If the RAF had been defeated in the Battle of Britain

pbehn said:

I cant see any really conclusive proof that a Swordfish could carry both a torpedo and ASV

Click to expand...

From "Radar Days" by Taffy Bowen, inventor of air intercept and ASV radar (page 101):

"A single Swordfish could not carry both a radar and a torpedo, so the tactic was for the search aircraft to be accompanied by one or more attack aircraft carrying torpedoes."

The navalised version of ASV radar suitable for installation on carrier based aircraft was ASV MkIII. Earlier versions were only fitted to CC a/c but the Mk III version was miniaturised enough to allow being fitted to the swordfish. It entered service on the FAA a/c from the end of 1940, with crews taking abouyt 3 months to become proficient in its use. It was fairly decent as a radar, able to track a surfaced uboat at ranges for up to 7 miles and a periscope out to about 3miles.

The original fit was quite bulky. The photo shown by kooperic shows a swordfish of a later mark, sometime in 1944, by which time the equipment was completely miniaturised and did not interfere with payload.

in 1941 the ASV MkIII looked as follows:

ASV Mk.III did not allow a torpedo to be carried. The much earlier metric ASV Mk.IIN was mounted on the inter wing struts so the torpedo could be carried. As ASV Mk.III was a magnetron based microwave unit it didn't enter service until after H2S long after the Battle of Denmark straights. March 1943, for the swordfish latter.

Koopernic said:

ASV Mk.III did not allow a torpedo to be carried. The much earlier metric ASV Mk.IIN was mounted on the inter wing struts so the torpedo could be carried. As ASV Mk.III was a magnetron based microwave unit it didn't enter service until after H2S long after the Battle of Denmark straights. March 1943, for the swordfish latter.

Click to expand...

I think you are right now that ive cross checked my information. I was relying on U-Boat Net which has the following:

"The history of ASV Mk.III is rather complicated. Because of personal conflicts, the original group that had developed airborne radar was dispersed. A new team was formed, tasked with the development of centimetric AI radar for nightfighters. The big advantage of a centimetric radar is that the beam can be directed accurately by a relatively small paraboloid reflector. This offered better range and resolution and eliminated the strong ground returns, which were unavoidable with the broad beams of the 1.5 meter radar sets. Centimetric radar was made possible by the development, by J.T. Randall and H.A.H. Boot, of the cavity magnetron. The first was tested on 21 February 1940. By June 1940, GEC had produced the first sealed magnetrons, suitable for use in aircraft.

Development concentrated on AI for nightfighthers, but in the autumn of 1940 the 10cm radar attracted naval interest, represented by Captain B.R. Willett and C.E. Horton. It was demonstrated to them that the ground-based, experimental radar equipment could track ships. On 11 November tests were conducted with the submarine HMS Usk, which was tracked at 7 miles. Some time was spent refining the equipment and defining the antennas, until a cylindrical paroboloid section was chosen for shipboard installations. By March 1941, a fully engineered 10cm radar was on board of the corvette HMS Orchis, and on 16 November 1941 the sinking of U-433 near Gibraltar was attributed to the "Type 271" 10cm radar. By May 1942, 236 ships carried centimetric radar".

However I did recheck my facts, and admit that it was the mk II that equipped the Swordfish in May 1941, used against the Bismarck. you live and learn I guess


ASV MKII was developed at the Royal Aircraft Establishment, Farnborough in early 1940.It differed from the Mk I mainly in that it was properly engineered and much more reliable. ASV Mk II was generally called a 1.5 metre radar, but its actual frequency was 1.7 metres. It had a range of up to 36 miles, and the minimum range was about a mile. Several thousand sets were manufactured and equipped a variety of RAF Coastal Command aircraft such as Hudsons, Whitleys, Sunderlands: Fleet Air Arm aircraft such as Swordfish; and American Navy patrol aircraft such as the Catalina. The first success was recorded on 30 November, 1940, when a Whitley Mk VI equipped with ASV Mk II damaged U-71 in the Bay of Biscay ASV Mk II rendered sterling service in the War at Sea in both the Atlantic, Mediterranean and the Pacific. 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. Swordfish and Wellington bombers, some fitted with ASV Mk II, operated from Malta and inflicted heavy damage in night attacks on Axis convoys supplying Rommel's forces. Long-range Catalinas, equipped with ASV Mk II, ranged the Pacific searching for Japanese warships. 'Black Cat' squadrons specialised in night attacks on Japanese shipping. By late 1942 German U-boats were carrying Metox receivers, which enabled them to detect ASV Mk II emissions. This set was increasingly replaced with ASV Mk III.


ASV mkIII was in production from March 1942, but its service delivery was somewhat delayed.

Thanks to kooperic for the correction

Koopernic said:

ASV Mk.III did not allow a torpedo to be carried. The much earlier metric ASV Mk.IIN was mounted on the inter wing struts so the torpedo could be carried. As ASV Mk.III was a magnetron based microwave unit it didn't enter service until after H2S long after the Battle of Denmark straights. March 1943, for the swordfish latter.

Click to expand...

It's mot just a question of where the antennas were carried. We must also consider the weight of the radar transmitter and receiver. Unless you have solid evidence of Swordfish carrying both the ASV MkII and a torpedo, I'd be inclined to put my money on Taffy Bowen's comments, given that he actually designed the thing and participated in the trials to determine its performance.

Now I will accept that Bowen's memory could be faulty and he could be transposing the 2 radars....but I'd still like to see photographic evidence of an ASV MkII-equipped Swordfish airborne while carrying a torpedo.

buffnut453 said:

It's mot just a question of where the antennas were carried. We must also consider the weight of the radar transmitter and receiver. Unless you have solid evidence of Swordfish carrying both the ASV MkII and a torpedo, I'd be inclined to put my money on Taffy Bowen's comments, given that he actually designed the thing and participated in the trials to determine its performance.

Now I will accept that Bowen's memory could be faulty and he could be transposing the 2 radars....but I'd still like to see photographic evidence of an ASV MkII-equipped Swordfish airborne while carrying a torpedo.

Click to expand...

Bowen is ONLY talking about ASV Mk.III. This 9cm microwave set entered service in late 1943 on the Swordfish. It's big and bulky and is carried where the torpedo was carried.

ASV MK Mk II is a completely different much lighter set of in service since 1940. The Swordfish version is the ASV IIN.

It doubt it weighed more than a hundred pounds. AI Mk IV weighed 300lb.
See my post 858 in this thread. It has pictures that enlarge.


You can see the radar yagi antenna array on the strut. No torpedo though.
This was secret.

Koopernic said:

Bowen is ONLY talking about ASV Mk.III. This 9cm microwave set entered service in late 1943 on the Swordfish. It's big and bulky and is carried where the torpedo was carried.

ASV MK Mk II is a completely different much lighter set of in service since 1940. The Swordfish version is the ASV IIN.

It doubt it weighed more than a hundred pounds. AI Mk IV weighed 300lb.
See my post 858 in this thread. It has pictures that enlarge.

View attachment 475758
You can see the radar Yaggi array on the strut. No torpedo though.
This was secret.

Click to expand...

Bowen was NOT talking about ASV MkIII. The page reference quoted in my previous post specifically relates to his descriptions of radar's role in the sinking of Bismarck, so please explain to me how he can possibly be referring to ASV MkIII?

I also don't know about the 9cm wavelength version of the Mk III (and have my doubts that it was referred to as the mk III by that time. the 10cm version of the airborne version was inproduction by March 1942 and was entering service a little later after that. Certainly not 1944.

I suspect the references to the 9cm wavelength sets are in reality either references to either the MkVII or the mkXI version.

The Swordfish could fly with a crew of 3 Pilot, Observer (navigator) and a Telegraphist Air Gunner. A Swordfish carrying ASVIIN only carried 2 men Pilot and Observer. Dont know what ASV IIN weighed but it wasnt a particulary large unit it didnt have a rotating PPI screen like more modern centimetric radars and the one I have seen was about the size of a old fashioned Cathose Ray Tube 20 inch TV.

I am going to guess ASVIIN weighed roughly the same as a TAG wearing all his kit plus Lewis Gun and seat

The Story of the Torpedoing of the Bismarck
None of the crews listed in the Flighs that attacked Bismarck is listed as having less than 3 men, except one on the final mission.

The only way this could happen is if the ASV IIN was easily removed from the aircraft or if Radar equipped Swordfish crews did not receive credit for their participation or if ASV IIN Swordfish could carry a torpedo and full crew or if the TAG crew member is listed as present erroneously.

ASV IIN looks like a miniaturised version of the RAFs ASV II. The IIN has a combined transmit and receive antenna as well to reduce antenna size instead of separate systems.

Radars like AI MK I through to IV and ASV I,II,IIN as well as Type 286,290,291 were all related developments.

RE: Enigma

I was asked by someone how long it would take to decrypt an Enigma message on their phone. This assumes a brute force attack, trying every possible key until you get the correct one.

I know the key space for a standard three rotor Enigma, it's a 76 bit key (rather better than the 56 bit Data Encryption Standard (DES) used on computers until 2002).

I don't know the computing power of his mobile phone, but I assumed that he could test 100,000 keys per second twenty four hours a day.

According to my back of a napkin calculation, if he set his phone to the task today he would have to wait not for hours, days or months to complete the task. He would have to wait for about twice the current age of the universe!

That's why the Germans were so confident of their system, and also why it was never broken by a brute force attack.

Cheers

Steve

stona said:

RE: Enigma

I was asked by someone how long it would take to decrypt an Enigma message on their phone. This assumes a brute force attack, trying every possible key until you get the correct one.

I know the key space for a standard three rotor Enigma, it's a 76 bit key (rather better than the 56 bit Data Encryption Standard (DES) used on computers until 2002).

I don't know the computing power of his mobile phone, but I assumed that he could test 100,000 keys per second twenty four hours a day.

According to my back of a napkin calculation, if he set his phone to the task today he would have to wait not for hours, days or months to complete the task. He would have to wait for about twice the current age of the universe!

That's why the Germans were so confident of their system, and also why it was never broken by a brute force attack.

Cheers

Steve

Click to expand...

From what I read about post war interviews of people working in Germany on Enigma they were not surprised that it was broken, they were very surprised that is was decoded "en mass" almost in real time.

stona said:

RE: Enigma

I was asked by someone how long it would take to decrypt an Enigma message on their phone. This assumes a brute force attack, trying every possible key until you get the correct one.

I know the key space for a standard three rotor Enigma, it's a 76 bit key (rather better than the 56 bit Data Encryption Standard (DES) used on computers until 2002).

I don't know the computing power of his mobile phone, but I assumed that he could test 100,000 keys per second twenty four hours a day.

According to my back of a napkin calculation, if he set his phone to the task today he would have to wait not for hours, days or months to complete the task. He would have to wait for about twice the current age of the universe!

That's why the Germans were so confident of their system, and also why it was never broken by a brute force attack.

Cheers

Steve

Click to expand...

You should have replied with something about Bon Jovi bringing the Enigma home.

pbehn said:

From what I read about post war interviews of people working in Germany on Enigma they were not surprised that it was broken, they were very surprised that is was decoded "en mass" almost in real time.

Click to expand...

When the full scope of the Allied code breaking effort against Enigma was disclosed in 1974 Doenitz was interviewed and was shocked that it had been broken at all.

Edit: In a letter he wrote shortly after the 1974 revelations he also claimed that he'd been suspicious, but had no evidence to argue with the cryptographic experts who claimed a break was impossible.

What the Germans underestimated was not the strength of the encryption which was strong enough to render the encryption secure for any meaningful time span; it still is secure from a brute force attack, even using modern computers. What they underestimated was the ability of the code breakers to exploit certain weaknesses in the system and their use of what we would now call signals intelligence (and the resulting use of cribs, guessed plaintext).

Cheers

Steve

stona said:

When the full scope of the Allied code breaking effort against Enigma was disclosed in 1974 Doenitz was interviewed and was shocked that it had been broken at all.

Edit: In a letter he wrote shortly after the 1974 revelations he also claimed that he'd been suspicious, but had no evidence to argue with the cryptographic experts who claimed a break was impossible.

What the Germans underestimated was not the strength of the encryption which was strong enough to render the encryption secure for any meaningful time span; it still is secure from a brute force attack, even using modern computers. What they underestimated was the ability of the code breakers to exploit certain weaknesses in the system and their use of what we would now call signals intelligence (and the resulting use of cribs, guessed plaintext).

Cheers

Steve

Click to expand...

Basically what I meant Steve. I meant the people who devised and operated the system. They knew all codes could be broken and that Enigma had certain weaknesses. I doubt they were aware of how much their own procedures were broken or not followed properly allowing a "way in" to breaking the codes.

pbehn said:

Basically what I meant Steve. I meant the people who devised and operated the system. They knew all codes could be broken and that Enigma had certain weaknesses. I doubt they were aware of how much their own procedures were broken or not followed properly allowing a "way in" to breaking the codes.

Click to expand...

You are quite right. The problem was that they concentrated on the level of encryption, which would certainly resist any kind of brute force attack in their assessments.
They knew there were weaknesses. For example, throughout the 1930s the Germans continually made what we would now call hardware upgrades as well as changes in procedure which successively defeated the Polish methods of breaking Enigma.
On 15th September 1938, the Germans entirely changed the procedure for enciphering the message keys, and the catalogue method devised from 1936, became completely useless. It was this change that led to the development of the Zygalski Sheets and, most famously, the Polish 'Bomba'.
The Polish Bomba was based on the principle that the random 3-letter message key was sent twice at the beginning of each message and that every now and then, a particular plaintext letter, yields the same ciphertext letter three positions further on.
As an example, assume the indicator is AWB TWY. We see that the letter W occurs twice in the second position. The codebreakers at Bletchley Park would later call such occurences females. As both letter groups (AWB and TWY) originate from the same plaintext (e.g. ZXS), we know that the letter X is encrypted into W twice with an interval of 3 steps. This is a unique property that can only occur with a limited number of settings.
If enough females were found, the Bomba could be used to recover the current Enigma settings in less than two hours. This is simply because not all possible settings have to be tested (which might take a very, very long time).

The Germans dropped this double encryption of the message key at the beginning of each message in May 1940 and rendered the Polish method useless once again.
The British 'Bombe' though based on the Polish system, used a completely different approach. It was based on the assumption that a known (or guessed) plaintext, a so-called crib, was present at a certain position in the message. This is where signals intelligence was involved.

Though the Germans did upgrade their machines throughout the war, the KM added a fourth rotor for example, there were always problems introducing a new piece of hardware across the entire network. The four rotor M4 machines had to be backwards compatible with earlier three rotor machines. The rewireable reflector ( UKW-D) could have posed a fatal threat to Bletchley Park, had it been more widely introduced, as could the programmable cipher wheel (Luckenfullerwalze) which featured 26 user configurable notches and allowed the number and position of the notches of each wheel to be changed frequently. It was planned to use this in conjunction with the UKW-D. the Enigma-Uhr was introduced by the Luftwaffe in 1944 and should have caused some serious problems for Allied code breakers. I can't explain how it works in a reasonably short post, but it was initially compromised by poor operational procedure on the part of operators who didn't understand how the system was supposed to be used.

The Germans were not overconfident about the encryption of Enigma, they were overconfident in the ability of the hundreds or thousands of operators to use it properly and securely.

I hope I've attached an interesting Bletchley Park file about the Enigma-uhr, which will save a lot of typing

Cheers

Steve

parsifal said:

received a dislike from someone called "PSL" no explanation yet as to why.

Click to expand...

So did I.
No explanation, no attempt to refute the points I made.

freebird said:

Hint - how successful was the LW at sinking British battleships, in the numerous instances where they were attacked?

The ships needed to defeat the U-Boats were corvettes, sloops and frigates, which wouldn't be used in the channel

The ships mentioned as sunk in these operations were freighters, not warships

Click to expand...

freebird said:

So did I.
No explanation, no attempt to refute the points I made.

Click to expand...

It might have been a mistake. Back then the "like" and "dislikes" were right next to each other. There were lots of false dislikes given when people were fat fingering on their phones. They were attempting to hit the like button, but accidentally hit the dislike.

We have since moved them apart to prevent that...

fastmongrel said:

The Swordfish could fly with a crew of 3 Pilot, Observer (navigator) and a Telegraphist Air Gunner. A Swordfish carrying ASVIIN only carried 2 men Pilot and Observer. Dont know what ASV IIN weighed but it wasnt a particulary large unit it didnt have a rotating PPI screen like more modern centimetric radars and the one I have seen was about the size of a old fashioned Cathose Ray Tube 20 inch TV.

I am going to guess ASVIIN weighed roughly the same as a TAG wearing all his kit plus Lewis Gun and seat

Click to expand...

This is incorrect. A Swordfish could and did carry a crew of three and a torpedo when equipped with ASV II:

The Story of the Torpedoing of the Bismarck

You'll note that three of the 9 Swordfish in the first strike against Bismarck had ASV II radar and all aircraft carried their full crew. The only time a Swordfish carried a crew of two was when the Observer was replaced by an internal 69IG fuel tank and this was the case for the Taranto strikes, IIRC.

Koopernic said:

I don't think I can even begin to comprehend what you are trying to say Tomo. Just say it directly rather than try satire.

The Bofors system worked because by the time it was introduced widely it was aimed by remote control and had good Ballistics. The Pompom had mediocre ballistics. As noted by reports of the Sinking of PoW and Repulse nearly a year latter they had a very limited effect compared to a pair of Boffors on the foredeck.

Firing away with multiple AAA with gunners located at 37mm/40mm caused problems with blast and smoke. That's one reason no one had a 50mm anti aircraft gun.

Whatever the limitations of the German Naval 3.7 cm mount and ROF it had good ballistics and was stabalised. I imagine it eventually received a gyro sight. They also never replaced them in Tirpitz or Prinz Eugen despite having the excellent 3,7cm FLAK 43 and earlier FLAK 37 I would assume they preferred to have the extra range and ability to fire continuously.

In terms of fire power relative to deck space the quad FLAK worked because it was not so large and didn't produce so much blast it needed to be aimed remotely.

Some of the better FLAK directors were removed from Bismarck and Prinz Eugen to complete Lützow which had been sold to the USSR.

Click to expand...

At least two and probably all 4 of the IJN torpedo bombers shot down by Force Z were downed by pom-pom fire. There is no record of the single Bofors on PoW scoring any hits, but it's fire was considered effective because it was equipped with tracer which appeared to disturb the aim of the incoming torpedo bombers.

Quad and Octuple pom-poms fitted on cruisers and larger ships were all fitted with an external gun director.