Hood's Last Trick

[Ramius]

I was looking at a map of the Battle of the Denmark Strait (the link at the bottom with several of the maps I was looking at is from our own Antonio Bonomi), and I was thinking that maybe the torpedoes that Prinz Eugen's GHG Hydrophones picked up was actually the Hood going down. The German's started taking evasive action to avoid the phantom torpedoes only a little while after the Hood went A-Bomb. Metal grinding, boilers exploding; many things on a sinking ship could cause high pitched sound. Lutjens maybe would have been more willing to go after Prince of Wales if he knew there were no British destroyers or cruisers waiting behind PoW's smoke screen to torpedo him

http://www.bismarck-class.dk/bismarck/h ... attle.html

[paulcadogan]

Marko,

If you read Prinz Eugen's War Diary, you'll see that her observers claimed to have actually SEEN the torpedo tracks approaching. They knew Hood had torpedoes and believed them to have been fired by her. Of course this was not the case as Hood's tubes were fixed in her hull and could not have been fired at the Germans at the angle at which she was approaching.

This "sighting" made both German ships turn away and thus helped PoW somewhat.

Here's a devilish thought There are persons who subscribe to an "alternative" theory that a U-boat was present at DS and torpedoed the Hood! Could it be that this supposed vessel was responsible for the tracks seen by PE??? A case of friendly fire????

Paul

[RF]

If a U-boatwas in the vicinity I think we would know about it by now. The idea of Hood being sunk at DS by a U-boat is no more credible than HMAS Sydney being sunk by a Japanese submarine instead of Kormoran.

The idea of Hood sinking causing the torpedo alarm on PE does sound plausible.

As far as I am aware Hollands six destroyers at DS were well astern of the Hood/POW and not sighted by the Germans. So Lutjens would not presumably be aware of their presence (although he may have suspected it) and in any case the destroyers would be too far back to assist POW in a prolonged action, unless it became very prolonged.

[paulcadogan]

If a U-boatwas in the vicinity I think we would know about it by now. The idea of Hood being sunk at DS by a U-boat is no more credible than HMAS Sydney being sunk by a Japanese submarine instead of Kormoran.

I know RF.. I was just being mischievous!

[Ramius]

I was thinking that the sound the Prinz Eugen heard was either her on the way down, or the echo of that or the initial explosion off the bottom. This is because of the small, but existant, time delay between the explosion and the hydrophone contact.

[Ramius]

I have been woundering about the effictiveness of the Prinz Eugen's hydrophones. Also, what the heck is the difference between a hydrophone and a passive sonar array

[tommy303]

Active detection equipment is that that sends out a high frequency sound impulse which bounces off a target and the echo is received back on the sending ship (SONAR). Active systems leave leave their own signature and the target will naturally know that the enemy is searching for them. Passive systems are those which use hydrophones to listen for properllor cavitations, machinery noises etc, but have no detectable signature of their own.

Prinz Eugen's underwater detection outfit consisted of a sophisticated active sonar unit called the S-Anlage (Sonderfernsteueranlage) made by AEG, and two passive sets, the Atlas NHG (Navigationshorchgeräte) consisting of two narrow beam hydrophones and used mainly for navigational purposes. The other was the GHG (Gruppenhorchgeräte). This was a series of 60 salt crystal microphone receivers mounted on each side of the hull in a horseshoe layout. The installation was built by Atlas It was used to detect propellor and machinery noises from surface ships, submarines, and torpedos.

In tactical terms, GHG was a passive early warning system and could be used to alert ship command of the presence of an enemy or to aid in homing in on a convoy. The actual range and effectiveness of the GHG was dependant on several factors:
1 Own speed and level of self noise
2.Target speed and noise level
3.Sea state (rough seas will generate various noise levels while salinity and currents will influence detection ranges)
4.Operator experience.
5.Position of target in relationship to ship heading (the microphones could not be directed very far aft fo the beam because of hull configuration and machinery and propellor noises).

Paul Schmalenbach, who served as a gunnery officer on the Prinz Eugen, stated that the usual detection range was between 4km and 26km, dependent on the above factors. Notably submarines could be detected at about 500 to 600m and torpedoes at about 2000m. Bearing accuracy was plus or minus 2*.

[tommy303]

It is difficult to say exactly what, if anything, the GHG operators on Prinz Eugen heard that might have made them think they had detected torpedoes in the water. As Ramius points out, it could have been noises from the Hood's wreck, or it might have been a pod of humpback whales telling their relatives that it was time to get out of Dodge cause us humans had gone nuts again.

Although there is no real evidence for it, the possibility exists that the Hood might have fired off the torpedoes she had loaded in her four above water tubes to get rid of them shortly after the shell from Prinz Eugen started the fire on the shelter deck. The location of the fire was two decks above the torpedo tube installation and it is remotely possible the torpedoes were jettisoned as a precaution. However, standing against that theory is the fact that Hood was never on a bearing which would have allowed the torpedos to come close enough to be detected by Prinz Eugen and no one on Prince of Wales saw the armoured torpedo doors openned or the torpedoes being fired. Neither, for that matter did Briggs on the compass platform with the captain and admiral, overhear any order to jettison them or any report that they had been fired off.

Personally, I tend to think whales might have been the cause. By May Humpbacks, rights and greys are well on their way north to their arctic waters feeding grounds. Up through WW2 there had not been much, if anything, done in the way of identifying and catagorizing biological ultra sound noises detectable by hydrophones. In the post war years, newer and more sophisticated hydrophones, often based on the GHG, were found to be able to detect whale songs and clicks and work began to classify and record them so that operators could differentiate between marine animals and 'enemy' submarines. A previously not encountered, high pitched sound, might well have tricked Prinz Eugen's GHG operators into thinking a torpedo was approaching, and although Captain Brinkmann claimed to have actually seen torpedo tracks.....well one often sees what one expects to see.

[Ramius]

Whales make sense, but so does the Hood in her death throes, so it probably was one of those two. But then the torpedoes trails, well... "OMG!!! A straight line, it's a torpedo!!! Sound the alarm..."

[paulcadogan]

This idea of whales is very interesting. There is much evidence today of the effect that underwater noise has on whales (though it may still be controversial), including sonar and the blasts used in seismic exploration for oil. One can imagine the effect that shells exploding in the sea - not to mention the underwater shock wave from Hood's explosion - might have had on a pod passing through the area.

Explosions could cause ear drum damage, rendering the animals unable to navigate by echolocation. This results in disorientation and, conceivably, increased vocalizing. There is also evidence of low frequency sound waves interfering with the whales' mechanism for preventing decompression sickness (the "bends") resulting in nitrogen bubbles forming in the blood and tissues, again leading to disorientation, along with organ damage and possibly death.

I'd be curious to find out if any whales beached themselves on the west coast of Iceland in the week following the DS battle!

But, thinking about it, I would suspect that any whales in the path of the battle would have taken evasive action as soon as the first shots were fired. How quickly they would have been able to get out of the way is the question.

Paul

[Bgile]

From personal experience I can say that it's very unlikely for whales to be confused for torpedoes. What mamal noise (we called it "biologics") does is make it difficult or impossible to listen for things on the bearings where they exist, sometimes over a fairly wide range of bearings. There is never any doubt whether it's man made though ... it just doesn't sound at all like machinery. A torpedo sounds a bit like a high speed electric drill.

To further confuse the "SONAR" definition, in the US Navy passive listening is also called SONAR. There is active sonar and passive sonar, and often the same equipment has both modes. I realize it was somewhat of a misnomer at least originally because of the "AR" for "and ranging", but today it's possible to get good ranges from passive sonar. That wasn't true in WWII.

[Antonio Bonomi]

Ciao all,

very interesting discussion going on here,..... the DS torpedo ALARM called by Prinz Eugen ..... and verified personally by Kpt zur See Helmut Brinkmann which, .... according to Fritz Otto Busch book, PG KTB and Adm Raeder report to Hitler on June 6th, 1941 at Berghof, ... went our on the open bridge of PG and saw with his binocular the torpedo tracks on the water .

Well,.. this is the key of what happened at 06.03, ..because as soon as he called the torpedo ALARM,.. Kpt Lindemann turned Bismarck to starboard of course,....immediately,... going out of any torpedo range right away ( they were around 12.000 meters, so within the torpedo range limits ).

Now,.. did you see the torpedo infos written on the PG original battle map ?

It is here, see how many times they called the ALARM and from which direction :

http://hmshood.com/history/denmarkstrai ... tlemap.gif

You can clearly read the 4 Torpedo ALARM calls ( in German of course = Torpedo Gerausche or Torpedo Laufbahn ), on my original copy of this map I purchased from Bundesarchiv they are marked in RED on the map, so they are very evident indeed :

1) At 06.03 from course 279 degrees a noise = Gerausche .

2) At 06.06 and 30 seconds from 220 degrees ... and this was a track = Laufbahn

3) At 06.07.... course not written on the map,..but you can calculate it even if PG is turning wild on that moment...

4) At 06.15 ... course not written and PG will start another wild manoeuvre ,..

.... forcing Kpt Lindemann and the Bismarck to do something really strange once again ... that one day I will explain to you all .

... research,.. and learn patiently,..... this is the key, .. it is a never ending story, .....

Bye Antonio

[Vic Dale]

Hi To All.

At 0555, Holland ordered a turn to port of 20 degrees and though it was presumably intended to open the after 'A'-arcs, it did not do so in PoW until the salvo fired at 0557:50, which is quite a long time. Hood was firing at Prinz Eugen - 3000m ahead of Bismarck, so it is unlikely that Hood's after "A" arcs opened at all during the engagement.

The bearing on which the British ships had their guns trained was easily spotted through the high powered gunnery optics and jasper himself makes this clear in his entry in Prinz Eugen's War diary.

Such a turn with no apparent gain could easily have alerted the Germans to the possibility that it was made in order to launch a fan shot of torpedoes. German torpedoes at the time could be programmed to turn up to 90 degrees away from the direction of their launch, so a torpedo attack from Hood who was known to carry this weapon and in fact did carry it could easily be the source of the noise which caused the alarm in the German ships.

When Hood went down, not all compartments will have been flooded, so the low power supply rooms and converter rooms may have still been running. Such low power units would switch to battery power automatically in the event of a power shut down, so the sound of high speed electric motors could have been detected as the hull became immersed in the water.

Another consideration is the possibility of one of Hood's "torpedoes" going rogue due to turbulence from the numerous shell splashes and might come round for another go, having missed the first time.

There was clearly nothing wrong with the GHG in either ship, since they detected Hood and PoW by sound location before their smoke was seen that morning. It may be felt that the operators were inexperienced or made a silly mistake, but an electric motor is an electric motor, wherther contained in a torpedo or in a sinking ship, so according to what they heard they were duty bound to alert central command, to the potential threat.

Better safe than sorry, because sorry could have meant one or both German ships stopped and defenceless in the Denmark Strait.

Regards Vic

[RF]

When Hood went down, not all compartments will have been flooded, so the low power supply rooms and converter rooms may have still been running. Such low power units would switch to battery power automatically in the event of a power shut down, so the sound of high speed electric motors could have been detected as the hull became immersed in the water.

Regards Vic

But they would have cut out at that point, so any sonar pick up of their noise would be momentary?

[Patrick McWilliams]

I have been woundering about the effictiveness of the Prinz Eugen's hydrophones.

Well, at 05.30 didn't they pick up the sound of two new ships to port, which turned out to be Hood and PoW when they came into binocular range about 15 mins later? Seems to indicate that they were functioning ok.