction to Norwegian/Arctic interdiction. Had a continuation of the Atlantic interdictions been planned, then a new supply network would have been set up ahead of time , perhaps by shifting some supply ships from the India ocean and some through the Channel into the mid Atlantic Region. Its not likely the allies would have 'lucked out' again with another code book in such a short time. If that does happen these raiders could sortie for months on end like in "Operation Berlin".

With regards to RN search capability, you guys have no idea just how hard it is to 'find' ships at sea. For the Bismarck strikes, EVEN though they had constant Cruiser shadowing the Bismarck with radar , the RN had to generate 112 sortie in multiple strikes to deliver what looks like 39 torpedoes launched to get 4 hits only one of which was critical. It seems like they were 3 searchers for each TB sortie launched.
"Eine mal is kein mal"

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Re: Tirpitz and Graf Zeppelin 1941

Post by alecsandros » Tue Dec 20, 2011 7:07 am

But as I understand it, your scenario revolves around a late 1941 sortie by TZ + GZ.
By then, Coastal Command strength was considerably larger, and the Royal Navy was a bigger fleet also. Escort carriers were also beginning to appear, the 50 DDs of the LL act were operational, etc. The airwings of the fleet carriers were larger than in 1940, particularly in the crucial domain of torpedo-bombers. Swordfish pilots had more experience than a year before. Albacores were present in larger numbers, and they had allmost twice the range of Swordfishes (800 miles vs 500 miles with torpedo loaded)

===

I don't underestimate the difficulty of finding ships in the open sea. But concentrated efforts (like the one against Bismarck) had realistic chances of success, especialy if 3-4 carriers were present.

But even if they are NOT found, how would the ships ressuply with 38cm shells and replace the lost aircraft from Graf Zeppelin ? They would need to head back to port, were they would be targeted by relentless air attacks, just as the twins had been...

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Re: Tirpitz and Graf Zeppelin 1941

Post by RF » Tue Dec 20, 2011 9:44 am

dunmunro wrote:
srgt rock wrote:I have another question. Where the British still trying to patrol the Iceland-Faroes Gap with surface ships at the end of 1941 or were they using ASV equipped aircraft?
Both, AFAIK.
These Atlantic entrance passages were continousely patrolled by British and US cruisers also to intercept German blockade runners which were ordered to avoid the Biscay ports. All were intercepted, and the Americans had a particular interest in German ships falsly flying the US flag.
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Re: Tirpitz and Graf Zeppelin 1941

Post by Paul L » Wed Dec 21, 2011 4:00 am

The situation being colorfully described is later in the war. Here is a passage from O'Hara on this subject.
Between April 1940 and June 1942 sixteen blockade runners sailed from Japanese waters to France and twelve arrived safely. By the end of 1942 however, Ultra had revealed the safe lanes blockade runners were using and in August 1943 the allies began to read the Enigma transmissions of the blockade runners themselves. In a second wave lasting between August 1942 and May 1943 only four of fifteen Axis blockade runners safely reached France.

Lets look at a simplifed model of the problem. At 20 knots a panzerschiff can travel 200nm in 10 hours and the three gaps are roughly 200 x 200 + 270 x 200 + 210 x 200 for a total sea area of about 136,000 nm². Any allied cruisers are likely to cruise in pairs at 15 knots so in the 10 hours it takes for the Germans to cross the patrol area, they can sweep about 150 x 60nm with radars or 9000 nm². So at any given time they need to have 15 pairs of cruiser on patrol in this area to insure 100% coverage. To have this continous coverage they need 3-4 times as many cruisers to ensure enough rotation to cover maintenance down time and refits etc. Thats a demand for 90-120 cruisers, just to patrol these seas. How many cruisers are on these patrols?
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Re: Tirpitz and Graf Zeppelin 1941

Post by RF » Thu Dec 22, 2011 9:22 am

Nothing like that force of cruisers would be required. Post Rheinubung the British had a pretty accurate idea of which German heavy ships were likely to break out into the Atlantic and when. Germany only had two panzerschiffe anyway and the one attempt made - by Lutzow - didn't even get to the passages before that ship was torpedoed.

Fear of Allied radar and lack of Atlantic supply ships was the major constraint on the Germans - the British were well aware of that so the cruiser patrols could be scaled down and were, but the watch was still maintained.
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