1000 Pounders versus Battleships

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Howard Mitchell
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RE: 1000 Pounders versus Battleships

Post by Howard Mitchell »

ORIGINAL: Big B

I "think" the story of the AA Directors being incapable of tracking slow-moving targets was first quoted in the book by Burkhard Baron von Mullenheim-Rechberg, "Battleship Bismarck, A Survivor's Story"

I'm not saying it is or isn't true - just that I believe that was where I read the statement, I'll look for the book.

If you look at my previous post you will see that I was quoting the good Baron:

‘the fact that the Bismarck did not shoot down a single one of the relatively large number of close, low-flying enemy planes has puzzled both experts and laymen. Ostensibly, such a complete failure ‘should not have happened’ and I cannot offer any plausible explanation for this apparently poor performance’.

Footnote on page 209 of the expanded 1991 edition.
While the battles the British fight may differ in the widest possible ways, they invariably have two common characteristics – they are always fought uphill and always at the junction of two or more map sheets.

General Sir William Slim
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RE: 1000 Pounders versus Battleships

Post by Big B »

Yes, I must have missed that.

But I was thinking (maybe I just have a bad memory) that in that book there was a direct statement saying that the director system "was not designed to track slow moving aircraft" - or something similar. Which is not quite the same as saying "I cannot offer any plausible explanation for this apparently poor performance".

The book I am thinking of is here at the house, and Mullenheim-Rechberg is featured in it - so I assume it's the same book. As soon as I can get my hands on it I'll go through it and see if I can find the quote I mentioned above (right now it is in a room where someone is sleeping who works graveyard and I don't want to disturb him).
Or - maybe I'm just wrong and no such quote exists.[&:]

ORIGINAL: Howard Mitchell

ORIGINAL: Big B

I "think" the story of the AA Directors being incapable of tracking slow-moving targets was first quoted in the book by Burkhard Baron von Mullenheim-Rechberg, "Battleship Bismarck, A Survivor's Story"

I'm not saying it is or isn't true - just that I believe that was where I read the statement, I'll look for the book.

If you look at my previous post you will see that I was quoting the good Baron:

‘the fact that the Bismarck did not shoot down a single one of the relatively large number of close, low-flying enemy planes has puzzled both experts and laymen. Ostensibly, such a complete failure ‘should not have happened’ and I cannot offer any plausible explanation for this apparently poor performance’.

Footnote on page 209 of the expanded 1991 edition.
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RE: 1000 Pounders versus Battleships

Post by Howard Mitchell »

ORIGINAL: Shark7

ORIGINAL: jwilkerson

Well go drill into the source Tiornu cited and evaluate the credability of that source and that source's source, etc.! Execute the historiographical process!
[:)]

But simplistically, thinking that an aircraft in a dive might be able to exceed its maximum "normal" speed by 50 MPH for a short time while diving from approach altitude down to ordnance delivery altitude, does not sound totally implausable.



Well the fact is that every aircraft can achieve a greater than max speed in a dive. There is no question of that. However, where you have to question is if the aircraft can withstand the G-Forces generated by that airspeed. And there is also a point of no return, meaning you reach a point where you cannot manuevre out of the dive. That would certainly be affected by the presense of a 1600 lbs, not particularly aerodynamic torpedo being strapped to the plane's belly.

Any plane can dive much faster than it can fly level, but at what point does the stress become so great that it snaps the wings, and also at what point does it become and uncontrollable dive? IE a dive that cannot be pulled out of.

Airspeed itself does not generate any G-force, only the rate at which the aircraft pulls out of the dive. If the aircraft pulled out gently then the G-force would be lower than in an abrupt pull-out. Pilots know the limits which their aircraft can manage with given loads (including 1600 lb. torpedoes), so I don't see this as a problem. The limit at which an aircraft takes structural damage from diving too fast varies from aircraft to aircraft. Before that point, only in some designs does it ever become a dive which cannot be pulled out of (given enough altitude). The P-38 is perhaps the most famous example of this, but few aircraft of the period were affected to the same degree iand many not at all.

The Swordfish was purpose-built as a carrier aircraft and so, unlike converted land-planes like the Seafire, was built to take a lot of stress. Don't be fooled by its antiquated looks - it had a strong airframe and was used for dive-bombing attacks. Terence Horsely in his book Find, Fix and Destroy, quoted in British Naval Aircraft since 1912 by Owen Thetford, said of it:

‘You could pull a Swordfish off the deck and put her in a climbing turn at 55 knots. It would manoeuvre in a vertical plane as easily as it would straight and level and even when diving from10,000 feet the ASI never rose much beyond 200 knots. The controls were not frozen rigid by the force of the slipstream and it was possible to hold the dive within 200 feet of the water’.

ASI is indicated air speed; the actual airspeed would have been somewhat greater. The bomb-equipped Swordfish at Taranto dropped their bombs from dive from 1,500 feet (British Naval Aviation, by Ray Sturtivant). Not very high, but if your maximum dive speed is around 200 knots probably high enough!
While the battles the British fight may differ in the widest possible ways, they invariably have two common characteristics – they are always fought uphill and always at the junction of two or more map sheets.

General Sir William Slim
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Howard Mitchell
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RE: 1000 Pounders versus Battleships

Post by Howard Mitchell »

ORIGINAL: Big B

Or - maybe I'm just wrong and no such quote exists.[&:]

No, I'm sure you are right Big B, I've read the same myself [:)]

...but so long ago that I can't remember where. Probably Kennedy's Pursuit of the Bismarck. but I've no time to look it up right now.
While the battles the British fight may differ in the widest possible ways, they invariably have two common characteristics – they are always fought uphill and always at the junction of two or more map sheets.

General Sir William Slim
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RE: 1000 Pounders versus Battleships

Post by Big B »

Well, at this point I have to think I'm wrong about any such statement being made. I've looked through the book and I can't find anything.
I think I have been taken-in by Urban Legend on that one.

However, what rtrapasso quoted above in post #133, about the mis-match of AA gun-directors with the slower moving rear AA turrets, seems logically to me to be the original source of legend about the inability of Bismarck's AA directors engaging slow aircraft.

B
ORIGINAL: rtrapasso
ORIGINAL: Big B

I "think" the story of the AA Directors being incapable of tracking slow-moving targets was first quoted in the book by Burkhard Baron von Mullenheim-Rechberg, "Battleship Bismarck, A Survivor's Story"

I'm not saying it is or isn't true - just that I believe that was where I read the statement, I'll look for the book.

Let me know if you find anything there... i did read an article based on Ludovik Kennedy's "Pursuit" that quotes a German gunner saying that the Swordfish were flying "too low and slow for him"... but i don't know if that is based on something more or not.
ORIGINAL: Howard Mitchell

ORIGINAL: Big B

Or - maybe I'm just wrong and no such quote exists.[&:]

No, I'm sure you are right Big B, I've read the same myself [:)]

...but so long ago that I can't remember where. Probably Kennedy's Pursuit of the Bismarck. but I've no time to look it up right now.
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RE: 1000 Pounders versus Battleships

Post by Feinder »

I gotta say, it's mildly amusing to see how often threads in this forum turn into squabbles about the Bismark.  Somebody ought to just add her into a Mod, and throw in Prinz Eugen while they're at it, and be done with it.
 
Let them survive the glorious WitP game engine, and resolve all these debates.
 
-F-
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RE: 1000 Pounders versus Battleships

Post by Tiornu »

Is this a new kind of AA gun?
Hee! I know I've discussed this topic too many times because I've made that exact mistake in this exact context before.
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RE: 1000 Pounders versus Battleships

Post by Big B »

[:)]
ORIGINAL: Feinder

I gotta say, it's mildly amusing to see how often threads in this forum turn into squabbles about the Bismark. Somebody ought to just add her into a Mod, and throw in Prinz Eugen while they're at it, and be done with it.

Let them survive the glorious WitP game engine, and resolve all these debates.

-F-
Since we've gone this far -
I may as well point out that according to the Ballard Expedition Bismarck was definitely "scuttled".[X(]
well, that's what the Wiki says anyway[:)]

[How's this for stirring the pot! [:D]]

Controversy

The second Bismarck expedition in 2001 was Anglo-American and funded by a UK TV channel. It followed-on from the same team's prior discovery of the long-lost wreckage of Hood which was located and filmed for the first time.

The Anglo-American team (David Mearns and Bill Jurens from the USA and Professor Eric Grove from the UK) conducted its own sonar survey from scratch to find the Bismarck wreck site, based solely on available information that it was resting at the foot of the only undersea volcano in that area. Then they used ROVs to film the hull externally and concluded that the ship sank due to combat damage, having received numerous artillery and torpedo hits from the British.

Ballard criticised this documentary, citing what he considered nationalistic, biased research of limited historic value due to lack of thoroughness. A new American expedition visited the site using smaller and more agile ROVs. These provided some interior shots of Bismarck for the first time, which were aired as part of a one-hour documentary film on the National Geographic Channel (NGC).

The third survey found no underwater penetrations of the ship's fully-armoured citadel and only four direct hit holes on it above the waterline, all of them on one side, as delivered by Rodney's 16 inch (406 mm) guns. Huge dents showed that the 14 inch (356 mm) shells fired by King George V bounced off the German belt armour[citation needed]. Interior ROV footage showed that the "terrible destruction" the Anglo-American expedition reported was in fact the torpedo bulges, which were designed to absorb the energy of torpedoes and plunging shells. Underneath the torn bulge sheeting, the ship's 320 mm (12.6 inch) thick main belt armour appeared to be intact.

The American expedition's final conclusions were strikingly different from the findings of the Anglo-American team. They estimated that Bismarck could still float for at least a day when the British vessels ceased fire and could have been captured by the Royal Navy. They concluded the direct cause of sinking was due to scuttling: sabotage of engine-room valves by her crew, as claimed by German survivors. A detailed look at a modern computer analysis of the hull's eventual impact on the sea bottom explains some damage as a result of hydrodynamic impact shock inside the ship, which was still apparently girded by an uninterrupted curtain of armour.

In all 2,876 shells of various calibres were fired by the British ships. Approximately 300-400 hit. Only two hits fully penetrating the main armour were located. These holes were on the starboard side, suggesting that they were 16-inch shells from Rodney. Two other penetrations above the main armour belt were found on the port side, and appeared to be by 14-inch shells. In all 714 14-inch and 16-inch shells were fired by the two battleships, of which about 80 hit Bismarck. Only four penetrated the belt but in successive hits the shells had destroyed A turret, B turret, each gun director and the bridge.

When senior Bismarck survivor the late Baron von Müllenheim-Rechberg was asked for his opinion on the controversy in a British television interview he simply replied politely, "Both sides sank the Bismarck."

And a full 3 page article from the NY Times:
http://www.nytimes.com/2002/12/03/scien ... 359ff9905e
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RE: 1000 Pounders versus Battleships

Post by Shark7 »

You know, I think we're all looking at the wrong thing when trying to determine how fast the Swordfish were moving on their attack runs. We are looking at the plane, which in this case is totally irrelevant.

The key factor here is not how fast the plane is capable of going, but rather what speed the plane must be going to successfully release a torpedo. That is the limiting factor. And I have no clue as to what that speed is, nor have I been able to find that info. If anyone can provide it, then we can determine if the Swordfish attack speed had any role in the tracking problem.

@Tiornu: Yes, that is what I was getting at. The dive itself isn't necessarily a problem for the plane (though it might be for the pilot), its the g-force and stress on the frame when you try to pull out of it. There comes a point where you can't pull out of the dive without snapping off the wings, or having to do it so gently that you run into the ground before being able to level off. That is what I meant by the uncontrollable dive...the point at which you can't escape the dive without destroying the aircraft or running straight into the ground.
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RE: 1000 Pounders versus Battleships

Post by Tiornu »

Underneath the torn bulge sheeting, the ship's 320 mm (12.6 inch) thick main belt armour appeared to be intact.

Since there is no 320mm belt armor under the bulge, you know something's wrong.
Bill Jurens, who was the naval architecture expert on two Bismarck expeditions counted a few penetrations of the armor belt but found no signs of large shells failing against the belt.
That is the limiting factor.

A speed of 100mph would certainly be within the limitations of the British torpedo. It was even within the limits of the famously limited American Mk 13 (110 knots and 50 feet).
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RE: 1000 Pounders versus Battleships

Post by Shark7 »

Then it is safe to assume that during the attack run, when the planes were most vulnerable, they were also moving quite slowly to allow for torpedo release.
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RE: 1000 Pounders versus Battleships

Post by witpqs »

@Tiornu

I think the point is proved about the 200 mph dive. I sure am surprised.

BTW, how for away from the target track would they have to launch? I'm wondering how long they would have flown low & slow.


@Howard Mitchell

You mention that actual airspeed is a little higher than indicated airspeed. Why?
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RE: 1000 Pounders versus Battleships

Post by bradfordkay »

" BTW, how for away from the target track would they have to launch?"

That would depend upon two factors: the range of the torpedo and the determination of the air crew. I would assume that the closer to the target the tropedo is released, the better the chance for a hit.
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RE: 1000 Pounders versus Battleships

Post by witpqs »

Also the minimum range for the torpedo to arm. Which I do not know.
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RE: 1000 Pounders versus Battleships

Post by Tiornu »

ORIGINAL: witpqs
BTW, how for away from the target track would they have to launch? I'm wondering how long they would have flown low & slow.
That's a good question. Perhaps someone has Lamb handy and can find an answer. There's another Swordfish book out there by David Wragg, reputedly a good one. Anybody got it?
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RE: 1000 Pounders versus Battleships

Post by Apollo11 »

Hi all,

Very interesting discussion - thanks guys! [:)]


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RE: 1000 Pounders versus Battleships

Post by rtrapasso »

ORIGINAL: Tiornu
ORIGINAL: witpqs
BTW, how for away from the target track would they have to launch? I'm wondering how long they would have flown low & slow.
That's a good question. Perhaps someone has Lamb handy and can find an answer. There's another Swordfish book out there by David Wragg, reputedly a good one. Anybody got it?

i suspect you can alter the "minimum" distance at will - there is usually a small propellor on the tip of the torpedo that is on a screw mechanism... when the torpedo moves through the water, the propellor turns a screw mechanism which eventually arms the torpedo... probably, by messing with the screw mechanism before launching the torpedo, you can change the arming distance.

i've never seen reference (or don't remember seeing) to the minimum arming run distances of air launched torpedoes, but typical ones for ship/boat launched torps are 200-500 yards... usually more toward the high end... i suspect airlaunched ones might be more toward the short end.

However, unless you've taken special precautions (i.e. wooden fins for shallow harbors, etc.) a torpedo dropped from a plane tends to go deep for some distance before returning to the running depth... so a torp dropped by plane TOO close to a target could actually run under the target.
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RE: 1000 Pounders versus Battleships

Post by Nikademus »

ORIGINAL: Feinder

I gotta say, it's mildly amusing to see how often threads in this forum turn into squabbles about the Bismark.  Somebody ought to just add her into a Mod, and throw in Prinz Eugen while they're at it, and be done with it.

Let them survive the glorious WitP game engine, and resolve all these debates.

-F-


Sorry.....i had no idea my innocent but 92.7% accurate statement would cause such controversey. Then again...Tiornu is a known troublemaker and party crasher who hogs the Kegger. [:D]
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RE: 1000 Pounders versus Battleships

Post by Big B »

ORIGINAL: witpqs

You mention that actual airspeed is a little higher than indicated airspeed. Why?

Because Indicated Air Speed is measured from a pitot tube which is pressure sensitive. The higher in altitude - the lower the pressure in the tube:
Indicated airspeed (IAS) is the airspeed read directly from the airspeed indicator on an aircraft, driven by the pitot-static system. IAS is directly related to calibrated airspeed (CAS), but includes instrument errors and position error.

An aircraft's indicated airspeed in knots is typically abbreviated KIAS for "Knots-Indicated Air Speed" (vs. KCAS for calibrated airspeed and KTAS for true airspeed).

IAS and V speeds

Unless an aircraft is at sea level under International Standard Atmosphere conditions (15°C, 1013 hPa, 0% humidity) and no wind, the IAS bears little relation to how fast an aircraft is moving in reference to the ground; however, because the air pressure and density affect IAS/CAS and an aircraft's flight characteristics in exactly the same way, IAS and CAS are extremely useful for controlling an aircraft, and the critical V speeds are usually given as IAS.

In aneroid instruments the indicated airspeed drops-off with increasing altitude as air pressure decreases, and this leads to an apparent falling-off of airspeed at higher altitudes. For this reason never exceed speeds (abbreviated VNE) are often given at several differing altitudes in the aircraft's operating manual, the VNE IAS figure falling as height is increased, as shown in the sample table below.


Diving below mph IAS
30,000 ft 370
25,000 ft 410
20,000 ft 450
15,000 ft 490
10,000 ft 540
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RE: 1000 Pounders versus Battleships

Post by Nikademus »

ORIGINAL: Tiornu

Since there is no 320mm belt armor under the bulge, you know something's wrong.
Bill Jurens, who was the naval architecture expert on two Bismarck expeditions counted a few penetrations of the armor belt but found no signs of large shells failing against the belt.

lol. I always thought the whole try to find shell holes in the belt was silly. More so given that figure I read.... that estimated that only 4% of shell hits strike the main armor belt.

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